MDEV-34860 Implement MAX_EXECUTION_TIME hint

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.

mysql-test/main/opt_hint_timeout.result

+#
+# MAX_EXECUTION_TIME hint testing
+#
+CREATE TABLE t1 (a INT, b VARCHAR(300));
+INSERT INTO t1 VALUES (1, 'string');
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+# Correct hint usage
+SELECT /*+ MAX_EXECUTION_TIME(10) */* FROM t1 a, t1 b;
+ERROR 70100: Query execution was interrupted (max_statement_time exceeded)
+EXPLAIN EXTENDED SELECT /*+ MAX_EXECUTION_TIME(000149) */* FROM t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	512	100.00	
+Warnings:
+Note	1003	select /*+ MAX_EXECUTION_TIME(000149) */ `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1`
+SELECT  /*+ MAX_EXECUTION_TIME(20) */ *, SLEEP(1) FROM t1 UNION SELECT 1, 2, 3;
+ERROR 70100: Query execution was interrupted (max_statement_time exceeded)
+(SELECT /*+ MAX_EXECUTION_TIME(30) */ *, SLEEP(1) FROM t1) UNION (SELECT 1, 2, 3);
+ERROR 70100: Query execution was interrupted (max_statement_time exceeded)
+((SELECT  /*+ MAX_EXECUTION_TIME(50) */ *, SLEEP(1) FROM t1));
+ERROR 70100: Query execution was interrupted (max_statement_time exceeded)
+# Hint duplication
+SELECT /*+ MAX_EXECUTION_TIME(10) MAX_EXECUTION_TIME(100) */ count(*) FROM t1;
+count(*)
+512
+Warnings:
+Warning	4202	Hint MAX_EXECUTION_TIME(100) is ignored as conflicting/duplicated
+# Wrong values
+SELECT /*+ MAX_EXECUTION_TIME(0) */ count(*) FROM t1;
+count(*)
+512
+Warnings:
+Warning	1912	Incorrect value '0' for option 'MAX_EXECUTION_TIME'
+SELECT /*+ MAX_EXECUTION_TIME(-1) */ count(*) FROM t1;
+count(*)
+512
+Warnings:
+Warning	1064	Optimizer hint syntax error near '-1) */ count(*) FROM t1' at line 1
+SELECT /*+ MAX_EXECUTION_TIME(4294967296) */ count(*) FROM t1;
+count(*)
+512
+Warnings:
+Warning	1912	Incorrect value '4294967296' for option 'MAX_EXECUTION_TIME'
+# Conflicting max_statement_time and hint (must issue a warning)
+SET STATEMENT max_statement_time=1 FOR
+SELECT /*+ MAX_EXECUTION_TIME(500) */ count(*) FROM t1 a;
+count(*)
+512
+Warnings:
+Warning	4202	Hint MAX_EXECUTION_TIME(500) is ignored as conflicting/duplicated
+
+# only SELECT statements supports the MAX_EXECUTION_TIME hint (warning):
+
+CREATE TABLE t2 (i INT);
+INSERT /*+ MAX_EXECUTION_TIME(10) */ INTO t2 SELECT 1;
+Warnings:
+Warning	4172	'MAX_EXECUTION_TIME(10)' is not allowed in this context
+REPLACE /*+ MAX_EXECUTION_TIME(15) */ INTO t2 SELECT 1;
+Warnings:
+Warning	4172	'MAX_EXECUTION_TIME(15)' is not allowed in this context
+UPDATE /*+ MAX_EXECUTION_TIME(23) */ t2 SET i = 1;
+Warnings:
+Warning	4172	'MAX_EXECUTION_TIME(23)' is not allowed in this context
+DELETE /*+ MAX_EXECUTION_TIME(5000) */ FROM t2 WHERE i = 1;
+Warnings:
+Warning	4172	'MAX_EXECUTION_TIME(5000)' is not allowed in this context
+# Not supported inside stored procedures/functions
+CREATE PROCEDURE p1() BEGIN SELECT /*+ MAX_EXECUTION_TIME(10) */ count(*) FROM t1 a, t1 b
+INTO @a; END|
+CALL p1();
+Warnings:
+Warning	4172	'MAX_EXECUTION_TIME(10)' is not allowed in this context
+DROP PROCEDURE p1;
+# Hint in a subquery is not allowed (warning):
+SELECT 1 FROM (SELECT /*+ MAX_EXECUTION_TIME(10) */ 1) a;
+1
+1
+Warnings:
+Warning	4172	'MAX_EXECUTION_TIME(10)' is not allowed in this context
+DROP TABLE t1, t2;

mysql-test/main/opt_hint_timeout.test

+--echo #
+--echo # MAX_EXECUTION_TIME hint testing
+--echo #
+
+CREATE TABLE t1 (a INT, b VARCHAR(300));
+INSERT INTO t1 VALUES (1, 'string');
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+
+-- disable_query_log
+-- disable_result_log
+analyze table t1;
+-- enable_result_log
+-- enable_query_log
+
+--echo # Correct hint usage
+--error ER_STATEMENT_TIMEOUT
+SELECT /*+ MAX_EXECUTION_TIME(10) */* FROM t1 a, t1 b;
+
+EXPLAIN EXTENDED SELECT /*+ MAX_EXECUTION_TIME(000149) */* FROM t1;
+
+--error ER_STATEMENT_TIMEOUT
+SELECT  /*+ MAX_EXECUTION_TIME(20) */ *, SLEEP(1) FROM t1 UNION SELECT 1, 2, 3;
+--error ER_STATEMENT_TIMEOUT
+(SELECT /*+ MAX_EXECUTION_TIME(30) */ *, SLEEP(1) FROM t1) UNION (SELECT 1, 2, 3);
+--error ER_STATEMENT_TIMEOUT
+((SELECT  /*+ MAX_EXECUTION_TIME(50) */ *, SLEEP(1) FROM t1));
+
+--echo # Hint duplication
+SELECT /*+ MAX_EXECUTION_TIME(10) MAX_EXECUTION_TIME(100) */ count(*) FROM t1;
+
+--echo # Wrong values
+SELECT /*+ MAX_EXECUTION_TIME(0) */ count(*) FROM t1;
+SELECT /*+ MAX_EXECUTION_TIME(-1) */ count(*) FROM t1;
+SELECT /*+ MAX_EXECUTION_TIME(4294967296) */ count(*) FROM t1;
+
+--echo # Conflicting max_statement_time and hint (must issue a warning)
+SET STATEMENT max_statement_time=1 FOR
+  SELECT /*+ MAX_EXECUTION_TIME(500) */ count(*) FROM t1 a;
+
+--echo
+--echo # only SELECT statements supports the MAX_EXECUTION_TIME hint (warning):
+--echo
+CREATE TABLE t2 (i INT);
+INSERT /*+ MAX_EXECUTION_TIME(10) */ INTO t2 SELECT 1;
+REPLACE /*+ MAX_EXECUTION_TIME(15) */ INTO t2 SELECT 1;
+UPDATE /*+ MAX_EXECUTION_TIME(23) */ t2 SET i = 1;
+DELETE /*+ MAX_EXECUTION_TIME(5000) */ FROM t2 WHERE i = 1;
+
+--echo # Not supported inside stored procedures/functions
+DELIMITER |;
+CREATE PROCEDURE p1() BEGIN SELECT /*+ MAX_EXECUTION_TIME(10) */ count(*) FROM t1 a, t1 b
+INTO @a; END|
+DELIMITER ;|
+
+CALL p1();
+DROP PROCEDURE p1;
+
+--echo # Hint in a subquery is not allowed (warning):
+SELECT 1 FROM (SELECT /*+ MAX_EXECUTION_TIME(10) */ 1) a;
+
+DROP TABLE t1, t2;
+

mysql-test/main/opt_hints.result

@@ -1799,6 +1799,14 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 Warnings:
 Note	1003	select /*+ QB_NAME(`a
 b`) */ 1 AS `1`
+# Identifiers starting with digits must be supported:
+CREATE OR REPLACE TABLE 0a (8a INT, KEY 6a(8a));
+EXPLAIN EXTENDED SELECT /*+ NO_MRR(0a 6a) BKA(0a)*/ 8a FROM 0a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	0a	system	NULL	NULL	NULL	NULL	0	0.00	Const row not found
+Warnings:
+Note	1003	select /*+ BKA(`0a`@`select#1`) NO_MRR(`0a`@`select#1` `6a`) */ NULL AS `8a` from `test`.`0a`
+DROP TABLE 0a;
 # hint syntax error: empty quoted identifier
 EXPLAIN EXTENDED SELECT /*+ QB_NAME(``) */ 1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
@@ -1876,7 +1884,7 @@ SELECT /*+ NO_ICP(10) */ 1;
 1
 1
 Warnings:
-Warning	4204	Unresolved table name `10`@`select#1` for NO_ICP hint
+Warning	1064	Optimizer hint syntax error near '10) */ 1' at line 1
 SELECT /*+ NO_ICP( */ 1;
 1
 1

mysql-test/main/opt_hints.test

@@ -914,6 +914,11 @@ EXPLAIN EXTENDED SELECT /*+ QB_NAME(`*b`) */ 1;
 EXPLAIN EXTENDED SELECT /*+ QB_NAME(`a
 b`) */ 1;
 
+--echo # Identifiers starting with digits must be supported:
+CREATE OR REPLACE TABLE 0a (8a INT, KEY 6a(8a));
+EXPLAIN EXTENDED SELECT /*+ NO_MRR(0a 6a) BKA(0a)*/ 8a FROM 0a;
+DROP TABLE 0a;
+
 --echo # hint syntax error: empty quoted identifier
 EXPLAIN EXTENDED SELECT /*+ QB_NAME(``) */ 1;
 

sql/log_event_server.cc

@@ -4804,7 +4804,7 @@ int Rows_log_event::do_apply_event(rpl_group_info *rgi)
     set/reset the slave thread's timer; a Rows_log_event update needs to set
     the timer itself
   */
-  thd->set_query_timer();
+  thd->set_query_timer_if_needed();
 
   /*
     If there are no tables open, this must be the first row event seen

sql/opt_hints.h

@@ -73,7 +73,7 @@
 #include "sql_bitmap.h"
 #include "sql_show.h"
 #include "mysqld_error.h"
-
+#include "opt_hints_parser.h"
 
 struct LEX;
 struct TABLE;
@@ -91,6 +91,7 @@ enum opt_hints_enum
   MRR_HINT_ENUM,
   NO_RANGE_HINT_ENUM,
   QB_NAME_HINT_ENUM,
+  MAX_EXEC_TIME_HINT_ENUM,
   MAX_HINT_ENUM
 };
 
@@ -304,6 +305,13 @@ class Opt_hints : public Sql_alloc
   void check_unresolved(THD *thd);
   virtual void append_name(THD *thd, String *str)= 0;
 
+  /**
+    Append additional hint arguments to the printed string if they exist.
+    For example, SEMIJOIN and SUBQUERY hints may have a list of strategies
+    as additional arguments
+  */
+  virtual void append_args(THD *thd, String *str) const {}
+
   virtual ~Opt_hints() {}
 
 private:
@@ -336,13 +344,29 @@ class Opt_hints : public Sql_alloc
 
 class Opt_hints_global : public Opt_hints
 {
-
 public:
+  const Optimizer_hint_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 void append_args(THD *thd, String *str) const override
+  {
+    if (max_exec_time_hint)
+      max_exec_time_hint->append_args(thd, str);
+  }
+
+  bool resolve(THD *thd);
 };
 
 

sql/opt_hints_parser.cc

@@ -57,11 +57,30 @@ Optimizer_hint_tokenizer::find_keyword(const LEX_CSTRING &str)
       return TokenID::keyword_QB_NAME;
     break;
 
+  case 18:
+    if ("MAX_EXECUTION_TIME"_Lex_ident_column.streq(str))
+      return TokenID::keyword_MAX_EXECUTION_TIME;
+    break;
+
   case 21:
     if ("NO_RANGE_OPTIMIZATION"_Lex_ident_column.streq(str))
       return TokenID::keyword_NO_RANGE_OPTIMIZATION;
     break;
   }
+
+  if (str.length > 0 && (str.str[0] >= '0' && str.str[0] <= '9'))
+  {
+    /*
+      If all characters are digits, qualify the token as a number,
+      otherwise as an identifier
+    */
+    for(size_t i = 1; i < str.length; i++)
+    {
+      if (str.str[i] < '0' || str.str[i] > '9')
+        return TokenID::tIDENT;
+    }
+    return TokenID::tUNSIGNED_NUMBER;
+  }
   return TokenID::tIDENT;
 }
 

sql/opt_hints_parser.h

@@ -22,6 +22,7 @@
 #include "simple_tokenizer.h"
 #include "sql_list.h"
 #include "sql_string.h"
+#include "sql_type_int.h"
 #include "simple_parser.h"
 
 class st_select_lex;
@@ -72,9 +73,11 @@ class Optimizer_hint_tokenizer: public Extended_string_tokenizer
     keyword_NO_RANGE_OPTIMIZATION,
     keyword_MRR,
     keyword_QB_NAME,
+    keyword_MAX_EXECUTION_TIME,
 
     // Other token types
-    tIDENT
+    tIDENT,
+    tUNSIGNED_NUMBER
   };
 
   class Token: public Lex_cstring
@@ -240,6 +243,13 @@ class Optimizer_hint_parser: public Optimizer_hint_tokenizer,
     using TOKEN::TOKEN;
   };
 
+  class Keyword_MAX_EXECUTION_TIME:
+      public TOKEN<Parser, TokenID::keyword_MAX_EXECUTION_TIME>
+  {
+  public:
+    using TOKEN::TOKEN;
+  };
+
   class Identifier: public TOKEN<Parser, TokenID::tIDENT>
   {
   public:
@@ -258,6 +268,28 @@ class Optimizer_hint_parser: public Optimizer_hint_tokenizer,
     }
   };
 
+  class Unsigned_Number: public TOKEN<Parser, TokenID::tUNSIGNED_NUMBER>
+  {
+  public:
+    using TOKEN::TOKEN;
+
+    /*
+      Converts token string to a non-negative number ( >=0 ).
+      Returns the converted number if the conversion succeeds.
+      Returns non-NULL ULonglong_null value on successful string conversion and
+      NULL ULonglong_null if the conversion failed or the number is negative
+    */
+    ULonglong_null get_ulonglong() const
+    {
+      int error;
+      char *end= const_cast<char *>(str + length);
+      longlong n= my_strtoll10(str, &end, &error);
+      if (error != 0 || end != str + length || n < 0)
+        return ULonglong_null(0, true);
+      return ULonglong_null(n, false);
+    }
+  };
+
   class LParen: public TOKEN<Parser, TokenID::tLPAREN>
   {
   public:
@@ -554,21 +586,40 @@ class Optimizer_hint_parser: public Optimizer_hint_tokenizer,
   };
 
 
+public:
+  // max_execution_time_hint ::= MAX_EXECUTION_TIME ( milliseconds )
+  class Max_execution_time_hint: public AND4<Parser,
+                                  Keyword_MAX_EXECUTION_TIME,
+                                  LParen,
+                                  Unsigned_Number,
+                                  RParen>
+  {
+  public:
+    using AND4::AND4;
+
+    bool resolve(Parse_context *pc) const;
+    void append_args(THD *thd, String *str) const;
+    ulong get_milliseconds() const;
+  };
+
   /*
     hint ::=   index_level_hint
              | table_level_hint
              | qb_name_hint
+             | statement_level_hint
   */
-  class Hint: public OR3<Parser,
+  class Hint: public OR4<Parser,
                          Index_level_hint,
                          Table_level_hint,
-                         Qb_name_hint>
+                         Qb_name_hint,
+                         Max_execution_time_hint>
   {
   public:
-    using OR3::OR3;
+    using OR4::OR4;
   };
 
 
+private:
   // hint_list ::= hint [ hint... ]
   class Hint_list_container: public List<Hint>
   {

sql/share/errmsg-utf8.txt

@@ -12292,3 +12292,7 @@ ER_UNRESOLVED_INDEX_HINT_NAME
         eng "Unresolved index name %s for %s hint"
 ER_HINTS_INSIDE_VIEWS_NOT_SUPPORTED
         eng "Optimizer hints are not supported inside view definitions"
+ER_WARN_BAD_MAX_EXECUTION_TIME
+        eng "Unsupported MAX_EXECUTION_TIME"
+ER_WARN_UNSUPPORTED_MAX_EXECUTION_TIME
+        eng "MAX_EXECUTION_TIME hint is supported by top-level standalone SELECT statements only"

sql/simple_parser.h

@@ -380,7 +380,7 @@ class Parser_templates
 
 
   /*
-    A rule consisting of a choice of thee rules:
+    A rule consisting of a choice of three rules:
       rule ::= rule1 | rule2 | rule3
 
     For the case when the three branches have incompatible storage
@@ -478,7 +478,50 @@ class Parser_templates
 
 
   /*
-    A list with at least MIN_COUNT elements (typlically 0 or 1),
+    A rule consisting of a choice of four rules:
+      rule ::= rule1 | rule2 | rule3 | rule4
+
+    For the case when the three branches have incompatible storage
+  */
+  template<class PARSER, class A, class B, class C, class D>
+  class OR4: public A, public B, public C, public D
+  {
+  public:
+    OR4()
+    { }
+    OR4(OR4 &&rhs)
+     :A(std::move(static_cast<A&&>(rhs))),
+      B(std::move(static_cast<B&&>(rhs))),
+      C(std::move(static_cast<C&&>(rhs))),
+      D(std::move(static_cast<D&&>(rhs)))
+    { }
+    OR4 & operator=(OR4 &&rhs)
+    {
+      A::operator=(std::move(static_cast<A&&>(rhs)));
+      B::operator=(std::move(static_cast<B&&>(rhs)));
+      C::operator=(std::move(static_cast<C&&>(rhs)));
+      D::operator=(std::move(static_cast<D&&>(rhs)));
+      return *this;
+    }
+    OR4(PARSER *p)
+     :A(p),
+      B(A::operator bool() ? B() : B(p)),
+      C(A::operator bool() || B::operator bool() ? C() : C(p)),
+      D(A::operator bool() || B::operator bool() || C::operator bool() ?
+          D() : D(p))
+    {
+      DBUG_ASSERT(!operator bool() || !p->is_error());
+    }
+    operator bool() const
+    {
+      return A::operator bool() || B::operator bool() || C::operator bool() ||
+             D::operator bool();
+    }
+  };
+
+
+  /*
+    A list with at least MIN_COUNT elements (typically 0 or 1),
     with or without a token separator between elements:
 
       list ::= element [ {, element }... ]       // with a separator

sql/sql_base.cc

@@ -8431,6 +8431,8 @@ bool setup_tables(THD *thd, Name_resolution_context *context,
   if (setup_natural_join_row_types(thd, from_clause, context))
     DBUG_RETURN(1);
 
+  if (thd->lex->opt_hints_global && select_lex->select_number == 1)
+    thd->lex->opt_hints_global->resolve(thd);
   if (qb_hints)
     qb_hints->check_unresolved(thd);
   DBUG_RETURN(0);

sql/sql_class.h

@@ -5826,7 +5826,7 @@ class THD: public THD_count, /* this must be first */
   thr_timer_t query_timer;
 
 public:
-  void set_query_timer()
+  void set_query_timer_if_needed()
   {
 #ifndef EMBEDDED_LIBRARY
     /*
@@ -5845,9 +5845,13 @@ class THD: public THD_count, /* this must be first */
     */
     if (!timeout_val || spcont || in_sub_stmt || query_timer.expired == 0)
       return;
-    thr_timer_settime(&query_timer, timeout_val);
+    set_query_timer_force(timeout_val);
 #endif
   }
+  void set_query_timer_force(ulonglong timeout_val)
+  {
+    thr_timer_settime(&query_timer, timeout_val);
+  }
   void reset_query_timer()
   {
 #ifndef EMBEDDED_LIBRARY

sql/sql_parse.cc

@@ -3822,7 +3822,7 @@ mysql_execute_command(THD *thd, bool is_called_from_prepared_stmt)
     thd->query_plan_flags|= QPLAN_ADMIN;
 
   /* Start timeouts */
-  thd->set_query_timer();
+  thd->set_query_timer_if_needed();
 
 #ifdef WITH_WSREP
   /* Check wsrep_mode rules before command execution. */