pgsql: Do execGrouping.c via expression eval machinery.

Do execGrouping.c via expression eval machinery.

This has a performance benefit on own, although not hugely so. The
primary benefit is that it will allow for to JIT tuple deforming and
comparator invocations.

Author: Andres Freund
Discussion: https://postgr.es/m/20171129080934.amqqkke2zjtekd4t@alap3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/773aec7aa98abd38d6d9435913bb8e14e392c274

Modified Files
--------------
src/backend/executor/execExpr.c | 118 +++++++++++++++
src/backend/executor/execExprInterp.c | 29 ++++
src/backend/executor/execGrouping.c | 236 +++++++-----------------------
src/backend/executor/nodeAgg.c | 143 +++++++++++-------
src/backend/executor/nodeGroup.c | 24 +--
src/backend/executor/nodeRecursiveunion.c | 5 +-
src/backend/executor/nodeSetOp.c | 48 +++---
src/backend/executor/nodeSubplan.c | 81 +++++++++-
src/backend/executor/nodeUnique.c | 31 ++--
src/backend/executor/nodeWindowAgg.c | 38 +++--
src/backend/utils/adt/orderedsetaggs.c | 56 +++----
src/include/executor/execExpr.h | 1 +
src/include/executor/executor.h | 28 ++--
src/include/executor/nodeAgg.h | 12 +-
src/include/nodes/execnodes.h | 14 +-
15 files changed, 498 insertions(+), 366 deletions(-)