| From: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
|---|---|
| To: | sql2pg <sekhar(dot)career(at)gmail(dot)com> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: WAL reducing size |
| Date: | 2017-12-04 21:12:50 |
| Message-ID: | 20171204211250.ljsaxf2jhedjjerj@alvherre.pgsql |
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| Thread: | |
| Lists: | pgsql-general |
sql2pg wrote:
> how about uncommitted(open transactions) . if a segment has 1 committed and
> 2 uncommitted transactions then will it keep the segment instead deleting it
> after checkpoint , since it has 2 uncommitted transactions
There is no connection between transaction commit and checkpoint
removing WAL files. WAL files are removed after two checkpoints have
occured, regardless of transactions that might be open. The on-disk
effects of those transactions that occured before the earlier checkpoint
are already on disk anyway. The commit record might appear at whatever
point in the future, and the rows will not become visible to other
transactions until then, regardless of what happened to the WAL
segments.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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