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When there is no index defined filesort is used to sort the result of a query. If there is a function in the select list and the result set should be ordered by it's value then this function will be evaluated twice. First time to get the value of the sort key and second time to send its value to a user. This happens because filesort when sorts a table remembers only values of its fields but not values of functions. All functions are affected. But taking into account that SP and UDF functions can be both expensive and non-deterministic a temporary table should be used to store their results and then sort it to avoid twice SP evaluation and to get a correct result. If an expression referenced in an ORDER clause contains a SP or UDF function, force the use of a temporary table. A new Item_processor function called func_type_checker_processor is added to check whether the expression contains a function of a particular type. mysql-test/t/udf.test: Added test case for bug#19862: Sort with filesort by function evaluates function twice mysql-test/t/sp.test: Added test case for bug#19862: Sort with filesort by function evaluates function twice mysql-test/r/sp.result: Added test case for bug#19862: Sort with filesort by function evaluates function twice mysql-test/r/udf.result: Added test case for bug#19862: Sort with filesort by function evaluates function twice sql/sql_select.cc: Fixed bug#19862: Sort with filesort by function evaluates function twice If an expression referenced in an ORDER clause contains a SP or UDF function, force the use of a temporary table. sql/item_func.h: Fixed bug#19862: Sort with filesort by function evaluates function twice A new Item_processor function called func_type_checker_processor is added to check whether the expression contains a function of a particular type. sql/item.h: Fixed bug#19862: Sort with filesort by function evaluates function twice A new Item_processor function called func_type_checker_processor is added to check whether the expression contains a function of a particular type. sql/item_func.cc: Fixed bug#19862: Sort with filesort by function evaluates function twice A new Item_processor function called func_type_checker_processor is added to check whether the expression contains a function of a particular type.
This is a release of MySQL, a dual-license SQL database server. MySQL is brought to you by the MySQL team at MySQL AB. License information can be found in these files: - For GPL (free) distributions, see the COPYING file. - For commercial distributions, see the MySQLEULA.txt file. For further information about MySQL or additional documentation, see: - The latest information about MySQL: http://www.mysql.com - The current MySQL documentation: http://dev.mysql.com/doc Some manual sections of special interest: - If you are migrating from an older version of MySQL, please read the "Upgrading from..." section first! - To see what MySQL can do, take a look at the features section. - For installation instructions, see the Installation chapter. - For future plans, see the TODO appendix. - For the new features/bugfix history, see the News appendix. - For the currently known bugs/misfeatures (known errors) see the problems appendix. - For a list of developers and other contributors, see the Credits appendix. A local copy of the MySQL Reference Manual can be found in the Docs directory in GNU Info format. You can also browse the manual online or download it in any of several formats at the URL given earlier in this file. ************************************************************ IMPORTANT: Bug or error reports should be sent to http://bugs.mysql.com.