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6fbc323c80
Fix things so that top-N sorting can be used in child Sort nodes of a MergeAppend node, when there is a LIMIT and no intervening joins or grouping. Actually doing this on the executor side isn't too bad, but it's a bit messier to get the planner to cost it properly. Per gripe from Robert Haas. In passing, fix an oversight in the original top-N-sorting patch: query_planner should not assume that a LIMIT can be used to make an explicit sort cheaper when there will be grouping or aggregation in between. Possibly this should be back-patched, but I'm not sure the mistake is serious enough to be a real problem in practice.
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/.