Horton

Re: [PoC] Improve dead tuple storage for lazy vacuum

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: John Naylor <john.naylor@enterprisedb.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, Nathan Bossart <nathandbossart@gmail.com>, Andres Freund <andres@anarazel.de>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Yura Sokolov <y.sokolov@postgrespro.ru>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2023-01-24T06:17:13Z
Lists: pgsql-hackers 
On Mon, Jan 23, 2023 at 6:00 PM John Naylor
<john.naylor@enterprisedb.com> wrote:
>
> Attached is a rebase to fix conflicts from recent commits.

I have reviewed v22-0022* patch and I have some comments.

1.
>It also changes to the column names max_dead_tuples and num_dead_tuples and to
>show the progress information in bytes.

I think this statement needs to be rephrased.

2.

/*
 *    vac_tid_reaped() -- is a particular tid deletable?
 *
 *        This has the right signature to be an IndexBulkDeleteCallback.
 *
 *        Assumes dead_items array is sorted (in ascending TID order).
 */

I think this comment 'Assumes dead_items array is sorted' is not valid anymore.

3.

We are changing the min value of 'maintenance_work_mem' to 2MB. Should
we do the same for the 'autovacuum_work_mem'?

4.
+
+    /* collected LP_DEAD items including existing LP_DEAD items */
+    int            lpdead_items;
+    OffsetNumber    deadoffsets[MaxHeapTuplesPerPage];

We are actually collecting dead offsets but the variable name says
'lpdead_items' instead of something like ndeadoffsets num_deadoffsets.
And the comment is also saying dead items.

5.
/*
 *    lazy_vacuum_heap_page() -- free page's LP_DEAD items listed in the
 *                          vacrel->dead_items array.
 *
 * Caller must have an exclusive buffer lock on the buffer (though a full
 * cleanup lock is also acceptable).  vmbuffer must be valid and already have
 * a pin on blkno's visibility map page.
 *
 * index is an offset into the vacrel->dead_items array for the first listed
 * LP_DEAD item on the page.  The return value is the first index immediately
 * after all LP_DEAD items for the same page in the array.
 */

This comment needs to be changed as this is referring to the
'vacrel->dead_items array' which no longer exists.

-- 
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com

Commits

  1. radixtree: Fix SIGSEGV at update of embeddable value to non-embeddable.

  2. Get rid of anonymous struct

  3. Teach radix tree to embed values at runtime

  4. Teach TID store to skip bitmap for small numbers of offsets

  5. Use bump context for TID bitmaps stored by vacuum

  6. Fix alignment of stack variable

  7. Use TidStore for dead tuple TIDs storage during lazy vacuum.

  8. Rethink create and attach APIs of shared TidStore.

  9. Fix inconsistent function prototypes with function definitions.

  10. Fix a calculation in TidStoreCreate().

  11. Fix potential integer handling issue in radixtree.h.

  12. Add TIDStore, to store sets of TIDs (ItemPointerData) efficiently.

  13. Fix link error for test_radixtree module on Windows

  14. Blind attempt to fix ODR violations

  15. Fix incorrect format specifier for int64

  16. Fix redefinition of typedefs

  17. Add template for adaptive radix tree

  18. Fix signedness error in 9f225e992 for gcc

  19. Introduce helper SIMD functions for small byte arrays

  20. Optimize vacuuming of relations with no indexes.

  21. Add bound check before bsearch() for performance

  22. Allocate consecutive blocks during parallel seqscans