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Fix SQL:2008 FETCH FIRST syntax to allow parameters.

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

Rectify that by making <x> and <y> 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
This commit is contained in:
Andrew Gierth
2018-05-21 17:02:17 +01:00
parent 806d08c048
commit 1da162e1f5
2 changed files with 39 additions and 20 deletions
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10
doc/src/sgml/ref/select.sgml
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@ -1399,10 +1399,12 @@ OFFSET <replaceable class="parameter">start</replaceable>
OFFSET <replaceable class="parameter">start</replaceable> { ROW | ROWS }
FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } ONLY
</synopsis>
In this syntax, to write anything except a simple integer constant for
<replaceable class="parameter">start</replaceable> or <replaceable
class="parameter">count</replaceable>, you must write parentheses
around it.
In this syntax, the <replaceable class="parameter">start</replaceable>
or <replaceable class="parameter">count</replaceable> value is required by
the standard to be a literal constant, a parameter, or a variable name;
as a <productname>PostgreSQL</productname> extension, other expressions
are allowed, but will generally need to be enclosed in parentheses to avoid
ambiguity.
If <replaceable class="parameter">count</replaceable> is
omitted in a <literal>FETCH</literal> clause, it defaults to 1.
<literal>ROW</literal>