Thread: Sorry I see my first question did not get posted (maybe because of the attatchments)
Sorry I see my first question did not get posted (maybe because of the attatchments)
From
"Joel Fradkin"
Date:
Basically the question was why would a view use an indexed search on one result set but a seq search on a larger result set. Same view only difference is how many rows are returned. The large result set was doing a seq search and did not return after several minutes. The same sql ran in 135 seconds on my MSSQL system. Joel Fradkin Wazagua, Inc. 2520 Trailmate Dr Sarasota, Florida 34243 Tel. 941-753-7111 ext 305 jfradkin@wazagua.com www.wazagua.com Powered by Wazagua Providing you with the latest Web-based technology & advanced tools. © 2004. WAZAGUA, Inc. All rights reserved. WAZAGUA, Inc This email message is for the use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and delete and destroy all copies of the original message, including attachments.
Joel Fradkin wrote: > Basically the question was why would a view use an indexed search on one > result set but a seq search on a larger result set. Same view only > difference is how many rows are returned. The large result set was doing a > seq search and did not return after several minutes. The same sql ran in 135 > seconds on my MSSQL system. Accessing an index 1000 times then reading 1000 rows may be slower than just reading a whole table of 2000 rows. You can examine what PostgreSQL thinks the query will cost by running an explain: EXPLAIN ANALYSE SELECT ... This will display two sets of figures for each stage, the expected costs and the actual. Finally, make sure your configuration settings are reasonable. Read through the guide at: http://www.varlena.com/varlena/GeneralBits/Tidbits/index.php There's a -performance list that specialises in dealing with these issues. If you post there, mention you've tuned as per GeneralBits and provide an example of the query, view definition and the output from explain. -- Richard Huxton Archonet Ltd