Re: wal-debug
От | Munteanu Gabriel |
---|---|
Тема | Re: wal-debug |
Дата | |
Msg-id | 00a101c2e1ce$5f821b70$4b5ae73e@SERVERXP обсуждение исходный текст |
Ответ на | wal-debug ("Munteanu Gabriel" <gmunteanu@rdslink.ro>) |
Ответы |
Re: wal-debug
Re: wal-debug |
Список | pgsql-general |
in the URL you sent me, i read the following: Write Ahead Logging (WAL) is a standard approach to transaction logging. Its detailed description may be found in most (if not all) books about transaction processing. Briefly, WAL's central concept is that changes to data files (where tables and indexes reside) must be written only after those changes have been logged - that is, when log records have been flushed to permanent storage. When we follow this procedure, we do not need to flush data pages to disk on every transaction commit, because we know that in the event of a crash we will be able to recover the database using the log: any changes that have not been applied to the data pages will first be redone from the log records (this is roll-forward recovery, also known as REDO) and then changes made by uncommitted transactions will be removed from the data pages (roll-backward recovery - UNDO). So, WAL is about logging. it logs every transaction that is made to the database. I want to disable logging of the transactions. i don't need undo' s and redo's. I don't want to know if someone has inserted something in the databse or not. AND, ESPECIALLY, i don't want any other writing in RAM or later on disk because of the logging. (WAL introduces an overhead, it writes in a buffer in RAM some data about the transactions and when the buffer is full or some other event occurs it writes it to disk). I am not doing something specially, I want to increase performance, that's all. and wanted to disable WAL. ----- Original Message ----- From: "Martijn van Oosterhout" <kleptog@svana.org> To: "Munteanu Gabriel" <gmunteanu@rdslink.ro> Cc: "postgres-general" <pgsql-general@postgresql.org> Sent: Monday, March 03, 2003 2:28 PM Subject: Re: [GENERAL] wal-debug Please read this: http://www.postgresql.org/docs/view.php?version=7.3&idoc=1&file=wal.html The upshot that it doesn't need to write as much to disk to commit a transaction and those write are sequential instead of scattered across the disk. What are you doing that makes you think WAL is bad?
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