| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | josh(at)agliodbs(dot)com |
| Cc: | pgsql-hackers(at)postgresql(dot)org, Simon Riggs <simon(at)2ndquadrant(dot)com>, testperf-general(at)pgfoundry(dot)org |
| Subject: | Re: [Testperf-general] Re: ExclusiveLock |
| Date: | 2004-11-18 22:55:22 |
| Message-ID: | 20948.1100818522@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Josh Berkus <josh(at)agliodbs(dot)com> writes:
>> The main problem on INSERTs is that it is usually the same few pages:
>> the lead data block and the lead index block. There are ways of
>> spreading the load out across an index, but I'm not sure what happens on
>> the leading edge of the data relation, but I think it hits the same
>> block each time.
> I actually have several test cases for this, can you give me a trace or
> profile suggestion that would show if this is happening?
If it is a problem, the LockBuffer calls in RelationGetBufferForTuple
would be the places showing contention delays.
It could also be that the contention is for the WALInsertLock, ie, the
right to stuff a WAL record into the shared buffers. This effect would
be the same even if you were inserting into N separate tables.
regards, tom lane
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