MDEV-5273 Prepared statement doesn't return metadata after prepare.

  Fix for SHOW CREATE DATABASE.

Author: Alexey Botchkov

sql/sql_prepare.cc

@@ -1812,6 +1812,14 @@ static bool mysql_test_create_table(Prepared_statement *stmt)
 }
 
 
+static bool send_stmt_metadata(THD *thd, Prepared_statement *stmt, List<Item> *fields)
+{
+  return send_prep_stmt(stmt, fields->elements) ||
+         thd->protocol->send_result_set_metadata(fields, Protocol::SEND_EOF) ||
+         thd->protocol->flush();
+}
+
+
 /**
   Validate and prepare for execution SHOW CREATE TABLE statement.
 
@@ -1824,7 +1832,7 @@ static bool mysql_test_create_table(Prepared_statement *stmt)
     TRUE              error, error message is set in THD
 */
 
-static int mysql_test_show_create_table(Prepared_statement *stmt,
+static bool mysql_test_show_create_table(Prepared_statement *stmt,
                                         TABLE_LIST *tables)
 {
   DBUG_ENTER("mysql_test_show_create_table");
@@ -1833,22 +1841,31 @@ static int mysql_test_show_create_table(Prepared_statement *stmt,
   char buff[2048];
   String buffer(buff, sizeof(buff), system_charset_info);
 
-  if (mysqld_show_create_get_fields(thd, tables, &fields, &buffer))
-    goto err_exit;
-    
-  if (!stmt->is_sql_prepare())
-  {
-    if (send_prep_stmt(stmt, fields.elements) ||
-        thd->protocol->send_result_set_metadata(&fields, Protocol::SEND_EOF) ||
-        thd->protocol->flush())
-      goto err_exit;
+  DBUG_RETURN(mysqld_show_create_get_fields(thd, tables, &fields, &buffer) ||
+              send_stmt_metadata(thd, stmt, &fields));
+}
 
-    DBUG_RETURN(2);
-  }
-  DBUG_RETURN(0);
 
-err_exit:
-  DBUG_RETURN(1);
+/**
+  Validate and prepare for execution SHOW CREATE DATABASE statement.
+
+  @param stmt               prepared statement
+
+  @retval
+    FALSE             success
+  @retval
+    TRUE              error, error message is set in THD
+*/
+
+static bool mysql_test_show_create_db(Prepared_statement *stmt)
+{
+  DBUG_ENTER("mysql_test_show_create_db");
+  THD *thd= stmt->thd;
+  List<Item> fields;
+
+  mysqld_show_create_db_get_fields(thd, &fields);
+    
+  DBUG_RETURN(send_stmt_metadata(thd, stmt, &fields));
 }
 
 
@@ -2186,8 +2203,14 @@ static bool check_prepared_statement(Prepared_statement *stmt)
     res= mysql_test_create_table(stmt);
     break;
   case SQLCOM_SHOW_CREATE:
-    res= mysql_test_show_create_table(stmt, tables);
-    if (res == 2)
+    if (!(res= mysql_test_show_create_table(stmt, tables)))
+    {
+      /* Statement and field info has already been sent */
+      DBUG_RETURN(FALSE);
+    }
+    break;
+  case SQLCOM_SHOW_CREATE_DB:
+    if (!(res= mysql_test_show_create_db(stmt)))
     {
       /* Statement and field info has already been sent */
       DBUG_RETURN(FALSE);

sql/sql_show.cc

@@ -1272,6 +1272,19 @@ mysqld_show_create(THD *thd, TABLE_LIST *table_list)
   DBUG_RETURN(error);
 }
 
+
+void mysqld_show_create_db_get_fields(THD *thd, List<Item> *field_list)
+{
+  MEM_ROOT *mem_root= thd->mem_root;
+  field_list->push_back(new (mem_root)
+                        Item_empty_string(thd, "Database", NAME_CHAR_LEN),
+                        mem_root);
+  field_list->push_back(new (mem_root)
+                        Item_empty_string(thd, "Create Database", 1024),
+                        mem_root);
+}
+
+
 bool mysqld_show_create_db(THD *thd, LEX_STRING *dbname,
                            LEX_STRING *orig_dbname,
                            const DDL_options_st &options)
@@ -1284,7 +1297,7 @@ bool mysqld_show_create_db(THD *thd, LEX_STRING *dbname,
 #endif
   Schema_specification_st create;
   Protocol *protocol=thd->protocol;
-  MEM_ROOT *mem_root= thd->mem_root;
+  List<Item> field_list;
   DBUG_ENTER("mysql_show_create_db");
 
 #ifndef NO_EMBEDDED_ACCESS_CHECKS
@@ -1318,13 +1331,8 @@ bool mysqld_show_create_db(THD *thd, LEX_STRING *dbname,
 
     load_db_opt_by_name(thd, dbname->str, &create);
   }
-  List<Item> field_list;
-  field_list.push_back(new (mem_root)
-                       Item_empty_string(thd, "Database", NAME_CHAR_LEN),
-                       mem_root);
-  field_list.push_back(new (mem_root)
-                       Item_empty_string(thd, "Create Database", 1024),
-                       mem_root);
+
+  mysqld_show_create_db_get_fields(thd, &field_list);
 
   if (protocol->send_result_set_metadata(&field_list,
                                          Protocol::SEND_NUM_ROWS |

sql/sql_show.h

@@ -88,6 +88,7 @@ int mysqld_dump_create_info(THD *thd, TABLE_LIST *table_list, int fd);
 bool mysqld_show_create_get_fields(THD *thd, TABLE_LIST *table_list,
                                    List<Item> *field_list, String *buffer);
 bool mysqld_show_create(THD *thd, TABLE_LIST *table_list);
+void mysqld_show_create_db_get_fields(THD *thd, List<Item> *field_list);
 bool mysqld_show_create_db(THD *thd, LEX_STRING *db_name,
                            LEX_STRING *orig_db_name,
                            const DDL_options_st &options);

tests/mysql_client_test.c

@@ -426,9 +426,14 @@ static void test_prepare_simple()
   strmov(query, "SHOW CREATE TABLE test_prepare_simple");
   stmt= mysql_simple_prepare(mysql, query);
   check_stmt(stmt);
-
   DIE_UNLESS(mysql_stmt_field_count(stmt) == 2);
+  mysql_stmt_close(stmt);
 
+  /* show create database */
+  strmov(query, "SHOW CREATE DATABASE test");
+  stmt= mysql_simple_prepare(mysql, query);
+  check_stmt(stmt);
+  DIE_UNLESS(mysql_stmt_field_count(stmt) == 2);
   mysql_stmt_close(stmt);
 
   /* now fetch the results ..*/