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MDEV-7773: Aggregate stored functions

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This commit implements aggregate stored functions. The basic idea behind
the feature is:

* Implement a special instruction FETCH GROUP NEXT ROW that will pause
the execution of the stored function. When the instruction is reached,
execution of the initial query resumes "as if" the function returned.
This gives the server the opportunity to advance to the next row in the
result set.

* Stored aggregates behave like regular aggregate functions. The
implementation of thus resides in the class Item_sum_sp. Because it is
an aggregate function, for each new row in the group, the
Item_sum_sp::add() method will be called. This is when execution resumes
and the function does another iteration to "add" one extra element to
the final result.

* When the end of group is reached, val_xxx() method will be called for
the item. This case is handled by another execute step for the stored
function, only with a special flag to force a call to the return
handler. See Item_sum_sp::execute() for details.

To allow this pause and resume semantic, we must preserve the function
context across executions. This is stored in Item_sp::sp_query_arena only for
aggregate stored functions, but has no impact for regular functions.

We also enforce aggregate functions to include the "FETCH GROUP NEXT ROW"
instruction.

Signed-off-by: Vicențiu Ciorbaru <vicentiu@mariadb.org>
This commit is contained in:
Varun Gupta
2017-11-22 21:09:24 +02:00
committed by Vicențiu Ciorbaru
parent 7448b01bb5
commit 60c446584c
33 changed files with 2307 additions and 84 deletions
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4
mysql-test/r/create_drop_function.result
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@ -3,8 +3,8 @@ CREATE FUNCTION f1(str char(20))
RETURNS CHAR(100)
RETURN CONCAT('Hello, ', str, '!');
SELECT * FROM mysql.proc WHERE name like 'f1';
db name type specific_name language sql_data_access is_deterministic security_type param_list returns body definer created modified sql_mode comment character_set_client collation_connection db_collation body_utf8
test f1 FUNCTION f1 SQL CONTAINS_SQL NO DEFINER str char(20) char(100) CHARSET latin1 RETURN CONCAT('Hello, ', str, '!') root@localhost 2014-09-30 08:00:00 2014-09-30 08:00:00 STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION latin1 latin1_swedish_ci latin1_swedish_ci RETURN CONCAT('Hello, ', str, '!')
db name type specific_name language sql_data_access is_deterministic security_type param_list returns body definer created modified sql_mode comment character_set_client collation_connection db_collation body_utf8 aggregate
test f1 FUNCTION f1 SQL CONTAINS_SQL NO DEFINER str char(20) char(100) CHARSET latin1 RETURN CONCAT('Hello, ', str, '!') root@localhost 2014-09-30 08:00:00 2014-09-30 08:00:00 STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION latin1 latin1_swedish_ci latin1_swedish_ci RETURN CONCAT('Hello, ', str, '!') NONE
SELECT f1('world');
f1('world')
Hello, world!