BiasQueriesAsOutlier

Set query optimization to biased toward outliers.

Synopsis

[SQL]    BiasQueriesAsOutlier=n

n is either 1 or 0. The default value is 0.

Description

When BiasQueriesAsOutlier is enabled (n = 1), InterSystems SQL optimizes for queries that primarily return outlier values. For further details on outlier selectivity, see Tune Table.

BiasQueriesAsOutlier and Runtime Plan Choice (RTPC) cannot both be applied to the same comparison condition in a query. If both the BiasQueriesAsOutlier and RTPC settings are set to 1, if RTPC is applied to a comparison condition (see Application of RTPC) then BiasQueriesAsOutlier is ignored for that comparison condition. When RTPC is set, InterSystems SQL determines whether to use outlier optimization on a per-query basis.

If AdaptiveMode is enabled (set to 1), then RTPC is automatically enabled; therefore, if RTPC is applied to a comparison condition, Adaptive Mode overrides the BiasQueriesAsOutlier setting and disables outlier bias.

In cases where RTPC is not applied to a comparison condition (regardless of the RTPC or AdaptiveMode settings being enabled), the current setting of BiasQueriesAsOutlier (enabled or disabled) can affect the query plan, review the query plan for more information.

Note:

Adaptive Mode replaces the earlier BiasQueriesAsOutlier mechanism. Please contact the WRC is you were previously using this setting and need assistance.

Changing This Parameter

You can change BiasQueriesAsOutlier with the Config.SQLOpens in a new tab class (as described in the class reference) or by editing the CPF in a text editor (as described in Editing the Active CPF).