Bug #25244533 : PERFORMANCE_SCHEMA DIGESTS THE SAME QUERY TO MULTIPLE DIFFERENT

                DIGESTS

Issue:
Part1:    When there are ';' in the queries, it is assumed that there are
          multiple queries and therefore parsing is done for each individual
          query one after another. During this process, digest storage was not
          reset properly and digest text of old query was seen.

Fix:      Reset digest storage beforem start parsing next query.

Part2:    In case of multiple queries, when a ';' is seen, its decided that
          current query ends here and a new query is about to start. But when
          delimiter is set to something else, for the first query, ';' is
          passed to digest code. As a result, ';' was seen in digest text and
          the digest created for the query is different from the digest which
          would have been created without the ';' in the query.

Fix:      Parser passes NUL (i.e. 0) to digest code when the first query parsing
          is over. Therefore, in digest code when a NUL (0) is encountered, check
          the last token. If it is ';', pop it out so that it is not included in
          query digest text and digest.

Author: mayprasa

sql/sql_digest.cc

@@ -1,4 +1,4 @@
-/* Copyright (c) 2008, 2015, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2008, 2016, Oracle and/or its affiliates. All rights reserved.
 
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -595,6 +595,16 @@ sql_digest_state* digest_add_token(sql_digest_state *state,
       state->m_last_id_index= (int)digest_storage->m_byte_count;
       break;
     }
+    case 0:
+    {
+      unsigned int temp_tok;
+      read_token(digest_storage,
+                 digest_storage->m_byte_count-SIZE_OF_A_TOKEN,
+                 & temp_tok);
+      if (temp_tok == ';')
+        digest_storage->m_byte_count-= SIZE_OF_A_TOKEN;
+      break;
+    }
     default:
     {
       /* Add this token to digest storage. */

sql/sql_parse.cc

@@ -1430,6 +1430,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
 
 /* PSI begin */
       thd->m_digest= & thd->m_digest_state;
+      thd->m_digest->reset(thd->m_token_array, max_digest_length);
 
       thd->m_statement_psi= MYSQL_START_STATEMENT(&thd->m_statement_state,
                                                   com_statement_info[command].m_key,