migrations: drop not null on path_tokens and name_tokens

documents.path_tokens and documents.name_tokens will be removed for
tsv_search_tokens. These are set to not null for now while that
implementation is in progress.

Updates b/130090305

Change-Id: Ic95e5592aa0164bd3b5dd9b070fffc64ef2158d9
Reviewed-on: https://team-review.git.corp.google.com/c/golang/discovery/+/456223
Reviewed-by: Robert Findley <rfindley@google.com>

migrations/000034_documents_drop_not_null_on_tokens.down.sql

@@ -0,0 +1,10 @@
+-- Copyright 2019 The Go Authors. All rights reserved.
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file.
+
+BEGIN;
+
+ALTER TABLE documents ALTER COLUMN name_tokens SET NOT NULL;
+ALTER TABLE documents ALTER COLUMN path_tokens SET NOT NULL;
+
+END;

migrations/000034_documents_drop_not_null_on_tokens.up.sql

@@ -0,0 +1,10 @@
+-- Copyright 2019 The Go Authors. All rights reserved.
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file.
+
+BEGIN;
+
+ALTER TABLE documents ALTER COLUMN name_tokens DROP NOT NULL;
+ALTER TABLE documents ALTER COLUMN path_tokens DROP NOT NULL;
+
+END;