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contrib/pg_trgm's make_trigrams() was coded to ignore multibyte character boundaries and just make trigrams from bytes if USE_WIDE_UPPER_LOWER wasn't defined. This is a bit odd, since there's no obvious reason why trigram compaction rules should depend on the presence of towlower() and friends. What's more, there was an Assert() that would fail if that code path was fed any multibyte characters. We need to do something about this since the pending regex-indexing patch has an assumption that you get just one "trgm" from any three characters. The best solution seems to be to remove the USE_WIDE_UPPER_LOWER dependency, which shouldn't really have been there in the first place. The second loop in make_trigrams() is now just a fast path and not a potentially incompatible algorithm. If there is anybody still using Postgres on machines without wcstombs() or towlower(), and they have non-ASCII data indexed by pg_trgm, they'll need to REINDEX those indexes after pg_upgrade to 9.3, else searches may fail incorrectly. It seems likely that there are no such installations, though. In passing, rename cnt_trigram to compact_trigram, which seems to better describe its functionality, and improve make_trigrams' test for whether it has to use the slow path or not (per a suggestion from Alexander Korotkov).
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. PostgreSQL has many language interfaces, many of which are listed here: http://www.postgresql.org/download See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Changes between all PostgreSQL releases are recorded in the file HISTORY. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at http://www.postgresql.org/download/. For more information look at our web site located at http://www.postgresql.org/.