10.3.5 Operands related to SQL optimization

5) pd_hashjoin_hashing_mode = TYPE1 | TYPE2
Operand default value
  • Default value in recommended mode: TYPE2
  • Default value in 0904 compatibility mode: TYPE1
Specifies the hashing method to be used when hash join, subquery hash execution is specified for the SQL extension optimizing option.
TYPE1: This hashing method is used in versions earlier than 07-02.
TYPE2: Provides more uniform hashing than TYPE1.
Specification guidelines
  • Normally, specify TYPE2. However, uniform hashing might not occur depending on the data in the column specified for the join condition. In this case, specify TYPE1.
  • If specifying TYPE1 does not produce the expected performance in a user system that has been upgraded to 07-02 or a later version, specify TYPE2.
6) pd_apply_search_ats_num = maximum-number-of-combinations-of-narrowing-values-applied-to-ATS-search-condition
~<unsigned integer>((255-30000))
Operand default value
  • Default value in recommended mode: 30000
  • Default value in 0904 compatibility mode: 255
Specifies for an indexed search a maximum number of combinations of narrowing values that can be applied to the ATS or RANGES search condition when an IN predicate or quantified predicate (= ANY (table subquery) or = SOME (table subquery)) is specified.
Specification guidelines
If you are upgrading from a HiRDB version earlier than 09-50, the specification guideline that you must follow differs depending on the HiRDB version before the upgrade.
  • When upgrading HiRDB version 08-04 or later:
    We recommend that you specify the same value that had been used before the upgrade.
  • When upgrading HiRDB version earlier than 08-04:
    We recommend that you specify 255.
    If an IN predicate or quantified predicate (= ANY (table subquery) or = SOME (table subquery)) has been specified in the RANGE or RANGES SQL statement and the number of combinations of search condition narrowing values exceeds 255, performance might be improved by modifying the value specified for this option. However, if there are no hits when the IN predicate is used, performance might deteriorate. For details about the types of search conditions, see the manual HiRDB Version 9 Command Reference.
Note
If the specified value is exceeded, the value is modified so that the search condition becomes different internally, and then the SQL is executed. For this reason, the access path might be other than what was anticipated.