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These functions are stated to be Oracle-compatible, but they weren't. Yugo Nagata noticed that while our code returns zero for a zero or negative fourth parameter (occur_index), Oracle throws an error. Further testing by me showed that there was also a discrepancy in the interpretation of a negative third parameter (beg_index): Oracle thinks that a negative beg_index indicates the last place where the target substring can *begin*, whereas our code thinks it is the last place where the target can *end*. Adjust the sample code to behave like Oracle in both these respects. Also change it to be a CDATA[] section, simplifying copying-and-pasting out of the documentation source file. And fix minor problems in the introductory comment, which wasn't very complete or accurate. Back-patch to all supported branches. Although this patch only touches documentation, we should probably call it out as a bug fix in the next minor release notes, since users who have adopted the functions will likely want to update their versions. Yugo Nagata and Tom Lane Discussion: https://postgr.es/m/20171229191705.c0b43a8c.nagata@sraoss.co.jp
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/.