Re: Why vacuum_index_cleanup is needed for TOAST relations?
От | Tomas Vondra |
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Тема | Re: Why vacuum_index_cleanup is needed for TOAST relations? |
Дата | |
Msg-id | 20190705141545.iyg47wbwgmo6ewqv@development обсуждение исходный текст |
Ответ на | Why vacuum_index_cleanup is needed for TOAST relations? (Nikolay Shaplov <dhyan@nataraj.su>) |
Список | pgsql-hackers |
On Fri, Jul 05, 2019 at 03:28:26PM +0300, Nikolay Shaplov wrote: >I am importing recent changes into my reloption patch and came to a question, >I did not find an answer... > >vacuum_index_cleanup option exists for both heap and toast relations. > >As I understand from documentation index cleanup is about is about reporting >access method that some tuples in table that were indexed are dead, and should >be cleaned. > >And as far as I get, we do not index any TOAST tuples directly. They are >obtained by getting relation tuple, and then deTOAST it. > >So I do not understand why do we need vacuum_index_cleanup for TOAST tables. >May be we should remove it from there?? > >Or if I am wrong, can you explain where it is needed? > I'm not sure I understand your question / suggestion correctly, but each TOAST table certainly has an index on (chunk_id, chunk_seq) - in fact it's a unique index backing a primary key. It's not clear to me what you mean by "index any TOAST tuples directly" or "getting relation tuple", perhaps you could explain. IMHO it's correct to have vacuum_index_cleanup even for TOAST tables. regards -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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