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MDEV-34860 Implement MAX_EXECUTION_TIME hint

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It places a limit N (a timeout value in milliseconds) on how long
a statement is permitted to execute before the server terminates it.

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

Only top-level SELECT statements support the hint.
This commit is contained in:
Oleg Smirnov
2024-08-07 22:10:50 +07:00
parent 1e2774d829
commit 67319f3e8d
20 changed files with 573 additions and 51 deletions
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37
sql/opt_hints.h
View File

@@ -65,6 +65,7 @@
#ifndef OPT_HINTS_INCLUDED
#define OPT_HINTS_INCLUDED
#include <functional>
#include "my_config.h"
#include "sql_alloc.h"
#include "sql_list.h"
@@ -73,7 +74,7 @@
#include "sql_bitmap.h"
#include "sql_show.h"
#include "mysqld_error.h"
#include "opt_hints_parser.h"
struct LEX;
struct TABLE;
@@ -91,6 +92,7 @@ enum opt_hints_enum
MRR_HINT_ENUM,
NO_RANGE_HINT_ENUM,
QB_NAME_HINT_ENUM,
MAX_EXEC_TIME_HINT_ENUM,
MAX_HINT_ENUM
};
@@ -100,9 +102,10 @@ struct st_opt_hint_info
LEX_CSTRING hint_name; // Hint name.
bool check_upper_lvl; // true if upper level hint check is needed (for hints
// which can be specified on more than one level).
bool switch_hint; // true if hint is not complex.
bool has_arguments; // true if hint has additional arguments.
};
typedef Optimizer_hint_parser Parser;
/**
Opt_hints_map contains information
@@ -304,6 +307,16 @@ public:
void check_unresolved(THD *thd);
virtual void append_name(THD *thd, String *str)= 0;
/**
Get the function appending additional hint arguments to the printed string,
if the arguments exist. For example, SEMIJOIN and SUBQUERY hints may have
a list of strategies as additional arguments
*/
virtual std::function<void(THD*, String*)> get_args_printer() const
{
return [](THD*, String*) {};
}
virtual ~Opt_hints() {}
private:
@@ -336,13 +349,31 @@ protected:
class Opt_hints_global : public Opt_hints
{
public:
const Parser::Max_execution_time_hint *max_exec_time_hint= nullptr;
/*
If MAX_EXECUTION_TIME() hint was provided, this pointer is set to
the SELECT_LEX which the hint is attached to.
NULL if MAX_EXECUTION_TIME() hint is missing.
*/
st_select_lex *max_exec_time_select_lex= nullptr;
Opt_hints_global(MEM_ROOT *mem_root_arg)
: Opt_hints(Lex_ident_sys(), NULL, mem_root_arg)
{}
virtual void append_name(THD *thd, String *str) override {}
virtual std::function<void(THD*, String*)> get_args_printer() const override
{
using std::placeholders::_1;
using std::placeholders::_2;
return std::bind(&Parser::Max_execution_time_hint::append_args,
max_exec_time_hint, _1, _2);
}
bool resolve(THD *thd);
};