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Re: Rewrite, normal execution vs. EXPLAIN ANALYZE

From: Marko Tiikkaja <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: David Fetter <david(at)fetter(dot)org>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Rewrite, normal execution vs. EXPLAIN ANALYZE
Date: 2010-07-23 19:06:09
Message-ID: 4C49E821.8060206@cs.helsinki.fi (view raw or flat)
Thread:
Lists: pgsql-hackers
On 7/23/2010 10:00 PM, Robert Haas wrote:
> On Fri, Jul 23, 2010 at 2:13 PM, Marko Tiikkaja
> <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi>  wrote:
>> Currently, I'm trying to make wCTEs behave a bit like RULEs do.  But if
>> every rewrite product takes a new snapshot, wCTEs will behave very
>> unpredictably.
>>
>> But because EXPLAIN ANALYZE does *not* take a new snapshot for every rewrite
>> product, I'm starting to think that maybe this isn't the behaviour we wanted
>> to begin with?
>
> Where should I be looking in the code for this?

ProcessQuery() and ExplainOnePlan().  ProcessQuery calls 
PushActiveSnapshot(GetTransactionSnapshot()) for every statement while 
ExplainOnePlan calls PushUpdatedSnapshot(GetActiveSnapshot()).


Regards,
Marko Tiikkaja

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