Hi, On 16 August 2012 15:40, J Ramesh Kumar <rameshj1977@xxxxxxxxx> wrote: > As you said, MySQL with MyISAM is better choice for my app. Because I don't > need transaction/backup. May be I'll try with InnoDB and find the disk > write/space difference. Is there any similar methods available in postgresql > like MyISAM engine ? You can try unlogged tables: http://www.postgresql.org/docs/9.1/static/sql-createtable.html If specified, the table is created as an unlogged table. Data written to unlogged tables is not written to the write-ahead log (see Chapter 29), which makes them considerably faster than ordinary tables. However, they are not crash-safe: an unlogged table is automatically truncated after a crash or unclean shutdown. The contents of an unlogged table are also not replicated to standby servers. Any indexes created on an unlogged table are automatically unlogged as well; however, unlogged GiST indexes are currently not supported and cannot be created on an unlogged table. > >>>> Ahhh but updates are the basically delete / inserts in disguise, so if >>>> there's enough, then yes, vacuum full would make a difference. > > The table which get update has very less data ie, only has 900 rows. Out of > 10500 tables, only one table is getting update frequently. Is there any way > to vacuum a specific table instead of whole database ? You can run "vacuum <table name>" but I doubt if that makes sense to run it manually when you have 1500 tx / sec. Postgres has HOT updates which have high change to reuse existing space: >From 8.3 release notes: Heap-Only Tuples (HOT) accelerate space reuse for most UPDATEs and DELETEs (Pavan Deolasee, with ideas from many others) UPDATEs and DELETEs leave dead tuples behind, as do failed INSERTs. Previously only VACUUM could reclaim space taken by dead tuples. With HOT dead tuple space can be automatically reclaimed at the time of INSERT or UPDATE if no changes are made to indexed columns. This allows for more consistent performance. Also, HOT avoids adding duplicate index entries. -- Ondrej Ivanic (ondrej.ivanic@xxxxxxxxx) -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
