Simon Riggs wrote:
On Sat, 2007-03-10 at 07:59 +0000, Simon Riggs wrote:
On Fri, 2007-03-09 at 18:05 -0500, Tom Lane wrote:
"Simon Riggs" <[EMAIL PROTECTED]> writes:
On Fri, 2007-03-09 at 16:45 -0500, Tom Lane wrote:
We do that anyway; but certainly Simon's patch ought not be injecting
an additional one.
It should be possible to pass that down from the planner to the
executor, in certain cases.
Huh? See HeapScanDesc->rs_nblocks.
Many thanks.
New patch enclosed, implementation as you've requested.
Not ready to apply yet, but good for testing.
A quick test using the setup for "Buffer cache is not scan resistant"
thread:
Firstly vanilla 8.3 from 20070310:
Shared Buffers Elapsed vmstat IO rate
-------------- ------- --------------
400MB 101 s 122 MB/s
128KB 79 s 155 MB/s [1]
Now apply cycle scan v2:
Shared Buffers Scan_recycle_buffers Elapsed vmstat IO rate
-------------- -------------------- ------- -------------
400MB 0 101 s 122 MB/s
400MB 8 78 s 155 MB/s
400MB 16 77 s 155 MB/s
400MB 32 78 s 155 MB/s
400MB 64 82 s 148 MB/s
400MB 128 93 s 128 MB/s
Certainly seems to have the desired effect!
Cheers
Mark
[1] I'm not seeing 166 MB/s like previous 8.2.3 data, however 8.3 PGDATA
is located further toward the end of the disk array - which I suspect is
limiting the IO rate a little.
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