Re: [PoC] Improve dead tuple storage for lazy vacuum - Mailing list pgsql-hackers

From Dilip Kumar
Subject Re: [PoC] Improve dead tuple storage for lazy vacuum
Date
Msg-id CAFiTN-tEqP3eWyK5F8CfQr-FeiCVuoFu3Jd8OGetgdWQE75zrg@mail.gmail.com
Whole thread Raw
In response to Re: [PoC] Improve dead tuple storage for lazy vacuum  (John Naylor <john.naylor@enterprisedb.com>)
Responses Re: [PoC] Improve dead tuple storage for lazy vacuum
List 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



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