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doc: clarify the effect of concurrent work_mem allocations

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Reported-by: Sami Imseih

Discussion: https://postgr.es/m/66590882-F48C-4A25-83E3-73792CF8C51F@amazon.com

Backpatch-through: 11
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Bruce Momjian 2023-09-26 19:44:21 -04:00
parent ba0eb75dac
commit a4a8c0de2b
1 changed files with 4 additions and 3 deletions
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doc/src/sgml/config.sgml
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@ -1582,9 +1582,10 @@ include_dir 'conf.d'
Specifies the amount of memory to be used by internal sort operations Specifies the amount of memory to be used by internal sort operations
and hash tables before writing to temporary disk files. The value and hash tables before writing to temporary disk files. The value
defaults to four megabytes (<literal>4MB</literal>). defaults to four megabytes (<literal>4MB</literal>).
Note that for a complex query, several sort or hash operations might be Note that a complex query might perform several sort and hash
running in parallel; each operation will be allowed to use as much memory operations at the same time, with each operation generally being
as this value specifies before it starts to write data into temporary allowed to use as much memory as this value specifies before it
starts to write data into temporary
files. Also, several running sessions could be doing such operations files. Also, several running sessions could be doing such operations
concurrently. Therefore, the total memory used could be many concurrently. Therefore, the total memory used could be many
times the value of <varname>work_mem</varname>; it is necessary to times the value of <varname>work_mem</varname>; it is necessary to