Bug #27460607: INCORRECT BEHAVIOR OF IODKU WHEN

               INSERT SELECT's SOURCE TABLE IS EMPTY

Issue:
------
When the VALUES part of ON DUPLICATE KEY UPDATE contains a
BLOB value, it is handled using the
LEX::insert_update_values_map.

The issue in this bug is similar to the one in
Bug #25361251. LEX::insert_update_values_map is initialized
but not freed. This is because in an INSERT...SELECT
statement, if the SELECT part doesn't produce any rows,
write_record() isn't called.

Solution:
---------
As part of the fix for Bug #25361251, I added
LEX::clear_values_map() to write_record(). But a better
place to do the cleanup would be the end of the functions
Sql_cmd_insert_select::execute and  Sql_cmd_insert::execute.

This will make the design more similar to 8.0/trunk of having
LEX::clear_values_map() at the end of Sql_cmd_dml::execute().

Author: Sreeharsha Ramanavarapu

sql/sql_insert.cc

@@ -1,5 +1,5 @@
 /*
-   Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
+   Copyright (c) 2000, 2018, 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
@@ -1902,7 +1902,6 @@ int write_record(THD *thd, TABLE *table, COPY_INFO *info, COPY_INFO *update)
     thd->get_transaction()->mark_modified_non_trans_table(
       Transaction_ctx::STMT);
   free_root(&mem_root, MYF(0));
-  thd->lex->clear_values_map();
   DBUG_RETURN(trg_error);
 
 err:
@@ -1922,7 +1921,6 @@ int write_record(THD *thd, TABLE *table, COPY_INFO *info, COPY_INFO *update)
     my_safe_afree(key, table->s->max_unique_length, MAX_KEY_LENGTH);
   table->column_bitmaps_set(save_read_set, save_write_set);
   free_root(&mem_root, MYF(0));
-  thd->lex->clear_values_map();
   DBUG_RETURN(1);
 }
 
@@ -3130,6 +3128,8 @@ bool Sql_cmd_insert::execute(THD *thd)
                     DBUG_ASSERT(!debug_sync_set_action(current_thd,
                                                        STRING_WITH_LEN(act)));
                   };);
+
+  thd->lex->clear_values_map();
   return res;
 }
 
@@ -3223,6 +3223,7 @@ bool Sql_cmd_insert_select::execute(THD *thd)
     thd->first_successful_insert_id_in_cur_stmt=
       thd->first_successful_insert_id_in_prev_stmt;
 
+  thd->lex->clear_values_map();
   return res;
 }