diff options
| author | Bruce Momjian <bruce@momjian.us> | 2023-09-26 19:44:21 -0400 |
|---|---|---|
| committer | Bruce Momjian <bruce@momjian.us> | 2023-09-26 19:44:21 -0400 |
| commit | c8afad9e634979ed0ba411cd38d659de8593ae18 (patch) | |
| tree | 3312252e7b2a49b2c0f23518cf3bd5d047758d2f | |
| parent | 1512fec1979c6e81d1f9c0032a7ef610a0037750 (diff) | |
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 d35187d9eda..5fb6e13a3c3 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -1692,9 +1692,10 @@ 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 @@ -1708,7 +1709,7 @@ 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 |