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Historically, the planner's LIKE/regex index optimizations were only carried out for specific index opfamilies. That's never been a great idea from the standpoint of extensibility, but it didn't matter so much as long as we had no practical way to extend such behaviors anyway. With the addition of planner support functions, and in view of ongoing work to support additional table and index AMs, it seems like a good time to relax this. Hence, recast the decisions in match_pattern_prefix() so that rather than decide which operators to generate by looking at what the index opfamily contains, we decide which operators to generate a-priori and then see if the opfamily supports them. This is much more defensible from a semantic standpoint anyway, since we know the semantics of the chosen operators precisely, and we only need to assume that the opfamily correctly implements operators it claims to support. The existing "pattern" opfamilies put a crimp in this approach, since we need to select the pattern operators if we want those to work. So we still have to special-case those opfamilies. But that seems all right, since in view of the addition of collations, the pattern opfamilies seem like a legacy hack that nobody will be building on. The only immediate effect of this change, so far as the core code is concerned, is that anchored LIKE/regex patterns can be mapped onto BRIN index searches, and exact-match patterns can be mapped onto hash indexes, not only btree and spgist indexes as before. That's not a terribly exciting result, but it does fix an omission mentioned in the ancient comments here. Note: no catversion bump, even though this touches pg_operator.dat, because it's only adding OID macros not changing the contents of postgres.bki. Per consideration of a report from Manuel Rigger. Discussion: https://postgr.es/m/CA+u7OA7nnGYy8rY0vdTe811NuA+Frr9nbcBO9u2Z+JxqNaud+g@mail.gmail.com |
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README
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: https://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. 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 https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.