Comment in src/backend/commands/vacuumlazy.c

On Mon, Mar 24, 2014 at 12:28 AM, Amit Langote <amitlangote09@gmail.com> wrote:

Hi,

Note the following comment in src/backend/commands/vacuumlazy.c:lazy_scan_heap()

1088 /* If no indexes, make log report that lazy_vacuum_heap
would've made */
1089 if (vacuumed_pages)
1090 ereport(elevel,

Just wondering if it would read better as:

1088 /* Make the log report that lazy_vacuum_heap would've made
had there been no indexes */

Is that correct?

No. Your rewrite means the opposite of what the comment means now.
vacuumed_pages will be non-zero only if the relation does NOT have
indexes.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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On Mon, Mar 31, 2014 at 11:44 PM, Robert Haas <robertmhaas@gmail.com> wrote:

On Mon, Mar 24, 2014 at 12:28 AM, Amit Langote <amitlangote09@gmail.com> wrote:

Hi,

Note the following comment in src/backend/commands/vacuumlazy.c:lazy_scan_heap()

1088 /* If no indexes, make log report that lazy_vacuum_heap
would've made */
1089 if (vacuumed_pages)
1090 ereport(elevel,

Just wondering if it would read better as:

1088 /* Make the log report that lazy_vacuum_heap would've made
had there been no indexes */

Is that correct?

No. Your rewrite means the opposite of what the comment means now.
vacuumed_pages will be non-zero only if the relation does NOT have
indexes.

You are correct. It does sound opposite of what is actually happening:

Somewhere in c:lazy_scan_heap(),

941 /*
942 * If there are no indexes then we can vacuum the page right now
943 * instead of doing a second scan.
944 */
945 if (nindexes == 0 &&
946 vacrelstats->num_dead_tuples > 0)
947 {
948 /* Remove tuples from heap */
949 lazy_vacuum_page(onerel, blkno, buf, 0, vacrelstats, &vmbuffer);
950 has_dead_tuples = false;
951
952 /*
953 * Forget the now-vacuumed tuples, and press on, but be careful
954 * not to reset latestRemovedXid since we want that value to be
955 * valid.
956 */
957 vacrelstats->num_dead_tuples = 0;
958 vacuumed_pages++;
959 }

Sorry about the noise.

--
Amit

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