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

        Fix for SHOW GRANTS statement.

3 files changed, 45 insertions, 4 deletions

diff --git a/sql/sql_acl.cc b/sql/sql_acl.cc
index c6793241f70..e5a80420470 100644
--- a/sql/sql_acl.cc
+++ b/sql/sql_acl.cc
@@ -7740,6 +7740,16 @@ static int show_grants_callback(ACL_USER_BASE *role, void *data)
 }
 
 
+void mysql_show_grants_get_fields(THD *thd, List<Item> *fields,
+                                  const char *name)
+{
+  Item_string *field=new (thd->mem_root) Item_string_ascii(thd, "", 0);
+  field->name= (char *) name;
+  field->max_length=1024;
+  fields->push_back(field, thd->mem_root);
+}
+
+
 /*
   SHOW GRANTS;  Send grants for a user to the client
 
@@ -7805,15 +7815,14 @@ bool mysql_show_grants(THD *thd, LEX_USER *lex_user)
   }
   DBUG_ASSERT(rolename || username);
 
-  Item_string *field=new (thd->mem_root) Item_string_ascii(thd, "", 0);
   List<Item> field_list;
-  field->name=buff;
-  field->max_length=1024;
   if (!username)
     strxmov(buff,"Grants for ",rolename, NullS);
   else
     strxmov(buff,"Grants for ",username,"@",hostname, NullS);
-  field_list.push_back(field, thd->mem_root);
+
+  mysql_show_grants_get_fields(thd, &field_list, buff);
+
   if (protocol->send_result_set_metadata(&field_list,
                                          Protocol::SEND_NUM_ROWS |
                                          Protocol::SEND_EOF))
diff --git a/sql/sql_acl.h b/sql/sql_acl.h
index 335a558cddb..0893504b72d 100644
--- a/sql/sql_acl.h
+++ b/sql/sql_acl.h
@@ -241,6 +241,8 @@ ulong get_table_grant(THD *thd, TABLE_LIST *table);
 ulong get_column_grant(THD *thd, GRANT_INFO *grant,
                        const char *db_name, const char *table_name,
                        const char *field_name);
+void mysql_show_grants_get_fields(THD *thd, List<Item> *fields,
+                                  const char *name);
 bool mysql_show_grants(THD *thd, LEX_USER *user);
 int fill_schema_enabled_roles(THD *thd, TABLE_LIST *tables, COND *cond);
 int fill_schema_applicable_roles(THD *thd, TABLE_LIST *tables, COND *cond);
diff --git a/sql/sql_prepare.cc b/sql/sql_prepare.cc
index 9b455433acf..ba63ac4430e 100644
--- a/sql/sql_prepare.cc
+++ b/sql/sql_prepare.cc
@@ -1870,6 +1870,29 @@ static bool mysql_test_show_create_db(Prepared_statement *stmt)
 
 
 /**
+  Validate and prepare for execution SHOW GRANTS statement.
+
+  @param stmt               prepared statement
+
+  @retval
+    FALSE             success
+  @retval
+    TRUE              error, error message is set in THD
+*/
+
+static bool mysql_test_show_grants(Prepared_statement *stmt)
+{
+  DBUG_ENTER("mysql_test_show_grants");
+  THD *thd= stmt->thd;
+  List<Item> fields;
+
+  mysql_show_grants_get_fields(thd, &fields, "Grants for");
+    
+  DBUG_RETURN(send_stmt_metadata(thd, stmt, &fields));
+}
+
+
+/**
   @brief Validate and prepare for execution CREATE VIEW statement
 
   @param stmt prepared statement
@@ -2216,6 +2239,13 @@ static bool check_prepared_statement(Prepared_statement *stmt)
       DBUG_RETURN(FALSE);
     }
     break;
+  case SQLCOM_SHOW_GRANTS:
+    if (!(res= mysql_test_show_grants(stmt)))
+    {
+      /* Statement and field info has already been sent */
+      DBUG_RETURN(FALSE);
+    }
+    break;
   case SQLCOM_CREATE_VIEW:
     if (lex->create_view_mode == VIEW_ALTER)
     {