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This patch largely reverts what I did in commits c9b0c678d and 78e73e875. The maximum cover length limit that I added in 78e73e875 (to band-aid over c9b0c678d's performance issues) creates too many user-visible behavior discrepancies, as complained of for example in bug #17691. The real problem with hlCover() is not what I thought at the time, but more that it seems to have been designed with only AND tsquery semantics in mind. It doesn't work quite right for OR, and even less so for NOT or phrase queries. However, we can improve that situation by building a variant of TS_execute() that returns a list of match locations. We already get an ExecPhraseData struct representing match locations for the primitive case of a simple match, as well as one for a phrase match; we just need to add some logic to combine these for AND and OR operators. The result is a list of ExecPhraseDatas, which hlCover can regard as having simple AND semantics, so that its old algorithm works correctly. There's still a lot not to like about ts_headline's behavior, but I think the remaining issues have to do with the heuristics used in mark_hl_words and mark_hl_fragments (which, likewise, were not revisited when phrase search was added). Improving those is a task for another day. Patch by me; thanks to Alvaro Herrera for review. Discussion: https://postgr.es/m/840.1669405935@sss.pgh.pa.us
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/.