pgsql: Round rowcount estimate for a partial path to an integer.

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From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: pgsql-committers(at)postgresql(dot)org
Subject: pgsql: Round rowcount estimate for a partial path to an integer.
Date: 2016-07-03 18:54:04
Message-ID: [email protected]
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Round rowcount estimate for a partial path to an integer.

I'd been wondering why I was sometimes seeing fractional rowcount
estimates in parallel-query situations, and this seems to be the
reason. (You won't see the fractional parts in EXPLAIN, because it
prints rowcounts with %.0f, but they are apparent in the debugger.)
A fractional rowcount is not any saner for a partial path than any
other kind of path, and it's equally likely to break cost estimation
for higher paths, so apply clamp_row_est() like we do in other places.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/c89d507649df9fbc21617e02ab4d5e765a28b7df

Modified Files
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src/backend/optimizer/path/costsize.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)