pgsql: hash: Refactor hash index creation.

hash: Refactor hash index creation.

The primary goal here is to move all of the related page modifications
to a single section of code, in preparation for adding write-ahead
logging. In passing, rename _hash_metapinit to _hash_init, since it
initializes more than just the metapage.

Amit Kapila. The larger patch series of which this is a part has been
reviewed and tested by Álvaro Herrera, Ashutosh Sharma, Mark Kirkwood,
Jeff Janes, and Jesper Pedersen.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/38305398cdc029e3a74bfad1815cb33f5b087336

Modified Files
--------------
src/backend/access/hash/hash.c | 4 +-
src/backend/access/hash/hashovfl.c | 62 -----------
src/backend/access/hash/hashpage.c | 203 +++++++++++++++++++++++++------------
src/include/access/hash.h | 10 +-
4 files changed, 144 insertions(+), 135 deletions(-)