On 2016/05/11 18:03, Ashutosh Bapat wrote:
On Wed, May 11, 2016 at 1:34 PM, Etsuro Fujita
<[email protected] <mailto:[email protected]>> wrote:
On 2016/05/11 16:49, Ashutosh Bapat wrote:
The patch is calculating user mapping when it's readily available
through RelOptInfo::fdw_private. That incurs a catalog lookup
unnecessarily. Instead, can we add new function makeOid, oidVal
on the
lines of makeInteger and intVal to store and retrieve an OID
resp. and
also corresponding print function? It might be helpful in future.
That might be an idea, but is the overhead in that re-calculation so
large?
A call to GetForeignTable would incur a catalog lookup which means a
catalog table/index scan if corresponding entry is not in the cache.
This is followed by GetUserMapping() which is another catalog access.
That's bound to be expensive than an makeOid(), oidVal() call.
Right, but such lookups have been incurred at the planning time (ie,
build_simple_rel), and corresponding entries would be in the cache. So,
the overhead in that recalculation at the execution time would be not
that large in practice. No?
Best regards,
Etsuro Fujita
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