pgsql: Tweak parse location assignment for CURRENT_DATE and related con

Tweak parse location assignment for CURRENT_DATE and related constructs.

All these constructs generate parse trees consisting of a Const and
a run-time type coercion (perhaps a FuncExpr or a CoerceViaIO).  Modify
the raw parse output so that we end up with the original token's location
attached to the type coercion node while the Const has location -1;
before, it was the other way around.  This makes no difference in terms
of what exprLocation() will say about the parse tree as a whole, so it
should not have any user-visible impact.  The point of changing it is that
we do not want contrib/pg_stat_statements to treat these constructs as
replaceable constants.  It will do the right thing if the Const has
location -1 rather than a valid location.

This is a pretty ugly hack, but then this code is ugly already; we should
someday replace this translation with special-purpose parse node(s) that
would allow ruleutils.c to reconstruct the original query text.

(See also commit 5d3fcc4c2e137417ef470d604fee5e452b22f6a7, which also
hacked location assignment rules for the benefit of pg_stat_statements.)

Back-patch to 9.2 where pg_stat_statements grew the ability to recognize
replaceable constants.

Kyotaro Horiguchi

Branch
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REL9_2_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/27ab1eb7e72924bc464d3fd1fd6c380e8ea34ac2

Modified Files
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src/backend/parser/gram.y |   37 +++++++++++++++++++++----------------
1 file changed, 21 insertions(+), 16 deletions(-)