Provides default selectivity estimates (in parts per million) to the optimizer for leading constant LIKE predicates.
1 to 1000000
150000
Can be set for an individual connection or the PUBLIC group. Takes effect immediately.
DEFAULT_LIKE_RANGE_SELECTIVITY_PPM sets
the default selectivity for LIKE predicates, of the form LIKE 'string%' where
the match string is a set of constant characters followed by a single
wildcard character (%). The optimizer relies on this option
when other selectivity information is not available.
If the column has either an LF index or a 1- or 2- or 3-byte FP index, the optimizer can get exact information and does not need to use this value.
Users can also specify selectivity in the query, as described in “User-supplied condition hints” on page 46 in Reference: Building Blocks, Tables, and Procedures.
“DEFAULT_LIKE_MATCH_SELECTIVITY_PPM option” and “FP_LOOKUP_SIZE option”
“The Fast Projection (FP) default index type” in Chapter 6, “Using Sybase IQ Indexes” in System Administration Guide: Volume 1
“LIKE conditions” in Chapter 2, “SQL Language Elements” in Reference: Building Blocks, Tables, and Procedures
Chapter 3, “Optimizing Queries and Deletions” in the Performance and Tuning Guide
