pgsql: Skip truncating ON COMMIT DELETE ROWS temp tables, if the transa

Skip truncating ON COMMIT DELETE ROWS temp tables, if the transaction hasn't
touched any temporary tables.

We could try harder, and keep track of whether we've inserted to any temp
tables, rather than accessed them, and which temp tables have been inserted
to. But this is dead simple, and already covers many interesting scenarios.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/c9d7dbacd387ab3814bc6b38010a9e72a02ea4f5

Modified Files
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src/backend/commands/tablecmds.c |    8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)