Willy-Bas Loos <willybas@xxxxxxxxx> wrote: > when benchmarking insert , can there be caching effects? Yes. > i insert, delete again, and insert again. > does anything cache the things that i deleted? Yes. How long you wait before another attempt could have a significant effect on timings. There are background processes writing dirty buffers, checkpointing with fsync to disk, and vacuuming to clean up those deleted rows. Until vacuum cleans them up, the deleted rows will still have index entries which might be searched. Competition with background processes could affect performance. You might have a table with space already allocated versus needing to ask the OS to add more space to it. You might be reusing WAL files versus creating new ones. Etc. Getting good benchmarks is hard to do. For starters, you need to decide how many of those things *should* be included in the benchmark. Then you need to manage things to measure what should be measured. -Kevin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
