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The text search functions that involve parsing raw text into lexemes are remarkably CPU-intensive, so estimating them at the same cost as most other built-in functions seems like a mistake; moreover, doing so turns out to discourage the optimizer from using functional indexes on these functions. After some debate, we've agreed to raise procost from 1 to 100 for to_tsvector(), plainto_tsvector(), to_tsquery(), ts_headline(), ts_match_tt(), and ts_match_tq(), which are all the text search functions that parse raw text. Also increase procost for the 2-argument form of ts_rewrite() (tsquery_rewrite_query); while this function doesn't do text parsing, it does execute a user-supplied SQL query, so its previous procost of 1 is clearly a drastic underestimate. It seems reasonable to assign it the same cost we assign to PL functions by default, so 100 is the number here too. I did not bother bumping catversion for this change, since it does not break catalog compatibility with the server executable nor result in any regression test changes. Per complaint from Andrew Gierth and subsequent discussion. |
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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. 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. 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/.