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13.7.3.1 ANALYZE TABLE Syntax
ANALYZE TABLE
generates table
statistics:
ANALYZE TABLE
without eitherHISTOGRAM
clause performs a key distribution analysis and stores the distribution for the named table or tables. ForMyISAM
tables,ANALYZE TABLE
for key distribution analysis is equivalent to using myisamchk --analyze.ANALYZE TABLE
with theUPDATE HISTOGRAM
clause generates histogram statistics for the named table columns and stores them in the data dictionary. Only one table name is permitted for this syntax.ANALYZE TABLE
with theDROP HISTOGRAM
clause removes histogram statistics for the named table columns from the data dictionary. Only one table name is permitted for this syntax.
If the innodb_read_only
system variable is enabled, ANALYZE
TABLE
may fail because it cannot update statistics
tables in the data dictionary, which use
InnoDB
. For ANALYZE
TABLE
operations that update the key distribution,
failure may occur even if the operation updates the table
itself (for example, if it is a MyISAM
table). To obtain the updated distribution statistics, set
information_schema_stats_expiry=0
.
This statement requires SELECT
and INSERT
privileges for the
table.
ANALYZE TABLE
works with
InnoDB
, NDB
, and
MyISAM
tables. It does not work with views.
ANALYZE TABLE
is supported for
partitioned tables, and you can use ALTER TABLE ...
ANALYZE PARTITION
to analyze one or more partitions;
for more information, see Section 13.1.9, “ALTER TABLE Syntax”, and
Section 23.3.4, “Maintenance of Partitions”.
During the analysis, the table is locked with a read lock for
InnoDB
and MyISAM
.
By default, the server writes ANALYZE
TABLE
statements to the binary log so that they
replicate to replication slaves. To suppress logging, specify
the optional NO_WRITE_TO_BINLOG
keyword or
its alias LOCAL
.
ANALYZE TABLE Output
ANALYZE TABLE
returns a result
set with the columns shown in the following table.
Column | Value |
---|---|
Table |
The table name |
Op |
analyze or histogram |
Msg_type |
status , error ,
info , note , or
warning |
Msg_text |
An informational message |
ANALYZE TABLE
without either
HISTOGRAM
clause performs a key
distribution analysis and stores the distribution for the
table or tables. Any existing histogram statistics remain
unaffected.
If the table has not changed since the last key distribution analysis, the table is not analyzed again.
MySQL uses the stored key distribution to decide the order in which tables should be joined for joins on something other than a constant. In addition, key distributions can be used when deciding which indexes to use for a specific table within a query.
For more information on how key distribution analysis works
within InnoDB
, see
Section 15.8.10.1, “Configuring Persistent Optimizer Statistics Parameters” and
Section 15.8.10.3, “Estimating ANALYZE TABLE Complexity for InnoDB Tables”. Also see
Section 15.6.1.7, “Limits on InnoDB Tables”. In particular, when you
enable the
innodb_stats_persistent
option, you must run ANALYZE
TABLE
after loading substantial data into an
InnoDB
table, or creating a new index for
one.
To check the stored key distribution cardinality, use the
SHOW INDEX
statement or the
INFORMATION_SCHEMA
STATISTICS
table. See
Section 13.7.6.22, “SHOW INDEX Syntax”, and
Section 25.25, “The INFORMATION_SCHEMA STATISTICS Table”.
ANALYZE TABLE
with the
HISTOGRAM
clauses enables management of
histogram statistics for table column values. For information
about histogram statistics, see
Section 8.9.6, “Optimizer Statistics”.
These histogram operations are available:
ANALYZE TABLE
with anUPDATE HISTOGRAM
clause generates histogram statistics for the named table columns and stores them in the data dictionary. Only one table name is permitted for this syntax.The optional
WITH
clauses specifies the number of buckets for the histogram. The value ofN
BUCKETSN
must be an integer in the range from 1 to 1024. If this clause is omitted, the number of buckets is 100.ANALYZE TABLE
with aDROP HISTOGRAM
clause removes histogram statistics for the named table columns from the data dictionary. Only one table name is permitted for this syntax.
Stored histogram management statements affect only the named columns. Consider these statements:
The first statement updates the histograms for columns
c1
, c2
, and
c3
, replacing any existing histograms for
those columns. The second statement updates the histograms for
c1
and c3
, leaving the
c2
histogram unaffected. The third
statement removes the histogram for c2
,
leaving those for c1
and
c3
unaffected.
Histogram generation is not supported for encrypted tables (to
avoid exposing data in the statistics) or
TEMPORARY
tables.
Histogram generation applies to columns of all data types
except geometry types (spatial data) and
JSON
.
Histograms can be generated for stored and virtual generated columns.
Histograms cannot be generated for columns that are covered by single-column unique indexes.
Histogram management statements attempt to perform as much of
the requested operation as possible, and report diagnostic
messages for the remainder. For example, if an UPDATE
HISTOGRAM
statement names multiple columns, but some
of them do not exist or have an unsupported data type,
histograms are generated for the other columns, and messages
are produced for the invalid columns.
The
histogram_generation_max_mem_size
system variable controls the maximum amount of memory
available for histogram generation. The global and session
values may be set at runtime.
Changing the global
histogram_generation_max_mem_size
value requires privileges sufficient to set global system
variables. Changing the session
histogram_generation_max_mem_size
value requires privileges sufficient to set restricted session
system variables. See
Section 5.1.9.1, “System Variable Privileges”.
For information about memory allocations performed for
histogram generation, monitor the Performance Schema
memory/sql/histograms
instrument. See
Section 26.12.16.10, “Memory Summary Tables”.
Histograms are affected by these DDL statements:
DROP TABLE
removes histograms for columns in the dropped table.DROP DATABASE
removes histograms for any table in the dropped database because the statement drops all tables in the database.RENAME TABLE
does not remove histograms. Instead, it renames histograms for the renamed table to be associated with the new table name.ALTER TABLE
statements that remove or modify a column remove histograms for that column.ALTER TABLE ... CONVERT TO CHARACTER SET
removes histograms for character columns because they are affected by the change of character set. Histograms for noncharacter columns remain unaffected.
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