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Round rowcount estimate for a partial path to an integer.

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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.
This commit is contained in:
Tom Lane 2016-07-03 14:53:37 -04:00
parent 3a4a33ad49
commit c89d507649
1 changed files with 1 additions and 1 deletions
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src/backend/optimizer/path/costsize.c
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@ -263,7 +263,7 @@ cost_seqscan(Path *path, PlannerInfo *root,
* because they'll anticipate receiving more rows than any given copy
* will actually get.
*/
path->rows /= parallel_divisor;
path->rows = clamp_row_est(path->rows / parallel_divisor);
/* The CPU cost is divided among all the workers. */
cpu_run_cost /= parallel_divisor;