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so that their elements are always taken as simple expressions over the query's input columns. It originally seemed like a good idea to make them act exactly like GROUP BY and ORDER BY, right down to the SQL92-era behavior of accepting output column names or numbers. However, that was not such a great idea, for two reasons: 1. It permits circular references, as exhibited in bug #5018: the output column could be the one containing the window function itself. (We actually had a regression test case illustrating this, but nobody thought twice about how confusing that would be.) 2. It doesn't seem like a good idea for, eg, "lead(foo) OVER (ORDER BY foo)" to potentially use two completely different meanings for "foo". Accordingly, narrow down the behavior of window clauses to use only the SQL99-compliant interpretation that the expressions are simple expressions.
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/.