Bug#15463: EXPLAIN SELECT..INTO hangs the client (QB, command line)

There were two distict bugs: parse error was returned for valid
statement and that error wasn't reported to the client.

The fix ensures that EXPLAIN SELECT..INTO is accepted by parser and any
other parse error will be reported to the client.


mysql-test/r/explain.result:
  Add result for bug#15463.
mysql-test/t/explain.test:
  Add test case for bug#15463.
sql/sql_parse.cc:
  Assert that if parsing error has occured then apropriate error message
  has been pushed into error stack.
sql/sql_yacc.yy:
  If there is no lex->result in select_var_ident rule, then we have
  to be in DESCRIBE mode.

4 files changed, 29 insertions, 5 deletions

diff --git a/mysql-test/r/explain.result b/mysql-test/r/explain.result
index d66dec741bd..75e1548cdee 100644
--- a/mysql-test/r/explain.result
+++ b/mysql-test/r/explain.result
@@ -53,3 +53,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	таб	ref	инд0,инд01	инд0	5	const	1	Using where; Using index
 drop table таб;
 set names latin1;
+select 3 into @v1;
+explain select 3 into @v1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
diff --git a/mysql-test/t/explain.test b/mysql-test/t/explain.test
index 2a3a23c5f96..a38771db233 100644
--- a/mysql-test/t/explain.test
+++ b/mysql-test/t/explain.test
@@ -43,3 +43,12 @@ drop table таб;
 set names latin1;
 
 # End of 4.1 tests
+
+
+#
+# Bug#15463: EXPLAIN SELECT..INTO hangs the client (QB, command line)
+#
+select 3 into @v1;
+explain select 3 into @v1;
+
+# End of 5.0 tests.
diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc
index 196e723299a..649714315a6 100644
--- a/sql/sql_parse.cc
+++ b/sql/sql_parse.cc
@@ -5709,6 +5709,7 @@ void mysql_parse(THD *thd, char *inBuf, uint length)
     }
     else
     {
+      DBUG_ASSERT(thd->net.report_error);
       DBUG_PRINT("info",("Command aborted. Fatal_error: %d",
 			 thd->is_fatal_error));
       query_cache_abort(&thd->net);
diff --git a/sql/sql_yacc.yy b/sql/sql_yacc.yy
index 6473163a6ec..261d10f3e79 100644
--- a/sql/sql_yacc.yy
+++ b/sql/sql_yacc.yy
@@ -5795,7 +5795,11 @@ select_var_ident:
 	     if (lex->result) 
 	       ((select_dumpvar *)lex->result)->var_list.push_back( new my_var($2,0,0,(enum_field_types)0));
 	     else
-	       YYABORT;
+               /*
+                 The parser won't create select_result instance only
+	         if it's an EXPLAIN.
+               */
+               DBUG_ASSERT(lex->describe);
 	   }
            | ident_or_text
            {
@@ -5807,10 +5811,8 @@ select_var_ident:
 	       my_error(ER_SP_UNDECLARED_VAR, MYF(0), $1.str);
 	       YYABORT;
 	     }
-	     if (! lex->result)
-	       YYABORT;
-	     else
-	     {
+	     if (lex->result)
+             {
                my_var *var;
 	       ((select_dumpvar *)lex->result)->
                  var_list.push_back(var= new my_var($1,1,t->offset,t->type));
@@ -5818,6 +5820,14 @@ select_var_ident:
 	       if (var)
 		 var->sp= lex->sphead;
 #endif
+             }
+	     else
+	     {
+               /*
+                 The parser won't create select_result instance only
+	         if it's an EXPLAIN.
+               */
+               DBUG_ASSERT(lex->describe);
 	     }
 	   }
            ;