Gregory Stark wrote: > "Gregory Stark" <[EMAIL PROTECTED]> writes: > > > "Bruce Momjian" <[EMAIL PROTECTED]> writes: > > > >> shared_buffers again was 32MB so all the data was in memory. > > > > The case where all the data is in memory is simply not interesting. The cost > > of TOAST is the random access seeks it causes. You seem to be intentionally > > avoiding testing the precise thing we're interested in. > > Also, something's not right with these results. 100,000 tuples --even if all > they contain is a toast pointer-- won't fit on a single page. And the toast > tables should vary in size depending on how many toast chunks are created.
The test creates _one_ row of length 100,000 and then finds out how long it takes to access it twenty times. I don't see how having the data outside cache helps us. For a large row with 2k chunks, I assume all the 2k chunks are going to be in the same 8k page. What I want to measure is the cost of accessing four 2k chunks vs. one 8k chunk, and I think we can conclude that is 6% of the access time. -- Bruce Momjian <[EMAIL PROTECTED]> http://momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
