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bc0f080928
We must filter out hashtable entries with frequencies less than those specified by the algorithm, else we risk emitting junk entries whose actual frequency is much less than other lexemes that did not get tabulated. This is bad enough by itself, but even worse is that tsquerysel() believes that the minimum frequency seen in pg_statistic is a hard upper bound for lexemes not included, and was thus underestimating the frequency of non-MCEs. Also, set the threshold frequency to something with a little bit of theory behind it, to wit assume that the input distribution is approximately Zipfian. This might need adjustment in future, but some preliminary experiments suggest that it's not too unreasonable. Back-patch to 8.4, where this code was introduced. Jan Urbanski, with some editorialization by Tom |
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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. 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/.