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On MySQL 5.7, I whenever I create an index, despite specifying its type (BTREE or HASH), the index created is always BTREE. Does anyone know how to enable HASH for indexing? I plan to use it on low cardinality columns.

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  • Which engine do you use (InnoDB, MyISAM, Memory ...) ? Commented Jan 30, 2017 at 9:18
  • InnoDB -------- Commented Jan 30, 2017 at 9:40
  • Hash, if it existed, would be only marginally better than BTree for point queries, and would be useless for "range" queries. So, they did not bother to include it. Commented Jan 30, 2017 at 18:10

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InnoDb and MyIsam don't support Hash index ( https://dev.mysql.com/doc/refman/5.7/en/create-index.html )

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But you can use adaptive hash index ( https://dev.mysql.com/doc/refman/5.7/en/innodb-adaptive-hash.html )

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