85b7efa1cd
This allows for example using LIKE with case-insensitive collations. There was previously no internal implementation of this, so it was met with a not-supported error. This adds the internal implementation and removes the error. The implementation follows the specification of the SQL standard for this. Unlike with deterministic collations, the LIKE matching cannot go character by character but has to go substring by substring. For example, if we are matching against LIKE 'foo%bar', we can't start by looking for an 'f', then an 'o', but instead with have to find something that matches 'foo'. This is because the collation could consider substrings of different lengths to be equal. This is all internal to MatchText() in like_match.c. The changes in GenericMatchText() in like.c just pass through the locale information to MatchText(), which was previously not needed. This matches exactly Generic_Text_IC_like() below. ILIKE is not affected. (It's unclear whether ILIKE makes sense under nondeterministic collations.) This also updates match_pattern_prefix() in like_support.c to support optimizing the case of an exact pattern with nondeterministic collations. This was already alluded to in the previous code. (includes documentation examples from Daniel Vérité and test cases from Paul A Jungwirth) Reviewed-by: Jian He <jian.universality@gmail.com> Discussion: https://www.postgresql.org/message-id/flat/700d2e86-bf75-4607-9cf2-f5b7802f6e88@eisentraut.org |
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PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.