| From: | Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru> |
|---|---|
| To: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: AS OF queries |
| Date: | 2017-12-28 16:36:30 |
| Message-ID: | 309e84e7-3636-1ef6-0608-34a44964ee69@postgrespro.ru |
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| Lists: | pgsql-hackers |
Attached please find new version of AS OF patch which allows to specify
time travel period.
Older versions outside this period may be reclaimed by autovacuum.
This behavior is controlled by "time_travel_period" parameter.
Zero value of this parameter disables time travel and postgres behaves
in standard way.
Actually you can still use AS AF construction but there is no warranty
that requested versions are not reclaimed and result of query actually
belongs to the specified time slice.
Value -1 means infinite history: versions are never reclaimed and
autovacuum is disabled.
And positive value of this parameter specifies maximal time travel
period in seconds.
As in case of disabled time travel, you can specify AS OF timestamp
older than this period.
But there is no warranty that requested versions still exist.
--
Konstantin Knizhnik
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
| Attachment | Content-Type | Size |
|---|---|---|
| asof-4.patch | text/x-patch | 36.0 KB |
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