Tom Lane wrote: > Heikki Linnakangas <[EMAIL PROTECTED]> writes: > > For the record, this patch has a small negative impact on scans like > > "SELECT * FROM foo LIMIT 1000". If such a scan is run repeatedly, in CVS > > HEAD the first 1000 rows will stay in buffer cache, but with the patch > > each scan will start from roughly where previous one stopped, requiring > > more pages to be read from disk each time. I don't think it's something > > to worry about in practice, but I thought I'd mention it. > > Urgh. The answers change depending on (more or less) the phase of the > moon? I've got a serious problem with that. You might look back to > 1997 when GEQO very nearly got tossed out entirely because it destroyed > reproducibility of query results.
What about the simple idea of just disabling the use of a sync scan when the query has LIMIT and no ORDER BY, and start always at block 0 in that case? -- Alvaro Herrera http://www.CommandPrompt.com/ PostgreSQL Replication, Consulting, Custom Development, 24x7 support ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
