Allow configuration of transformation for case-insensitive queries

[ViktarRVR]

We use Spring Data JPA + Querydsl JPA. If we perform queries with ignoreCase keyword in repository methods Spring data JPA use UPPER function on parameters in SQL(as described in documentation, Table 3. Supported keywords inside method names), but Querydsl JPA uses LOWER function. We should use two types of indexes or don't use ignoreCase keyword in repository methods.

It would be great, if it was possible to configured to use UPPER function or LOWER function in Spring Data JPA.

See also #3540

[mp911de]

FTR: https://github.com/querydsl/querydsl/blob/99e3ca936f46471bc61d9af6e1a3dbb16f3f12b3/querydsl-jpa/src/main/java/com/querydsl/jpa/JPQLTemplates.java

[steveratay]

I ran into the same problem in the query by example code. It also appears to be hard-coded to use a lower conversion. As stated above, this is challenging because I only want to maintain a single case-insensitive index on either the upper or lowercase version of certain columns.

See https://github.com/spring-projects/spring-data-jpa/blob/main/src/main/java/org/springframework/data/jpa/convert/QueryByExamplePredicateBuilder.java#L182.

It would be great if this were able to be customized in the ExampleMatcher methods.

[gregturn]

Whereas another knob would work, I wonder if it isn't simpler to just update things to use lower across the board.

[schauder]

Going consistently with lower sounds like a good way to go. Please make sure to have this change included in release notes since it might disable existing indexes and therefore cause a performance degradation when not addressed.

[gregturn]

This has been merged to main and to 3.0.x.