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SHOW EXPLAIN: better comments

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This commit is contained in:
Sergey Petrunya
2012-06-19 18:10:32 +04:00
parent 1ce0c706b3
commit 6eb2ce5863
3 changed files with 31 additions and 33 deletions
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29
sql/sql_class.h
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@ -1522,16 +1522,29 @@ extern "C" void my_message_sql(uint error, const char *str, myf MyFlags);
class select_result_explain_buffer;
/*
SHOW EXPLAIN request object.
The thread that runs SHOW EXPLAIN statement creates a Show_explain_request
object R, and then schedules APC call of
Show_explain_request::get_explain_data((void*)&R).
*/
class Show_explain_request
{
public:
THD *target_thd;
THD *request_thd;
THD *target_thd; /* thd that we're running SHOW EXPLAIN for */
THD *request_thd; /* thd that run SHOW EXPLAIN command */
/* If true, there was some error when producing EXPLAIN output. */
bool failed_to_produce;
/* SHOW EXPLAIN will be stored here */
select_result_explain_buffer *explain_buf;
/* Query that we've got SHOW EXPLAIN for */
String query_str;
static void get_explain_data(void *arg);
@ -2414,11 +2427,11 @@ public:
/*
This is what allows this thread to serve as a target for others to
schedule Async Procedure Calls on.
Allows this thread to serve as a target for others to schedule Async
Procedure Calls on.
It's possible to schedule arbitrary C function call but currently this
facility is used only by SHOW EXPLAIN code (See Show_explain_request)
It's possible to schedule arbitrary C++ function calls. Currently, only
Show_explain_request uses this.
*/
Apc_target apc_target;