postgres.git / summary / log / commit / refs

commit    530050d8d2850d0453bb56e2bfa7cae216ee8a18
Author:   David Rowley <drowley@postgresql.org>
Date:     Thu Apr 10 23:36:21 2025 +0000
First released in: 18.0

    Add code comment explaining ins_since_vacuum and aborted inserts
    
    Sami complained that there's a discrepancy between n_mod_since_analyze
    and n_ins_since_vacuum, as the former only accounts for committed changes
    and the latter tracks committed and aborted inserts.  Nobody seemed
    overly concerned that this would cause any concerning issues.  The
    repercussions, from what I can tell, are limited to causing an
    autovacuum to trigger for inserts sooner than it otherwise might. For
    typical ratios of commits to aborts, it's unlikely to ever be noticed.
    
    Fixing things to make it so n_ins_since_vacuum only displays committed
    inserts would require an additional field in PgStat_TableCounts, which
    does not quite seem worthwhile at this stage.  This commit just adds a
    comment with some details to mention that we know about it, which will
    hopefully prevent repeat discussions.
    
    Reported-by: Sami Imseih <samimseih@gmail.com>
    Author: David Rowley <drowleyml@gmail.com>
    Reviewed-by: Sami Imseih <samimseih@gmail.com>
    Discussion: https://postgr.es/m/CAApHDvpgV3a-R2EGmPOh0L-x3pHbZpM3y4dySWfy+UqUazwDQA@mail.gmail.com


 src/backend/utils/activity/pgstat_relation.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/backend/utils/activity/pgstat_relation.c b/src/backend/utils/activity/pgstat_relation.c
index d64595a165c..eeb2d43cb10 100644
--- a/src/backend/utils/activity/pgstat_relation.c
+++ b/src/backend/utils/activity/pgstat_relation.c
@@ -868,7 +868,16 @@ pgstat_relation_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
 	tabentry->live_tuples += lstats->counts.delta_live_tuples;
 	tabentry->dead_tuples += lstats->counts.delta_dead_tuples;
 	tabentry->mod_since_analyze += lstats->counts.changed_tuples;
+
+	/*
+	 * Using tuples_inserted to update ins_since_vacuum does mean that we'll
+	 * track aborted inserts too.  This isn't ideal, but otherwise probably
+	 * not worth adding an extra field for.  It may just amount to autovacuums
+	 * triggering for inserts more often than they maybe should, which is
+	 * probably not going to be common enough to be too concerned about here.
+	 */
 	tabentry->ins_since_vacuum += lstats->counts.tuples_inserted;
+
 	tabentry->blocks_fetched += lstats->counts.blocks_fetched;
 	tabentry->blocks_hit += lstats->counts.blocks_hit;
 


[parent: 39729ec01d25]