Informix - Problem description
Problem IT35205 | Status: Closed |
SELECT USING "FIRST N" SYNTAX DOESN'T SEEM TO HAVE ESTIMATED COST ADJUSTED CONSISTENTLY POSSIBLY LEADING TO WORSE QUERY PLANS | |
product: | |
INFORMIX SERVER / 5725A3900 / C10 - IDS 12.10 | |
Problem description: | |
The inconsistent costing is not really exposed to the customer via set explain output. To see that 2 identical plans seem to get 2 different estimated cost can really only be seen in internal server tracing code. The result of that cost discrepancy does result in different query plans being picked and a slower executing plan being produced. Here is the slower plan that is picked by the optimizer when not using optmizer directives: QUERY: (OPTIMIZATION TIMESTAMP: 11-08-2020 11:40:00) ------ select first 1 ... Estimated Cost: 858 Estimated # of Rows Returned: 2222 1) informix.b: SEQUENTIAL SCAN Filters: ((NVL (informix.b.charcol , 'N' ) = 'N' AND informix.b.intcol IN (4 , 5 , 11 )) AND informix.b.datetimecol | |
Problem Summary: | |
**************************************************************** * USERS AFFECTED: * * Users of Informix Server prior to 12.10.xC16 and 14.10.xC7. * **************************************************************** * PROBLEM DESCRIPTION: * * See Error Description * **************************************************************** * RECOMMENDATION: * * Upgrade to Informix Server 12.10.xC16 or 14.10.xC7. * **************************************************************** | |
Local Fix: | |
Solution | |
Workaround | |
**************************************************************** * USERS AFFECTED: * * Users of Informix Server prior to 12.10.xC16 and 14.10.xC7. * **************************************************************** * PROBLEM DESCRIPTION: * * See Error Description * **************************************************************** * RECOMMENDATION: * * Upgrade to Informix Server 12.10.xC16 or 14.10.xC7. * **************************************************************** | |
Comment | |
Fixed in Informix Server 12.10.xC16 and 14.10.xC7. | |
Timestamps | |
Date - problem reported : Date - problem closed : Date - last modified : | 08.12.2020 02.05.2023 02.05.2023 |
Problem solved at the following versions (IBM BugInfos) | |
Problem solved according to the fixlist(s) of the following version(s) |