JOIN_SIMPLIFICATION_THRESHOLD option

Function

Controls the minimum number of tables being joined together before any join optimizer simplifications are applied.

Allowed values

Integer from 1 to 64

Scope

Can be set temporary, for an individual connection, or for the PUBLIC group. Takes effect immediately.

Default

15

Description

The query optimizer simplifies its optimization of join order by separate handling of both lookup tables (that is, non-selective 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 may improve the time required to optimize queries containing many joins, but it also may prevent the optimizer from finding the best possible join plan.

Normally you should not need to change this value. If you do, Sybase recommends setting JOIN_SIMPLIFICATION_THRESHOLD as a temporary or user option, and to a value of at least 9.