Timeline for Mysql on RDS avoiding index_merge
Current License: CC BY-SA 3.0
10 events
| when toggle format | what | by | license | comment | |
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| Oct 11, 2022 at 23:38 | comment | added | Rick James |
Another tip: If you have INDEX(a) and INDEX(a,b) get rid of the former; sometimes the Optimizer uses the former when the latter is clearly better.
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| Apr 14, 2020 at 0:58 | comment | added | Rick James |
MySQL is quite happy to use a composite index with the ANDing of multiple tests in the WHERE. It simply punts on a dynamic CONCAT; that is it ignores the index and scans the table (slow).
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| Apr 13, 2020 at 9:15 | comment | added | Hitesh Vaghani | @RickJames sorry for the spelling mistake. it is merging of all column. We had done so from two-column which was an integer(which was creating the same problem) and indexed. We created one extra column which is text(i.e. 'col1-col2' and indexed it so want to know if anyone has done it before and how it the results? | |
| Apr 13, 2020 at 6:16 | comment | added | Rick James | @HiteshVaghani - what does "margin" mean in that context? | |
| Apr 13, 2020 at 5:07 | comment | added | Hitesh Vaghani | @Krynble Did you try with manually creating a margin of all column - separated and run a query on the single index? | |
| Jul 19, 2017 at 17:10 | comment | added | Krynble | Yeah, it does, a lot faster, but I still find mysql being dumb. Sometimes it simply prefers to run a full table scan instead of using the new composite index. Makes me wanna shoot myself. | |
| Jul 17, 2017 at 23:32 | comment | added | Rick James | Thanks. No surprises in what you added. Does it run faster with the composite index? | |
| Jul 17, 2017 at 23:22 | comment | added | Krynble | Hi Rick, I added the information you asked! | |
| Jul 17, 2017 at 23:22 | vote | accept | Krynble | ||
| Jul 10, 2017 at 16:02 | history | answered | Rick James | CC BY-SA 3.0 |