Bulk execution affected rows include rows changed by stored functions

The affected-rows count of a bulk operation (COM_STMT_BULK_EXECUTE) also counts the rows changed by DML in stored functions called by the statement. A non-bulk statement does not.

How to repeat

CREATE TABLE tu (id INT PRIMARY KEY, val INT);

CREATE TABLE tc (c INT);

INSERT INTO tc VALUES (0);

INSERT INTO tu VALUES (1,0),(2,0),(3,0);

CREATE FUNCTION f2(x INT) RETURNS INT MODIFIES SQL DATA

BEGIN UPDATE tc SET c=c+1; RETURN x; END;

-- bulk, 3 parameter sets: (10,1), (20,2), (30,3)

UPDATE tu SET val=f2(?) WHERE id=?;

-- bulk, 3 parameter sets: (1,10), (2,20), (3,30)

CREATE TABLE tu2 (id INT, val INT);

INSERT INTO tu2 VALUES (?, f2(?));

Both bulk statements change 3 rows of the target table, and the data is correct, but mysql_stmt_affected_rows() returns 6 for each. The plain statement UPDATE tu SET val=f2(5) WHERE id=1 returns 1.

Reproduced on 10.11 (10.11.19 debug) and 11.4 (11.4.13 debug, source revision 4813c2f0a8a79e4e4c000cc8c9447096fafe7033).

The function's UPDATE calls my_ok(), and in bulk mode Diagnostics_area::set_ok_status() adds to m_affected_rows (DA_OK_BULK) instead of replacing it. For triggers, mysql_insert() skips my_ok() when SUB_STMT_TRIGGER is set, but there is no such check for stored functions, or for UPDATE/DELETE.

Related: MDEV-41213 (the same problem for bulk unit results) and MDEV-41267 (a stored function's INSERT consumes the bulk parameter sets).