Implement MAX_EXECUTION_TIME hint

The hint limits the time of statement execution to the number of milliseconds given in the hint argument. The syntax is as follows:

SELECT /*+ MAX_EXECUTION_TIME(milliseconds) */ ... 

Only top-level SELECT statements support the hint. Trying to apply it to INSERT, REPLACE, UPDATE and DELETE must issue a warning. The hint is not supported inside stored procedures, triggers, events and subqueries.

Correctly handle situations where max_statement_time variable is set like here:

SET STATEMENT max_statement_time=1 FOR

SELECT /*+ MAX_EXECUTION_TIME(500) */ count(*) FROM t1 a;

In this case a warning must be issued, and the hint MAX_EXECUTION_TIME must be ignored.