In order to call mysql_execute_command (the function that executes a statement) for a prepared statement and not damage its parse tree, we backup and restore the active Query_arena of THD.
This state may be one of the following:
One can use helper methods of Query_arena to check this state
Additionally, st_select_lex_unit::first_execution contains a flag for the state of each subquery in a complex statement. A separate variable is needed because not all subqueries may get executed during the first execution of a statement.
If a transformation is a non-destructive, it should not be registered, but performed only once in the permanent memory root. Additionally, be careful to not supply a pointer to stack as the first argument of change_item_tree(); that will lead to stack corruption when a tree is restored.
MySQL Related Interview Questions
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A Guided Tour Of The Mysql Source Code
Important Algorithms And Structures
How Mysql Performs Different Selects
How Mysql Transforms Subqueries
Mysql Client/server Protocol
Prepared Statements And Stored Routines
Myisam Storage Engine
Innodb Storage Engine
Writing A Custom Storage Engine
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