A fix and a test case for Bug#24179 "select b into $var" fails with

--cursor_protocol": fix a misleading error message in case of
SELECT .. INTO.


sql/sql_class.cc:
  Implement select_result::check_simple_select hierarchy to 
  support correct error messages in case of SELECT .. INTO and C API 
  cursors.
sql/sql_class.h:
  Set the error message inside the function that checks for the error
  condition (simple_select, renamed to check_simple_select).
sql/sql_prepare.cc:
  Use a new method that now sets the error.
tests/mysql_client_test.c:
  Add a test case for Bug#24179 "select b into $var" fails with 
  --cursor_protocol" (check for the right error message and error code).

3 files changed, 25 insertions, 4 deletions

diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index d2f1e9ed0d9..f46cd2353eb 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -885,6 +885,13 @@ void select_result::cleanup()
   /* do nothing */
 }
 
+bool select_result::check_simple_select() const
+{
+  my_error(ER_SP_BAD_CURSOR_QUERY, MYF(0));
+  return TRUE;
+}
+
+
 static String default_line_term("\n",default_charset_info);
 static String default_escaped("\\",default_charset_info);
 static String default_field_term("\t",default_charset_info);
@@ -1553,6 +1560,13 @@ int select_dumpvar::prepare(List<Item> &list, SELECT_LEX_UNIT *u)
 }
 
 
+bool select_dumpvar::check_simple_select() const
+{
+  my_error(ER_SP_BAD_CURSOR_SELECT, MYF(0));
+  return TRUE;
+}
+
+
 void select_dumpvar::cleanup()
 {
   vars.empty();
diff --git a/sql/sql_class.h b/sql/sql_class.h
index 41845dc5c76..ec03b9cb4a6 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -1724,7 +1724,14 @@ public:
   virtual bool initialize_tables (JOIN *join=0) { return 0; }
   virtual void send_error(uint errcode,const char *err);
   virtual bool send_eof()=0;
-  virtual bool simple_select() { return 0; }
+  /**
+    Check if this query returns a result set and therefore is allowed in
+    cursors and set an error message if it is not the case.
+
+    @retval FALSE     success
+    @retval TRUE      error, an error message is set
+  */
+  virtual bool check_simple_select() const;
   virtual void abort() {}
   /*
     Cleanup instance of this class for next execution of a prepared
@@ -1762,7 +1769,7 @@ public:
   bool send_fields(List<Item> &list, uint flags);
   bool send_data(List<Item> &items);
   bool send_eof();
-  bool simple_select() { return 1; }
+  virtual bool check_simple_select() const { return FALSE; }
   void abort();
 };
 
@@ -2202,6 +2209,7 @@ public:
   int prepare(List<Item> &list, SELECT_LEX_UNIT *u);
   bool send_data(List<Item> &items);
   bool send_eof();
+  virtual bool check_simple_select() const;
   void cleanup();
 };
 
diff --git a/sql/sql_prepare.cc b/sql/sql_prepare.cc
index 1e7601c0951..8b2c2cd3674 100644
--- a/sql/sql_prepare.cc
+++ b/sql/sql_prepare.cc
@@ -2906,10 +2906,9 @@ bool Prepared_statement::execute(String *expanded_query, bool open_cursor)
     in INSERT ... SELECT and similar commands.
   */
 
-  if (open_cursor && lex->result && !lex->result->simple_select())
+  if (open_cursor && lex->result && lex->result->check_simple_select())
   {
     DBUG_PRINT("info",("Cursor asked for not SELECT stmt"));
-    my_error(ER_SP_BAD_CURSOR_QUERY, MYF(0));
     return TRUE;
   }