pgsql: tableam: basic documentation.

tableam: basic documentation.

This adds documentation about the user oriented parts of table access
methods (i.e. the default_table_access_method GUC and the USING clause
for CREATE TABLE etc), adds a basic chapter about the table access
method interface, and adds a note to storage.sgml that it's contents
don't necessarily apply for non-builtin AMs.

Author: Haribabu Kommi and Andres Freund
Discussion: https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b73c3a11963c8bb783993cfffabb09f558f86e37

Modified Files
--------------
doc/src/sgml/catalogs.sgml | 9 +-
doc/src/sgml/config.sgml | 17 ++++
doc/src/sgml/filelist.sgml | 1 +
doc/src/sgml/indexam.sgml | 12 ++-
doc/src/sgml/postgres.sgml | 1 +
doc/src/sgml/ref/create_access_method.sgml | 14 ++--
doc/src/sgml/ref/create_materialized_view.sgml | 16 ++++
doc/src/sgml/ref/create_table.sgml | 19 ++++-
doc/src/sgml/ref/create_table_as.sgml | 15 ++++
doc/src/sgml/ref/select_into.sgml | 10 +++
doc/src/sgml/storage.sgml | 17 +++-
doc/src/sgml/tableam.sgml | 110 +++++++++++++++++++++++++
src/include/access/tableam.h | 3 +
13 files changed, 228 insertions(+), 16 deletions(-)