Fixed bug #35193.

View definition as SELECT ... FROM DUAL WHERE ... has
valid syntax, but use of such view in SELECT or
SHOW CREATE VIEW syntax causes unexpected syntax error.

Server omits FROM DUAL clause when storing view body
string in a .frm file for further evaluation.
However, syntax of SELECT-witout-FROM query is more
restrictive than SELECT FROM DUAL syntax, and doesn't
allow the WHERE clause.

NOTE: this syntax difference is not documented.


View registration procedure has been modified to
preserve original structure of view's body.



mysql-test/r/view.result:
  Added test case for bug #35193.
mysql-test/t/view.test:
  Added test case for bug #35193.
sql/sql_select.cc:
  Fixed bug #35193.
  The st_select_lex::print function always omits FROM DUAL clause,
  even if original SELECT query has the WHERE clause.
  
  The mysql_register_view function uses this function to reconstruct
  a body of view's AS clause for further evaluation and stores that
  reconstructed clause in a .frm file.
  
  SELECT without FROM syntax is more restrictive than 
  SELECT FROM DUAL syntax: second one allows
  the WHERE clause, but first one is not.
  
  Use of this view in SELECT or SHOW CREATE VIEW queries
  causes unexpected syntax errors.
  
  
  The st_select_lex::print function has been modified to
  reconstruct FROM DUAL clause in queries when needed.
  
  
  TODO: Syntax difference is not documented and should be
  eliminated, however improvement of
  the SELECT-without-FROM syntax is not trivial and leads to
  significant modification of grammar file because of additional
  shift/reduce conflicts.

1 files changed, 8 insertions, 0 deletions

diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 6392f7c4299..bb3030a721c 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -15806,6 +15806,14 @@ void st_select_lex::print(THD *thd, String *str)
     /* go through join tree */
     print_join(thd, str, &top_join_list);
   }
+  else if (where)
+  {
+    /*
+      "SELECT 1 FROM DUAL WHERE 2" should not be printed as 
+      "SELECT 1 WHERE 2": the 1st syntax is valid, but the 2nd is not.
+    */
+    str->append(STRING_WITH_LEN(" from DUAL "));
+  }
 
   // Where
   Item *cur_where= where;