diff --git a/mysql-test/r/parser_precedence.result b/mysql-test/r/parser_precedence.result
new file mode 100644
index 00000000000..e2d35521ca9
--- /dev/null
+++ b/mysql-test/r/parser_precedence.result
@@ -0,0 +1,356 @@
+drop table if exists t1_30237_bool;
+create table t1_30237_bool(A boolean, B boolean, C boolean);
+insert into t1_30237_bool values
+(FALSE, FALSE, FALSE),
+(FALSE, FALSE, NULL),
+(FALSE, FALSE, TRUE),
+(FALSE, NULL, FALSE),
+(FALSE, NULL, NULL),
+(FALSE, NULL, TRUE),
+(FALSE, TRUE, FALSE),
+(FALSE, TRUE, NULL),
+(FALSE, TRUE, TRUE),
+(NULL, FALSE, FALSE),
+(NULL, FALSE, NULL),
+(NULL, FALSE, TRUE),
+(NULL, NULL, FALSE),
+(NULL, NULL, NULL),
+(NULL, NULL, TRUE),
+(NULL, TRUE, FALSE),
+(NULL, TRUE, NULL),
+(NULL, TRUE, TRUE),
+(TRUE, FALSE, FALSE),
+(TRUE, FALSE, NULL),
+(TRUE, FALSE, TRUE),
+(TRUE, NULL, FALSE),
+(TRUE, NULL, NULL),
+(TRUE, NULL, TRUE),
+(TRUE, TRUE, FALSE),
+(TRUE, TRUE, NULL),
+(TRUE, TRUE, TRUE) ;
+Testing OR, XOR, AND
+select A, B, A OR B, A XOR B, A AND B
+from t1_30237_bool where C is null order by A, B;
+A	B	A OR B	A XOR B	A AND B
+NULL	NULL	NULL	NULL	NULL
+NULL	0	NULL	NULL	0
+NULL	1	1	NULL	NULL
+0	NULL	NULL	NULL	0
+0	0	0	0	0
+0	1	1	1	0
+1	NULL	1	NULL	NULL
+1	0	1	1	0
+1	1	1	0	1
+Testing that OR is associative 
+select A, B, C, (A OR B) OR C, A OR (B OR C), A OR B OR C
+from t1_30237_bool order by A, B, C;
+A	B	C	(A OR B) OR C	A OR (B OR C)	A OR B OR C
+NULL	NULL	NULL	NULL	NULL	NULL
+NULL	NULL	0	NULL	NULL	NULL
+NULL	NULL	1	1	1	1
+NULL	0	NULL	NULL	NULL	NULL
+NULL	0	0	NULL	NULL	NULL
+NULL	0	1	1	1	1
+NULL	1	NULL	1	1	1
+NULL	1	0	1	1	1
+NULL	1	1	1	1	1
+0	NULL	NULL	NULL	NULL	NULL
+0	NULL	0	NULL	NULL	NULL
+0	NULL	1	1	1	1
+0	0	NULL	NULL	NULL	NULL
+0	0	0	0	0	0
+0	0	1	1	1	1
+0	1	NULL	1	1	1
+0	1	0	1	1	1
+0	1	1	1	1	1
+1	NULL	NULL	1	1	1
+1	NULL	0	1	1	1
+1	NULL	1	1	1	1
+1	0	NULL	1	1	1
+1	0	0	1	1	1
+1	0	1	1	1	1
+1	1	NULL	1	1	1
+1	1	0	1	1	1
+1	1	1	1	1	1
+select count(*) from t1_30237_bool
+where ((A OR B) OR C) != (A OR (B OR C));
+count(*)
+0
+Testing that XOR is associative 
+select A, B, C, (A XOR B) XOR C, A XOR (B XOR C), A XOR B XOR C
+from t1_30237_bool order by A, B, C;
+A	B	C	(A XOR B) XOR C	A XOR (B XOR C)	A XOR B XOR C
+NULL	NULL	NULL	NULL	NULL	NULL
+NULL	NULL	0	NULL	NULL	NULL
+NULL	NULL	1	NULL	NULL	NULL
+NULL	0	NULL	NULL	NULL	NULL
+NULL	0	0	NULL	NULL	NULL
+NULL	0	1	NULL	NULL	NULL
+NULL	1	NULL	NULL	NULL	NULL
+NULL	1	0	NULL	NULL	NULL
+NULL	1	1	NULL	NULL	NULL
+0	NULL	NULL	NULL	NULL	NULL
+0	NULL	0	NULL	NULL	NULL
+0	NULL	1	NULL	NULL	NULL
+0	0	NULL	NULL	NULL	NULL
+0	0	0	0	0	0
+0	0	1	1	1	1
+0	1	NULL	NULL	NULL	NULL
+0	1	0	1	1	1
+0	1	1	0	0	0
+1	NULL	NULL	NULL	NULL	NULL
+1	NULL	0	NULL	NULL	NULL
+1	NULL	1	NULL	NULL	NULL
+1	0	NULL	NULL	NULL	NULL
+1	0	0	1	1	1
+1	0	1	0	0	0
+1	1	NULL	NULL	NULL	NULL
+1	1	0	0	0	0
+1	1	1	1	1	1
+select count(*) from t1_30237_bool
+where ((A XOR B) XOR C) != (A XOR (B XOR C));
+count(*)
+0
+Testing that AND is associative 
+select A, B, C, (A AND B) AND C, A AND (B AND C), A AND B AND C
+from t1_30237_bool order by A, B, C;
+A	B	C	(A AND B) AND C	A AND (B AND C)	A AND B AND C
+NULL	NULL	NULL	NULL	NULL	NULL
+NULL	NULL	0	0	0	0
+NULL	NULL	1	NULL	NULL	NULL
+NULL	0	NULL	0	0	0
+NULL	0	0	0	0	0
+NULL	0	1	0	0	0
+NULL	1	NULL	NULL	NULL	NULL
+NULL	1	0	0	0	0
+NULL	1	1	NULL	NULL	NULL
+0	NULL	NULL	0	0	0
+0	NULL	0	0	0	0
+0	NULL	1	0	0	0
+0	0	NULL	0	0	0
+0	0	0	0	0	0
+0	0	1	0	0	0
+0	1	NULL	0	0	0
+0	1	0	0	0	0
+0	1	1	0	0	0
+1	NULL	NULL	NULL	NULL	NULL
+1	NULL	0	0	0	0
+1	NULL	1	NULL	NULL	NULL
+1	0	NULL	0	0	0
+1	0	0	0	0	0
+1	0	1	0	0	0
+1	1	NULL	NULL	NULL	NULL
+1	1	0	0	0	0
+1	1	1	1	1	1
+select count(*) from t1_30237_bool
+where ((A AND B) AND C) != (A AND (B AND C));
+count(*)
+0
+Testing that AND has precedence over OR
+select A, B, C, (A OR B) AND C, A OR (B AND C), A OR B AND C
+from t1_30237_bool order by A, B, C;
+A	B	C	(A OR B) AND C	A OR (B AND C)	A OR B AND C
+NULL	NULL	NULL	NULL	NULL	NULL
+NULL	NULL	0	0	NULL	NULL
+NULL	NULL	1	NULL	NULL	NULL
+NULL	0	NULL	NULL	NULL	NULL
+NULL	0	0	0	NULL	NULL
+NULL	0	1	NULL	NULL	NULL
+NULL	1	NULL	NULL	NULL	NULL
+NULL	1	0	0	NULL	NULL
+NULL	1	1	1	1	1
+0	NULL	NULL	NULL	NULL	NULL
+0	NULL	0	0	0	0
+0	NULL	1	NULL	NULL	NULL
+0	0	NULL	0	0	0
+0	0	0	0	0	0
+0	0	1	0	0	0
+0	1	NULL	NULL	NULL	NULL
+0	1	0	0	0	0
+0	1	1	1	1	1
+1	NULL	NULL	NULL	1	1
+1	NULL	0	0	1	1
+1	NULL	1	1	1	1
+1	0	NULL	NULL	1	1
+1	0	0	0	1	1
+1	0	1	1	1	1
+1	1	NULL	NULL	1	1
+1	1	0	0	1	1
+1	1	1	1	1	1
+select count(*) from t1_30237_bool
+where (A OR (B AND C)) != (A OR B AND C);
+count(*)
+0
+select A, B, C, (A AND B) OR C, A AND (B OR C), A AND B OR C
+from t1_30237_bool order by A, B, C;
+A	B	C	(A AND B) OR C	A AND (B OR C)	A AND B OR C
+NULL	NULL	NULL	NULL	NULL	NULL
+NULL	NULL	0	NULL	NULL	NULL
+NULL	NULL	1	1	NULL	1
+NULL	0	NULL	NULL	NULL	NULL
+NULL	0	0	0	0	0
+NULL	0	1	1	NULL	1
+NULL	1	NULL	NULL	NULL	NULL
+NULL	1	0	NULL	NULL	NULL
+NULL	1	1	1	NULL	1
+0	NULL	NULL	NULL	0	NULL
+0	NULL	0	0	0	0
+0	NULL	1	1	0	1
+0	0	NULL	NULL	0	NULL
+0	0	0	0	0	0
+0	0	1	1	0	1
+0	1	NULL	NULL	0	NULL
+0	1	0	0	0	0
+0	1	1	1	0	1
+1	NULL	NULL	NULL	NULL	NULL
+1	NULL	0	NULL	NULL	NULL
+1	NULL	1	1	1	1
+1	0	NULL	NULL	NULL	NULL
+1	0	0	0	0	0
+1	0	1	1	1	1
+1	1	NULL	1	1	1
+1	1	0	1	1	1
+1	1	1	1	1	1
+select count(*) from t1_30237_bool
+where ((A AND B) OR C) != (A AND B OR C);
+count(*)
+0
+Testing that AND has precedence over XOR
+select A, B, C, (A XOR B) AND C, A XOR (B AND C), A XOR B AND C
+from t1_30237_bool order by A, B, C;
+A	B	C	(A XOR B) AND C	A XOR (B AND C)	A XOR B AND C
+NULL	NULL	NULL	NULL	NULL	NULL
+NULL	NULL	0	0	NULL	NULL
+NULL	NULL	1	NULL	NULL	NULL
+NULL	0	NULL	NULL	NULL	NULL
+NULL	0	0	0	NULL	NULL
+NULL	0	1	NULL	NULL	NULL
+NULL	1	NULL	NULL	NULL	NULL
+NULL	1	0	0	NULL	NULL
+NULL	1	1	NULL	NULL	NULL
+0	NULL	NULL	NULL	NULL	NULL
+0	NULL	0	0	0	0
+0	NULL	1	NULL	NULL	NULL
+0	0	NULL	0	0	0
+0	0	0	0	0	0
+0	0	1	0	0	0
+0	1	NULL	NULL	NULL	NULL
+0	1	0	0	0	0
+0	1	1	1	1	1
+1	NULL	NULL	NULL	NULL	NULL
+1	NULL	0	0	1	1
+1	NULL	1	NULL	NULL	NULL
+1	0	NULL	NULL	1	1
+1	0	0	0	1	1
+1	0	1	1	1	1
+1	1	NULL	0	NULL	NULL
+1	1	0	0	1	1
+1	1	1	0	0	0
+select count(*) from t1_30237_bool
+where (A XOR (B AND C)) != (A XOR B AND C);
+count(*)
+0
+select A, B, C, (A AND B) XOR C, A AND (B XOR C), A AND B XOR C
+from t1_30237_bool order by A, B, C;
+A	B	C	(A AND B) XOR C	A AND (B XOR C)	A AND B XOR C
+NULL	NULL	NULL	NULL	NULL	NULL
+NULL	NULL	0	NULL	NULL	NULL
+NULL	NULL	1	NULL	NULL	NULL
+NULL	0	NULL	NULL	NULL	NULL
+NULL	0	0	0	0	0
+NULL	0	1	1	NULL	1
+NULL	1	NULL	NULL	NULL	NULL
+NULL	1	0	NULL	NULL	NULL
+NULL	1	1	NULL	0	NULL
+0	NULL	NULL	NULL	0	NULL
+0	NULL	0	0	0	0
+0	NULL	1	1	0	1
+0	0	NULL	NULL	0	NULL
+0	0	0	0	0	0
+0	0	1	1	0	1
+0	1	NULL	NULL	0	NULL
+0	1	0	0	0	0
+0	1	1	1	0	1
+1	NULL	NULL	NULL	NULL	NULL
+1	NULL	0	NULL	NULL	NULL
+1	NULL	1	NULL	NULL	NULL
+1	0	NULL	NULL	NULL	NULL
+1	0	0	0	0	0
+1	0	1	1	1	1
+1	1	NULL	NULL	NULL	NULL
+1	1	0	1	1	1
+1	1	1	0	0	0
+select count(*) from t1_30237_bool
+where ((A AND B) XOR C) != (A AND B XOR C);
+count(*)
+0
+Testing that XOR has precedence over OR
+select A, B, C, (A XOR B) OR C, A XOR (B OR C), A XOR B OR C
+from t1_30237_bool order by A, B, C;
+A	B	C	(A XOR B) OR C	A XOR (B OR C)	A XOR B OR C
+NULL	NULL	NULL	NULL	NULL	NULL
+NULL	NULL	0	NULL	NULL	NULL
+NULL	NULL	1	1	NULL	1
+NULL	0	NULL	NULL	NULL	NULL
+NULL	0	0	NULL	NULL	NULL
+NULL	0	1	1	NULL	1
+NULL	1	NULL	NULL	NULL	NULL
+NULL	1	0	NULL	NULL	NULL
+NULL	1	1	1	NULL	1
+0	NULL	NULL	NULL	NULL	NULL
+0	NULL	0	NULL	NULL	NULL
+0	NULL	1	1	1	1
+0	0	NULL	NULL	NULL	NULL
+0	0	0	0	0	0
+0	0	1	1	1	1
+0	1	NULL	1	1	1
+0	1	0	1	1	1
+0	1	1	1	1	1
+1	NULL	NULL	NULL	NULL	NULL
+1	NULL	0	NULL	NULL	NULL
+1	NULL	1	1	0	1
+1	0	NULL	1	NULL	1
+1	0	0	1	1	1
+1	0	1	1	0	1
+1	1	NULL	NULL	0	NULL
+1	1	0	0	0	0
+1	1	1	1	0	1
+select count(*) from t1_30237_bool
+where ((A XOR B) OR C) != (A XOR B OR C);
+count(*)
+0
+select A, B, C, (A OR B) XOR C, A OR (B XOR C), A OR B XOR C
+from t1_30237_bool order by A, B, C;
+A	B	C	(A OR B) XOR C	A OR (B XOR C)	A OR B XOR C
+NULL	NULL	NULL	NULL	NULL	NULL
+NULL	NULL	0	NULL	NULL	NULL
+NULL	NULL	1	NULL	NULL	NULL
+NULL	0	NULL	NULL	NULL	NULL
+NULL	0	0	NULL	NULL	NULL
+NULL	0	1	NULL	1	1
+NULL	1	NULL	NULL	NULL	NULL
+NULL	1	0	1	1	1
+NULL	1	1	0	NULL	NULL
+0	NULL	NULL	NULL	NULL	NULL
+0	NULL	0	NULL	NULL	NULL
+0	NULL	1	NULL	NULL	NULL
+0	0	NULL	NULL	NULL	NULL
+0	0	0	0	0	0
+0	0	1	1	1	1
+0	1	NULL	NULL	NULL	NULL
+0	1	0	1	1	1
+0	1	1	0	0	0
+1	NULL	NULL	NULL	1	1
+1	NULL	0	1	1	1
+1	NULL	1	0	1	1
+1	0	NULL	NULL	1	1
+1	0	0	1	1	1
+1	0	1	0	1	1
+1	1	NULL	NULL	1	1
+1	1	0	1	1	1
+1	1	1	0	1	1
+select count(*) from t1_30237_bool
+where (A OR (B XOR C)) != (A OR B XOR C);
+count(*)
+0
+drop table t1_30237_bool;
diff --git a/mysql-test/t/parser_precedence.test b/mysql-test/t/parser_precedence.test
new file mode 100644
index 00000000000..a3a80776fb1
--- /dev/null
+++ b/mysql-test/t/parser_precedence.test
@@ -0,0 +1,93 @@
+
+--disable_warnings
+drop table if exists t1_30237_bool;
+--enable_warnings
+
+create table t1_30237_bool(A boolean, B boolean, C boolean);
+
+insert into t1_30237_bool values
+(FALSE, FALSE, FALSE),
+(FALSE, FALSE, NULL),
+(FALSE, FALSE, TRUE),
+(FALSE, NULL, FALSE),
+(FALSE, NULL, NULL),
+(FALSE, NULL, TRUE),
+(FALSE, TRUE, FALSE),
+(FALSE, TRUE, NULL),
+(FALSE, TRUE, TRUE),
+(NULL, FALSE, FALSE),
+(NULL, FALSE, NULL),
+(NULL, FALSE, TRUE),
+(NULL, NULL, FALSE),
+(NULL, NULL, NULL),
+(NULL, NULL, TRUE),
+(NULL, TRUE, FALSE),
+(NULL, TRUE, NULL),
+(NULL, TRUE, TRUE),
+(TRUE, FALSE, FALSE),
+(TRUE, FALSE, NULL),
+(TRUE, FALSE, TRUE),
+(TRUE, NULL, FALSE),
+(TRUE, NULL, NULL),
+(TRUE, NULL, TRUE),
+(TRUE, TRUE, FALSE),
+(TRUE, TRUE, NULL),
+(TRUE, TRUE, TRUE) ;
+
+--echo Testing OR, XOR, AND
+select A, B, A OR B, A XOR B, A AND B
+  from t1_30237_bool where C is null order by A, B;
+
+--echo Testing that OR is associative 
+select A, B, C, (A OR B) OR C, A OR (B OR C), A OR B OR C
+ from t1_30237_bool order by A, B, C;
+
+select count(*) from t1_30237_bool
+  where ((A OR B) OR C) != (A OR (B OR C));
+
+--echo Testing that XOR is associative 
+select A, B, C, (A XOR B) XOR C, A XOR (B XOR C), A XOR B XOR C
+  from t1_30237_bool order by A, B, C;
+
+select count(*) from t1_30237_bool
+  where ((A XOR B) XOR C) != (A XOR (B XOR C));
+
+--echo Testing that AND is associative 
+select A, B, C, (A AND B) AND C, A AND (B AND C), A AND B AND C
+  from t1_30237_bool order by A, B, C;
+
+select count(*) from t1_30237_bool
+  where ((A AND B) AND C) != (A AND (B AND C));
+
+--echo Testing that AND has precedence over OR
+select A, B, C, (A OR B) AND C, A OR (B AND C), A OR B AND C
+  from t1_30237_bool order by A, B, C;
+select count(*) from t1_30237_bool
+  where (A OR (B AND C)) != (A OR B AND C);
+select A, B, C, (A AND B) OR C, A AND (B OR C), A AND B OR C
+  from t1_30237_bool order by A, B, C;
+select count(*) from t1_30237_bool
+  where ((A AND B) OR C) != (A AND B OR C);
+
+--echo Testing that AND has precedence over XOR
+select A, B, C, (A XOR B) AND C, A XOR (B AND C), A XOR B AND C
+  from t1_30237_bool order by A, B, C;
+select count(*) from t1_30237_bool
+  where (A XOR (B AND C)) != (A XOR B AND C);
+select A, B, C, (A AND B) XOR C, A AND (B XOR C), A AND B XOR C
+  from t1_30237_bool order by A, B, C;
+select count(*) from t1_30237_bool
+  where ((A AND B) XOR C) != (A AND B XOR C);
+
+--echo Testing that XOR has precedence over OR
+select A, B, C, (A XOR B) OR C, A XOR (B OR C), A XOR B OR C
+  from t1_30237_bool order by A, B, C;
+select count(*) from t1_30237_bool
+  where ((A XOR B) OR C) != (A XOR B OR C);
+select A, B, C, (A OR B) XOR C, A OR (B XOR C), A OR B XOR C
+  from t1_30237_bool order by A, B, C;
+select count(*) from t1_30237_bool
+  where (A OR (B XOR C)) != (A OR B XOR C);
+
+drop table t1_30237_bool;
+
diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index 9afc0507817..da71b3ef512 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -1361,6 +1361,7 @@ public:
   Item_cond(List<Item> &nlist)
     :Item_bool_func(), list(nlist), abort_on_null(0) {}
   bool add(Item *item) { return list.push_back(item); }
+  bool add_at_head(Item *item) { return list.push_front(item); }
   void add_at_head(List<Item> *nlist) { list.prepand(nlist); }
   bool fix_fields(THD *, Item **ref);
 
@@ -1554,6 +1555,15 @@ public:
   Item *neg_transformer(THD *thd);
 };
 
+inline bool is_cond_and(Item *item)
+{
+  if (item->type() != Item::COND_ITEM)
+    return FALSE;
+
+  Item_cond *cond_item= (Item_cond*) item;
+  return (cond_item->functype() == Item_func::COND_AND_FUNC);
+}
+
 class Item_cond_or :public Item_cond
 {
 public:
@@ -1575,6 +1585,14 @@ public:
   Item *neg_transformer(THD *thd);
 };
 
+inline bool is_cond_or(Item *item)
+{
+  if (item->type() != Item::COND_ITEM)
+    return FALSE;
+
+  Item_cond *cond_item= (Item_cond*) item;
+  return (cond_item->functype() == Item_func::COND_OR_FUNC);
+}
 
 /*
   XOR is Item_cond, not an Item_int_func because we could like to
diff --git a/sql/sql_yacc.yy b/sql/sql_yacc.yy
index d71e756e91c..4230e6ee371 100644
--- a/sql/sql_yacc.yy
+++ b/sql/sql_yacc.yy
@@ -458,10 +458,10 @@ bool my_yyoverflow(short **a, YYSTYPE **b, ulong *yystacksize);
 
 %pure_parser					/* We have threads */
 /*
-  Currently there is 251 shift/reduce conflict. We should not introduce
-  new conflicts any more.
+  Currently there are 245 shift/reduce conflicts.
+  We should not introduce new conflicts any more.
 */
-%expect 251
+%expect 245
 
 %token  END_OF_INPUT
 
@@ -1011,7 +1011,8 @@ bool my_yyoverflow(short **a, YYSTYPE **b, ulong *yystacksize);
 /* A dummy token to force the priority of table_ref production in a join. */
 %left   TABLE_REF_PRIORITY
 %left   SET_VAR
-%left	OR_OR_SYM OR_SYM OR2_SYM XOR
+%left	OR_OR_SYM OR_SYM OR2_SYM
+%left	XOR
 %left	AND_SYM AND_AND_SYM
 %left	BETWEEN_SYM CASE_SYM WHEN_SYM THEN_SYM ELSE
 %left	EQ EQUAL_SYM GE GT_SYM LE LT NE IS LIKE REGEXP IN_SYM
@@ -1024,6 +1025,7 @@ bool my_yyoverflow(short **a, YYSTYPE **b, ulong *yystacksize);
 %left	NEG '~'
 %right	NOT_SYM NOT2_SYM
 %right	BINARY COLLATE_SYM
+%left   INTERVAL_SYM
 
 %type <lex_str>
         IDENT IDENT_QUOTED TEXT_STRING DECIMAL_NUM FLOAT_NUM NUM LONG_NUM HEX_NUM
@@ -1066,7 +1068,8 @@ bool my_yyoverflow(short **a, YYSTYPE **b, ulong *yystacksize);
 %type <item>
 	literal text_literal insert_ident order_ident
 	simple_ident select_item2 expr opt_expr opt_else sum_expr in_sum_expr
-	variable variable_aux bool_term bool_factor bool_test bool_pri 
+	variable variable_aux bool_factor
+        bool_test bool_pri
 	predicate bit_expr bit_term bit_factor value_expr term factor
 	table_wild simple_expr udf_expr
 	expr_or_default set_expr_or_default interval_expr
@@ -4464,53 +4467,103 @@ optional_braces:
 	| '(' ')' {};
 
 /* all possible expressions */
-expr:	
-	  bool_term { Select->expr_list.push_front(new List<Item>); }
-          bool_or_expr
+expr:
+          bool_factor
+        | expr or expr %prec OR_SYM
           {
-            List<Item> *list= Select->expr_list.pop();
-            if (list->elements)
+            /*
+              Design notes:
+              Do not use a manually maintained stack like thd->lex->xxx_list,
+              but use the internal bison stack ($$, $1 and $3) instead.
+              Using the bison stack is:
+              - more robust to changes in the grammar,
+              - guaranteed to be in sync with the parser state,
+              - better for performances (no memory allocation).
+            */
+            Item_cond_or *item1;
+            Item_cond_or *item3;
+            if (is_cond_or($1))
             {
-              list->push_front($1);
-              $$= new Item_cond_or(*list);
-              /* optimize construction of logical OR to reduce
-                 amount of objects for complex expressions */
+              item1= (Item_cond_or*) $1;
+              if (is_cond_or($3))
+              {
+                item3= (Item_cond_or*) $3;
+                /*
+                  (X1 OR X2) OR (Y1 OR Y2) ==> OR (X1, X2, Y1, Y2)
+                */
+                item3->add_at_head(item1->argument_list());
+                $$ = $3;
+              }
+              else
+              {
+                /*
+                  (X1 OR X2) OR Y ==> OR (X1, X2, Y)
+                */
+                item1->add($3);
+                $$ = $1;
+              }
+            }
+            else if (is_cond_or($3))
+            {
+              item3= (Item_cond_or*) $3;
+              /*
+                X OR (Y1 OR Y2) ==> OR (X, Y1, Y2)
+              */
+              item3->add_at_head($1);
+              $$ = $3;
             }
             else
-              $$= $1;
-            delete list;
-          }
-	;
-
-bool_or_expr:
-	/* empty */
-        | bool_or_expr or bool_term
-          { Select->expr_list.head()->push_back($3); }
-        ;
-
-bool_term:
-	bool_term XOR bool_term { $$= new Item_cond_xor($1,$3); }
-	| bool_factor { Select->expr_list.push_front(new List<Item>); }
-          bool_and_expr
-          {
-            List<Item> *list= Select->expr_list.pop();
-            if (list->elements)
             {
-              list->push_front($1);
-              $$= new Item_cond_and(*list);
-              /* optimize construction of logical AND to reduce
-                 amount of objects for complex expressions */
+              /* X OR Y */
+              $$ = new (YYTHD->mem_root) Item_cond_or($1, $3);
+            }
+          }
+        | expr XOR expr %prec XOR
+          {
+            /* XOR is a proprietary extension */
+            $$ = new (YYTHD->mem_root) Item_cond_xor($1, $3);
+          }
+        | expr and expr %prec AND_SYM
+          {
+            /* See comments in rule expr: expr or expr */
+            Item_cond_and *item1;
+            Item_cond_and *item3;
+            if (is_cond_and($1))
+            {
+              item1= (Item_cond_and*) $1;
+              if (is_cond_and($3))
+              {
+                item3= (Item_cond_and*) $3;
+                /*
+                  (X1 AND X2) AND (Y1 AND Y2) ==> AND (X1, X2, Y1, Y2)
+                */
+                item3->add_at_head(item1->argument_list());
+                $$ = $3;
+              }
+              else
+              {
+                /*
+                  (X1 AND X2) AND Y ==> AND (X1, X2, Y)
+                */
+                item1->add($3);
+                $$ = $1;
+              }
+            }
+            else if (is_cond_and($3))
+            {
+              item3= (Item_cond_and*) $3;
+              /*
+                X AND (Y1 AND Y2) ==> AND (X, Y1, Y2)
+              */
+              item3->add_at_head($1);
+              $$ = $3;
             }
             else
-              $$= $1;
-            delete list;
+            {
+              /* X AND Y */
+              $$ = new (YYTHD->mem_root) Item_cond_and($1, $3);
+            }
           }
-	;
-
-bool_and_expr:
-	/* empty */
-        | bool_and_expr and bool_factor
-          { Select->expr_list.head()->push_back($3); }
         ;
 
 bool_factor:
@@ -4648,7 +4701,8 @@ all_or_any: ALL     { $$ = 1; }
         ;
 
 interval_expr:
-         INTERVAL_SYM expr { $$=$2; }
+          INTERVAL_SYM expr %prec INTERVAL_SYM
+          { $$=$2; }
         ;
 
 simple_expr: