BUG#18874 - Setting myisam_repair_threads > 1, index cardinality always 1

Fixed by moving update_key_parts() down to be after write_index().

myisam/sort.c

@@ -480,13 +480,6 @@ int thr_write_keys(MI_SORT_PARAM *sort_param)
     if (!got_error)
     {
       share->state.key_map|=(ulonglong) 1 << sinfo->key;
-      if (param->testflag & T_STATISTICS)
-        update_key_parts(sinfo->keyinfo, rec_per_key_part, sinfo->unique,
-                         param->stats_method == MI_STATS_METHOD_IGNORE_NULLS?
-                         sinfo->notnull: NULL,
-                         (ulonglong) info->state->records);
-
-
       if (!sinfo->buffpek.elements)
       {
         if (param->testflag & T_VERBOSE)
@@ -498,6 +491,11 @@ int thr_write_keys(MI_SORT_PARAM *sort_param)
             flush_ft_buf(sinfo) || flush_pending_blocks(sinfo))
           got_error=1;
       }
+      if (!got_error && param->testflag & T_STATISTICS)
+        update_key_parts(sinfo->keyinfo, rec_per_key_part, sinfo->unique,
+                         param->stats_method == MI_STATS_METHOD_IGNORE_NULLS?
+                         sinfo->notnull: NULL,
+                         (ulonglong) info->state->records);
     }
     my_free((gptr) sinfo->sort_keys,MYF(0));
     my_free(mi_get_rec_buff_ptr(info, sinfo->rec_buff),

mysql-test/r/repair.result

@@ -37,3 +37,14 @@ Table	Op	Msg_type	Msg_text
 test.t1	repair	warning	Number of rows changed from 0 to 1
 test.t1	repair	status	OK
 drop table t1;
+CREATE TABLE t1(a INT, KEY(a));
+INSERT INTO t1 VALUES(1),(2),(3),(4),(5);
+SET myisam_repair_threads=2;
+REPAIR TABLE t1;
+Table	Op	Msg_type	Msg_text
+test.t1	repair	status	OK
+SHOW INDEX FROM t1;
+Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment
+t1	1	a	1	a	A	5	NULL	NULL	YES	BTREE	
+SET myisam_repair_threads=@@global.myisam_repair_threads;
+DROP TABLE t1;

mysql-test/t/repair.test

@@ -34,4 +34,15 @@ repair table t1;
 repair table t1 use_frm;
 drop table t1;
 
+#
+# BUG#18874 - Setting myisam_repair_threads > 1, index cardinality always 1
+#
+CREATE TABLE t1(a INT, KEY(a));
+INSERT INTO t1 VALUES(1),(2),(3),(4),(5);
+SET myisam_repair_threads=2;
+REPAIR TABLE t1;
+SHOW INDEX FROM t1;
+SET myisam_repair_threads=@@global.myisam_repair_threads;
+DROP TABLE t1;
+
 # End of 4.1 tests