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| author | Bruce Momjian <bruce@momjian.us> | 2023-09-26 19:44:22 -0400 |
|---|---|---|
| committer | Bruce Momjian <bruce@momjian.us> | 2023-09-26 19:44:22 -0400 |
| commit | 2ef5c5e736b8b13d777d5ecc66099a785ca108ad (patch) | |
| tree | fdc778de73ff41007cedce66b1a7587aba174244 | |
| parent | 430f4497b02f3536b190cf5dca5da564eea151f4 (diff) | |
| download | postgresql-2ef5c5e736b8b13d777d5ecc66099a785ca108ad.tar.gz postgresql-2ef5c5e736b8b13d777d5ecc66099a785ca108ad.zip | |
doc: clarify the effect of concurrent work_mem allocations
Reported-by: Sami Imseih
Discussion: https://postgr.es/m/66590882-F48C-4A25-83E3-73792CF8C51F@amazon.com
Backpatch-through: 11
| -rw-r--r-- | doc/src/sgml/config.sgml | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 431701d2ecf..4647539e403 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -1884,9 +1884,10 @@ include_dir 'conf.d' (such as a sort or hash table) before writing to temporary disk files. If this value is specified without units, it is taken as kilobytes. The default value is four megabytes (<literal>4MB</literal>). - Note that for a complex query, several sort or hash operations might be - running in parallel; each operation will generally be allowed - to use as much memory as this value specifies before it starts + Note that a complex query might perform several sort and hash + operations at the same time, with each operation generally being + 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 concurrently. Therefore, the total memory used could be many times the value @@ -1900,7 +1901,7 @@ include_dir 'conf.d' <para> Hash-based operations are generally more sensitive to memory availability than equivalent sort-based operations. The - memory available for hash tables is computed by multiplying + memory limit for a hash table is computed by multiplying <varname>work_mem</varname> by <varname>hash_mem_multiplier</varname>. This makes it possible for hash-based operations to use an amount of memory |