pgsql: pg_prewarm: Add automatic prewarm feature.

pg_prewarm: Add automatic prewarm feature.

Periodically while the server is running, and at shutdown, write out a
list of blocks in shared buffers. When the server reaches consistency
-- unfortunatey, we can't do it before that point without breaking
things -- reload those blocks into any still-unused shared buffers.

Mithun Cy and Robert Haas, reviewed and tested by Beena Emerson,
Amit Kapila, Jim Nasby, and Rafia Sabih.

Discussion: http://postgr.es/m/CAD__OugubOs1Vy7kgF6xTjmEqTR4CrGAv8w+ZbaY_+MZeitukw@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/79ccd7cbd5ca44bee0191d12e9e65abf702899e7

Modified Files
--------------
contrib/file_fdw/data/list1.csv | 2 +
contrib/file_fdw/data/list2.bad | 2 +
contrib/file_fdw/data/list2.csv | 2 +
contrib/pg_prewarm/Makefile | 4 +-
contrib/pg_prewarm/autoprewarm.c | 924 ++++++++++++++++++++++++++++
contrib/pg_prewarm/pg_prewarm--1.1--1.2.sql | 14 +
contrib/pg_prewarm/pg_prewarm.control | 2 +-
doc/src/sgml/pgprewarm.sgml | 69 ++-
src/backend/storage/buffer/freelist.c | 17 +
src/include/storage/buf_internals.h | 1 +
src/tools/pgindent/typedefs.list | 2 +
11 files changed, 1035 insertions(+), 4 deletions(-)