pg_sift is distributed under the PostgreSQL License (see LICENSE). It contains data and an algorithm derived from the following third-party works. Unicode character data ---------------------- src/bm25/analyze_tables.h and src/bm25/analyze_tables/ are generated by a generator script from the Unicode 16.0.0 Character Database (Scripts.txt, DerivedCoreProperties.txt, emoji-data.txt and the case folding and decomposition data of the same version). The tables are Data Files under the Unicode License v3: UNICODE LICENSE V3 COPYRIGHT AND PERMISSION NOTICE Copyright © 1991-2026 Unicode, Inc. NOTICE TO USER: Carefully read the following legal agreement. BY DOWNLOADING, INSTALLING, COPYING OR OTHERWISE USING DATA FILES, AND/OR SOFTWARE, YOU UNEQUIVOCALLY ACCEPT, AND AGREE TO BE BOUND BY, ALL OF THE TERMS AND CONDITIONS OF THIS AGREEMENT. IF YOU DO NOT AGREE, DO NOT DOWNLOAD, INSTALL, COPY, DISTRIBUTE OR USE THE DATA FILES OR SOFTWARE. Permission is hereby granted, free of charge, to any person obtaining a copy of data files and any associated documentation (the "Data Files") or software and any associated documentation (the "Software") to deal in the Data Files or Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, and/or sell copies of the Data Files or Software, and to permit persons to whom the Data Files or Software are furnished to do so, provided that either (a) this copyright and permission notice appear with all copies of the Data Files or Software, or (b) this copyright and permission notice appear in associated Documentation. THE DATA FILES AND SOFTWARE ARE PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR HOLDERS INCLUDED IN THIS NOTICE BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THE DATA FILES OR SOFTWARE. Except as contained in this notice, the name of a copyright holder shall not be used in advertising or otherwise to promote the sale, use or other dealings in these Data Files or Software without prior written authorization of the copyright holder. Snowball English (Porter2) stemmer ---------------------------------- src/bm25/analyze_stem.c implements the Snowball English stemming algorithm (snowball/algorithms/english.sbl) directly in C. The algorithm is by Martin Porter; the Snowball distribution is licensed under the BSD 3-clause license: Copyright (c) 2001, Dr Martin Porter, Copyright (c) 2002, Richard Boulton. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. SQLite ------ The SQLite extension (sqlite/, released as the sift-sqlite archive) is compiled against the loadable-extension headers (sqlite3.h, sqlite3ext.h) of the SQLite development package of the build machine and loads into the SQLite library of the application that uses it. It contains no SQLite source code and links no SQLite library. SQLite is in the public domain (https://sqlite.org/copyright.html). The host implementation in sqlite/host/ is not PostgreSQL's: it is a small re-implementation, written for this repository under the PostgreSQL License, of the slice of the PostgreSQL backend API that the engine sources in src/ use. The sift-sqlite archive includes this file because it carries the same Unicode tables and Snowball stemmer as pg_sift. Not distributed with pg_sift ------------------------- The checks under tools/ and bench/ download reference data at run time (the Unicode Character Database, the snowball-data English vocabulary, Simple English Wikipedia, GeoNames) and compare against other engines; none of it is part of this repository or of the installed extension.