On Wed, Aug 12, 2015 at 01:58:40AM +0530, Diwas Joshi wrote:

hello sergei, After I mailed you the last patch, I kept working further. I guess the code has come to a point where it is giving some results. So, I did the following things: Earlier we were storing all the parameters in a select query inside lex->value_list, but since there can be multiple functions in a query, I declared a list for parameters inside table_list so we can store params corresponding to each table function in it.

Good.

Then instead of function name i created a table with table alias defined in the function and change the table name to table alias inside select query as well. This makes it possible for the queries inside the function definition to access the temporary table we created. There is a problem with this approach that there might already be a table present in the database with that name, I am still thinking of a solution for it but we can discuss a solution for it later.

Yes, you're right. There is a problem here. It is not limited to the already existing tables with the same name. Let's work with this example: delimiter | CREATE FUNCTION f10(param1 VARCHAR(11)) RETURNS TABLE return_table(name VARCHAR(11)) deterministic BEGIN insert into return_table values('foo'); END| DELIMITER ; MariaDB [test]> select name from f10('aaa'); +------+ | name | +------+ | foo | +------+ 1 row in set (0.29 sec) Good. However, attempts to invoke the same function multiple times fail: MariaDB [test]> select name from f10('aaa') as TBL1 , f10('bbb') as TBL2; ERROR 1050 (42S01): Table 'return_table' already exists Your code uses this approach: 1. Create a temporary table in a manner similar to how user-specified CREATE TEMPORARY TABLE works. 2. Rely on regular MySQL's name resolution process to "see" the temporary table. The properties of this solution are: - If a temporary table has the same name as a regular db table, temporary table will "shadow" the regular table (this is ok). - user-created temporary tables are per-thread. Other threads do not see the temp. table (good). However, everything that executes within the thread will see the temp. table. For example, if a query calls two Table Functions, they will both see each others return tables. This is a problem. I think, a better approach would be: - switch to something like create_tmp_table() for creation of temporary tables. Tables that are created this way are normally not visible to the name resolution code. - Patch the name resolution code so that the statements inside a Table Function see the return table of that Table Function. BR Sergei -- Sergei Petrunia, Software Developer MariaDB Corporation | Skype: sergefp | Blog: http://s.petrunia.net/blog