On Apr 5, 2005 3:48 PM, Simon Riggs <[EMAIL PROTECTED]> wrote: > B-trees aren't unique to PostgreSQL; the explanation developed here > would work equally well for any database system that used tree-based > indexes. Do we still think that MySQL can do this when PostgreSQL > cannot? How? > > Do we have performance test results showing the same application load > without the degradation? We don't need to look at the source code to > measure MySQL performance...
http://www.amber.org/~petrilli/diagrams/comparison_mysql_pgsql.png That chart shows MySQL (using INSERT against MyISAM tables) and PostgreSQL (using COPY) running with the exact same code otherwise. Note that MySQL does hit a bit of a wall, but nothing as drastic as PostgreSQL and actually maintains something "more flat". The red and blue dashed lines are the 95th percentile point. My suspicion is that what we're seeing is WAL issues, not particularly index issues. The indices just fill up the WAL faster because there's more data. This is a wag basically, but it would seem to explain the difference. In both cases, the indices were identical. Five on each. One interesting thing... PostgreSQL starts out a good bit faster, but looses in the end. Chris -- | Christopher Petrilli | [EMAIL PROTECTED] ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings
