Fix improper repetition of previous results from a hashed aggregate.
ExecReScanAgg's check for whether it could re-use a previously calculated
hashtable neglected the possibility that the Agg node might reference
PARAM_EXEC Params that are not referenced by its input plan node. That's
okay if the Params are in upper tlist or qual expressions; but if one
appears in aggregate input expressions, then the hashtable contents need
to be recomputed when the Param's value changes.
To avoid unnecessary performance degradation in the case of a Param that
isn't within an aggregate input, add logic to the planner to determine
which Params are within aggregate inputs. This requires a new field in
struct Agg, but fortunately we never write plans to disk, so this isn't
an initdb-forcing change.
Per report from Jeevan Chalke. This has been broken since forever,
so back-patch to all supported branches.
projects / postgresql / commit