Version sans cache

Mise en cache désactivé. Réglage défaut pour cette page : actif (code DEF204)
Si l'affichage est trop lent, vous pouvez désactiver le mode utilisateur pour visualiser la version en cache.

Rechercher dans le manuel MySQL

5.6.4.3 Rewriter Query Rewrite Plugin Reference

Table des matières

The following discussion serves as a reference to these components associated with the Rewriter query rewrite plugin:

  • The Rewriter rules table in the query_rewrite database

  • Rewriter procedures and functions

  • Rewriter system and status variables

5.6.4.3.1 Rewriter Query Rewrite Plugin Rules Table

The rewrite_rules table in the query_rewrite database provides persistent storage for the rules that the Rewriter plugin uses to decide whether to rewrite statements.

Users communicate with the plugin by modifying the set of rules stored in this table. The plugin communicates information to users by setting the table's message column.

Note

The rules table is loaded into the plugin by the flush_rewrite_rules stored procedure. Unless that procedure has been called following the most recent table modification, the table contents do not necessarily correspond to the set of rules the plugin is using.

The rewrite_rules table has these columns:

  • id

    The rule ID. This column is the table primary key. You can use the ID to uniquely identify any rule.

  • pattern

    The template that indicates the pattern for statements that the rule matches. Use ? to represent parameter markers that match data values.

  • pattern_database

    The database used to match unqualified table names in statements. Qualified table names in statements match qualified names in the pattern if corresponding database and table names are identical. Unqualified table names in statements match unqualified names in the pattern only if the default database is the same as pattern_database and the table names are identical.

  • replacement

    The template that indicates how to rewrite statements matching the pattern column value. Use ? to represent parameter markers that match data values. In rewritten statements, the plugin replaces ? parameter markers in replacement using data values matched by the corresponding markers in pattern.

  • enabled

    Whether the rule is enabled. Load operations (performed by invoking the flush_rewrite_rules() stored procedure) load the rule from the table into the Rewriter in-memory cache only if this column is YES.

    This column makes it possible to deactivate a rule without removing it: Set the column to a value other than YES and reload the table into the plugin.

  • message

    The plugin uses this column for communicating with users. If no error occurs when the rules table is loaded into memory, the plugin sets the message column to NULL. A non-NULL value indicates an error and the column contents are the error message. Errors can occur under these circumstances:

    • Either the pattern or the replacement is an incorrect SQL statement that produces syntax errors.

    • The replacement contains more ? parameter markers than the pattern.

    If a load error occurs, the plugin also sets the Rewriter_reload_error status variable to ON.

  • pattern_digest

    This column is used for debugging and diagnostics. If the column exists when the rules table is loaded into memory, the plugin updates it with the pattern digest. This column may be useful if you are trying to determine why some statement fails to be rewritten.

  • normalized_pattern

    This column is used for debugging and diagnostics. If the column exists when the rules table is loaded into memory, the plugin updates it with the normalized form of the pattern. This column may be useful if you are trying to determine why some statement fails to be rewritten.

Table des matières Haut

5.6.4.3.2 Rewriter Query Rewrite Plugin Procedures and Functions

Rewriter plugin operation uses a stored procedure that loads the rules table into its in-memory cache, and a helper user-defined function (UDF). Under normal operation, users invoke only the stored procedure. The UDF is intended to be invoked by the stored procedure, not directly by users.

  • flush_rewrite_rules()

    This stored procedure uses the load_rewrite_rules() UDF to load the contents of the rewrite_rules table into the Rewriter in-memory cache.

    Calling flush_rewrite_rules() implies COMMIT.

    Invoke this procedure after you modify the rules table to cause the plugin to update its cache from the new table contents. If any errors occur, the plugin sets the message column for the appropriate rule rows in the table and sets the Rewriter_reload_error status variable to ON.

  • load_rewrite_rules()

    This UDF is a helper routine used by the flush_rewrite_rules() stored procedure.

Table des matières Haut

5.6.4.3.3 Rewriter Query Rewrite Plugin System Variables

The Rewriter query rewrite plugin supports the following system variables. These variables are available only if the plugin is installed (see Section 5.6.4.1, “Installing or Uninstalling the Rewriter Query Rewrite Plugin”).

Table des matières Haut

5.6.4.3.4 Rewriter Query Rewrite Plugin Status Variables

The Rewriter query rewrite plugin supports the following status variables. These variables are available only if the plugin is installed (see Section 5.6.4.1, “Installing or Uninstalling the Rewriter Query Rewrite Plugin”).

  • Rewriter_number_loaded_rules

    The number of rewrite plugin rewrite rules successfully loaded from the rewrite_rules table into memory for use by the Rewriter plugin.

  • Rewriter_number_reloads

    The number of times the rewrite_rules table has been loaded into the in-memory cache used by the Rewriter plugin.

  • Rewriter_number_rewritten_queries

    The number of queries rewritten by the Rewriter query rewrite plugin since it was loaded.

  • Rewriter_reload_error

    Whether an error occurred the most recent time that the rewrite_rules table was loaded into the in-memory cache used by the Rewriter plugin. If the value is OFF, no error occurred. If the value is ON, an error occurred; check the message column of the rewriter_rules table for error messages.


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-rewriter-query-rewrite-plugin-reference.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