| 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 <mahi6run(at)gmail(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, Robert Haas <robertmhaas(at)gmail(dot)com>, 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: | 2019-11-30 13:48:11 |
| Message-ID: | 1194051575121691@vla5-4a37cde0b550.qloud-c.yandex.net |
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| Lists: | pgsql-hackers |
Hello
Its possible to change order of index processing by parallel leader? In v35 patchset I see following order:
- start parallel processes
- leader and parallel workers processed index lixt and possible skip some entries
- after that parallel leader recheck index list and process the skipped indexes
- WaitForParallelWorkersToFinish
I think it would be better to:
- start parallel processes
- parallel leader goes through index list and process only indexes which are skip_parallel_index_vacuum = true
- parallel workers processes indexes with skip_parallel_index_vacuum = false
- parallel leader start participate with remainings parallel-safe index processing
- WaitForParallelWorkersToFinish
This would be less running time and better load balance across leader and workers in case of few non-parallel and few parallel indexes.
(if this is expected and required by some reason, we need a comment in code)
Also few notes to vacuumdb:
Seems we need version check at least in vacuum_one_database and prepare_vacuum_command. Similar to SKIP_LOCKED or DISABLE_PAGE_SKIPPING features.
discussion question: difference between --parallel and --jobs parameters will be confusing? We need more description for this options?
regards, Sergei
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