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Chapter 14.1.1, small typo on costs? 2+ messages / 2 participants [nested] [flat]
* Chapter 14.1.1, small typo on costs? @ 2020-10-25 11:07 PG Doc comments form <noreply@postgresql.org> 2020-10-25 19:16 ` Re: Chapter 14.1.1, small typo on costs? Tom Lane <tgl@sss.pgh.pa.us> 0 siblings, 1 reply; 2+ messages in thread From: PG Doc comments form @ 2020-10-25 11:07 UTC (permalink / raw) To: pgsql-docs@lists.postgresql.org; +Cc: github@jurr.org The following documentation comment has been logged on the website: Page: https://www.postgresql.org/docs/13/using-explain.html Description: I am reading 14.1.1 and at the very end (just before 14.1.2) I see: "which shows that the planner thinks that sorting onek by index-scanning is about 12% more expensive than sequential-scan-and-sort." I feel that 12% is incorrect, but I'm not quite sure. The costs are 268.19 and 292.65, and that's about 9% more expensive? I'm not entirely sure though; just reading up on explain plans :) With kind regards, Jurrie ^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: Chapter 14.1.1, small typo on costs? 2020-10-25 11:07 Chapter 14.1.1, small typo on costs? PG Doc comments form <noreply@postgresql.org> @ 2020-10-25 19:16 ` Tom Lane <tgl@sss.pgh.pa.us> 0 siblings, 0 replies; 2+ messages in thread From: Tom Lane @ 2020-10-25 19:16 UTC (permalink / raw) To: github@jurr.org; +Cc: pgsql-docs@lists.postgresql.org PG Doc comments form <noreply@postgresql.org> writes: > I am reading 14.1.1 and at the very end (just before 14.1.2) I see: > "which shows that the planner thinks that sorting onek by index-scanning is > about 12% more expensive than sequential-scan-and-sort." > I feel that 12% is incorrect, but I'm not quite sure. The costs are 268.19 > and 292.65, and that's about 9% more expensive? No, the comparison this has in mind is 224.79 (the indexscan on onek in the last plan) versus 200.33 (the sort on onek in the previous plan). So 12% is about right. regards, tom lane ^ permalink raw reply [nested|flat] 2+ messages in thread
end of thread, other threads:[~2020-10-25 19:16 UTC | newest] Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2020-10-25 11:07 Chapter 14.1.1, small typo on costs? PG Doc comments form <noreply@postgresql.org> 2020-10-25 19:16 ` Tom Lane <tgl@sss.pgh.pa.us>
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