Hi hackers,
Vik Fearing asked off-list why hash joins appear to read slightly more
temporary data than they write. The reason is that we notch up a
phantom block read when we hit the end of each file. Harmless but it
looks a bit weird and it's easily fixed.
Unpatched, a 16 batch hash join reports that we read 30 more blocks
than we wrote (2 per batch after the first, as expected):
Buffers: shared hit=434 read=16234, temp read=5532 written=5502
With the attached patch:
Buffers: shared hit=547 read=16121, temp read=5502 written=5502
--
Thomas Munro
http://www.enterprisedb.com
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