pgsql: Fix volatile function evaluation in eager aggregation

Fix volatile function evaluation in eager aggregation

Pushing aggregates containing volatile functions below a join can
violate volatility semantics by changing the number of times the
function is executed.

Here we check the Aggref nodes in the targetlist and havingQual for
volatile functions and disable eager aggregation when such functions
are present.

Author: Richard Guo <guofenglinux(at)gmail(dot)com>
Reviewed-by: Matheus Alcantara <matheusssilv97(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAMbWs48A53PY1Y4zoj7YhxPww9fO1hfnbdntKfA855zpXfVFRA@mail.gmail.com

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/3a08a2a8b4fd36a9fa0da0253d1ca053c19047d5

Modified Files
--------------
src/backend/optimizer/plan/initsplan.c | 11 ++++++++
src/test/regress/expected/eager_aggregate.out | 38 +++++++++++++++++++++++++++
src/test/regress/sql/eager_aggregate.sql | 14 ++++++++++
3 files changed, 63 insertions(+)