Rechercher dans le manuel MySQL
22.5.10.4 The ndbinfo cluster_locks Table
The cluster_locks
table provides information
about current lock requests holding and waiting for locks on
NDB
tables in an NDB Cluster, and is intended
as a companion table to
cluster_operations
.
Information obtain from the cluster_locks
table may be useful in investigating stalls and deadlocks.
The following table provides information about the columns in
the cluster_locks
table. For each column, the
table shows the name, data type, and a brief description.
Additional information can be found in the notes following the
table.
Table 22.378 Columns of the cluster_locks table
Column Name | Type | Description |
---|---|---|
node_id |
integer | ID of reporting node |
block_instance |
integer | ID of reporting LDM instance |
tableid |
integer | ID of table containing this row |
fragmentid |
integer | ID of fragment containing locked row |
rowid |
integer | ID of locked row |
transid |
integer | Transaction ID |
mode |
string | Lock request mode |
state |
string | Lock state |
detail |
string | Whether this is first holding lock in row lock queue |
op |
string | Operation type |
duration_millis |
integer | Milliseconds spent waiting or holding lock |
lock_num |
integer | ID of lock object |
waiting_for |
integer | Waiting for lock with this ID |
The table ID (tableid
column) is assigned
internally, and is the same as that used in other
ndbinfo
tables. It is also shown in the
output of ndb_show_tables.
The transaction ID (transid
column) is the
identifier generated by the NDB API for the transaction
requesting or holding the current lock.
The mode
column shows the lock mode; this is
always one of S
(indicating a shared lock) or
X
(an exclusive lock). If a transaction holds
an exclusive lock on a given row, all other locks on that row
have the same transaction ID.
The state
column shows the lock state. Its
value is always one of H
(holding) or
W
(waiting). A waiting lock request waits for
a lock held by a different transaction.
When the detail
column contains a
*
(asterisk character), this means that this
lock is the first holding lock in the affected row's lock
queue; otherwise, this column is empty. This information can be
used to help identify the unique entries in a list of lock
requests.
The op
column shows the type of operation
requesting the lock. This is always one of the values
READ
, INSERT
,
UPDATE
, DELETE
,
SCAN
, or REFRESH
.
The duration_millis
column shows the number
of milliseconds for which this lock request has been waiting or
holding the lock. This is reset to 0 when a lock is granted for
a waiting request.
The lock ID (lockid
column) is unique to this
node and block instance.
The lock state is shown in the lock_state
column; if this is W
, the lock is waiting to
be granted, and the waiting_for
column shows
the lock ID of the lock object this request is waiting for.
Otherwise, the waiting_for
column is empty.
waiting_for
can refer only to locks on the
same row, as identified by node_id
,
block_instance
, tableid
,
fragmentid
, and rowid
.
Traduction non disponible
Le manuel MySQL n'est pas encore traduit en français sur l'infobrol. Seule la version anglaise est disponible pour l'instant.
Document créé le 26/06/2006, dernière modification le 26/10/2018
Source du document imprimé : https://www.gaudry.be/mysql-rf-mysql-cluster-ndbinfo-cluster-locks.html
L'infobrol est un site personnel dont le contenu n'engage que moi. Le texte est mis à disposition sous licence CreativeCommons(BY-NC-SA). Plus d'info sur les conditions d'utilisation et sur l'auteur.
Références
Ces références et liens indiquent des documents consultés lors de la rédaction de cette page, ou qui peuvent apporter un complément d'information, mais les auteurs de ces sources ne peuvent être tenus responsables du contenu de cette page.
L'auteur de ce site est seul responsable de la manière dont sont présentés ici les différents concepts, et des libertés qui sont prises avec les ouvrages de référence. N'oubliez pas que vous devez croiser les informations de sources multiples afin de diminuer les risques d'erreurs.