pgsql: Modernize result-tuple construction in pltcl_trigger_handler().

Modernize result-tuple construction in pltcl_trigger_handler().

Use Tcl_ListObjGetElements instead of Tcl_SplitList. Aside from being
possibly more efficient in its own right, this means we are no longer
responsible for freeing a malloc'd result array, so we can get rid of
a PG_TRY/PG_CATCH block.

Use heap_form_tuple instead of SPI_modifytuple. We don't need the
extra generality of the latter, since we're always replacing all
columns. Nor do we need its memory-context-munging, since at this
point we're already out of the SPI environment.

Per comparison of this code to tuple-building code submitted by Jim Nasby.
I've abandoned the thought of merging the two cases into a single routine,
but we may as well make the older code simpler and faster where we can.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/2178cbf40d3d75d87ab9b55579ac1cb0621baeff

Modified Files
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src/pl/tcl/pltcl.c | 167 +++++++++++++++++++++++------------------------------
1 file changed, 73 insertions(+), 94 deletions(-)