The Ultimate Guide to High Availability with MariaDB

FirstMatch strategy

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The idea

FirstMatch is an execution strategy for Semi-join subqueries.

Its execution is very similar to how IN/EXISTS subqueries were executed in MySQL 5.x.

select * from Country 
where Country.code IN (select City.Country 
                       from City 
                       where City.Population > 1*1000*1000)
      and Country.continent='Europe'

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