# Avoided filesort, but more rows to exmaine, need advice! **URL:** \ **Category:** Other MySQL® Questions\ **Created:** [November 26, 2008, 4:24pm UTC](https://forums.percona.com/t/avoided-filesort-but-more-rows-to-exmaine-need-advice/1010 "2008-11-26T16:24:53Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![matthew016](https://avatars.discourse-cdn.com/v4/letter/m/5fc32e/32.png) [@matthew016](https://forums.percona.com/u/matthew016)\ **Post date:** [November 26, 2008, 4:24pm UTC](https://forums.percona.com/t/avoided-filesort-but-more-rows-to-exmaine-need-advice/1010/1 "2008-11-26T16:24:53Z")
Hi, I am pretty new in optimizing tables with index and may need some help. This is my query: EXPLAIN SELECT timestamp FROM Meting\_INT\_COPY WHERE blockid = ‘200811252000’ ORDER BY timestamp DESC LIMIT 1 If I have an index(blockid), EXPLAIN will return the following information: type possible\_keys key rows Extra ref index\_blockid index\_blockid 2638 Using where; Using filesort If I add an index(blockid,timestamp) EXPLAIN will display the following: type possible\_keys key rows Extra ref index\_blockid,index\_blockid\_timestamp index\_blockid\_timestamp 8248 Using where; Using index The index(blockid,timestamp) avoid the filesort + returns the result from index ! (Using where; Using index) But why for the index(blockid) 2638 rows are returned to examine and for a more specific index(blockid,timestamp) 8248 rows are returned ? Thank you very much for any answer ! ---
**Author:** ![MarkRose](https://avatars.discourse-cdn.com/v4/letter/m/85f322/32.png) [@MarkRose](https://forums.percona.com/u/MarkRose)\ **Post date:** [March 21, 2009, 7:48pm UTC](https://forums.percona.com/t/avoided-filesort-but-more-rows-to-exmaine-need-advice/1010/2 "2009-03-21T19:48:31Z")
If you run the query without the LIMIT 1 at the end, I bet you would see more row examined without the additional index. It just so happens that the non-indexed execution is stumbling upon a matching row early into its search.