pgsql: Fix SQL:2008 FETCH FIRST syntax to allow parameters.

pgsql: Fix SQL:2008 FETCH FIRST syntax to allow parameters.

Fix SQL:2008 FETCH FIRST syntax to allow parameters.

OFFSET  ROWS FETCH FIRST  ROWS ONLY syntax is supposed to accept
, which includes parameters as well as
literals. When this syntax was added all those years ago, it was done
inconsistently, with  and  being different subsets of the
standard syntax.

Rectify that by making  and  accept the same thing, and allowing
either a (signed) numeric literal or a c_expr there, which allows for
parameters, variables, and parenthesized arbitrary expressions.

Per bug #15200 from Lukas Eder.

Backpatch all the way, since this has been broken from the start.

Discussion: https://postgr.es/m/877enz476l.fsf@news-spur.riddles.org.uk
Discussion: http://postgr.es/m/152647780335.27204.16895288237122418685@wrigleys.postgresql.org

Branch
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REL9_4_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/769e6fcd1a350ad3720030bcfa00d8c7ec9cf970

Modified Files
--------------
doc/src/sgml/ref/select.sgml | 14 +++++++------
src/backend/parser/gram.y    | 49 +++++++++++++++++++++++++++++---------------
2 files changed, 41 insertions(+), 22 deletions(-)