The following options influence the speed at which queries are processed.
AGGREGATION_PREFERENCE Controls the choice of algorithms for processing an aggregate (GROUP BY, DISTINCT, SET functions). This option is designed primarily for internal use; do not use it unless you are an experienced database administrator.
DEFAULT_LIKE_MATCH_SELECTIVITY Sets
the default selectivity for generic LIKE predicates, for example, LIKE 'string%string' where % is
a wildcard character. The optimizer relies on this option when other selectivity
information is not available and the match string does not start with
a set of constant characters followed by a single wildcard.
DEFAULT_LIKE_RANGE_SELECTIVITY Sets
the default selectivity for leading constant 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.
EARLY_PREDICATE_EXECUTION Controls whether simple local predicates are executed before join optimization. Under most circumstances, it should not be changed.
IN_SUBQUERY_PREFERENCE Controls the choice of algorithms for processing IN subqueries. This option is designed primarily for internal use; do not use it unless you are an experienced database administrator.
INDEX_PREFERENCE Sets the index to use for query processing. The Sybase IQ optimizer normally chooses the best index available to process local WHERE clause predicates and other operations which can be done within an IQ index. This option is used to override the optimizer choice for testing purposes; under most circumstances it should not be changed.
JOIN_PREFERENCE Controls the choice of algorithms when processing joins. This option is designed primarily for internal use; do not use it unless you are an experienced database administrator.
JOIN_SIMPLIFICATION_THRESHOLD Controls the minimum number of tables being joined together before any join optimizer simplifications are applied. Normally you should not need to change this value.
MAX_HASH_ROWS Sets the maximum estimated number of rows the query optimizer will consider for a hash algorithm. The default is 1,250,000 rows. For example, if there is a join between two tables, and the estimated number of rows entering the join from both tables exceeds this option value, the optimizer will not consider a hash join. On systems with more than 50MB per user of TEMP_CACHE_MEMORY_MB, you may want to consider a higher value for this option.
MAX_JOIN_ENUMERATION Sets the maximum number of tables to be optimized for join order after optimizer simplifications have been applied. Normally you should not need to set this option.
