Introduce autovacuum_vacuum_max_threshold.

One way autovacuum chooses tables to vacuum is by comparing the
number of updated or deleted tuples with a value calculated using
autovacuum_vacuum_threshold and autovacuum_vacuum_scale_factor.
The threshold specifies the base value for comparison, and the
scale factor specifies the fraction of the table size to add to it.
This strategy ensures that smaller tables are vacuumed after fewer
updates/deletes than larger tables, which is reasonable in many
cases but can result in infrequent vacuums on very large tables.
This is undesirable for a couple of reasons, such as very large
tables incurring a huge amount of bloat between vacuums.

This new parameter provides a way to set a limit on the value
calculated with autovacuum_vacuum_threshold and
autovacuum_vacuum_scale_factor so that very large tables are
vacuumed more frequently.  By default, it is set to 100,000,000
tuples, but it can be disabled by setting it to -1.  It can also be
adjusted for individual tables by changing storage parameters.

Author: Nathan Bossart <[email protected]>
Co-authored-by: Frédéric Yhuel <[email protected]>
Reviewed-by: Melanie Plageman <[email protected]>
Reviewed-by: Robert Haas <[email protected]>
Reviewed-by: Laurenz Albe <[email protected]>
Reviewed-by: Michael Banck <[email protected]>
Reviewed-by: Joe Conway <[email protected]>
Reviewed-by: Sami Imseih <[email protected]>
Reviewed-by: David Rowley <[email protected]>
Reviewed-by: wenhui qiu <[email protected]>
Reviewed-by: Vinícius Abrahão <[email protected]>
Reviewed-by: Robert Treat <[email protected]>
Reviewed-by: Alena Rybakina <[email protected]>
Discussion: https://postgr.es/m/956435f8-3b2f-47a6-8756-8c54ded61802%40dalibo.com

1 files changed, 12 insertions, 0 deletions

diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 0ab921a169b..09ec9bb6990 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -120,6 +120,7 @@ int			autovacuum_max_workers;
 int			autovacuum_work_mem = -1;
 int			autovacuum_naptime;
 int			autovacuum_vac_thresh;
+int			autovacuum_vac_max_thresh;
 double		autovacuum_vac_scale;
 int			autovacuum_vac_ins_thresh;
 double		autovacuum_vac_ins_scale;
@@ -2895,6 +2896,8 @@ recheck_relation_needs_vacanalyze(Oid relid,
  * threshold.  This threshold is calculated as
  *
  * threshold = vac_base_thresh + vac_scale_factor * reltuples
+ * if (threshold > vac_max_thresh)
+ *     threshold = vac_max_thresh;
  *
  * For analyze, the analysis done is that the number of tuples inserted,
  * deleted and updated since the last analyze exceeds a threshold calculated
@@ -2933,6 +2936,7 @@ relation_needs_vacanalyze(Oid relid,
 
 	/* constants from reloptions or GUC variables */
 	int			vac_base_thresh,
+				vac_max_thresh,
 				vac_ins_base_thresh,
 				anl_base_thresh;
 	float4		vac_scale_factor,
@@ -2974,6 +2978,11 @@ relation_needs_vacanalyze(Oid relid,
 		? relopts->vacuum_threshold
 		: autovacuum_vac_thresh;
 
+	/* -1 is used to disable max threshold */
+	vac_max_thresh = (relopts && relopts->vacuum_max_threshold >= -1)
+		? relopts->vacuum_max_threshold
+		: autovacuum_vac_max_thresh;
+
 	vac_ins_scale_factor = (relopts && relopts->vacuum_ins_scale_factor >= 0)
 		? relopts->vacuum_ins_scale_factor
 		: autovacuum_vac_ins_scale;
@@ -3047,6 +3056,9 @@ relation_needs_vacanalyze(Oid relid,
 			reltuples = 0;
 
 		vacthresh = (float4) vac_base_thresh + vac_scale_factor * reltuples;
+		if (vac_max_thresh >= 0 && vacthresh > (float4) vac_max_thresh)
+			vacthresh = (float4) vac_max_thresh;
+
 		vacinsthresh = (float4) vac_ins_base_thresh + vac_ins_scale_factor * reltuples;
 		anlthresh = (float4) anl_base_thresh + anl_scale_factor * reltuples;