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22.3.3.9 MySQL Server Options and Variables for NDB Cluster
This section provides information about MySQL server options, server and status variables that are specific to NDB Cluster. For general information on using these, and for other options and variables not specific to NDB Cluster, see Section 5.1, “The MySQL Server”.
For NDB Cluster configuration parameters used in the cluster
configuration file (usually named
config.ini
), see
Section 22.3, “Configuration of NDB Cluster”.
22.3.3.9.1 MySQL Server Options for NDB Cluster
This section provides descriptions of mysqld server options relating to NDB Cluster. For information about mysqld options not specific to NDB Cluster, and for general information about the use of options with mysqld, see Section 5.1.7, “Server Command Options”.
For information about command-line options used with other NDB
Cluster processes (ndbd,
ndb_mgmd, and ndb_mgm),
see Section 22.4.31, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.
For information about command-line options used with
NDB
utility programs (such as
ndb_desc, ndb_size.pl,
and ndb_show_tables), see
Section 22.4, “NDB Cluster Programs”.
-
Table 22.209 Type and value information for ndbcluster
Property Value Name ndbcluster
Command Line Yes System Variable No Status Variable No Option File Yes Scope Dynamic No Type Default, Range FALSE (Version: 8.0) Notes DESCRIPTION: Enable NDB Cluster (if this version of MySQL supports it)
Disabled by
--skip-ndbcluster
.The
NDBCLUSTER
storage engine is necessary for using NDB Cluster. If a mysqld binary includes support for theNDBCLUSTER
storage engine, the engine is disabled by default. Use the--ndbcluster
option to enable it. Use--skip-ndbcluster
to explicitly disable the engine.The
--ndbcluster
option is ignored (and theNDB
storage engine is not enabled) if--initialize
is also used. (It is neither necessary nor desirable to use this option together with--initialize
.) --ndb-allow-copying-alter-table=[ON|OFF]
Table 22.210 Type and value information for ndb-allow-copying-alter-table
Property Value Name ndb-allow-copying-alter-table
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Both Dynamic Yes Type Default, Range ON (Version: 8.0) Notes DESCRIPTION: Set to OFF to keep ALTER TABLE from using copying operations on NDB tables
Let
ALTER TABLE
and other DDL statements use copying operations onNDB
tables. Set toOFF
to keep this from happening; doing so may improve performance of critical applications.-
Table 22.211 Type and value information for ndb-batch-size
Property Value Name ndb-batch-size
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic No Type Default, Range 32768 / 0 - 31536000 (Version: 8.0) Notes DESCRIPTION: Size (in bytes) to use for NDB transaction batches
This sets the size in bytes that is used for NDB transaction batches.
--ndb-cluster-connection-pool=
#
Table 22.212 Type and value information for ndb-cluster-connection-pool
Property Value Name ndb-cluster-connection-pool
Command Line Yes System Variable Yes Status Variable Yes Option File Yes Scope Global Dynamic No Type Default, Range 1 / 1 - 63 (Version: 8.0) Notes DESCRIPTION: Number of connections to the cluster used by MySQL
By setting this option to a value greater than 1 (the default), a mysqld process can use multiple connections to the cluster, effectively mimicking several SQL nodes. Each connection requires its own
[api]
or[mysqld]
section in the cluster configuration (config.ini
) file, and counts against the maximum number of API connections supported by the cluster.Suppose that you have 2 cluster host computers, each running an SQL node whose mysqld process was started with
--ndb-cluster-connection-pool=4
; this means that the cluster must have 8 API slots available for these connections (instead of 2). All of these connections are set up when the SQL node connects to the cluster, and are allocated to threads in a round-robin fashion.This option is useful only when running mysqld on host machines having multiple CPUs, multiple cores, or both. For best results, the value should be smaller than the total number of cores available on the host machine. Setting it to a value greater than this is likely to degrade performance severely.
ImportantBecause each SQL node using connection pooling occupies multiple API node slots—each slot having its own node ID in the cluster—you must not use a node ID as part of the cluster connection string when starting any mysqld process that employs connection pooling.
Setting a node ID in the connection string when using the
--ndb-cluster-connection-pool
option causes node ID allocation errors when the SQL node attempts to connect to the cluster.--ndb-cluster-connection-pool-nodeids=
list
Table 22.213 Type and value information for ndb-cluster-connection-pool-nodeids
Property Value Name ndb-cluster-connection-pool-nodeids
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic No Type Default, Range / (Version: 8.0) Notes DESCRIPTION: Comma-separated list of node IDs for connections to the cluster used by MySQL; the number of nodes in the list must be the same as the value set for --ndb-cluster-connection-pool
Specifies a comma-separated list of node IDs for connections to the cluster used by an SQL node. The number of nodes in this list must be the same as the value set for the
--ndb-cluster-connection-pool
option.--ndb-blob-read-batch-bytes=
bytes
Table 22.214 Type and value information for ndb-blob-read-batch-bytes
Property Value Name ndb-blob-read-batch-bytes
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Both Dynamic Yes Type Default, Range 65536 / 0 - 4294967295 (Version: NDB 8.0) Notes DESCRIPTION: Specifies size in bytes that large BLOB reads should be batched into. 0 = no limit.
This option can be used to set the size (in bytes) for batching of
BLOB
data reads in NDB Cluster applications. When this batch size is exceeded by the amount ofBLOB
data to be read within the current transaction, any pendingBLOB
read operations are immediately executed.The maximum value for this option is 4294967295; the default is 65536. Setting it to 0 has the effect of disabling
BLOB
read batching.NoteIn NDB API applications, you can control
BLOB
write batching with thesetMaxPendingBlobReadBytes()
andgetMaxPendingBlobReadBytes()
methods.--ndb-blob-write-batch-bytes=
bytes
Table 22.215 Type and value information for ndb-blob-write-batch-bytes
Property Value Name ndb-blob-write-batch-bytes
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Both Dynamic Yes Type Default, Range 65536 / 0 - 4294967295 (Version: 8.0) Notes DESCRIPTION: Specifies size in bytes that large BLOB writes should be batched into. 0 = no limit.
This option can be used to set the size (in bytes) for batching of
BLOB
data writes in NDB Cluster applications. When this batch size is exceeded by the amount ofBLOB
data to be written within the current transaction, any pendingBLOB
write operations are immediately executed.The maximum value for this option is 4294967295; the default is 65536. Setting it to 0 has the effect of disabling
BLOB
write batching.NoteIn NDB API applications, you can control
BLOB
write batching with thesetMaxPendingBlobWriteBytes()
andgetMaxPendingBlobWriteBytes()
methods.--ndb-connectstring=
connection_string
Table 22.216 Type and value information for ndb-connectstring
Property Value Name ndb-connectstring
Command Line Yes System Variable No Status Variable No Option File Yes Scope Dynamic No Type Default, Range (Version: 8.0) Notes DESCRIPTION: Point to the management server that distributes the cluster configuration
When using the
NDBCLUSTER
storage engine, this option specifies the management server that distributes cluster configuration data. See Section 22.3.3.3, “NDB Cluster Connection Strings”, for syntax.--ndb-default-column-format=[FIXED|DYNAMIC]
Table 22.217 Type and value information for ndb-default-column-format
Property Value Name ndb-default-column-format
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range DYNAMIC / FIXED, DYNAMIC (Version: NDB 8.0) Default, Range FIXED / FIXED, DYNAMIC (Version: NDB 8.0) Notes DESCRIPTION: Use this value (FIXED or DYNAMIC) by default for COLUMN_FORMAT and ROW_FORMAT options when creating or adding columns to a table.
Sets the default
COLUMN_FORMAT
andROW_FORMAT
for new tables (see Section 13.1.20, “CREATE TABLE Syntax”). The default isFIXED
.--ndb-deferred-constraints=[0|1]
Table 22.218 Type and value information for ndb-deferred-constraints
Property Value Name ndb-deferred-constraints
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Both Dynamic Yes Type Default, Range 0 / 0 - 1 (Version: 8.0) Notes DESCRIPTION: Specifies that constraint checks on unique indexes (where these are supported) should be deferred until commit time. Not normally needed or used; for testing purposes only.
Controls whether or not constraint checks on unique indexes are deferred until commit time, where such checks are supported.
0
is the default.This option is not normally needed for operation of NDB Cluster or NDB Cluster Replication, and is intended primarily for use in testing.
-
Table 22.219 Type and value information for ndb-schema-dist-timeout
Property Value Name ndb-schema-dist-timeout
Command Line Yes System Variable Yes Option File Yes Scope Global Dynamic No Type: Default, Range integer: 120 / 5 - 1200 (Version: 8.0.17) Notes DESCRIPTION: How long to wait before detecting timeout during schema distribution
Specifies the maximum time in seconds that this mysqld waits for a schema operation to complete before marking it as having timed out.
--ndb-distribution=[KEYHASH|LINHASH]
Table 22.220 Type and value information for ndb-distribution
Property Value Name ndb-distribution
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range KEYHASH / LINHASH, KEYHASH (Version: 8.0) Notes DESCRIPTION: Default distribution for new tables in NDBCLUSTER (KEYHASH or LINHASH, default is KEYHASH)
Controls the default distribution method for
NDB
tables. Can be set to either ofKEYHASH
(key hashing) orLINHASH
(linear hashing).KEYHASH
is the default.-
Table 22.221 Type and value information for ndb-log-apply-status
Property Value Name ndb-log-apply-status
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic No Type Default, Range OFF (Version: 8.0) Notes DESCRIPTION: Cause a MySQL server acting as a slave to log mysql.ndb_apply_status updates received from its immediate master in its own binary log, using its own server ID. Effective only if the server is started with the --ndbcluster option.
Causes a slave mysqld to log any updates received from its immediate master to the
mysql.ndb_apply_status
table in its own binary log using its own server ID rather than the server ID of the master. In a circular or chain replication setting, this allows such updates to propagate to themysql.ndb_apply_status
tables of any MySQL servers configured as slaves of the current mysqld.In a chain replication setup, using this option allows downstream (slave) clusters to be aware of their positions relative to all of their upstream contributors (masters).
In a circular replication setup, this option causes changes to
ndb_apply_status
tables to complete the entire circuit, eventually propagating back to the originating NDB Cluster. This also allows a cluster acting as a master to see when its changes (epochs) have been applied to the other clusters in the circle.This option has no effect unless the MySQL server is started with the
--ndbcluster
option. --ndb-log-empty-epochs=[ON|OFF]
Table 22.222 Type and value information for ndb-log-empty-epochs
Property Value Name ndb-log-empty-epochs
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range OFF (Version: 8.0) Notes DESCRIPTION: When enabled, causes epochs in which there were no changes to be written to the ndb_apply_status and ndb_binlog_index tables, even when --log-slave-updates is enabled.
Causes epochs during which there were no changes to be written to the
ndb_apply_status
andndb_binlog_index
tables, even when--log-slave-updates
is enabled.By default this option is disabled. Disabling
--ndb-log-empty-epochs
causes epoch transactions with no changes not to be written to the binary log, although a row is still written even for an empty epoch inndb_binlog_index
.Because
--ndb-log-empty-epochs=1
causes the size of thendb_binlog_index
table to increase independently of the size of the binary log, users should be prepared to manage the growth of this table, even if they expect the cluster to be idle a large part of the time.--ndb-log-empty-update=[ON|OFF]
Table 22.223 Type and value information for ndb-log-empty-update
Property Value Name ndb-log-empty-update
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range OFF (Version: 8.0) Notes DESCRIPTION: When enabled, causes updates that produced no changes to be written to the ndb_apply_status and ndb_binlog_index tables, even when --log-slave-updates is enabled.
Causes updates that produced no changes to be written to the
ndb_apply_status
andndb_binlog_index
tables, even when--log-slave-updates
is enabled.By default this option is disabled (
OFF
). Disabling--ndb-log-empty-update
causes updates with no changes not to be written to the binary log.--ndb-log-exclusive-reads=[0|1]
Table 22.224 Type and value information for ndb-log-exclusive-reads
Property Value Name ndb-log-exclusive-reads
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Both Dynamic Yes Type Default, Range 0 (Version: 8.0) Notes DESCRIPTION: Log primary key reads with exclusive locks; allow conflict resolution based on read conflicts
Starting the server with this option causes primary key reads to be logged with exclusive locks, which allows for NDB Cluster Replication conflict detection and resolution based on read conflicts. You can also enable and disable these locks at runtime by setting the value of the
ndb_log_exclusive_reads
system variable to 1 or 0, respectively. 0 (disable locking) is the default.For more information, see Read conflict detection and resolution.
-
Table 22.225 Type and value information for ndb-log-orig
Property Value Name ndb-log-orig
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic No Type Default, Range OFF (Version: 8.0) Notes DESCRIPTION: Log originating server id and epoch in mysql.ndb_binlog_index table
Log the originating server ID and epoch in the
ndb_binlog_index
table.NoteThis makes it possible for a given epoch to have multiple rows in
ndb_binlog_index
, one for each originating epoch.For more information, see Section 22.6.4, “NDB Cluster Replication Schema and Tables”.
-
Table 22.226 Type and value information for ndb-log-transaction-id
Property Value Name ndb-log-transaction-id
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic No Type Default, Range OFF (Version: 8.0) Notes DESCRIPTION: Write NDB transaction IDs in the binary log.
Causes a slave mysqld to write the NDB transaction ID in each row of the binary log. The default value is
FALSE
.This option is not supported in mainline MySQL Server 8.0. It is required to enable NDB Cluster Replication conflict detection and resolution using the
NDB$EPOCH_TRANS()
function (see NDB$EPOCH_TRANS()). For more information, see Section 22.6.11, “NDB Cluster Replication Conflict Resolution”.The deprecated option
--log-bin-use-v1-row-events
, which defaults toOFF
, must not be set toON
when you use--ndb-log-transaction-id
. -
Table 22.227 Type and value information for ndb-log-update-minimal
Property Value Name ndb-log-update-minimal
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range OFF (Version: NDB 8.0) Default, Range OFF (Version: NDB 8.0) Default, Range OFF (Version: NDB 8.0) Notes DESCRIPTION: Log updates in a minimal format.
Log updates in a minimal fashion, by writing only the primary key values in the before image, and only the changed columns in the after image. This may cause compatibility problems if replicating to storage engines other than
NDB
. -
Table 22.228 Type and value information for ndb-mgmd-host
Property Value Name ndb-mgmd-host
Command Line Yes System Variable No Status Variable No Option File Yes Scope Dynamic No Type Default, Range localhost:1186 (Version: 8.0) Notes DESCRIPTION: Set the host (and port, if desired) for connecting to management server
Can be used to set the host and port number of a single management server for the program to connect to. If the program requires node IDs or references to multiple management servers (or both) in its connection information, use the
--ndb-connectstring
option instead. -
Table 22.229 Type and value information for ndb-nodeid
Property Value Name ndb-nodeid
Command Line Yes System Variable No Status Variable Yes Option File Yes Scope Global Dynamic No Type Default, Range / 1 - 63 (Version: NDB 8.0) Default, Range / 1 - 255 (Version: NDB 8.0) Notes DESCRIPTION: NDB Cluster node ID for this MySQL server
Set this MySQL server's node ID in an NDB Cluster.
The
--ndb-nodeid
option overrides any node ID set with--ndb-connectstring
, regardless of the order in which the two options are used.In addition, if
--ndb-nodeid
is used, then either a matching node ID must be found in a[mysqld]
or[api]
section ofconfig.ini
, or there must be an “open”[mysqld]
or[api]
section in the file (that is, a section without aNodeId
orId
parameter specified). This is also true if the node ID is specified as part of the connection string.Regardless of how the node ID is determined, its is shown as the value of the global status variable
Ndb_cluster_node_id
in the output ofSHOW STATUS
, and ascluster_node_id
in theconnection
row of the output ofSHOW ENGINE NDBCLUSTER STATUS
.For more information about node IDs for NDB Cluster SQL nodes, see Section 22.3.3.7, “Defining SQL and Other API Nodes in an NDB Cluster”.
-
Table 22.230 Type and value information for ndbinfo
Property Value Name ndbinfo
Command Line Yes System Variable No Option File No Scope Dynamic No Type: Default, Range enumeration: ON, OFF, FORCE (Version: 8.0.13) Notes DESCRIPTION: Enable ndbinfo plugin, if supported
Enables the plugin for the
ndbinfo
information database. By default this is ON wheneverNDBCLUSTER
is enabled. --ndb-optimization-delay=
milliseconds
Table 22.231 Type and value information for ndb-optimization-delay
Property Value Name ndb-optimization-delay
Command Line Yes System Variable Yes Status Variable No Option File No Scope Global Dynamic Yes Type Default, Range 10 / 0 - 100000 (Version: 8.0) Notes DESCRIPTION: Sets the number of milliseconds to wait between processing sets of rows by OPTIMIZE TABLE on NDB tables
Set the number of milliseconds to wait between sets of rows by
OPTIMIZE TABLE
statements onNDB
tables. The default is 10.--ndb-recv-thread-activation-threshold=
threshold
Table 22.232 Type and value information for ndb-recv-thread-activation-threshold
Property Value Name ndb-recv-thread-activation-threshold
Command Line Yes System Variable No Status Variable No Option File Yes Scope Dynamic No Type Default, Range 8 / 0 (MIN_ACTIVATION_THRESHOLD) - 16 (MAX_ACTIVATION_THRESHOLD) (Version: NDB 8.0) Notes DESCRIPTION: Activation threshold when receive thread takes over the polling of the cluster connection (measured in concurrently active threads)
When this number of concurrently active threads is reached, the receive thread takes over polling of the cluster connection.
--ndb-recv-thread-cpu-mask=
bitmask
Table 22.233 Type and value information for ndb-recv-thread-cpu-mask
Property Value Name ndb-recv-thread-cpu-mask
Command Line Yes System Variable No Status Variable No Option File Yes Scope Dynamic No Type Default, Range [empty] (Version: 8.0) Notes DESCRIPTION: CPU mask for locking receiver threads to specific CPUs; specified as hexadecimal. See documentation for details.
Set a CPU mask for locking receiver threads to specific CPUs. This is specified as a hexadecimal bitmask; for example,
0x33
means that one CPU is used per receiver thread. An empty string (no locking of receiver threads) is the default.ndb-transid-mysql-connection-map=
state
Table 22.234 Type and value information for ndb-transid-mysql-connection-map
Property Value Name ndb-transid-mysql-connection-map
Command Line Yes System Variable No Status Variable No Option File No Scope Dynamic No Type Default, Range ON / ON, OFF, FORCE (Version: 8.0) Notes DESCRIPTION: Enable or disable the ndb_transid_mysql_connection_map plugin; that is, enable or disable the INFORMATION_SCHEMA table having that name
Enables or disables the plugin that handles the
ndb_transid_mysql_connection_map
table in theINFORMATION_SCHEMA
database. Takes one of the valuesON
,OFF
, orFORCE
.ON
(the default) enables the plugin.OFF
disables the plugin, which makesndb_transid_mysql_connection_map
inaccessible.FORCE
keeps the MySQL Server from starting if the plugin fails to load and start.You can see whether the
ndb_transid_mysql_connection_map
table plugin is running by checking the output ofSHOW PLUGINS
.-
Table 22.235 Type and value information for ndb-wait-connected
Property Value Name ndb-wait-connected
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic No Type Default, Range 0 / 0 - 31536000 (Version: 8.0) Default, Range 30 / 0 - 31536000 (Version: NDB 8.0) Default, Range 0 / 0 - 31536000 (Version: 8.0) Default, Range 30 / 0 - 31536000 (Version: NDB 8.0) Notes DESCRIPTION: Time (in seconds) for the MySQL server to wait for connection to cluster management and data nodes before accepting MySQL client connections
This option sets the period of time that the MySQL server waits for connections to NDB Cluster management and data nodes to be established before accepting MySQL client connections. The time is specified in seconds. The default value is
30
. -
Table 22.236 Type and value information for ndb-wait-setup
Property Value Name ndb-wait-setup
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic No Type Default, Range 15 / 0 - 31536000 (Version: NDB 8.0) Default, Range 15 / 0 - 31536000 (Version: NDB 8.0) Default, Range 15 / 0 - 31536000 (Version: NDB 8.0) Default, Range 30 / 0 - 31536000 (Version: NDB 8.0) Default, Range 15 / 0 - 31536000 (Version: NDB 8.0) Default, Range 30 / 0 - 31536000 (Version: NDB 8.0) Notes DESCRIPTION: Time (in seconds) for the MySQL server to wait for NDB engine setup to complete
This variable shows the period of time that the MySQL server waits for the
NDB
storage engine to complete setup before timing out and treatingNDB
as unavailable. The time is specified in seconds. The default value is30
. -
Table 22.237 Type and value information for server-id-bits
Property Value Name server-id-bits
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic No Type Default, Range 32 / 7 - 32 (Version: 8.0) Notes DESCRIPTION: Sets the number of least significant bits in the server_id actually used for identifying the server, permitting NDB API applications to store application data in the most significant bits. server_id must be less than 2 to the power of this value.
This option indicates the number of least significant bits within the 32-bit
server_id
which actually identify the server. Indicating that the server is actually identified by fewer than 32 bits makes it possible for some of the remaining bits to be used for other purposes, such as storing user data generated by applications using the NDB API's Event API within theAnyValue
of anOperationOptions
structure (NDB Cluster uses theAnyValue
to store the server ID).When extracting the effective server ID from
server_id
for purposes such as detection of replication loops, the server ignores the remaining bits. The--server-id-bits
option is used to mask out any irrelevant bits ofserver_id
in the IO and SQL threads when deciding whether an event should be ignored based on the server ID.This data can be read from the binary log by mysqlbinlog, provided that it is run with its own
--server-id-bits
option set to 32 (the default).The value of
server_id
must be less than 2 ^server_id_bits
; otherwise, mysqld refuses to start.This system variable is supported only by NDB Cluster. It is not supported in the standard MySQL 8.0 Server.
-
Table 22.238 Type and value information for skip-ndbcluster
Property Value Name skip-ndbcluster
Command Line Yes System Variable No Status Variable No Option File Yes Scope Dynamic No Type Notes DESCRIPTION: Disable the NDB Cluster storage engine
Disable the
NDBCLUSTER
storage engine. This is the default for binaries that were built withNDBCLUSTER
storage engine support; the server allocates memory and other resources for this storage engine only if the--ndbcluster
option is given explicitly. See Section 22.3.1, “Quick Test Setup of NDB Cluster”, for an example.
This section provides detailed information about MySQL server
system variables that are specific to NDB Cluster and the
NDB
storage engine. For system
variables not specific to NDB Cluster, see
Section 5.1.8, “Server System Variables”. For general
information on using system variables, see
Section 5.1.9, “Using System Variables”.
-
Table 22.239 Type and value information for ndb_autoincrement_prefetch_sz
Property Value Name ndb_autoincrement_prefetch_sz
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Both Dynamic Yes Type Default, Range 32 / 1 - 256 (Version: 8.0) Default, Range 1 / 1 - 256 (Version: NDB 8.0) Default, Range 32 / 1 - 256 (Version: NDB 8.0) Default, Range 1 / 1 - 256 (Version: NDB 8.0) Default, Range 32 / 1 - 256 (Version: NDB 8.0) Default, Range 1 / 1 - 256 (Version: NDB 8.0) Default, Range 32 / 1 - 256 (Version: NDB 8.0) Default, Range 1 / 1 - 256 (Version: NDB 8.0) Default, Range 1 / 1 - 65536 (Version: NDB 8.0) Default, Range 32 / 1 - 256 (Version: NDB 8.0) Default, Range 1 / 1 - 65536 (Version: NDB 8.0) Default, Range 1 / 1 - 65536 (Version: NDB 8.0) Notes DESCRIPTION: NDB auto-increment prefetch size
Determines the probability of gaps in an autoincremented column. Set it to
1
to minimize this. Setting it to a high value for optimization makes inserts faster, but decreases the likelihood that consecutive autoincrement numbers will be used in a batch of inserts. The mininum and default value is 1. The maximum value forndb_autoincrement_prefetch_sz
is 65536.This variable affects only the number of
AUTO_INCREMENT
IDs that are fetched between statements; within a given statement, at least 32 IDs are obtained at a time. The default value is 1.ImportantThis variable does not affect inserts performed using
INSERT ... SELECT
. -
Table 22.240 Type and value information for ndb_cache_check_time
Property Value Name ndb_cache_check_time
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range 0 / - (Version: 8.0) Notes DESCRIPTION: Number of milliseconds between checks of cluster SQL nodes made by the MySQL query cache
The number of milliseconds that elapse between checks of NDB Cluster SQL nodes by the MySQL query cache. Setting this to 0 (the default and minimum value) means that the query cache checks for validation on every query.
The recommended maximum value for this variable is 1000, which means that the check is performed once per second. A larger value means that the check is performed and possibly invalidated due to updates on different SQL nodes less often. It is generally not desirable to set this to a value greater than 2000.
NoteThe query cache
ndb_cache_check_time
are deprecated in MySQL 5.7; the query cache was removed in MySQL 8.0. -
Table 22.241 Type and value information for ndb_clear_apply_status
Property Value Name ndb_clear_apply_status
Command Line Yes System Variable Yes Status Variable No Option File No Scope Global Dynamic Yes Type Default, Range ON (Version: 8.0) Notes DESCRIPTION: Causes RESET SLAVE to clear all rows from the ndb_apply_status table; ON by default
By the default, executing
RESET SLAVE
causes an NDB Cluster replication slave to purge all rows from itsndb_apply_status
table. You can disable this by settingndb_clear_apply_status=OFF
. -
Table 22.242 Type and value information for ndb_data_node_neighbour
Property Value Name ndb_data_node_neighbour
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range 0 / 0 - 255 (Version: NDB 8.0) Notes DESCRIPTION: Specifies cluster data node "closest" to this MySQL Server, for transaction hinting and fully replicated tables
Sets the ID of a “nearest” data node—that is, a preferred nonlocal data node is chosen to execute the transaction, rather than one running on the same host as the SQL or API node. This used to ensure that when a fully replicated table is accessed, we access it on this data node, to ensure that the local copy of the table is always used whenever possible. This can also be used for providing hints for transactions.
This can improve data access times in the case of a node that is physically closer than and thus has higher network throughput than others on the same host.
See Section 13.1.20.11, “Setting NDB_TABLE Options”, for further information.
NoteAn equivalent method
set_data_node_neighbour()
is provided for use in NDB API applications. -
Table 22.243 Type and value information for ndb_default_column_format
Property Value Name ndb_default_column_format
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range DYNAMIC / FIXED, DYNAMIC (Version: NDB 8.0) Default, Range FIXED / FIXED, DYNAMIC (Version: NDB 8.0) Notes DESCRIPTION: Sets default row format and column format (FIXED or DYNAMIC) used for new NDB tables
Sets the default
COLUMN_FORMAT
andROW_FORMAT
for new tables (see Section 13.1.20, “CREATE TABLE Syntax”). The default isFIXED
. -
Table 22.244 Type and value information for ndb_deferred_constraints
Property Value Name ndb_deferred_constraints
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Both Dynamic Yes Type Default, Range 0 / 0 - 1 (Version: 8.0) Notes DESCRIPTION: Specifies that constraint checks should be deferred (where these are supported). Not normally needed or used; for testing purposes only.
Controls whether or not constraint checks are deferred, where these are supported.
0
is the default.This variable is not normally needed for operation of NDB Cluster or NDB Cluster Replication, and is intended primarily for use in testing.
-
Table 22.245 Type and value information for ndb_distribution
Property Value Name ndb_distribution
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range KEYHASH / LINHASH, KEYHASH (Version: 8.0) Notes DESCRIPTION: Default distribution for new tables in NDBCLUSTER (KEYHASH or LINHASH, default is KEYHASH)
Controls the default distribution method for
NDB
tables. Can be set to either ofKEYHASH
(key hashing) orLINHASH
(linear hashing).KEYHASH
is the default. -
Table 22.246 Type and value information for ndb_eventbuffer_free_percent
Property Value Name ndb_eventbuffer_free_percent
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range 20 / 1 - 99 (Version: 8.0) Notes DESCRIPTION: Percentage of free memory that should be available in event buffer before resumption of buffering, after reaching limit set by ndb_eventbuffer_max_alloc
Sets the percentage of the maximum memory allocated to the event buffer (ndb_eventbuffer_max_alloc) that should be available in event buffer after reaching the maximum, before starting to buffer again.
-
Table 22.247 Type and value information for ndb_eventbuffer_max_alloc
Property Value Name ndb_eventbuffer_max_alloc
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range 0 / 0 - 4294967295 (Version: 8.0) Notes DESCRIPTION: Maximum memory that can be allocated for buffering events by the NDB API. Defaults to 0 (no limit).
Sets the maximum amount memory (in bytes) that can be allocated for buffering events by the NDB API. 0 means that no limit is imposed, and is the default.
-
Table 22.248 Type and value information for ndb_extra_logging
Property Value Name ndb_extra_logging
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range 0 / - (Version: 8.0) Default, Range 1 / - (Version: NDB 8.0) Notes DESCRIPTION: Controls logging of NDB Cluster schema, connection, and data distribution events in the MySQL error log
This variable enables recording in the MySQL error log of information specific to the
NDB
storage engine.When this variable is set to 0, the only information specific to
NDB
that is written to the MySQL error log relates to transaction handling. If it set to a value greater than 0 but less than 10,NDB
table schema and connection events are also logged, as well as whether or not conflict resolution is in use, and otherNDB
errors and information. If the value is set to 10 or more, information aboutNDB
internals, such as the progress of data distribution among cluster nodes, is also written to the MySQL error log. The default is 1. -
Table 22.249 Type and value information for ndb_force_send
Property Value Name ndb_force_send
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Both Dynamic Yes Type Default, Range TRUE (Version: 8.0) Notes DESCRIPTION: Forces sending of buffers to NDB immediately, without waiting for other threads
Forces sending of buffers to
NDB
immediately, without waiting for other threads. Defaults toON
. -
Table 22.250 Type and value information for ndb_fully_replicated
Property Value Name ndb_fully_replicated
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Both Dynamic Yes Type Default, Range OFF (Version: NDB 8.0) Notes DESCRIPTION: Whether new NDB tables are fully replicated
Determines whether new
NDB
tables are fully replicated. This setting can be overridden for an individual table usingCOMMENT="NDB_TABLE=FULLY_REPLICATED=..."
in aCREATE TABLE
orALTER TABLE
statement; see Section 13.1.20.11, “Setting NDB_TABLE Options”, for syntax and other information. -
Table 22.251 Type and value information for ndb_index_stat_enable
Property Value Name ndb_index_stat_enable
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Both Dynamic Yes Type Default, Range OFF (Version: 8.0) Default, Range ON (Version: NDB 8.0) Notes DESCRIPTION: Use NDB index statistics in query optimization
Use
NDB
index statistics in query optimization. The default isON
. -
Table 22.252 Type and value information for ndb_index_stat_option
Property Value Name ndb_index_stat_option
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Both Dynamic Yes Type Default, Range loop_enable=1000ms,loop_idle=1000ms,loop_busy=100ms, update_batch=1,read_batch=4,idle_batch=32,check_batch=8, check_delay=10m,delete_batch=8, clean_delay=1m,error_batch=4, error_delay=1m,evict_batch=8,evict_delay=1m,cache_limit=32M, cache_lowpct=90,zero_total=0 (Version: 8.0) Default, Range loop_checkon=1000ms,loop_idle=1000ms,loop_busy=100ms, update_batch=1,read_batch=4,idle_batch=32,check_batch=32, check_delay=1m,delete_batch=8,clean_delay=0,error_batch=4, error_delay=1m,evict_batch=8,evict_delay=1m,cache_limit=32M, cache_lowpct=90 (Version: NDB 8.0) Notes DESCRIPTION: Comma-separated list of tunable options for NDB index statistics; the list should contain no spaces
This variable is used for providing tuning options for NDB index statistics generation. The list consist of comma-separated name-value pairs of option names and values, and this list must not contain any space characters.
Options not used when setting
ndb_index_stat_option
are not changed from their default values. For example, you can setndb_index_stat_option = 'loop_idle=1000ms,cache_limit=32M'
.Time values can be optionally suffixed with
h
(hours),m
(minutes), ors
(seconds). Millisecond values can optionally be specified usingms
; millisecond values cannot be specified usingh
,m
, ors
.) Integer values can be suffixed withK
,M
, orG
.The names of the options that can be set using this variable are shown in the table that follows. The table also provides brief descriptions of the options, their default values, and (where applicable) their minimum and maximum values.
Table 22.253 ndb_index_stat_option options and values
Name Description Default/Units Minimum/Maximum loop_enable
1000 ms 0/4G loop_idle
Time to sleep when idle 1000 ms 0/4G loop_busy
Time to sleep when more work is waiting 100 ms 0/4G update_batch
1 0/4G read_batch
4 1/4G idle_batch
32 1/4G check_batch
8 1/4G check_delay
How often to check for new statistics 10 m 1/4G delete_batch
8 0/4G clean_delay
1 m 0/4G error_batch
4 1/4G error_delay
1 m 1/4G evict_batch
8 1/4G evict_delay
Clean LRU cache, from read time 1 m 0/4G cache_limit
Maximum amount of memory in bytes used for cached index statistics by this mysqld; clean up the cache when this is exceeded. 32 M 0/4G cache_lowpct
90 0/100 zero_total
Setting this to 1 resets all accumulating counters in ndb_index_stat_status
to 0. This option value is also reset to 0 when this is done.0 0/1 -
Table 22.254 Type and value information for ndb_join_pushdown
Property Value Name ndb_join_pushdown
Command Line No System Variable Yes Status Variable No Option File No Scope Both Dynamic Yes Type Default, Range TRUE (Version: NDB 8.0) Notes DESCRIPTION: Enables pushing down of joins to data nodes
This variable controls whether joins on
NDB
tables are pushed down to the NDB kernel (data nodes). Previously, a join was handled using multiple accesses ofNDB
by the SQL node; however, whenndb_join_pushdown
is enabled, a pushable join is sent in its entirety to the data nodes, where it can be distributed among the data nodes and executed in parallel on multiple copies of the data, with a single, merged result being returned to mysqld. This can reduce greatly the number of round trips between an SQL node and the data nodes required to handle such a join.By default,
ndb_join_pushdown
is enabled.Conditions for NDB pushdown joins. In order for a join to be pushable, it must meet the following conditions:
Only columns can be compared, and all columns to be joined must use exactly the same data type.
This means that expressions such as
t1.a = t2.a +
cannot be pushed down, and that (for example) a join on anconstant
INT
column and aBIGINT
column also cannot be pushed down.Explicit locking is not supported; however, the
NDB
storage engine's characteristic implicit row-based locking is enforced.This means that a join using
FOR UPDATE
cannot be pushed down.In order for a join to be pushed down, child tables in the join must be accessed using one of the
ref
,eq_ref
, orconst
access methods, or some combination of these methods.Outer joined child tables can only be pushed using
eq_ref
.If the root of the pushed join is an
eq_ref
orconst
, only child tables joined byeq_ref
can be appended. (A table joined byref
is likely to become the root of another pushed join.)If the query optimizer decides on
Using join cache
for a candidate child table, that table cannot be pushed as a child. However, it may be the root of another set of pushed tables.Joins referencing tables explicitly partitioned by
[LINEAR] HASH
,LIST
, orRANGE
currently cannot be pushed down.
You can see whether a given join can be pushed down by checking it with
EXPLAIN
; when the join can be pushed down, you can see references to thepushed join
in theExtra
column of the output, as shown in this example:- mysql> EXPLAIN
- -> FROM employees e
- *************************** 1. row ***************************
- id: 1
- select_type: SIMPLE
- table: d
- possible_keys: PRIMARY
- key_len: NULL
- ref: NULL
- rows: 9
- *************************** 2. row ***************************
- id: 1
- select_type: SIMPLE
- table: de
- type: ref
- possible_keys: PRIMARY,emp_no,dept_no
- key: dept_no
- key_len: 4
- ref: employees.d.dept_no
- rows: 5305
- *************************** 3. row ***************************
- id: 1
- select_type: SIMPLE
- table: e
- type: eq_ref
- possible_keys: PRIMARY
- key: PRIMARY
- key_len: 4
- ref: employees.de.emp_no
- rows: 1
- *************************** 4. row ***************************
- id: 1
- select_type: SIMPLE
- table: t
- type: ref
- possible_keys: PRIMARY,emp_no
- key: emp_no
- key_len: 4
- ref: employees.de.emp_no
- rows: 19
NoteIf inner joined child tables are joined by
ref
, and the result is ordered or grouped by a sorted index, this index cannot provide sorted rows, which forces writing to a sorted tempfile.Two additional sources of information about pushed join performance are available:
The status variables
Ndb_pushed_queries_defined
,Ndb_pushed_queries_dropped
,Ndb_pushed_queries_executed
, andNdb_pushed_reads
.The counters in the
ndbinfo.counters
table that belong to theDBSPJ
kernel block. See Section 22.5.10.10, “The ndbinfo counters Table”, for information about these counters. See also The DBSPJ Block, in the NDB Cluster API Developer Guide.
-
Table 22.255 Type and value information for ndb_log_apply_status
Property Value Name ndb_log_apply_status
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic No Type Default, Range OFF (Version: 8.0) Notes DESCRIPTION: Whether or not a MySQL server acting as a slave logs mysql.ndb_apply_status updates received from its immediate master in its own binary log, using its own server ID
A read-only variable which shows whether the server was started with the
--ndb-log-apply-status
option. -
Table 22.256 Type and value information for ndb_log_bin
Property Value Name ndb_log_bin
Command Line Yes System Variable Yes Status Variable No Option File No Scope Both Dynamic Yes Type Default, Range ON (Version: 8.0) Notes DESCRIPTION: Write updates to NDB tables in the binary log. Effective only if binary logging is enabled with --log-bin.
Causes updates to
NDB
tables to be written to the binary log. The setting for this variable has no effect if binary logging is not already enabled on the server usinglog_bin
. In NDB 8.0.16 and later,ndb_log_bin
defaults to 0 (FALSE). -
Table 22.257 Type and value information for ndb_log_binlog_index
Property Value Name ndb_log_binlog_index
Command Line Yes System Variable Yes Status Variable No Option File No Scope Global Dynamic Yes Type Default, Range ON (Version: 8.0) Notes DESCRIPTION: Insert mapping between epochs and binary log positions into the ndb_binlog_index table. Defaults to ON. Effective only if binary logging is enabled on the server.
Causes a mapping of epochs to positions in the binary log to be inserted into the
ndb_binlog_index
table. Setting this variable has no effect if binary logging is not already enabled for the server usinglog_bin
. (In addition,ndb_log_bin
must not be disabled.)ndb_log_binlog_index
defaults to1
(ON
); normally, there is never any need to change this value in a production environment. -
Table 22.258 Type and value information for ndb_log_empty_epochs
Property Value Name ndb_log_empty_epochs
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range OFF (Version: 8.0) Notes DESCRIPTION: When enabled, epochs in which there were no changes are written to the ndb_apply_status and ndb_binlog_index tables, even when log_slave_updates is enabled
When this variable is set to 0, epoch transactions with no changes are not written to the binary log, although a row is still written even for an empty epoch in
ndb_binlog_index
. -
Table 22.259 Type and value information for ndb_log_empty_update
Property Value Name ndb_log_empty_update
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range OFF (Version: 8.0) Notes DESCRIPTION: When enabled, updates which produce no changes are written to the ndb_apply_status and ndb_binlog_index tables, even when log_slave_updates is enabled
When this variable is set to
ON
(1
), update transactions with no changes are written to the binary log, even when--log-slave-updates
is enabled. -
Table 22.260 Type and value information for ndb_log_exclusive_reads
Property Value Name ndb_log_exclusive_reads
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Both Dynamic Yes Type Default, Range 0 (Version: 8.0) Notes DESCRIPTION: Log primary key reads with exclusive locks; allow conflict resolution based on read conflicts
This variable determines whether primary key reads are logged with exclusive locks, which allows for NDB Cluster Replication conflict detection and resolution based on read conflicts. To enable these locks, set the value of
ndb_log_exclusive_reads
to 1. 0, which disables such locking, is the default.For more information, see Read conflict detection and resolution.
-
Table 22.261 Type and value information for ndb_log_orig
Property Value Name ndb_log_orig
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic No Type Default, Range OFF (Version: 8.0) Notes DESCRIPTION: Whether the id and epoch of the originating server are recorded in the mysql.ndb_binlog_index table. Set using the --ndb-log-orig option when starting mysqld.
Shows whether the originating server ID and epoch are logged in the
ndb_binlog_index
table. Set using the--ndb-log-orig
server option. -
Table 22.262 Type and value information for ndb_log_transaction_id
Property Value Name ndb_log_transaction_id
Command Line No System Variable Yes Status Variable No Option File No Scope Global Dynamic No Type Default, Range OFF (Version: 8.0) Notes DESCRIPTION: Whether NDB transaction IDs are written into the binary log (Read-only.)
This read-only, Boolean system variable shows whether a slave mysqld writes NDB transaction IDs in the binary log (required to use “active-active” NDB Cluster Replication with
NDB$EPOCH_TRANS()
conflict detection). To change the setting, use the--ndb-log-transaction-id
option.ndb_log_transaction_id
is not supported in mainline MySQL Server 8.0.For more information, see Section 22.6.11, “NDB Cluster Replication Conflict Resolution”.
-
Table 22.263 Type and value information for ndb_metadata_check
Property Value Name ndb_metadata_check
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type: Default, Range boolean: ON (Version: 8.0.16) Notes DESCRIPTION: Enable auto-detection of NDB metadata changes with respect to MySQL data dictionary; enabled by default
Beginning with NDB 8.0.16,
NDB
uses a background thread to check for metadata changes eachndb_metadata_check_interval
seconds as compared with the MySQL data dictionary. This metadata change detection thread can be disabled by settingndb_metadata_check
toOFF
. The thread is enabled by default. -
Table 22.264 Type and value information for ndb_metadata_check_interval
Property Value Name ndb_metadata_check_interval
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type: Default, Range integer: 60 / 0 - 31536000 (Version: 8.0.16) Notes DESCRIPTION: Interval in seconds to perform check for NDB metadata changes with respect to MySQL data dictionary
In NDB 8.0.16 and later, NDB runs a metadata change detection thread in the background to determine when the NDB dictionary has changed with respect to the MySQL data dictionary. By default,the interval between such checks is 60 seconds; this can be adjusted by setting the value of
ndb_metadata_check_interval
. To enable or disable the thread, usendb_metadata_check
. -
Table 22.265 Type and value information for ndb_optimized_node_selection
Property Value Name ndb_optimized_node_selection
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic No Type Default, Range ON (Version: 8.0) Default, Range 3 / 0 - 3 (Version: NDB 8.0) Notes DESCRIPTION: Determines how an SQL node chooses a cluster data node to use as transaction coordinator
There are two forms of optimized node selection, described here:
The SQL node uses promixity to determine the transaction coordinator; that is, the “closest” data node to the SQL node is chosen as the transaction coordinator. For this purpose, a data node having a shared memory connection with the SQL node is considered to be “closest” to the SQL node; the next closest (in order of decreasing proximity) are: TCP connection to
localhost
; SCI connection; TCP connection from a host other thanlocalhost
.The SQL thread uses distribution awareness to select the data node. That is, the data node housing the cluster partition accessed by the first statement of a given transaction is used as the transaction coordinator for the entire transaction. (This is effective only if the first statement of the transaction accesses no more than one cluster partition.)
This option takes one of the integer values
0
,1
,2
, or3
.3
is the default. These values affect node selection as follows:0
: Node selection is not optimized. Each data node is employed as the transaction coordinator 8 times before the SQL thread proceeds to the next data node.1
: Proximity to the SQL node is used to determine the transaction coordinator.2
: Distribution awareness is used to select the transaction coordinator. However, if the first statement of the transaction accesses more than one cluster partition, the SQL node reverts to the round-robin behavior seen when this option is set to0
.3
: If distribution awareness can be employed to determine the transaction coordinator, then it is used; otherwise proximity is used to select the transaction coordinator. (This is the default behavior.)
Proximity is determined as follows:
Start with the value set for the
Group
parameter (default 55).For an API node sharing the same host with other API nodes, decrement the value by 1. Assuming the default value for
Group
, the effective value for data nodes on same host as the API node is 54, and for remote data nodes 55.Setting
ndb_data_node_neighbour
further decreases the effectiveGroup
value by 50, causing this node to be regarded as the nearest node. This is needed only when all data nodes are on hosts other than that hosts the API node and it is desirable to dedicate one of them to the API node. In normal cases, the default adjustment described previously is sufficient.
Frequent changes in
ndb_data_node_neighbour
are not advisable, since this changes the state of the cluster connection and thus may disrupt the selection algorithm for new transactions from each thread until it stablilizes. -
Table 22.266 Type and value information for ndb_read_backup
Property Value Name ndb_read_backup
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range OFF (Version: NDB 8.0) Notes DESCRIPTION: Enable read from any replica
Enable read from any replica for any
NDB
table subsequently created. ndb_recv_thread_activation_threshold
Table 22.267 Type and value information for ndb_recv_thread_activation_threshold
Property Value Name ndb_recv_thread_activation_threshold
Command Line No System Variable No Status Variable No Option File No Scope Dynamic No Type Default, Range 8 / 0 (MIN_ACTIVATION_THRESHOLD) - 16 (MAX_ACTIVATION_THRESHOLD) (Version: NDB 8.0) Notes DESCRIPTION: Activation threshold when receive thread takes over the polling of the cluster connection (measured in concurrently active threads)
When this number of concurrently active threads is reached, the receive thread takes over polling of the cluster connection.
This variable is global in scope. It can also be set on startup using the
--ndb-recv-thread-activation-threshold
option.-
Table 22.268 Type and value information for ndb_recv_thread_cpu_mask
Property Value Name ndb_recv_thread_cpu_mask
Command Line No System Variable Yes Status Variable No Option File No Scope Global Dynamic Yes Type Default, Range [empty] (Version: 8.0) Notes DESCRIPTION: CPU mask for locking receiver threads to specific CPUs; specified as hexadecimal. See documentation for details.
CPU mask for locking receiver threads to specific CPUs. This is specified as a hexadecimal bitmask. For example,
0x33
means that one CPU is used per receiver thread. An empty string is the default; settingndb_recv_thread_cpu_mask
to this value removes any receiver thread locks previously set.This variable is global in scope. It can also be set on startup using the
--ndb-recv-thread-cpu-mask
option. ndb_report_thresh_binlog_epoch_slip
Table 22.269 Type and value information for ndb_report_thresh_binlog_epoch_slip
Property Value Name ndb_report_thresh_binlog_epoch_slip
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range 3 / 0 - 256 (Version: 8.0) Default, Range 10 / 0 - 256 (Version: NDB 8.0) Notes DESCRIPTION: NDB 7.5.4 and later: Threshold for number of epochs completely buffered, but not yet consumed by binlog injector thread which when exceeded generates BUFFERED_EPOCHS_OVER_THRESHOLD event buffer status message; prior to NDB 7.5.4: Threshold for number of epochs to lag behind before reporting binary log status
This represents the threshold for the number of epochs completely buffered in the event buffer, but not yet consumed by the binlog injector thread. When this degree of slippage (lag) is exceeded, an event buffer status message is reported, with
BUFFERED_EPOCHS_OVER_THRESHOLD
supplied as the reason (see Section 22.5.7.3, “Event Buffer Reporting in the Cluster Log”). Slip is increased when an epoch is received from data nodes and buffered completely in the event buffer; it is decreased when an epoch is consumed by the binlog injector thread, it is reduced. Empty epochs are buffered and queued, and so included in this calculation only when this is enabled using theNdb::setEventBufferQueueEmptyEpoch()
method from the NDB API.ndb_report_thresh_binlog_mem_usage
Table 22.270 Type and value information for ndb_report_thresh_binlog_mem_usage
Property Value Name ndb_report_thresh_binlog_mem_usage
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range 10 / 0 - 10 (Version: 8.0) Notes DESCRIPTION: This is a threshold on the percentage of free memory remaining before reporting binary log status
This is a threshold on the percentage of free memory remaining before reporting binary log status. For example, a value of
10
(the default) means that if the amount of available memory for receiving binary log data from the data nodes falls below 10%, a status message is sent to the cluster log.-
Table 22.271 Type and value information for ndb_row_checksum
Property Value Name ndb_row_checksum
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type integer Default, Range 1 / 0 - 1 (Version: NDB 8.0) Notes DESCRIPTION: When enabled, set row checksums; enabled by default
Traditionally,
NDB
has created tables with row checksums, which checks for hardware issues at the expense of performance. Settingndb_row_checksum
to 0 means that row checksums are not used for new or altered tables, which has a significant impact on performance for all types of queries. This variable is set to 1 by default, to provide backward-compatible behavior. -
Table 22.272 Type and value information for slave_allow_batching
Property Value Name slave_allow_batching
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range off (Version: 8.0) Notes DESCRIPTION: Turns update batching on and off for a replication slave
Whether or not batched updates are enabled on NDB Cluster replication slaves.
Setting this variable has an effect only when using replication with the
NDB
storage engine; in MySQL Server 8.0, it is present but does nothing. For more information, see Section 22.6.6, “Starting NDB Cluster Replication (Single Replication Channel)”. ndb_show_foreign_key_mock_tables
Table 22.273 Type and value information for ndb_show_foreign_key_mock_tables
Property Value Name ndb_show_foreign_key_mock_tables
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range OFF (Version: 8.0) Notes DESCRIPTION: Show the mock tables used to support foreign_key_checks=0
Show the mock tables used by
NDB
to supportforeign_key_checks=0
. When this is enabled, extra warnings are shown when creating and dropping the tables. The real (internal) name of the table can be seen in the output ofSHOW CREATE TABLE
.-
Table 22.274 Type and value information for ndb_slave_conflict_role
Property Value Name ndb_slave_conflict_role
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic Yes Type Default, Range NONE / NONE, PRIMARY, SECONDARY, PASS (Version: 8.0) Notes DESCRIPTION: Role for slave to play in conflict detection and resolution. Value is one of PRIMARY, SECONDARY, PASS, or NONE (default). Can be changed only when slave SQL thread is stopped. See documentation for further information.
Determine the role of this SQL node (and NDB Cluster) in a circular (“active-active”) replication setup.
ndb_slave_conflict_role
can take any one of the valuesPRIMARY
,SECONDARY
,PASS
, orNULL
(the default). The slave SQL thread must be stopped before you can changendb_slave_conflict_role
. In addition, it is not possible to change directly betweenPASS
and either ofPRIMARY
orSECONDARY
directly; in such cases, you must ensure that the SQL thread is stopped, then executeSET @@GLOBAL.ndb_slave_conflict_role = 'NONE'
first.For more information, see Section 22.6.11, “NDB Cluster Replication Conflict Resolution”.
-
Table 22.275 Type and value information for ndb_table_no_logging
Property Value Name ndb_table_no_logging
Command Line No System Variable Yes Status Variable No Option File No Scope Session Dynamic Yes Type Default, Range FALSE (Version: 8.0) Notes DESCRIPTION: NDB tables created when this setting is enabled are not checkpointed to disk (although table schema files are created). The setting in effect when the table is created with or altered to use NDBCLUSTER persists for the lifetime of the table.
When this variable is set to
ON
or1
, it causesNDB
tables not to be checkpointed to disk. More specifically, this setting applies to tables which are created or altered usingENGINE NDB
whenndb_table_no_logging
is enabled, and continues to apply for the lifetime of the table, even ifndb_table_no_logging
is later changed. Suppose thatA
,B
,C
, andD
are tables that we create (and perhaps also alter), and that we also change the setting forndb_table_no_logging
as shown here:After the previous sequence of events, tables
A
andB
are not checkpointed;A
was created withENGINE NDB
and B was altered to useNDB
, both whilendb_table_no_logging
was enabled. However, tablesC
andD
are logged;C
was altered to useNDB
andD
was created usingENGINE NDB
, both whilendb_table_no_logging
was disabled. Settingndb_table_no_logging
back to1
orON
does not cause tableC
orD
to be checkpointed.Notendb_table_no_logging
has no effect on the creation ofNDB
table schema files; to suppress these, usendb_table_temporary
instead. -
Table 22.276 Type and value information for ndb_table_temporary
Property Value Name ndb_table_temporary
Command Line No System Variable Yes Status Variable No Option File No Scope Session Dynamic Yes Type Default, Range FALSE (Version: 8.0) Notes DESCRIPTION: NDB tables are not persistent on disk: no schema files are created and the tables are not logged
When set to
ON
or1
, this variable causesNDB
tables not to be written to disk: This means that no table schema files are created, and that the tables are not logged.NoteSetting this variable currently has no effect. This is a known issue; see Bug #34036.
-
Table 22.277 Type and value information for ndb_use_copying_alter_table
Property Value Name ndb_use_copying_alter_table
Command Line No System Variable Yes Status Variable No Option File No Scope Both Dynamic No Type Notes DESCRIPTION: Use copying ALTER TABLE operations in NDB Cluster
Forces
NDB
to use copying of tables in the event of problems with onlineALTER TABLE
operations. The default value isOFF
. -
Table 22.278 Type and value information for ndb_use_exact_count
Property Value Name ndb_use_exact_count
Command Line No System Variable Yes Status Variable No Option File No Scope Both Dynamic Yes Type Default, Range ON (Version: 8.0) Default, Range OFF (Version: NDB 8.0) Notes DESCRIPTION: Use exact row count when planning queries
Forces
NDB
to use a count of records duringSELECT COUNT(*)
query planning to speed up this type of query. The default value isOFF
, which allows for faster queries overall. -
Table 22.279 Type and value information for ndb_use_transactions
Property Value Name ndb_use_transactions
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Both Dynamic Yes Type Default, Range ON (Version: 8.0) Notes DESCRIPTION: Forces NDB to use a count of records during SELECT COUNT(*) query planning to speed up this type of query
You can disable
NDB
transaction support by setting this variable's values toOFF
(not recommended). The default isON
. -
Table 22.280 Type and value information for ndb_version
Property Value Name ndb_version
Command Line No System Variable Yes Status Variable No Option File No Scope Global Dynamic No Type Default, Range (Version: 8.0) Notes DESCRIPTION: Shows build and NDB engine version as an integer
NDB
engine version, as a composite integer. -
Table 22.281 Type and value information for ndb_version_string
Property Value Name ndb_version_string
Command Line No System Variable Yes Status Variable No Option File No Scope Global Dynamic No Type Default, Range (Version: 8.0) Notes DESCRIPTION: Shows build information including NDB engine version in ndb-x.y.z format
NDB
engine version inndb-
format.x.y.z
-
Table 22.282 Type and value information for server_id_bits
Property Value Name server_id_bits
Command Line Yes System Variable Yes Status Variable No Option File Yes Scope Global Dynamic No Type Default, Range 32 / 7 - 32 (Version: 8.0) Notes DESCRIPTION: The effective value of server_id if the server was started with the --server-id-bits option set to a nondefault value
The effective value of
server_id
if the server was started with the--server-id-bits
option set to a nondefault value.If the value of
server_id
greater than or equal to 2 to the power ofserver_id_bits
, mysqld refuses to start.This system variable is supported only by NDB Cluster.
server_id_bits
is not supported by the standard MySQL Server. -
Table 22.283 Type and value information for transaction_allow_batching
Property Value Name transaction_allow_batching
Command Line No System Variable Yes Status Variable No Option File No Scope Session Dynamic Yes Type Default, Range FALSE (Version: 8.0) Notes DESCRIPTION: Allows batching of statements within a transaction. Disable AUTOCOMMIT to use.
When set to
1
orON
, this variable enables batching of statements within the same transaction. To use this variable,autocommit
must first be disabled by setting it to0
orOFF
; otherwise, settingtransaction_allow_batching
has no effect.It is safe to use this variable with transactions that performs writes only, as having it enabled can lead to reads from the “before” image. You should ensure that any pending transactions are committed (using an explicit
COMMIT
if desired) before issuing aSELECT
.Importanttransaction_allow_batching
should not be used whenever there is the possibility that the effects of a given statement depend on the outcome of a previous statement within the same transaction.This variable is currently supported for NDB Cluster only.
The system variables in the following list all relate to the
ndbinfo
information
database.
-
Table 22.284 Type and value information for ndbinfo_database
Property Value Name ndbinfo_database
Command Line No System Variable Yes Status Variable No Option File No Scope Global Dynamic No Type Default, Range ndbinfo (Version: 8.0) Notes DESCRIPTION: The name used for the NDB information database; read only
Shows the name used for the
NDB
information database; the default isndbinfo
. This is a read-only variable whose value is determined at compile time; you can set it by starting the server using--ndbinfo-database=
, which sets the value shown for this variable but does not actually change the name used for the NDB information database.name
-
Table 22.285 Type and value information for ndbinfo_max_bytes
Property Value Name ndbinfo_max_bytes
Command Line Yes System Variable Yes Status Variable No Option File No Scope Both Dynamic Yes Type Default, Range 0 / - (Version: 8.0) Notes DESCRIPTION: Used for debugging only
Used in testing and debugging only.
-
Table 22.286 Type and value information for ndbinfo_max_rows
Property Value Name ndbinfo_max_rows
Command Line Yes System Variable Yes Status Variable No Option File No Scope Both Dynamic Yes Type Default, Range 10 / - (Version: 8.0) Notes DESCRIPTION: Used for debugging only
Used in testing and debugging only.
-
Table 22.287 Type and value information for ndbinfo_offline
Property Value Name ndbinfo_offline
Command Line No System Variable Yes Status Variable No Option File No Scope Global Dynamic Yes Type Default, Range OFF (Version: 8.0) Notes DESCRIPTION: Put the ndbinfo database into offline mode, in which no rows are returned from tables or views
Place the
ndbinfo
database into offline mode, in which tables and views can be opened even when they do not actually exist, or when they exist but have different definitions inNDB
. No rows are returned from such tables (or views). -
Table 22.288 Type and value information for ndbinfo_show_hidden
Property Value Name ndbinfo_show_hidden
Command Line Yes System Variable Yes Status Variable No Option File No Scope Both Dynamic Yes Type Default, Range OFF (Version: 8.0) Notes DESCRIPTION: Whether to show ndbinfo internal base tables in the mysql client. The default is OFF.
Whether or not the
ndbinfo
database's underlying internal tables are shown in themysql
client. The default isOFF
. -
Table 22.289 Type and value information for ndbinfo_table_prefix
Property Value Name ndbinfo_table_prefix
Command Line Yes System Variable Yes Status Variable No Option File No Scope Both Dynamic Yes Type Default, Range ndb$ (Version: 8.0) Notes DESCRIPTION: The prefix to use for naming ndbinfo internal base tables
The prefix used in naming the ndbinfo database's base tables (normally hidden, unless exposed by setting
ndbinfo_show_hidden
). This is a read-only variable whose default value isndb$
. You can start the server with the--ndbinfo-table-prefix
option, but this merely sets the variable and does not change the actual prefix used to name the hidden base tables; the prefix itself is determined at compile time. -
Table 22.290 Type and value information for ndbinfo_version
Property Value Name ndbinfo_version
Command Line No System Variable Yes Status Variable No Option File No Scope Global Dynamic No Type Default, Range (Version: 8.0) Notes DESCRIPTION: The version of the ndbinfo engine; read only
Shows the version of the
ndbinfo
engine in use; read-only.
This section provides detailed information about MySQL server
status variables that relate to NDB Cluster and the
NDB
storage engine. For status
variables not specific to NDB Cluster, and for general
information on using status variables, see
Section 5.1.10, “Server Status Variables”.
The MySQL server can ask the
NDBCLUSTER
storage engine if it knows about a table with a given name. This is called discovery.Handler_discover
indicates the number of times that tables have been discovered using this mechanism.Ndb_api_bytes_sent_count_session
Amount of data (in bytes) sent to the data nodes in this client session.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_bytes_sent_count_slave
Amount of data (in bytes) sent to the data nodes by this slave.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Amount of data (in bytes) sent to the data nodes by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_bytes_received_count_session
Amount of data (in bytes) received from the data nodes in this client session.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_bytes_received_count_slave
Amount of data (in bytes) received from the data nodes by this slave.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Amount of data (in bytes) received from the data nodes by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_event_data_count_injector
The number of row change events received by the NDB binlog injector thread.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of row change events received by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_event_nondata_count_injector
The number of events received, other than row change events, by the NDB binary log injector thread.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of events received, other than row change events, by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_event_bytes_count_injector
The number of bytes of events received by the NDB binlog injector thread.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of bytes of events received by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of operations in this client session based on or using primary keys. This includes operations on blob tables, implicit unlock operations, and auto-increment operations, as well as user-visible primary key operations.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of operations by this slave based on or using primary keys. This includes operations on blob tables, implicit unlock operations, and auto-increment operations, as well as user-visible primary key operations.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of operations by this MySQL Server (SQL node) based on or using primary keys. This includes operations on blob tables, implicit unlock operations, and auto-increment operations, as well as user-visible primary key operations.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_pruned_scan_count_session
The number of scans in this client session that have been pruned to a single partition.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_pruned_scan_count_slave
The number of scans by this slave that have been pruned to a single partition.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of scans by this MySQL Server (SQL node) that have been pruned to a single partition.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_range_scan_count_session
The number of range scans that have been started in this client session.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_range_scan_count_slave
The number of range scans that have been started by this slave.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of range scans that have been started by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_read_row_count_session
The total number of rows that have been read in this client session. This includes all rows read by any primary key, unique key, or scan operation made in this client session.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The total number of rows that have been read by this slave. This includes all rows read by any primary key, unique key, or scan operation made by this slave.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The total number of rows that have been read by this MySQL Server (SQL node). This includes all rows read by any primary key, unique key, or scan operation made by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_scan_batch_count_session
The number of batches of rows received in this client session. 1 batch is defined as 1 set of scan results from a single fragment.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_scan_batch_count_slave
The number of batches of rows received by this slave. 1 batch is defined as 1 set of scan results from a single fragment.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of batches of rows received by this MySQL Server (SQL node). 1 batch is defined as 1 set of scan results from a single fragment.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_table_scan_count_session
The number of table scans that have been started in this client session, including scans of internal tables,.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_table_scan_count_slave
The number of table scans that have been started by this slave, including scans of internal tables,.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of table scans that have been started by this MySQL Server (SQL node), including scans of internal tables,.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_abort_count_session
The number of transactions aborted in this client session.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_abort_count_slave
The number of transactions aborted by this slave.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of transactions aborted by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_close_count_session
The number of transactions closed in this client session. This value may be greater than the sum of
Ndb_api_trans_commit_count_session
andNdb_api_trans_abort_count_session
, since some transactions may have been rolled back.Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_close_count_slave
The number of transactions closed by this slave. This value may be greater than the sum of
Ndb_api_trans_commit_count_slave
andNdb_api_trans_abort_count_slave
, since some transactions may have been rolled back.Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of transactions closed by this MySQL Server (SQL node). This value may be greater than the sum of
Ndb_api_trans_commit_count
andNdb_api_trans_abort_count
, since some transactions may have been rolled back.Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_commit_count_session
The number of transactions committed in this client session.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_commit_count_slave
The number of transactions committed by this slave.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of transactions committed by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_local_read_row_count_session
The total number of rows that have been read in this client session. This includes all rows read by any primary key, unique key, or scan operation made in this client session.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_local_read_row_count_slave
The total number of rows that have been read by this slave. This includes all rows read by any primary key, unique key, or scan operation made by this slave.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_local_read_row_count
The total number of rows that have been read by this MySQL Server (SQL node). This includes all rows read by any primary key, unique key, or scan operation made by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_start_count_session
The number of transactions started in this client session.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_trans_start_count_slave
The number of transactions started by this slave.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of transactions started by this MySQL Server (SQL node).
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of operations in this client session based on or using unique keys.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of operations by this slave based on or using unique keys.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
The number of operations by this MySQL Server (SQL node) based on or using unique keys.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_exec_complete_count_session
The number of times a thread has been blocked in this client session while waiting for execution of an operation to complete. This includes all
execute()
calls as well as implicit executes for blob and auto-increment operations not visible to clients.Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_exec_complete_count_slave
The number of times a thread has been blocked by this slave while waiting for execution of an operation to complete. This includes all
execute()
calls as well as implicit executes for blob and auto-increment operations not visible to clients.Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_exec_complete_count
The number of times a thread has been blocked by this MySQL Server (SQL node) while waiting for execution of an operation to complete. This includes all
execute()
calls as well as implicit executes for blob and auto-increment operations not visible to clients.Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_meta_request_count_session
The number of times a thread has been blocked in this client session waiting for a metadata-based signal, such as is expected for DDL requests, new epochs, and seizure of transaction records.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_meta_request_count_slave
The number of times a thread has been blocked by this slave waiting for a metadata-based signal, such as is expected for DDL requests, new epochs, and seizure of transaction records.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_meta_request_count
The number of times a thread has been blocked by this MySQL Server (SQL node) waiting for a metadata-based signal, such as is expected for DDL requests, new epochs, and seizure of transaction records.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_nanos_count_session
Total time (in nanoseconds) spent in this client session waiting for any type of signal from the data nodes.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_nanos_count_slave
Total time (in nanoseconds) spent by this slave waiting for any type of signal from the data nodes.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Total time (in nanoseconds) spent by this MySQL Server (SQL node) waiting for any type of signal from the data nodes.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_scan_result_count_session
The number of times a thread has been blocked in this client session while waiting for a scan-based signal, such as when waiting for more results from a scan, or when waiting for a scan to close.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it relates to the current session only, and is not affected by any other clients of this mysqld.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_scan_result_count_slave
The number of times a thread has been blocked by this slave while waiting for a scan-based signal, such as when waiting for more results from a scan, or when waiting for a scan to close.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope. If this MySQL server does not act as a replication slave, or does not use NDB tables, this value is always 0.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
Ndb_api_wait_scan_result_count
The number of times a thread has been blocked by this MySQL Server (SQL node) while waiting for a scan-based signal, such as when waiting for more results from a scan, or when waiting for a scan to close.
Although this variable can be read using either
SHOW GLOBAL STATUS
orSHOW SESSION STATUS
, it is effectively global in scope.For more information, see Section 22.5.17, “NDB API Statistics Counters and Variables”.
If the server is acting as an NDB Cluster node, then the value of this variable its node ID in the cluster.
If the server is not part of an NDB Cluster, then the value of this variable is 0.
If the server is part of an NDB Cluster, the value of this variable is the host name or IP address of the Cluster management server from which it gets its configuration data.
If the server is not part of an NDB Cluster, then the value of this variable is an empty string.
If the server is part of an NDB Cluster, the value of this variable is the number of the port through which it is connected to the Cluster management server from which it gets its configuration data.
If the server is not part of an NDB Cluster, then the value of this variable is 0.
Shows the number of times that a row was rejected on the current SQL node due to NDB Cluster Replication conflict resolution using
NDB$MAX_DELETE_WIN()
, since the last time that this mysqld was started.For more information, see Section 22.6.11, “NDB Cluster Replication Conflict Resolution”.
Used in NDB Cluster Replication conflict resolution, this variable shows the number of times that a row was not applied on the current SQL node due to “greatest timestamp wins” conflict resolution since the last time that this mysqld was started.
For more information, see Section 22.6.11, “NDB Cluster Replication Conflict Resolution”.
Used in NDB Cluster Replication conflict resolution, this variable shows the number of times that a row was not applied as the result of “same timestamp wins” conflict resolution on a given mysqld since the last time it was restarted.
For more information, see Section 22.6.11, “NDB Cluster Replication Conflict Resolution”.
Used in NDB Cluster Replication conflict resolution, this variable shows the number of rows found to be in conflict using
NDB$EPOCH()
conflict resolution on a given mysqld since the last time it was restarted.For more information, see Section 22.6.11, “NDB Cluster Replication Conflict Resolution”.
Shows the number of rows found to be in conflict in NDB Cluster Replication conflict resolution, when using
NDB$EPOCH2()
, on the master designated as the primary since the last time it was restarted.For more information, see NDB$EPOCH2().
Used in NDB Cluster Replication conflict resolution, this variable shows the number of rows found to be in conflict using
NDB$EPOCH_TRANS()
conflict resolution on a given mysqld since the last time it was restarted.For more information, see Section 22.6.11, “NDB Cluster Replication Conflict Resolution”.
Used in NDB Cluster Replication conflict resolution, this variable shows the number of rows found to be in conflict using
NDB$EPOCH_TRANS2()
conflict resolution on a given mysqld since the last time it was restarted.For more information, see NDB$EPOCH2_TRANS().
Ndb_conflict_last_conflict_epoch
The most recent epoch in which a conflict was detected on this slave. You can compare this value with
Ndb_slave_max_replicated_epoch
; ifNdb_slave_max_replicated_epoch
is greater thanNdb_conflict_last_conflict_epoch
, no conflicts have yet been detected.See Section 22.6.11, “NDB Cluster Replication Conflict Resolution”, for more information.
Ndb_conflict_reflected_op_discard_count
When using NDB Cluster Replication conflict resolution, this is the number of reflected operations that were not applied on the secondary, due to encountering an error during execution.
See Section 22.6.11, “NDB Cluster Replication Conflict Resolution”, for more information.
Ndb_conflict_reflected_op_prepare_count
When using conflict resolution with NDB Cluster Replication, this status variable contains the number of reflected operations that have been defined (that is, prepared for execution on the secondary).
See Section 22.6.11, “NDB Cluster Replication Conflict Resolution”.
When using conflict resolution with NDB Cluster Replication, this gives the number of refresh operations that have been prepared for execution on the secondary.
See Section 22.6.11, “NDB Cluster Replication Conflict Resolution”, for more information.
Ndb_conflict_last_stable_epoch
Number of rows found to be in conflict by a transactional conflict function
See Section 22.6.11, “NDB Cluster Replication Conflict Resolution”, for more information.
Ndb_conflict_trans_row_conflict_count
Used in NDB Cluster Replication conflict resolution, this status variable shows the number of rows found to be directly in-conflict by a transactional conflict function on a given mysqld since the last time it was restarted.
Currently, the only transactional conflict detection function supported by NDB Cluster is NDB$EPOCH_TRANS(), so this status variable is effectively the same as
Ndb_conflict_fn_epoch_trans
.For more information, see Section 22.6.11, “NDB Cluster Replication Conflict Resolution”.
Ndb_conflict_trans_row_reject_count
Used in NDB Cluster Replication conflict resolution, this status variable shows the total number of rows realigned due to being determined as conflicting by a transactional conflict detection function. This includes not only
Ndb_conflict_trans_row_conflict_count
, but any rows in or dependent on conflicting transactions.For more information, see Section 22.6.11, “NDB Cluster Replication Conflict Resolution”.
Ndb_conflict_trans_reject_count
Used in NDB Cluster Replication conflict resolution, this status variable shows the number of transactions found to be in conflict by a transactional conflict detection function.
For more information, see Section 22.6.11, “NDB Cluster Replication Conflict Resolution”.
Ndb_conflict_trans_detect_iter_count
Used in NDB Cluster Replication conflict resolution, this shows the number of internal iterations required to commit an epoch transaction. Should be (slightly) greater than or equal to
Ndb_conflict_trans_conflict_commit_count
.For more information, see Section 22.6.11, “NDB Cluster Replication Conflict Resolution”.
Ndb_conflict_trans_conflict_commit_count
Used in NDB Cluster Replication conflict resolution, this shows the number of epoch transactions committed after they required transactional conflict handling.
For more information, see Section 22.6.11, “NDB Cluster Replication Conflict Resolution”.
When using delete-delete conflict detection, this is the number of delete-delete conflicts detected, where a delete operation is applied, but the indicated row does not exist.
Provides the number of round trips to the
NDB
kernel made by operations.The epoch most recently committed by
NDB
.The epoch most recently committed by this
NDB
client.The number of times since this server was last started that the NDB metadata change detection thread has discovered changes with respect to the MySQL data dictionary.
If the server is part of an NDB Cluster, the value of this variable is the number of data nodes in the cluster.
If the server is not part of an NDB Cluster, then the value of this variable is 0.
The total number of joins pushed down to the NDB kernel for distributed handling on the data nodes.
NoteJoins tested using
EXPLAIN
that can be pushed down contribute to this number.The number of joins that were pushed down to the NDB kernel but that could not be handled there.
The number of joins successfully pushed down to
NDB
and executed there.The number of rows returned to mysqld from the NDB kernel by joins that were pushed down.
This variable holds a count of the number of scans executed by
NDBCLUSTER
since the NDB Cluster was last started whereNDBCLUSTER
was able to use partition pruning.Using this variable together with
Ndb_scan_count
can be helpful in schema design to maximize the ability of the server to prune scans to a single table partition, thereby involving only a single data node.This variable holds a count of the total number of scans executed by
NDBCLUSTER
since the NDB Cluster was last started.Ndb_slave_max_replicated_epoch
The most recently committed epoch on this slave. You can compare this value with
Ndb_conflict_last_conflict_epoch
; ifNdb_slave_max_replicated_epoch
is the greater of the two, no conflicts have yet been detected.For more information, see Section 22.6.11, “NDB Cluster Replication Conflict Resolution”.
If this MySQL Server is connected to an NDB cluster, this read-only variable shows the cluster system name. Otherwise, the value is an empty string.
The number of transactions using hints that have been started in the current session. Compare with
Ndb_api_trans_start_count_session
to obtain the proportion of all NDB transactions able to use hints. Added in NDB 8.0.17.
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