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ba42002461
performance problem pointed out by phil@vodafone: to wit, we were spending O(N^2) time to check dropped-ness in an N-deep join tree, even in the case where the tree was freshly constructed and couldn't possibly mention any dropped columns. Instead of recursing in get_rte_attribute_is_dropped(), change the data structure definition: the joinaliasvars list of a JOIN RTE must have a NULL Const instead of a Var at any position that references a now-dropped column. This costs nothing during normal parse-rewrite-plan path, and instead we have a linear-time update to make when loading a stored rule that might contain now-dropped columns. While at it, move the responsibility for acquring locks on relations referenced by rules into this separate function (which I therefore chose to call AcquireRewriteLocks). This saves effort --- namely, duplicated lock grabs in parser and rewriter --- in the normal path at a cost of one extra non-locked heap_open() in the stored-rule path; seems a good tradeoff. A fringe benefit is that it is now *much* clearer that we acquire lock on relations referenced in rules before we make any rewriter decisions based on their properties. (I don't know of any bug of that ilk, but it wasn't exactly clear before.) |
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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. The JDBC, ODBC, C++, Python, and Tcl interfaces have been moved to the PostgreSQL Projects Web Site at http://gborg.postgresql.org for separate maintenance. A Perl DBI/DBD driver is available from CPAN. 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 ftp://ftp.postgresql.org/pub/. For more information look at our web site located at http://www.postgresql.org/.