PostgreSQL: work_mem tuning and log_temp_files
work_mem is used for sorts, aggregates, and a few other operations. This is non-shared memory, which is allocated per-operation (one to several times per query); the setting is used to put a limit on the amount of RAM any single operation can grab before being forced to disk through temp files. If it is been forced to the disk that can cause a bad execution time
With PostgreSQL 8.3 a new variable got added names as “log_temp_files” that enables/disables whether temporary files are logged when deleted. These temp files can be created for sorts, hashes, and temporary query results.
log_temp_files can be used to better tune the values for work_mem after analyzing the usage of temp files (from the db server logs) for a certain query so that you can minimize or nullify the temp file usage by raising the values for work_mem.
-Shoaib (shoaibmir[@]gmail.com)
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Comment by rudy1133 — April 11, 2008 @ 3:21 pm