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Re: Very slow query when too many joins
Posted by: Rick James
Date: July 20, 2016 09:37AM

James...
Each 'attribute' (field_id:value pair) needs a JOIN to look up (for a given ads_id).
(His original posting said "183" twice, that was probably a typo.)

The large number of JOINs is one of the evils of EAV schema design. (The index I suggested makes them faster.)

The slowdown at 26 joins is another evil. (The setting I suggested may help with that.)

The bottom line is that EAV does not scale and should be avoided. He needs 29 or so lookups. With JSON, only 1 is needed. Instead, the application splits apart the JSON and formats the output. But that is much faster.

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Re: Very slow query when too many joins
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