Thread: pgsql: Fix support for CREATE TABLE IF NOT EXISTS AS EXECUTE

Fix support for CREATE TABLE IF NOT EXISTS AS EXECUTE

The grammar IF NOT EXISTS for CTAS is supported since 9.5 and documented
as such, however the case of using EXECUTE as query has never been
covered as EXECUTE CTAS statements and normal CTAS statements are parsed
separately.

Author: Andreas Karlsson
Discussion: https://postgr.es/m/2ddcc188-e37c-a0be-32bf-a56b07c3559e@proxel.se
Backpatch-through: 9.5

Branch
------
REL9_6_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/d08fae3773ea3b9930d3efc0429a38614c2dd706

Modified Files
--------------
src/backend/parser/gram.y                  | 18 ++++++++++++++++++
src/test/regress/expected/create_table.out | 14 ++++++++++++++
src/test/regress/sql/create_table.sql      |  8 ++++++++
3 files changed, 40 insertions(+)