Bug#21904 (parser problem when using IN with a double "(())")

Before this fix, a IN predicate of the form: "IN (( subselect ))", with two
parenthesis, would be evaluated as a single row subselect: if the subselect
returns more that 1 row, the statement would fail.

The SQL:2003 standard defines a special exception in the specification,
and mandates that this particular form of IN predicate shall be equivalent
to "IN ( subselect )", which involves a table subquery and works with more
than 1 row.

This fix implements "IN (( subselect ))", "IN ((( subselect )))" etc
as per the SQL:2003 requirement.

All the details related to the implementation of this change have been
commented in the code, and the relevant sections of the SQL:2003 spec
are given for reference, so they are not repeated here.

Having access to the spec is a requirement to review in depth this patch.


mysql-test/r/subselect.result:
  Implement IN predicate special exceptions with subselects.
mysql-test/t/subselect.test:
  Implement IN predicate special exceptions with subselects.
sql/item_subselect.cc:
  Implement IN predicate special exceptions with subselects.
sql/item_subselect.h:
  Implement IN predicate special exceptions with subselects.
sql/sql_yacc.yy:
  Implement IN predicate special exceptions with subselects, cleanup.

mysql-test/r/subselect.result

@@ -3592,3 +3592,116 @@ FROM t1) t;
 COUNT(*)
 3000
 DROP TABLE t1,t2;
+DROP TABLE IF EXISTS t1;
+DROP TABLE IF EXISTS t2;
+DROP TABLE IF EXISTS t1xt2;
+CREATE TABLE t1 (
+id_1 int(5) NOT NULL,
+t varchar(4) DEFAULT NULL
+);
+CREATE TABLE t2 (
+id_2 int(5) NOT NULL,
+t varchar(4) DEFAULT NULL
+);
+CREATE TABLE t1xt2 (
+id_1 int(5) NOT NULL,
+id_2 int(5) NOT NULL
+);
+INSERT INTO t1 VALUES (1, 'a'), (2, 'b'), (3, 'c'), (4, 'd');
+INSERT INTO t2 VALUES (2, 'bb'), (3, 'cc'), (4, 'dd'), (12, 'aa');
+INSERT INTO t1xt2 VALUES (2, 2), (3, 3), (4, 4);
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN (SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1));
+id_1
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN ((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1)));
+id_1
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN (((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1))));
+id_1
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN (SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1));
+id_1
+1
+2
+3
+4
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN ((SELECT t1xt2.id_2 FROM t1xt2 where t1.id_1 = t1xt2.id_1)));
+id_1
+1
+2
+3
+4
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN (((SELECT t1xt2.id_2 FROM t1xt2 where t1.id_1 = t1xt2.id_1))));
+id_1
+1
+2
+3
+4
+insert INTO t1xt2 VALUES (1, 12);
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN (SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1));
+id_1
+1
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN ((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1)));
+id_1
+1
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN (((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1))));
+id_1
+1
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN (SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1));
+id_1
+2
+3
+4
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN ((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1)));
+id_1
+2
+3
+4
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN (((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1))));
+id_1
+2
+3
+4
+insert INTO t1xt2 VALUES (2, 12);
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN (SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1));
+id_1
+1
+2
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN ((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1)));
+id_1
+1
+2
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN (((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1))));
+id_1
+1
+2
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN (SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1));
+id_1
+3
+4
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN ((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1)));
+id_1
+3
+4
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN (((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1))));
+id_1
+3
+4
+DROP TABLE t1;
+DROP TABLE t2;
+DROP TABLE t1xt2;

mysql-test/t/subselect.test

@@ -2496,3 +2496,103 @@ SELECT SQL_NO_CACHE COUNT(*)
           FROM t1) t;
 
 DROP TABLE t1,t2;
+
+#
+# Bug#21904 (parser problem when using IN with a double "(())")
+#
+
+--disable_warnings
+DROP TABLE IF EXISTS t1;
+DROP TABLE IF EXISTS t2;
+DROP TABLE IF EXISTS t1xt2;
+--enable_warnings
+
+CREATE TABLE t1 (
+  id_1 int(5) NOT NULL,
+  t varchar(4) DEFAULT NULL
+);
+
+CREATE TABLE t2 (
+  id_2 int(5) NOT NULL,
+  t varchar(4) DEFAULT NULL
+);
+
+CREATE TABLE t1xt2 (
+  id_1 int(5) NOT NULL,
+  id_2 int(5) NOT NULL
+);
+
+INSERT INTO t1 VALUES (1, 'a'), (2, 'b'), (3, 'c'), (4, 'd');
+
+INSERT INTO t2 VALUES (2, 'bb'), (3, 'cc'), (4, 'dd'), (12, 'aa');
+
+INSERT INTO t1xt2 VALUES (2, 2), (3, 3), (4, 4);
+
+# subselect returns 0 rows
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN (SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1));
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN ((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1)));
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN (((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1))));
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN (SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1));
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN ((SELECT t1xt2.id_2 FROM t1xt2 where t1.id_1 = t1xt2.id_1)));
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN (((SELECT t1xt2.id_2 FROM t1xt2 where t1.id_1 = t1xt2.id_1))));
+
+insert INTO t1xt2 VALUES (1, 12);
+
+# subselect returns 1 row
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN (SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1));
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN ((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1)));
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN (((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1))));
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN (SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1));
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN ((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1)));
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN (((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1))));
+
+insert INTO t1xt2 VALUES (2, 12);
+
+# subselect returns more than 1 row
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN (SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1));
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN ((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1)));
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 IN (((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1))));
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN (SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1));
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN ((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1)));
+
+SELECT DISTINCT t1.id_1 FROM t1 WHERE
+(12 NOT IN (((SELECT t1xt2.id_2 FROM t1xt2 WHERE t1.id_1 = t1xt2.id_1))));
+
+DROP TABLE t1;
+DROP TABLE t2;
+DROP TABLE t1xt2;
+

sql/item_subselect.cc

@@ -52,6 +52,10 @@ Item_subselect::Item_subselect():
 void Item_subselect::init(st_select_lex *select_lex,
 			  select_subselect *result)
 {
+  /*
+    Please see Item_singlerow_subselect::invalidate_and_restore_select_lex(),
+    which depends on alterations to the parse tree implemented here.
+  */
 
   DBUG_ENTER("Item_subselect::init");
   DBUG_PRINT("enter", ("select_lex: 0x%lx", (long) select_lex));
@@ -92,6 +96,12 @@ void Item_subselect::init(st_select_lex *select_lex,
   DBUG_VOID_RETURN;
 }
 
+st_select_lex *
+Item_subselect::get_select_lex()
+{
+  return unit->first_select();
+}
+
 void Item_subselect::cleanup()
 {
   DBUG_ENTER("Item_subselect::cleanup");
@@ -265,6 +275,26 @@ Item_singlerow_subselect::Item_singlerow_subselect(st_select_lex *select_lex)
   DBUG_VOID_RETURN;
 }
 
+st_select_lex *
+Item_singlerow_subselect::invalidate_and_restore_select_lex()
+{
+  DBUG_ENTER("Item_singlerow_subselect::invalidate_and_restore_select_lex");
+  st_select_lex *result= get_select_lex();
+
+  DBUG_ASSERT(result);
+
+  /*
+    This code restore the parse tree in it's state before the execution of
+    Item_singlerow_subselect::Item_singlerow_subselect(),
+    and in particular decouples this object from the SELECT_LEX,
+    so that the SELECT_LEX can be used with a different flavor
+    or Item_subselect instead, as part of query rewriting.
+  */
+  unit->item= NULL;
+
+  DBUG_RETURN(result);
+}
+
 Item_maxmin_subselect::Item_maxmin_subselect(THD *thd_param,
                                              Item_subselect *parent,
 					     st_select_lex *select_lex,

sql/item_subselect.h

@@ -126,6 +126,12 @@ class Item_subselect :public Item_result_field
   virtual void reset_value_registration() {}
   enum_parsing_place place() { return parsing_place; }
 
+  /**
+    Get the SELECT_LEX structure associated with this Item.
+    @return the SELECT_LEX structure associated with this Item
+  */
+  st_select_lex* get_select_lex();
+
   friend class select_subselect;
   friend class Item_in_optimizer;
   friend bool Item_field::fix_fields(THD *, Item **);
@@ -169,6 +175,16 @@ class Item_singlerow_subselect :public Item_subselect
   bool null_inside();
   void bring_value();
 
+  /**
+    This method is used to implement a special case of semantic tree
+    rewriting, mandated by a SQL:2003 exception in the specification.
+    The only caller of this method is handle_sql2003_note184_exception(),
+    see the code there for more details.
+    Do not call this method for other purposes.
+    @return the SELECT_LEX structure that was given in the constructor.
+  */
+  st_select_lex* invalidate_and_restore_select_lex();
+
   friend class select_singlerow_subselect;
 };
 

sql/sql_yacc.yy

@@ -277,6 +277,81 @@ void case_stmt_action_end_case(LEX *lex, bool simple)
   lex->sphead->do_cont_backpatch();
 }
 
+/**
+  Helper to resolve the SQL:2003 Syntax exception 1) in <in predicate>.
+  See SQL:2003, Part 2, section 8.4 <in predicate>, Note 184, page 383.
+  This function returns the proper item for the SQL expression
+  <code>left [NOT] IN ( expr )</code>
+  @param thd the current thread
+  @param left the in predicand
+  @param equal true for IN predicates, false for NOT IN predicates
+  @param expr first and only expression of the in value list
+  @return an expression representing the IN predicate.
+*/
+Item* handle_sql2003_note184_exception(THD *thd, Item* left, bool equal,
+                                       Item *expr)
+{
+  /*
+    Relevant references for this issue:
+    - SQL:2003, Part 2, section 8.4 <in predicate>, page 383,
+    - SQL:2003, Part 2, section 7.2 <row value expression>, page 296,
+    - SQL:2003, Part 2, section 6.3 <value expression primary>, page 174,
+    - SQL:2003, Part 2, section 7.15 <subquery>, page 370,
+    - SQL:2003 Feature F561, "Full value expressions".
+
+    The exception in SQL:2003 Note 184 means:
+    Item_singlerow_subselect, which corresponds to a <scalar subquery>,
+    should be re-interpreted as an Item_in_subselect, which corresponds
+    to a <table subquery> when used inside an <in predicate>.
+
+    Our reading of Note 184 is reccursive, so that all:
+    - IN (( <subquery> ))
+    - IN ((( <subquery> )))
+    - IN '('^N <subquery> ')'^N
+    - etc
+    should be interpreted as a <table subquery>, no matter how deep in the
+    expression the <subquery> is.
+  */
+
+  Item *result;
+
+  DBUG_ENTER("handle_sql2003_note184_exception");
+
+  if (expr->type() == Item::SUBSELECT_ITEM)
+  {
+    Item_subselect *expr2 = (Item_subselect*) expr;
+
+    if (expr2->substype() == Item_subselect::SINGLEROW_SUBS)
+    {
+      Item_singlerow_subselect *expr3 = (Item_singlerow_subselect*) expr2;
+      st_select_lex *subselect;
+
+      /*
+        Implement the mandated change, by altering the semantic tree:
+          left IN Item_singlerow_subselect(subselect)
+        is modified to
+          left IN (subselect)
+        which is represented as
+          Item_in_subselect(left, subselect)
+      */
+      subselect= expr3->invalidate_and_restore_select_lex();
+      result= new (thd->mem_root) Item_in_subselect(left, subselect);
+
+      if (! equal)
+        result = negate_expression(thd, result);
+
+      DBUG_RETURN(result);
+    }
+  }
+
+  if (equal)
+    result= new (thd->mem_root) Item_func_eq(left, expr);
+  else
+    result= new (thd->mem_root) Item_func_ne(left, expr);
+
+  DBUG_RETURN(result);
+}
+
 %}
 %union {
   int  num;
@@ -4402,28 +4477,34 @@ bool_pri:
 
 predicate:
           bit_expr IN_SYM '(' subselect ')'
-	  { $$= new Item_in_subselect($1, $4); }
+          {
+            $$= new (YYTHD->mem_root) Item_in_subselect($1, $4);
+          }
         | bit_expr not IN_SYM '(' subselect ')'
-          { $$= negate_expression(YYTHD, new Item_in_subselect($1, $5)); }
+          {
+            THD *thd= YYTHD;
+            Item *item= new (thd->mem_root) Item_in_subselect($1, $5);
+            $$= negate_expression(thd, item);
+          }
         | bit_expr IN_SYM '(' expr ')'
           {
-              $$= new Item_func_eq($1, $4);
+            $$= handle_sql2003_note184_exception(YYTHD, $1, true, $4);
           }
         | bit_expr IN_SYM '(' expr ',' expr_list ')'
           { 
             $6->push_front($4);
             $6->push_front($1);
-              $$= new Item_func_in(*$6);
+            $$= new (YYTHD->mem_root) Item_func_in(*$6);
           }
         | bit_expr not IN_SYM '(' expr ')'
           {
-              $$= new Item_func_ne($1, $5);
+            $$= handle_sql2003_note184_exception(YYTHD, $1, false, $5);
           }
         | bit_expr not IN_SYM '(' expr ',' expr_list ')'
           {
             $7->push_front($5);
             $7->push_front($1);
-              Item_func_in *item = new Item_func_in(*$7);
+            Item_func_in *item = new (YYTHD->mem_root) Item_func_in(*$7);
             item->negate();
             $$= item;
           }