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ri_triggers.c

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    • Tom Lane's avatar
      8d65da1f
      Support ordered-set (WITHIN GROUP) aggregates. · 8d65da1f
      Tom Lane authored
      This patch introduces generic support for ordered-set and hypothetical-set
      aggregate functions, as well as implementations of the instances defined in
      SQL:2008 (percentile_cont(), percentile_disc(), rank(), dense_rank(),
      percent_rank(), cume_dist()).  We also added mode() though it is not in the
      spec, as well as versions of percentile_cont() and percentile_disc() that
      can compute multiple percentile values in one pass over the data.
      
      Unlike the original submission, this patch puts full control of the sorting
      process in the hands of the aggregate's support functions.  To allow the
      support functions to find out how they're supposed to sort, a new API
      function AggGetAggref() is added to nodeAgg.c.  This allows retrieval of
      the aggregate call's Aggref node, which may have other uses beyond the
      immediate need.  There is also support for ordered-set aggregates to
      install cleanup callback functions, so that they can be sure that
      infrastructure such as tuplesort objects gets cleaned up.
      
      In passing, make some fixes in the recently-added support for variadic
      aggregates, and make some editorial adjustments in the recent FILTER
      additions for aggregates.  Also, simplify use of IsBinaryCoercible() by
      allowing it to succeed whenever the target type is ANY or ANYELEMENT.
      It was inconsistent that it dealt with other polymorphic target types
      but not these.
      
      Atri Sharma and Andrew Gierth; reviewed by Pavel Stehule and Vik Fearing,
      and rather heavily editorialized upon by Tom Lane
      8d65da1f
      History
      Support ordered-set (WITHIN GROUP) aggregates.
      Tom Lane authored
      This patch introduces generic support for ordered-set and hypothetical-set
      aggregate functions, as well as implementations of the instances defined in
      SQL:2008 (percentile_cont(), percentile_disc(), rank(), dense_rank(),
      percent_rank(), cume_dist()).  We also added mode() though it is not in the
      spec, as well as versions of percentile_cont() and percentile_disc() that
      can compute multiple percentile values in one pass over the data.
      
      Unlike the original submission, this patch puts full control of the sorting
      process in the hands of the aggregate's support functions.  To allow the
      support functions to find out how they're supposed to sort, a new API
      function AggGetAggref() is added to nodeAgg.c.  This allows retrieval of
      the aggregate call's Aggref node, which may have other uses beyond the
      immediate need.  There is also support for ordered-set aggregates to
      install cleanup callback functions, so that they can be sure that
      infrastructure such as tuplesort objects gets cleaned up.
      
      In passing, make some fixes in the recently-added support for variadic
      aggregates, and make some editorial adjustments in the recent FILTER
      additions for aggregates.  Also, simplify use of IsBinaryCoercible() by
      allowing it to succeed whenever the target type is ANY or ANYELEMENT.
      It was inconsistent that it dealt with other polymorphic target types
      but not these.
      
      Atri Sharma and Andrew Gierth; reviewed by Pavel Stehule and Vik Fearing,
      and rather heavily editorialized upon by Tom Lane