Configure the Predictive Governor with MariaDB Xpand

This page is part of MariaDB's Documentation.

The parent of this page is: Query Tuning Recommendations for MariaDB Xpand

Topics on this page:

Overview
Compatibility
Configure the Predictive Governor Threshold
Disable the Predictive Governor
System Variables

Overview

The predictive governor prevents execution of queries that are estimated to process an excessive number of rows as a result of a join. This may be the result of a join query that is poorly indexed, or that is written such that it does not use available indexes.

Compatibility

MariaDB Xpand 6.1

Configure the Predictive Governor Threshold

To set a threshold for the predictive governor, use the sierra_predictive_governor_threshold system variable:

SET GLOBAL sierra_predictive_governor_threshold=<number_of_rows>;

If a query would exceed the threshold, the following error is thrown:

ERROR 1 (HY000): [70660] Could not generate plan in sierra:
sierra_predictive_governor: Excess execution predicted

Disable the Predictive Governor

To disable the predictive governor, use the sierra_predictive_governor system variable:

SET GLOBAL sierra_predictive_governor=OFF;

System Variables

The following system variables configure the predictive governor functionality:

System Variable	Description
`sierra_predictive_governor`	Enable the predictive governor (default: `true`).
`sierra_predictive_governor_threshold`	Number of rows processed by a query before the predictive governor prevents execution (default: `100000000000`).