Bug#44306: Assertion fail on duplicate key error in

'INSERT ... SELECT' statements
            
The code that produces result rows expected that a duplicate row
error could not occur in INSERT ... SELECT statements with 
unfulfilled WHERE conditions. This may happen, however, if the 
SELECT list contains only aggregate functions.
Fixed by checking if an error occured before trying to send EOF
to the client.

mysql-test/r/insert_select.result

@@ -765,6 +765,11 @@ f1	f2
 2	2
 10	10
 DROP TABLE t1, t2;
+CREATE TABLE t1 ( a INT KEY, b INT );
+INSERT INTO t1 VALUES ( 0, 1 );
+INSERT INTO t1 ( b ) SELECT MAX( b ) FROM t1 WHERE b = 2;
+ERROR 23000: Duplicate entry '0' for key 'PRIMARY'
+DROP TABLE t1;
 SET SQL_MODE='STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';
 CREATE TABLE t1 (c VARCHAR(30), INDEX ix_c (c(10)));
 CREATE TABLE t2 (d VARCHAR(10));

mysql-test/t/insert_select.test

@@ -323,6 +323,16 @@ INSERT INTO t2 (f1, f2)
 SELECT * FROM t2;
 DROP TABLE t1, t2;
 
+#
+# Bug#44306: Assertion fail on duplicate key error in 'INSERT ... SELECT' 
+# statements
+#
+CREATE TABLE t1 ( a INT KEY, b INT );
+INSERT INTO t1 VALUES ( 0, 1 );
+--error ER_DUP_ENTRY
+INSERT INTO t1 ( b ) SELECT MAX( b ) FROM t1 WHERE b = 2;
+DROP TABLE t1;
+
 #
 # Bug #26207: inserts don't work with shortened index
 #

sql/sql_select.cc

@@ -7084,15 +7084,17 @@ return_zero_rows(JOIN *join, select_result *result,TABLE_LIST *tables,
   if (!(result->send_fields(fields,
                               Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF)))
   {
+    bool send_error= FALSE;
     if (send_row)
     {
       List_iterator_fast<Item> it(fields);
       Item *item;
       while ((item= it++))
 	item->no_rows_in_result();
-      result->send_data(fields);
+      send_error= result->send_data(fields);
     }
-    result->send_eof();				// Should be safe
+    if (!send_error)
+      result->send_eof();				// Should be safe
   }
   /* Update results for FOUND_ROWS */
   join->thd->limit_found_rows= join->thd->examined_row_count= 0;