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From: Craig Milhiser <[email protected]>
To: [email protected]
Subject: Is index deduplication active on an index
Date: Fri, 23 Aug 2024 15:24:50 -0400
Message-ID: <CA+wnhO2gfnajw+3sFWC70obWw8xV+qKAmPwmERukM93C4dFVEw@mail.gmail.com> (raw)

Is there a way I can determine if index deduplication is active on the
indexes?

I inherited a database that has been upgraded from v12 to 13 to 16. I
checked the upgrade scripts used and there was not a reindex run during the
upgrades. Someone may have run a reindex over the years.

Then I can reindex if needed those indexes created prior to v13.

I looked in pg_index but I did not find a field. Perhaps it is in a flag in
indoption but I did not see that in the definition in
src/include/catalog/pg_index.h. I see the allequalimage flag to protect the
conditions described in the documentation. But I do not know if that flag
is reused to signify this index has been evaluated for deduplication due to
a reindex and it is safe. A comment in _bt_allequalimage in
src/backend/access/nbtree/nbtutils.c says the flag is stored in the index
meta page. Is there a way to find index deduplication is active for an
index from a postgresql client?

Thanks

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