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Known problems
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- MySQL (at least 5.0.45, 5.0.51) has problems with queries dealing with
huge rowset. After certain threshold (involving around 500,000 rows) the
optimizator stop using INDEXes.
* You can check if it is actually happening with 'EXPLAIN <query>' command,
* To force usage of indexes it is possible to add "FORCE INDEX (PRIMARY)"
keyword after table name in SELECT query.
* The $MYSQL_FORCE_INDEXES configuration option is forces usage of indexes
when necesary and is intended to fix the described behaviour.
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