Horton

Re: GiST VACUUM

x4mmm@yandex-team.ru

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From: Andrey Borodin <x4mmm@yandex-team.ru>
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Michael Paquier <michael@paquier.xyz>, Thomas Munro <thomas.munro@enterprisedb.com>, Robert Haas <robertmhaas@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, Костя Кузнецов <chapaev28@ya.ru>
Date: 2019-03-24T16:50:41Z
Lists: pgsql-hackers 

> 22 марта 2019 г., в 17:03, Heikki Linnakangas <hlinnaka@iki.fi> написал(а):
> 

I was working on new version of gist check in amcheck and understand one more thing:

/* Can this page be recycled yet? */
bool
gistPageRecyclable(Page page)
{
    return PageIsNew(page) ||
        (GistPageIsDeleted(page) &&
         TransactionIdPrecedes(GistPageGetDeleteXid(page), RecentGlobalXmin));
}

Here RecentGlobalXmin can wraparound and page will become unrecyclable for half of xid cycle. Can we prevent it by resetting PageDeleteXid to InvalidTransactionId before doing RecordFreeIndexPage()?
(Seems like same applies to GIN...)

Best regards, Andrey Borodin.

Commits

  1. Use full 64-bit XID for checking if a deleted GiST page is old enough.

  2. Refactor checks for deleted GiST pages.

  3. Delete empty pages during GiST VACUUM.

  4. Scan GiST indexes in physical order during VACUUM.

  5. Prevent GIN deleted pages from being reclaimed too early