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MDEV-3798: EXPLAIN UPDATE/DELETE

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Update the SHOW EXPLAIN code to work with the 
new architecture (part#1):
Before, SHOW EXPLAIN operated on real query plan structures, 
which meant it had to check when SELECTs are created/deleted.
SELECTs would call apc_target->enable() when they got a query 
plan and disable() when their query plan was deleted.

Now, Explain data structure becomes available at once (and we
call apc_target->enable()) and then it stays until it is deleted
(when that happens, we call apc_target->disable()).
This commit is contained in:
Sergey Petrunya
2013-10-14 20:09:33 +04:00
parent f67f8fd00f
commit 105e3ae6c9
11 changed files with 76 additions and 45 deletions
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24
sql/sql_explain.h
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@@ -221,10 +221,13 @@ class Explain_insert;
class Explain_query : public Sql_alloc
{
public:
Explain_query();
Explain_query(THD *thd);
~Explain_query();
/* Add a new node */
void add_node(Explain_node *node);
void add_insert_plan(Explain_insert *insert_plan_arg);
void add_upd_del_plan(Explain_update *upd_del_plan_arg);
/* This will return a select, or a union */
Explain_node *get_node(uint select_id);
@@ -233,13 +236,7 @@ public:
Explain_select *get_select(uint select_id);
Explain_union *get_union(uint select_id);
/* Explain_delete inherits from Explain_update */
Explain_update *upd_del_plan;
/* Query "plan" for INSERTs */
Explain_insert *insert_plan;
/* Produce a tabular EXPLAIN output */
int print_explain(select_result_sink *output, uint8 explain_flags);
@@ -251,11 +248,22 @@ public:
/* If true, at least part of EXPLAIN can be printed */
bool have_query_plan() { return insert_plan || upd_del_plan|| get_node(1) != NULL; }
void query_plan_ready();
MEM_ROOT *mem_root;
private:
/* Explain_delete inherits from Explain_update */
Explain_update *upd_del_plan;
/* Query "plan" for INSERTs */
Explain_insert *insert_plan;
Dynamic_array<Explain_union*> unions;
Dynamic_array<Explain_select*> selects;
THD *thd; // for APC start/stop
bool apc_enabled;
/*
Debugging aid: count how many times add_node() was called. Ideally, it
should be one, we currently allow O(1) query plan saves for each