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.


Rechercher dans le manuel MySQL

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

  1. Consulter le document html Langue du document :en Manuel MySQL : https://dev.mysql.com/

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.

Table des matières Haut