Re: sqlsmith crash incremental sort
Tom Lane <tgl@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: James Coleman <jtc331@gmail.com>, Justin Pryzby <pryzby@telsasoft.com>,
pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2020-04-17T01:26:40Z
Lists: pgsql-hackers
Tomas Vondra <tomas.vondra@2ndquadrant.com> writes: > I think we have essentially three options: > 1) assuming there's just a single group > 2) assuming each row is a separate group > 3) something in between > If (1) and (2) are worst/best-case scenarios, maybe we should pick > something in between. We have DEFAULT_NUM_DISTINCT (200) which > essentially says "we don't know what the number of groups is" so maybe > we should use that. I wouldn't recommend picking either the best or worst cases. Possibly DEFAULT_NUM_DISTINCT is a sane choice, though it's fair to wonder if it's quite applicable to the case where we already know we've grouped by some columns. regards, tom lane
Commits
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Simplify cost_incremental_sort a bit
- 60fbb4d76250 13.0 landed
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Fix cost_incremental_sort for expressions with varno 0
- de0dc1a84710 13.0 landed