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Per recent discussion, it's important for all computed datums (not only the results of input functions) to not contain any ill-defined (uninitialized) bits. Failing to ensure that can result in equal() reporting that semantically indistinguishable Consts are not equal, which in turn leads to bizarre and undesirable planner behavior, such as in a recent example from David Johnston. We might eventually try to fix this in a general manner by allowing datatypes to define identity-testing functions, but for now the path of least resistance is to expect datatypes to force all unused bits into consistent states. Per some testing by Noah Misch, array and path functions seem to be the only ones presenting risks at the moment, so I looked through all the functions in adt/array*.c and geo_ops.c and fixed them as necessary. In the array functions, the easiest/safest fix is to allocate result arrays with palloc0 instead of palloc. Possibly in future someone will want to look into whether we can just zero the padding bytes, but that looks too complex for a back-patchable fix. In the path functions, we already had a precedent in path_in for just zeroing the one known pad field, so duplicate that code as needed. Back-patch to all supported branches. |
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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/.