Charset Narrowing optimization
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Charset Narrowing is an optimization to make comparisons like utf8mb3_key_column=utf8mb4_expression sargable.
It was introduced in MariaDB 10.6.16, MariaDB 10.10.7, MariaDB 10.11.6, MariaDB 11.0.4, MariaDB 11.1.3, MariaDB 11.2.2 where it is OFF by default, and in MariaDB 11.3.1, where it is ON by default.
What it is
Controlling the optimization
The optimization is controlled by an optimizer_switch flag. Specify
set optimizer_switch='cset_narrowing=on';
to enable the optimization.
References
- MDEV-32113: utf8mb3_key_col=utf8mb4_value cannot be used for ref access
- Blog post: Making “tbl.utf8mb3_key_column=utf8mb4_expr” sargable
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