ALTER TABLE IGNORE didn't ignore duplicates for unique add index for InnoDB

mysql-test/suite/innodb/r/innodb_mysql.result

@@ -2617,6 +2617,13 @@ rows	3
 Extra	Using index
 DROP TABLE t1;
 #
+# ALTER TABLE IGNORE didn't ignore duplicates for unique add index
+#
+create table t1 (a int primary key, b int) engine = innodb;
+insert into t1 values (1,1),(2,1);
+alter ignore table t1 add unique `main` (b);
+drop table t1;
+#
 End of 5.1 tests
 #
 # Test for bug #39932 "create table fails if column for FK is in different

mysql-test/suite/innodb/t/innodb_mysql.test

@@ -840,6 +840,15 @@ CREATE INDEX b ON t1(a,b,c,d);
 
 DROP TABLE t1;
 
+--echo #
+--echo # ALTER TABLE IGNORE didn't ignore duplicates for unique add index
+--echo #
+
+create table t1 (a int primary key, b int) engine = innodb;
+insert into t1 values (1,1),(2,1);
+alter ignore table t1 add unique `main` (b);
+drop table t1;
+
 --echo #
 
 

sql/sql_table.cc

@@ -7136,6 +7136,16 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
           /* Non-primary unique key. */
           needed_online_flags|=  HA_ONLINE_ADD_UNIQUE_INDEX;
           needed_fast_flags|= HA_ONLINE_ADD_UNIQUE_INDEX_NO_WRITES;
+          if (ignore)
+          {
+            /*
+              If ignore is used, we have to remove all duplicate rows,
+              which require a full table copy.
+            */
+            need_copy_table= ALTER_TABLE_DATA_CHANGED;
+            pk_changed= 2;                      // Don't change need_copy_table
+            break;
+          }
         }
       }
       else