BUG#25575: ERROR 1052 (Column in from clause is ambiguous) with sub-join

 Two problems here:

 Problem 1:

 While constructing the join columns list the optimizer does as follows:
  1. Sets the join_using_fields/natural_join members of the right JOIN 
   operand.
  2. Makes a "table reference" (TABLE_LIST) to parent the two tables.
  3. Assigns the join_using_fields/is_natural_join of the wrapper table
   using join_using_fields/natural_join of the rightmost table
  4. Sets join_using_fields to NULL for the right JOIN operand.
  5. Passes the parent table up to the same procedure on the upper 
   level.

 Step 1 overrides the the join_using_fields that are set for a nested 
 join wrapping table in step 4.
 Fixed by making a designated variable SELECT_LEX::prev_join_using to 
 pass the data from step 1 to step 4 without destroying the wrapping 
 table data.

 Problem 2:

 The optimizer checks for ambiguous columns while transforming 
 NATURAL JOIN/JOIN USING to JOIN ON. While doing that there was no
 distinction between columns that are used in the generated join
 condition (where ambiguity can be checked) and the other columns
 (where ambiguity can be checked only when resolving references
 coming from outside the JOIN construct itself).
 Fixed by allowing the non-USING columns to be present in multiple 
 copies in both sides of the join and moving the ambiguity check 
 to the place where unqualified references to the join columns are
 resolved (find_field_in_natural_join()).

Author: gkodinov/kgeorge@macbook.gmz

mysql-test/r/join_nested.result

@@ -1605,3 +1605,31 @@ WHERE t1.id='5';
 id	ct	pc	nm
 5	NULL	NULL	NULL
 DROP TABLE t1,t2,t3,t4;
+CREATE TABLE t1 (a INT, b INT);
+CREATE TABLE t2 (a INT);
+CREATE TABLE t3 (a INT, c INT);
+CREATE TABLE t4 (a INT, c INT);
+CREATE TABLE t5 (a INT, c INT);
+SELECT b FROM t1 JOIN (t2 LEFT JOIN t3 USING (a) LEFT JOIN t4 USING (a)
+LEFT JOIN t5 USING (a)) USING (a);
+b
+SELECT c FROM t1 JOIN (t2 LEFT JOIN t3 USING (a) LEFT JOIN t4 USING (a)
+LEFT JOIN t5 USING (a)) USING (a);
+ERROR 23000: Column 'c' in field list is ambiguous
+SELECT b FROM t1 JOIN (t2 JOIN t3 USING (a) JOIN t4 USING (a)
+JOIN t5 USING (a)) USING (a);
+b
+SELECT c FROM t1 JOIN (t2 JOIN t3 USING (a) JOIN t4 USING (a)
+JOIN t5 USING (a)) USING (a);
+ERROR 23000: Column 'c' in field list is ambiguous
+DROP TABLE t1,t2,t3,t4,t5;
+CREATE TABLE t1 (a INT, b INT);
+CREATE TABLE t2 (a INT, b INT);
+CREATE TABLE t3 (a INT, b INT);
+INSERT INTO t1 VALUES (1,1);
+INSERT INTO t2 VALUES (1,1);
+INSERT INTO t3 VALUES (1,1);
+SELECT * FROM t1 JOIN (t2 JOIN t3 USING (b)) USING (a);
+ERROR 23000: Column 'a' in from clause is ambiguous
+DROP TABLE t1,t2,t3;
+End of 5.0 tests

mysql-test/t/join_nested.test

@@ -1045,3 +1045,42 @@ SELECT t1.*, t4.nm
     WHERE t1.id='5';
 
 DROP TABLE t1,t2,t3,t4;
+
+#
+# BUG#25575: ERROR 1052 (Column in from clause is ambiguous) with sub-join
+#
+CREATE TABLE t1 (a INT, b INT);
+CREATE TABLE t2 (a INT);
+CREATE TABLE t3 (a INT, c INT);
+CREATE TABLE t4 (a INT, c INT);
+CREATE TABLE t5 (a INT, c INT);
+
+SELECT b FROM t1 JOIN (t2 LEFT JOIN t3 USING (a) LEFT JOIN t4 USING (a)
+LEFT JOIN t5 USING (a)) USING (a);
+
+--error ER_NON_UNIQ_ERROR
+SELECT c FROM t1 JOIN (t2 LEFT JOIN t3 USING (a) LEFT JOIN t4 USING (a)
+LEFT JOIN t5 USING (a)) USING (a);
+
+SELECT b FROM t1 JOIN (t2 JOIN t3 USING (a) JOIN t4 USING (a)
+JOIN t5 USING (a)) USING (a);
+
+--error ER_NON_UNIQ_ERROR
+SELECT c FROM t1 JOIN (t2 JOIN t3 USING (a) JOIN t4 USING (a)
+JOIN t5 USING (a)) USING (a);
+
+DROP TABLE t1,t2,t3,t4,t5;
+CREATE TABLE t1 (a INT, b INT);
+CREATE TABLE t2 (a INT, b INT);
+CREATE TABLE t3 (a INT, b INT);
+
+INSERT INTO t1 VALUES (1,1);
+INSERT INTO t2 VALUES (1,1);
+INSERT INTO t3 VALUES (1,1);
+
+--error ER_NON_UNIQ_ERROR
+SELECT * FROM t1 JOIN (t2 JOIN t3 USING (b)) USING (a);
+
+DROP TABLE t1,t2,t3;
+
+--echo End of 5.0 tests

sql/mysql_priv.h

@@ -982,7 +982,8 @@ bool push_new_name_resolution_context(THD *thd,
                                       TABLE_LIST *left_op,
                                       TABLE_LIST *right_op);
 void add_join_on(TABLE_LIST *b,Item *expr);
-void add_join_natural(TABLE_LIST *a,TABLE_LIST *b,List<String> *using_fields);
+void add_join_natural(TABLE_LIST *a,TABLE_LIST *b,List<String> *using_fields,
+                      SELECT_LEX *lex);
 bool add_proc_to_list(THD *thd, Item *item);
 TABLE *unlink_open_table(THD *thd,TABLE *list,TABLE *find);
 void update_non_unique_table_error(TABLE_LIST *update,

sql/sql_base.cc

@@ -2945,7 +2945,7 @@ find_field_in_natural_join(THD *thd, TABLE_LIST *table_ref, const char *name,
 {
   List_iterator_fast<Natural_join_column>
     field_it(*(table_ref->join_columns));
-  Natural_join_column *nj_col;
+  Natural_join_column *nj_col, *curr_nj_col;
   Field *found_field;
   Query_arena *arena, backup;
   DBUG_ENTER("find_field_in_natural_join");
@@ -2956,14 +2956,21 @@ find_field_in_natural_join(THD *thd, TABLE_LIST *table_ref, const char *name,
 
   LINT_INIT(found_field);
 
-  for (;;)
+  for (nj_col= NULL, curr_nj_col= field_it++; curr_nj_col; 
+       curr_nj_col= field_it++)
   {
-    if (!(nj_col= field_it++))
-      DBUG_RETURN(NULL);
-
-    if (!my_strcasecmp(system_charset_info, nj_col->name(), name))
-      break;
+    if (!my_strcasecmp(system_charset_info, curr_nj_col->name(), name))
+    {
+      if (nj_col)
+      {
+        my_error(ER_NON_UNIQ_ERROR, MYF(0), name, thd->where);
+        DBUG_RETURN(NULL);
+      }
+      nj_col= curr_nj_col;
+    }
   }
+  if (!nj_col)
+    DBUG_RETURN(NULL);
 
   if (nj_col->view_field)
   {
@@ -3774,9 +3781,16 @@ mark_common_columns(THD *thd, TABLE_LIST *table_ref_1, TABLE_LIST *table_ref_2,
   {
     bool found= FALSE;
     const char *field_name_1;
+    /* true if field_name_1 is a member of using_fields */
+    bool is_using_column_1;
     if (!(nj_col_1= it_1.get_or_create_column_ref(leaf_1)))
       goto err;
     field_name_1= nj_col_1->name();
+    is_using_column_1= using_fields && 
+      test_if_string_in_list(field_name_1, using_fields);
+    DBUG_PRINT ("info", ("field_name_1=%s.%s", 
+                         nj_col_1->table_name() ? nj_col_1->table_name() : "", 
+                         field_name_1));
 
     /*
       Find a field with the same name in table_ref_2.
@@ -3793,17 +3807,27 @@ mark_common_columns(THD *thd, TABLE_LIST *table_ref_1, TABLE_LIST *table_ref_2,
       if (!(cur_nj_col_2= it_2.get_or_create_column_ref(leaf_2)))
         goto err;
       cur_field_name_2= cur_nj_col_2->name();
+      DBUG_PRINT ("info", ("cur_field_name_2=%s.%s", 
+                           cur_nj_col_2->table_name() ? 
+                             cur_nj_col_2->table_name() : "", 
+                           cur_field_name_2));
 
       /*
         Compare the two columns and check for duplicate common fields.
         A common field is duplicate either if it was already found in
         table_ref_2 (then found == TRUE), or if a field in table_ref_2
         was already matched by some previous field in table_ref_1
         (then cur_nj_col_2->is_common == TRUE).
+        Note that it is too early to check the columns outside of the
+        USING list for ambiguity because they are not actually "referenced"
+        here. These columns must be checked only on unqualified reference 
+        by name (e.g. in SELECT list).
       */
       if (!my_strcasecmp(system_charset_info, field_name_1, cur_field_name_2))
       {
-        if (found || cur_nj_col_2->is_common)
+        DBUG_PRINT ("info", ("match c1.is_common=%d", nj_col_1->is_common));
+        if (cur_nj_col_2->is_common ||
+            (found && (!using_fields || is_using_column_1)))
         {
           my_error(ER_NON_UNIQ_ERROR, MYF(0), field_name_1, thd->where);
           goto err;
@@ -3829,9 +3853,7 @@ mark_common_columns(THD *thd, TABLE_LIST *table_ref_1, TABLE_LIST *table_ref_2,
       clause (if present), mark them as common fields, and add a new
       equi-join condition to the ON clause.
     */
-    if (nj_col_2 &&
-        (!using_fields ||
-          test_if_string_in_list(field_name_1, using_fields)))
+    if (nj_col_2 && (!using_fields ||is_using_column_1))
     {
       Item *item_1=   nj_col_1->create_item(thd);
       Item *item_2=   nj_col_2->create_item(thd);
@@ -3886,6 +3908,13 @@ mark_common_columns(THD *thd, TABLE_LIST *table_ref_1, TABLE_LIST *table_ref_2,
                   eq_cond);
 
       nj_col_1->is_common= nj_col_2->is_common= TRUE;
+      DBUG_PRINT ("info", ("%s.%s and %s.%s are common", 
+                           nj_col_1->table_name() ? 
+                             nj_col_1->table_name() : "", 
+                           nj_col_1->name(),
+                           nj_col_2->table_name() ? 
+                             nj_col_2->table_name() : "", 
+                           nj_col_2->name()));
 
       if (field_1)
       {

sql/sql_lex.h

@@ -587,6 +587,20 @@ class st_select_lex: public st_select_lex_node
   int cur_pos_in_select_list;
 
   List<udf_func>     udf_list;                  /* udf function calls stack */
+  /* 
+    This is a copy of the original JOIN USING list that comes from
+    the parser. The parser :
+      1. Sets the natural_join of the second TABLE_LIST in the join
+         and the st_select_lex::prev_join_using.
+      2. Makes a parent TABLE_LIST and sets its is_natural_join/
+       join_using_fields members.
+      3. Uses the wrapper TABLE_LIST as a table in the upper level.
+    We cannot assign directly to join_using_fields in the parser because
+    at stage (1.) the parent TABLE_LIST is not constructed yet and
+    the assignment will override the JOIN USING fields of the lower level
+    joins on the right.
+  */
+  List<String> *prev_join_using;
 
   void init_query();
   void init_select();

sql/sql_parse.cc

@@ -6365,11 +6365,8 @@ TABLE_LIST *st_select_lex::nest_last_join(THD *thd)
         If this is a JOIN ... USING, move the list of joined fields to the
         table reference that describes the join.
       */
-      if (table->join_using_fields)
-      {
-        ptr->join_using_fields= table->join_using_fields;
-        table->join_using_fields= NULL;
-      }
+      if (prev_join_using)
+        ptr->join_using_fields= prev_join_using;
     }
   }
   join_list->push_front(ptr);
@@ -6625,6 +6622,7 @@ void add_join_on(TABLE_LIST *b, Item *expr)
     a			Left join argument
     b			Right join argument
     using_fields        Field names from USING clause
+    lex                 The current st_select_lex
   
   IMPLEMENTATION
     This function marks that table b should be joined with a either via
@@ -6653,10 +6651,11 @@ void add_join_on(TABLE_LIST *b, Item *expr)
     None
 */
 
-void add_join_natural(TABLE_LIST *a, TABLE_LIST *b, List<String> *using_fields)
+void add_join_natural(TABLE_LIST *a, TABLE_LIST *b, List<String> *using_fields,
+                      SELECT_LEX *lex)
 {
   b->natural_join= a;
-  b->join_using_fields= using_fields;
+  lex->prev_join_using= using_fields;
 }
 
 

sql/sql_yacc.yy

@@ -5280,11 +5280,11 @@ join_table:
             YYERROR_UNLESS($1 && $3);
 	  }
 	  '(' using_list ')'
-          { add_join_natural($1,$3,$7); $$=$3; }
+          { add_join_natural($1,$3,$7,Select); $$=$3; }
 	| table_ref NATURAL JOIN_SYM table_factor
 	  {
             YYERROR_UNLESS($1 && ($$=$4));
-            add_join_natural($1,$4,NULL);
+            add_join_natural($1,$4,NULL,Select);
           }
 
 /* LEFT JOIN variants */
@@ -5311,11 +5311,15 @@ join_table:
             YYERROR_UNLESS($1 && $5);
 	  }
 	  USING '(' using_list ')'
-          { add_join_natural($1,$5,$9); $5->outer_join|=JOIN_TYPE_LEFT; $$=$5; }
+          { 
+            add_join_natural($1,$5,$9,Select); 
+            $5->outer_join|=JOIN_TYPE_LEFT; 
+            $$=$5; 
+          }
 	| table_ref NATURAL LEFT opt_outer JOIN_SYM table_factor
 	  {
             YYERROR_UNLESS($1 && $6);
- 	    add_join_natural($1,$6,NULL);
+ 	    add_join_natural($1,$6,NULL,Select);
 	    $6->outer_join|=JOIN_TYPE_LEFT;
 	    $$=$6;
 	  }
@@ -5349,12 +5353,12 @@ join_table:
 	    LEX *lex= Lex;
             if (!($$= lex->current_select->convert_right_join()))
               YYABORT;
-            add_join_natural($$,$5,$9);
+            add_join_natural($$,$5,$9,Select);
           }
 	| table_ref NATURAL RIGHT opt_outer JOIN_SYM table_factor
 	  {
             YYERROR_UNLESS($1 && $6);
-	    add_join_natural($6,$1,NULL);
+	    add_join_natural($6,$1,NULL,Select);
 	    LEX *lex= Lex;
             if (!($$= lex->current_select->convert_right_join()))
               YYABORT;

sql/table.cc

@@ -2628,6 +2628,7 @@ Field *Natural_join_column::field()
 
 const char *Natural_join_column::table_name()
 {
+  DBUG_ASSERT(table_ref);
   return table_ref->alias;
 }