| From: | Konstantin Knizhnik <knizhnik(at)garret(dot)ru> |
|---|---|
| To: | pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Sync scan & regression tests |
| Date: | 2023-08-06 19:20:57 |
| Message-ID: | 6e6b91a6-afc5-d446-7e4a-2716860dd10e@garret.ru |
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| Thread: | |
| Lists: | pgsql-hackers |
Hi hackers,
Is it is ok, that regression tests do not pass with small value of
shared buffers (for example 1Mb)?
Two tests are failed because of sync scan - this tests cluster.sql and
portals.sql perform seqscan without explicit order by and expect that
data will be returned in particular order. But because of sync scan it
doesn't happen. Small shared buffers are needed to satisfy seqscan
criteria in heapam.c: `scan->rs_nblocks > NBuffers / 4` for tenk1 table.
More general question - is it really good that in situation when there
is actually no concurrent queries, seqscan is started not from the first
page?
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