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commit    001a537b83ec6e2ab8fa8af44458b0502c94dd5e
Author:   Michael Paquier <michael@paquier.xyz>
Date:     Mon Dec 09 05:35:39 2024 +0000

    Improve comment about dropped entries in pgstat.c
    
    pgstat_write_statsfile() discards any entries marked as dropped from
    being written to the stats file at shutdown, and also included an
    assertion based on the same condition.
    
    The intention of the assertion is to track that no pgstats entries
    should be left around as terminating backends should drop any entries
    they still hold references on before the stats file is written by the
    checkpointer, and it not worth taking down the server in this case if
    there is a bug making that possible.
    
    Let's improve the comment of this area to document clearly what's
    intended.
    
    Based on a discussion with Bertrand Drouvot and Anton A. Melnikov.
    
    Author: Bertrand Drouvot
    Discussion: https://postgr.es/m/a13e8cdf-b97a-4ecb-8f42-aaa367974e29@postgrespro.ru
    Backpatch-through: 15


 src/backend/utils/activity/pgstat.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c
index 6f8d2378266..18b7d9b47d6 100644
--- a/src/backend/utils/activity/pgstat.c
+++ b/src/backend/utils/activity/pgstat.c
@@ -1655,7 +1655,15 @@ pgstat_write_statsfile(XLogRecPtr redo)
 
 		CHECK_FOR_INTERRUPTS();
 
-		/* we may have some "dropped" entries not yet removed, skip them */
+		/*
+		 * We should not see any "dropped" entries when writing the stats
+		 * file, as all backends and auxiliary processes should have cleaned
+		 * up their references before they terminated.
+		 *
+		 * However, since we are already shutting down, it is not worth
+		 * crashing the server over any potential cleanup issues, so we simply
+		 * skip such entries if encountered.
+		 */
 		Assert(!ps->dropped);
 		if (ps->dropped)
 			continue;


[parent: 2d0152d6147b]