Simon Riggs wrote: > GIT significantly reduces the size of clustered indexes, greatly > improving the number of index pointers that can be held in memory for > very large indexes. That translates directly into a reduction in I/O for > large databases on typical hardware, for primary operations, file > backups and recovery (and this, log replication). Test results validated > that and showed increased performance, over and above that experienced > with HOT, when tested together. > > Now there may be problems with the GIT code as it stands, but we should > acknowledge that the general technique has been proven to improve > performance on a recent PostgreSQL codebase. This is an unsurprising > result, since SQLServer, Sybase, DB2, Oracle and Teradata (at least) all > use indexes of this category to improve real-world performance. The idea > is definitely not a benchmark-only feature. > > Many users would be very interested if we could significantly reduce the > size of the main index on their largest tables.
Yes, basically GIT allows index compression for clustered tables, and stated that way it is clear it would be a big feature if we had it for 8.4. > I would at least like to see clustered indexes acknowledged as a TODO > item, so we keep the door open for a future implementation based around > the basic concept of GIT. Yes, it is already a TODO: * Consider compressing indexes by storing key values duplicated in several rows as a single index entry -- Bruce Momjian <[EMAIL PROTECTED]> http://momjian.us EnterpriseDB http://enterprisedb.com + If your life is a hard drive, Christ can be your backup. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
