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For some reason, in the original coding of the PlaceHolderVar mechanism I had supposed that PlaceHolderVars couldn't propagate into subqueries. That is of course entirely possible. When it happens, we need to treat an outer-level PlaceHolderVar much like an outer Var or Aggref, that is SS_replace_correlation_vars() needs to replace the PlaceHolderVar with a Param, and then when building the finished SubPlan we have to provide the PlaceHolderVar expression as an actual parameter for the SubPlan. The handling of the contained expression is a bit delicate but it can be treated exactly like an Aggref's expression. In addition to the missing logic in subselect.c, prepjointree.c was failing to search subqueries for PlaceHolderVars that need their relids adjusted during subquery pullup. It looks like everyplace else that touches PlaceHolderVars got it right, though. Per report from Mark Murawski. In 9.1 and HEAD, queries affected by this oversight would fail with "ERROR: Upper-level PlaceHolderVar found where not expected". But in 9.0 and 8.4, you'd silently get possibly-wrong answers, since the value transmitted into the subquery wouldn't go to null when it should. |
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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/.