Don't panic when altering retention policy

Fixes issue #2846

CHANGELOG.md

@@ -8,6 +8,7 @@
 - [2838](https://github.com/influxdb/influxdb/pull/2838) -- Set auto-created retention policy period to infinite.
 - [2829](https://github.com/influxdb/influxdb/pull/2829) -- Re-enable Graphite support as a new Service-style component.
 - [2814](https://github.com/influxdb/influxdb/issues/2814) -- Convert collectd to a service.
+- [2852](https://github.com/influxdb/influxdb/pull/2852) -- Don't panic when altering retention policies. Thanks for the report @huhongbo
 
 ## v0.9.0-rc32 [2015-06-07]
 

meta/statement_executor_test.go

@@ -367,9 +367,9 @@ func TestStatementExecutor_ExecuteStatement_AlterRetentionPolicy(t *testing.T) {
 			t.Fatalf("unexpected database: %s", database)
 		} else if name != "rp0" {
 			t.Fatalf("unexpected name: %s", name)
-		} else if *rpu.Duration != 7*24*time.Hour {
+		} else if rpu.Duration != nil && *rpu.Duration != 7*24*time.Hour {
 			t.Fatalf("unexpected duration: %v", *rpu.Duration)
-		} else if *rpu.ReplicaN != 2 {
+		} else if rpu.ReplicaN != nil && *rpu.ReplicaN != 2 {
 			t.Fatalf("unexpected replication factor: %v", *rpu.ReplicaN)
 		}
 		return nil
@@ -387,6 +387,16 @@ func TestStatementExecutor_ExecuteStatement_AlterRetentionPolicy(t *testing.T) {
 	if res := e.ExecuteStatement(stmt); res.Err != nil {
 		t.Fatalf("unexpected error: %s", res.Err)
 	}
+
+	stmt = influxql.MustParseStatement(`ALTER RETENTION POLICY rp0 ON foo DURATION 7d`)
+	if res := e.ExecuteStatement(stmt); res.Err != nil {
+		t.Fatalf("unexpected error: %s", res.Err)
+	}
+
+	stmt = influxql.MustParseStatement(`ALTER RETENTION POLICY rp0 ON foo REPLICATION 2`)
+	if res := e.ExecuteStatement(stmt); res.Err != nil {
+		t.Fatalf("unexpected error: %s", res.Err)
+	}
 }
 
 // Ensure a ALTER RETENTION POLICY statement returns errors from the store.

meta/store.go

@@ -719,7 +719,7 @@ func (s *Store) UpdateRetentionPolicy(database, name string, rpu *RetentionPolic
 	}
 
 	var replicaN *uint32
-	if rpu.Duration != nil {
+	if rpu.ReplicaN != nil {
 		value := uint32(*rpu.ReplicaN)
 		replicaN = &value
 	}