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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 | c3f7e91a191bfce657ed27ea59781fb427c46c06 (patch) | |
| tree | ba01c3b94a10b96e3f2dac6141c1b6685ef35eb9 | |
| parent | 7bb0f4a25d1b2bff7f2938176cd59a704c625b86 (diff) | |
| download | postgresql-c3f7e91a191bfce657ed27ea59781fb427c46c06.tar.gz postgresql-c3f7e91a191bfce657ed27ea59781fb427c46c06.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 958b41c1387..1adbba7f8f4 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -1824,9 +1824,10 @@ 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 @@ -1840,7 +1841,7 @@ 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 |