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

Attachment: 0001-Don-t-count-EOF-as-a-temporary-buffer-read-in-EXPLAI.patch
Description: Binary data

Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:

Reply via email to