Re: Use %u to print user mapping's umid and userid

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От Ashutosh Bapat
Тема Re: Use %u to print user mapping's umid and userid
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Msg-id CAFjFpRd+v=Gb95QwVusy9tLwni6v1X9OOnheybBo-vMA7wie6g@mail.gmail.com
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Ответ на Re: Use %u to print user mapping's umid and userid  (Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>)
Ответы Re: Use %u to print user mapping's umid and userid
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On Wed, May 11, 2016 at 1:34 PM, Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp> 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.

--
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company

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