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Commite19594c

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Reduce the default value of vacuum_cost_page_miss.
When commitf425b60 introduced cost based vacuum delays back in 2004,the defaults reflected then-current trends in hardware, as well ascertain historical limitations in PostgreSQL. There have been enormousimprovements in both areas since that time. The cost limit GUC defaultsfinally became much more representative of current trends followingcommitcbccac3, which decreased autovacuum_vacuum_cost_delay's defaultby 10x for PostgreSQL 12 (it went from 20ms to only 2ms).The relative costs have shifted too. This should also be accounted forby the defaults. More specifically, the relative importance of avoidingdirtying pages within VACUUM has greatly increased, primarily due tomain memory capacity scaling and trends in flash storage. WithinPostgres itself, improvements like sequential access during indexvacuuming (at least in nbtree and GiST indexes) have also beencontributing factors.To reflect all this, decrease the default of vacuum_cost_page_miss to 2.Since the default of vacuum_cost_page_dirty remains 20, dirtying a pageis now considered 10x "costlier" than a page miss by default.Author: Peter Geoghegan <pg@bowt.ie>Discussion:https://postgr.es/m/CAH2-WzmLPFnkWT8xMjmcsm7YS3+_Qi3iRWAb2+_Bc8UhVyHfuA@mail.gmail.com
1 parent69059d3 commite19594c

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4 files changed

+4
-4
lines changed

4 files changed

+4
-4
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‎doc/src/sgml/config.sgml

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@@ -2116,7 +2116,7 @@ include_dir 'conf.d'
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The estimated cost for vacuuming a buffer that has to be read from
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disk. This represents the effort to lock the buffer pool,
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lookup the shared hash table, read the desired block in from
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the disk and scan its content. The default value is10.
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the disk and scan its content. The default value is2.
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</para>
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</listitem>
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</varlistentry>

‎src/backend/utils/init/globals.c

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@@ -137,7 +137,7 @@ intmax_parallel_workers = 8;
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intMaxBackends=0;
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intVacuumCostPageHit=1;/* GUC parameters for vacuum */
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intVacuumCostPageMiss=10;
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intVacuumCostPageMiss=2;
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intVacuumCostPageDirty=20;
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intVacuumCostLimit=200;
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doubleVacuumCostDelay=0;

‎src/backend/utils/misc/guc.c

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@@ -2413,7 +2413,7 @@ static struct config_int ConfigureNamesInt[] =
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NULL
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},
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&VacuumCostPageMiss,
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10,0,10000,
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2,0,10000,
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NULL,NULL,NULL
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},
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‎src/backend/utils/misc/postgresql.conf.sample

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@@ -164,7 +164,7 @@
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#vacuum_cost_delay = 0# 0-100 milliseconds (0 disables)
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#vacuum_cost_page_hit = 1# 0-10000 credits
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#vacuum_cost_page_miss =10# 0-10000 credits
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#vacuum_cost_page_miss =2# 0-10000 credits
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#vacuum_cost_page_dirty = 20# 0-10000 credits
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#vacuum_cost_limit = 200# 1-10000 credits
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