41dd50e84d
Cause the path extraction operators to return their lefthand input, not NULL, if the path array has no elements. This seems more consistent since the case ought to correspond to applying the simple extraction operator (->) zero times. Cause other corner cases in field/element/path extraction to return NULL rather than failing. This behavior is arguably more useful than throwing an error, since it allows an expression index using these operators to be built even when not all values in the column are suitable for the extraction being indexed. Moreover, we already had multiple inconsistencies between the path extraction operators and the simple extraction operators, as well as inconsistencies between the JSON and JSONB code paths. Adopt a uniform rule of returning NULL rather than throwing an error when the JSON input does not have a structure that permits the request to be satisfied. Back-patch to 9.4. Update the release notes to list this as a behavior change since 9.3.
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/.