I'm not saying I fully understand the MySQL optimizer, as
I never had to deal with it before... but:
Why should it use an index if the statement is returning ALL
rows? It might be faster to read them into memory ( 75853
isn't really much ) and sort them there instead of moving the
diskhead back and forth between the index and the data.
> i'm having a problem with mysql. when i put an index on a
> datetime column, it's never used.
> for example the
> sql: 'EXPLAIN SELECT * FROM actions ORDER BY datum'
> table type possible_keys key key_len ref rows Extra
> actions ALL NULL NULL NULL NULL 75853 Using filesort
> even if i use the
> sql: 'EXPLAIN SELECT * FROM actions USE INDEX (datum) ORDER BY datum'
> mysql doesn' use the index :-((
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