Performance issues in viewing rivers on specific systems #8
Description
We've been working in various email threads trying to figure out why performance in viewing rivers is so slow on feedland.com.
Here's a copy of the last email I'm responding to in the next comment.
I am fairly confident that a new index with columns
flDeleted, feedUrl, pubDate(in that order) would improve this query as-is. 5 minutes sorting 1.08M rows seems incredibly long, even if the query is sub-optimal. It's difficult to speculate what might be causing poor performance.I'd like to experiment using a JOIN instead of a sub-select. I believe a join would be able to apply the
pubDatecondition to the entire recordset. Whereas thein()is: first retrieving all the records for all the feedUrls returned by the subselect, putting those in a temp table, and sorting that temp table.A snapshot of the database would help validate this.