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Re: concurrent_insert
Posted by: Rick James
Date: June 02, 2014 11:53AM

Executive summary: Switch to InnoDB and forget about "concurrent_insert".

Details:

If you have a performance problem, let's see more details.

I rarely (1 time in 100?) see performance issue that would benefit significantly by the level of detail you are mentioning.

In some situations MySQL can insert 100 rows per second; in some situations, 10,000. The difference has to do with how the INSERT statement is performed, what disk subsystem you have, etc.; not concurrent_insert.

Furthermore, since concurrent_insert applies only to MyISAM tables, there is a bigger issue... If you switch to InnoDB, you get "concurrent inserts" without having to set anything, and you get other performance boosts.

ALWAYS does not (as far as I know) have a _direct_ negative performance impact. However, since INSERTs will go _only_ onto the 'end' of the .MYD file, you _may_ get a heavily fragmented table. This impacts the cacheability of the table, hence _may_ hurt performance.

With InnoDB, INSERTs are placed in the table according to the PRIMARY KEY. SELECTs and INSERTs don't conflict with each other if they are not touching the same part of the table.

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