pgsql: Convert eval_const_expressions's long series of IsA tests into a

Convert eval_const_expressions's long series of IsA tests into a switch.

This function has now grown enough cases that a switch seems appropriate.
This results in a measurable speed improvement on some platforms, and
should certainly not hurt. The code's in need of a pgindent run now,
though.

Andres Freund

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/a04161f2eab55f72b3c3dba9baed0ec09e7f633f

Modified Files
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src/backend/optimizer/util/clauses.c | 56 +++++++++++++++++++---------------
1 files changed, 31 insertions(+), 25 deletions(-)