| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | latestCompletedXid |
| Date: | 2008-10-10 09:51:53 |
| Message-ID: | 1223632313.7007.140.camel@ebony.2ndQuadrant |
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| Lists: | pgsql-hackers |
Currently, we advance latestCompletedXid during
ProcArrayEndTransaction() for both commits and aborts.
If a transaction aborts, its effects are invisible to us just the same
as if the transaction is still running.
ISTM that we need not move latestCompletedXid as a result of an abort.
Only a commit could change what we see as visible.
This must be true, because if a backend had a FATAL error but yet exited
before it ran ProcArrayEndTransaction() we would not move
latestCompletedXid forward either.
Avoiding this will make snapshots smaller in some cases, but it's really
just a correctness thing.
--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Training, Services and Support
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