| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Noah Misch <noah(at)leadboat(dot)com> |
| Cc: | Kevin Grittner <kgrittn(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Kevin Grittner <kgrittn(at)postgresql(dot)org>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, "pgsql-committers(at)postgresql(dot)org" <pgsql-committers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] Re: pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold < |
| Date: | 2016-04-16 20:56:30 |
| Message-ID: | 20160416205630.puxsglckxi3sn5ec@alap3.anarazel.de |
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| Lists: | pgsql-committers pgsql-hackers |
On 2016-04-16 16:44:52 -0400, Noah Misch wrote:
> That is more controversial than the potential ~2% regression for
> old_snapshot_threshold=-1. Alvaro[2] and Robert[3] are okay releasing
> that way, and Andres[4] is not.
FWIW, I could be kinda convinced that it's temporarily ok, if there'd be
a clear proposal on the table how to solve the scalability issue around
MaintainOldSnapshotTimeMapping(). Postponing the optimization around
something as trivial as a spinlock around reading an LSN is one thing,
postponing something we don't know the solution to is anohter.
Andres
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