The Rewriter Query Rewrite Plugin Rewriter Query Rewrite Plugin Procedures and Functions Rewriter Query Rewrite Plugin System Variables • rewriter_enabled • load_rewrite_rules() • flush_rewrite_rules() • normalized_pattern • pattern_digest • 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: If a load error occurs, the plugin also sets the  Rewriter_reload_error  status variable to  ON . 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. 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. Rewriter  plugin operation uses a stored procedure that loads the rules table into its in-memory cache, and a helper loadable function. Under normal operation, users invoke only the stored procedure. The function is intended to be invoked by the stored procedure, not directly by users. This stored procedure uses the  load_rewrite_rules()  function 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 . This function is a helper routine used by the  flush_rewrite_rules()  stored procedure. 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” ). •Either the pattern or the replacement is an incorrect SQL statement that produces syntax errors. •The replacement contains more  ?  parameter markers than the pattern. System Variable rewriter_enabled Scope Global Dynamic Yes 1094