Bug#19978: INSERT .. ON DUPLICATE erroneously reports some records were

updated.

INSERT ... ON DUPLICATE KEY UPDATE reports that a record was updated when
the duplicate key occurs even if the record wasn't actually changed
because the update values are the same as those in the record.

Now the compare_record() function is used to check whether the record was
changed and the update of a record reported only if the record differs
from the original one.

mysql-test/r/insert_select.result

@@ -705,3 +705,15 @@ use bug21774_1;
 INSERT INTO bug21774_2.t1 SELECT t1.* FROM t1;
 DROP DATABASE bug21774_1;
 DROP DATABASE bug21774_2;
+USE test;
+create table t1(f1 int primary key, f2 int);
+insert into t1 values (1,1);
+affected rows: 1
+insert into t1 values (1,1) on duplicate key update f2=1;
+affected rows: 0
+insert into t1 values (1,1) on duplicate key update f2=2;
+affected rows: 2
+select * from t1;
+f1	f2
+1	2
+drop table t1;

mysql-test/t/insert_select.test

@@ -265,4 +265,17 @@ INSERT INTO bug21774_2.t1 SELECT t1.* FROM t1;
 
 DROP DATABASE bug21774_1;
 DROP DATABASE bug21774_2;
+USE test;
 
+#
+# Bug#19978: INSERT .. ON DUPLICATE erroneously reports some records were
+#            updated.
+#
+create table t1(f1 int primary key, f2 int);
+--enable_info
+insert into t1 values (1,1);
+insert into t1 values (1,1) on duplicate key update f2=1;
+insert into t1 values (1,1) on duplicate key update f2=2;
+--disable_info
+select * from t1;
+drop table t1;

sql/mysql_priv.h

@@ -701,6 +701,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
 		      char* packet, uint packet_length);
 void log_slow_statement(THD *thd);
 bool check_dup(const char *db, const char *name, TABLE_LIST *tables);
+bool compare_record(TABLE *table, query_id_t query_id);
 
 bool table_cache_init(void);
 void table_cache_free(void);

sql/sql_insert.cc

@@ -1194,15 +1194,21 @@ int write_record(THD *thd, TABLE *table,COPY_INFO *info)
           }
           goto err;
         }
+        if ((table->file->table_flags() & HA_PARTIAL_COLUMN_READ) ||
+            compare_record(table, query_id))
+        {
           info->updated++;
 
           if (table->next_number_field)
-          table->file->adjust_next_insert_id_after_explicit_value(table->next_number_field->val_int());
+            table->file->adjust_next_insert_id_after_explicit_value(
+              table->next_number_field->val_int());
 
           trg_error= (table->triggers &&
                       table->triggers->process_triggers(thd, TRG_EVENT_UPDATE,
-                                                      TRG_ACTION_AFTER, TRUE));
+                                                        TRG_ACTION_AFTER,
+                                                        TRUE));
           info->copied++;
+        }
         goto ok_or_after_trg_err;
       }
       else /* DUP_REPLACE */

sql/sql_update.cc

@@ -26,7 +26,7 @@
 
 /* Return 0 if row hasn't changed */
 
-static bool compare_record(TABLE *table, query_id_t query_id)
+bool compare_record(TABLE *table, query_id_t query_id)
 {
   if (table->s->blob_fields + table->s->varchar_fields == 0)
     return cmp_record(table,record[1]);