| From: | Sergei Kornilov <sk(at)zsrv(dot)org> |
|---|---|
| To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Masahiko Sawada <masahiko(dot)sawada(at)2ndquadrant(dot)com> |
| Cc: | Mahendra Singh Thalor <mahi6run(at)gmail(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Amit Langote <langote_amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, David Steele <david(at)pgmasters(dot)net>, Claudio Freire <klaussfreire(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] Block level parallel vacuum |
| Date: | 2020-01-09 12:01:44 |
| Message-ID: | 12150251578571304@myt4-a1257bff88cb.qloud-c.yandex.net |
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| Lists: | pgsql-hackers |
Hello
I noticed that parallel vacuum uses min_parallel_index_scan_size GUC to skip small indexes but this is not mentioned in documentation for both vacuum command and GUC itself.
+ /* Determine the number of parallel workers to launch */
+ if (lps->lvshared->for_cleanup)
+ {
+ if (lps->lvshared->first_time)
+ nworkers = lps->nindexes_parallel_cleanup +
+ lps->nindexes_parallel_condcleanup - 1;
+ else
+ nworkers = lps->nindexes_parallel_cleanup - 1;
+
+ }
+ else
+ nworkers = lps->nindexes_parallel_bulkdel - 1;
(lazy_parallel_vacuum_indexes)
Perhaps we need to add a comment for future readers, why we reduce the number of workers by 1. Maybe this would be cleaner?
+ /* Determine the number of parallel workers to launch */
+ if (lps->lvshared->for_cleanup)
+ {
+ if (lps->lvshared->first_time)
+ nworkers = lps->nindexes_parallel_cleanup +
+ lps->nindexes_parallel_condcleanup;
+ else
+ nworkers = lps->nindexes_parallel_cleanup;
+
+ }
+ else
+ nworkers = lps->nindexes_parallel_bulkdel;
+
+ /* The leader process will participate */
+ nworkers--;
I have no more comments after reading the patches.
regards, Sergei
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