pgsql: Basic planner and executor integration for JIT.

Basic planner and executor integration for JIT.

This adds simple cost based plan time decision about whether JIT
should be performed. jit_above_cost, jit_optimize_above_cost are
compared with the total cost of a plan, and if the cost is above them
JIT is performed / optimization is performed respectively.

For that PlannedStmt and EState have a jitFlags (es_jit_flags) field
that stores information about what JIT operations should be performed.

EState now also has a new es_jit field, which can store a
JitContext. When there are no errors the context is released in
standard_ExecutorEnd().

It is likely that the default values for jit_[optimize_]above_cost
will need to be adapted further, but in my test these values seem to
work reasonably.

Author: Andres Freund, with feedback by Peter Eisentraut
Discussion: https://postgr.es/m/20170901064131.tazjxwus3k2w3ybh@alap3.anarazel.de

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/cc415a56d09a8da7c919088036b6097b70f10791

Modified Files
--------------
src/backend/executor/execMain.c               |  8 ++++++++
src/backend/executor/execParallel.c           |  3 +++
src/backend/executor/execUtils.c              |  3 +++
src/backend/jit/jit.c                         |  2 ++
src/backend/nodes/copyfuncs.c                 |  1 +
src/backend/nodes/outfuncs.c                  |  1 +
src/backend/nodes/readfuncs.c                 |  1 +
src/backend/optimizer/plan/planner.c          | 15 +++++++++++++++
src/backend/utils/misc/guc.c                  | 20 ++++++++++++++++++++
src/backend/utils/misc/postgresql.conf.sample |  6 ++++++
src/include/jit/jit.h                         |  2 ++
src/include/nodes/execnodes.h                 |  8 ++++++++
src/include/nodes/plannodes.h                 |  2 ++
13 files changed, 72 insertions(+)