Re: Recursive query syntax ambiguity

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Martijn van Oosterhout <kleptog(at)svana(dot)org>
Cc: Gregory Stark <stark(at)enterprisedb(dot)com>, PostgreSQL Development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Recursive query syntax ambiguity
Date: 2007-02-05 16:23:58
Message-ID: 446.1170692638@sss.pgh.pa.us
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Martijn van Oosterhout <kleptog(at)svana(dot)org> writes:
> However, I don't know it matters. You only need to cost the plan if
> there are alternate paths and given the plan structure is strongly
> constrained, I'm not sure how much it matters.

It does, since the whole thing could be a subquery, in which case there
could be options available at the outer level. I doubt we'll be able to
be really smart, but that doesn't mean we can just punt.

> In the case of read-committed mode, will two seq-scans always
> return the same result?

They definitely should, since we'll be using the same snapshot
throughout the query.

regards, tom lane

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