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pgsql: Insert CHECK_FOR_INTERRUPTS() calls into btree and hash index

From: tgl(at)postgresql(dot)org (Tom Lane)
To: pgsql-committers(at)postgresql(dot)org
Subject: pgsql: Insert CHECK_FOR_INTERRUPTS() calls into btree and hash index
Date: 2009-05-05 19:36:32
Message-ID: (view raw or whole thread)
Lists: pgsql-committers
Log Message:
Insert CHECK_FOR_INTERRUPTS() calls into btree and hash index scans at the
points where we step right or left to the next page.  This should ensure
reasonable response time to a query cancel request during an unsuccessful
index scan, as seen in recent gripe from Marc Cousin.  It's a bit trickier
than it might seem at first glance, because CHECK_FOR_INTERRUPTS() is a no-op
if executed while holding a buffer lock.  So we have to do it just at the
point where we've dropped one page lock and not yet acquired the next.

Remove CHECK_FOR_INTERRUPTS calls at the top level of btgetbitmap and
hashgetbitmap, since they're pointless given the added checks.

I think that GIST is okay already --- at least, there's a CHECK_FOR_INTERRUPTS
at a plausible-looking place in gistnext().  I don't claim to know GIN well
enough to try to poke it for this, if indeed it has a problem at all.

This is a pre-existing issue, but in view of the lack of prior complaints
I'm not going to risk back-patching.

Modified Files:
        hash.c (r1.109 -> r1.110)
        hashsearch.c (r1.55 -> r1.56)
        nbtree.c (r1.168 -> r1.169)
        nbtsearch.c (r1.119 -> r1.120)

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Subject: pgsql: Install a "dead man switch" to allow the postmaster to detect
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