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commit    fbe4cb3bd49f9e524f53ef77c775c1bad4d0312a
Author:   Peter Geoghegan <pg@bowt.ie>
Date:     Tue Mar 16 20:38:52 2021 +0000
First released in: 14.0

    Fix comment about promising tuples.
    
    Oversight in commit d168b666823, which added bottom-up index deletion.


 src/backend/access/heap/heapam.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 3b435c107d0..7cb87f4a3b3 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -7879,8 +7879,10 @@ bottomup_sort_and_shrink(TM_IndexDeleteOp *delstate)
 	/*
 	 * We're about ready to sort block groups to determine the optimal order
 	 * for visiting heap blocks.  But before we do, round the number of
-	 * promising tuples for each block group up to the nearest power-of-two
-	 * (except for block groups where npromisingtids is already 0).
+	 * promising tuples for each block group up to the next power-of-two,
+	 * unless it is very low (less than 4), in which case we round up to 4.
+	 * npromisingtids is far too noisy to trust when choosing between a pair
+	 * of block groups that both have very low values.
 	 *
 	 * This scheme divides heap blocks/block groups into buckets.  Each bucket
 	 * contains blocks that have _approximately_ the same number of promising


[parent: 65445469d6de]