Re: [HACKERS] getting rid of SnapshotNow

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Noah Misch <noah(at)leadboat(dot)com>, pgsql-hackers(at)postgresql(dot)org, pgsql-odbc(at)postgresql(dot)org
Subject: Re: [HACKERS] getting rid of SnapshotNow
Date: 2013-07-19 17:20:17
Message-ID: 20130719172017.GD4130@eldon.alvh.no-ip.org
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Robert Haas escribió:

> 4. If we use GetActiveSnapshot, all the comments about about a fresh
> MVCC snapshot still apply. However, the snapshot in question could be
> even more stale, especially in repeatable read or serializable mode.
> However, this might be thought a more consistent behavior than what we
> have now. And I'm guessing that this function is typically run as its
> own transaction, so in practice this doesn't seem much different from
> an MVCC snapshot, only cheaper.
>
> At the moment, I dislike #2 and slightly prefer #4 to #3.

+1 for #4, and if we ever need more then we can provide a non-default
way to get at #2.

--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

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