JOIN_SIMPLIFICATION_THRESHOLD Option

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Option can be set at the database (PUBLIC) or user level. At the database level, the value becomes the default for any new user, but has no impact on existing users. At the user level, overrides the PUBLIC value for that user only. No system privilege is required to set option for self. System privilege is required to set at database level or at user level for any user other than self.

Requires the SET ANY PUBLIC OPTION system privilege to set this option. Can be set temporary for an individual connection or for the PUBLIC role. Takes effect immediately.

The query optimizer simplifies its optimization of join order by separate handling of both lookup tables (that is, nonselective dimension tables) and tables that are effective Cartesian products. After simplification, it optimizes the remaining tables for join order, up to the limit set by MAX_JOIN_ENUMERATION.

Setting this option to a value greater than the current value for MAX_JOIN_ENUMERATION has no effect.

Setting this value below the value for MAX_JOIN_ENUMERATION might improve the time required to optimize queries containing many joins, but may also prevent the optimizer from finding the best possible join plan.

If you change this value, set the JOIN_SIMPLIFICATION_THRESHOLD as a temporary or user option, and to a value of at least 9.