diff --git a/server/src/scripts/sidebar-know-of-migration.js b/server/src/scripts/sidebar-know-of-migration.js
new file mode 100644
index 000000000..6a821885a
--- /dev/null
+++ b/server/src/scripts/sidebar-know-of-migration.js
@@ -0,0 +1,68 @@
+// @flow
+
+import bots from 'lib/facts/bots.json';
+import { threadTypes, type ThreadType } from 'lib/types/thread-types';
+
+import { dbQuery, SQL } from '../database/database';
+import { createScriptViewer } from '../session/scripts';
+import { updateRoles } from '../updaters/role-updaters';
+import {
+  recalculateThreadPermissions,
+  commitMembershipChangeset,
+} from '../updaters/thread-permission-updaters';
+import RelationshipChangeset from '../utils/relationship-changeset';
+import { main } from './utils';
+
+async function updatePrivateThreads() {
+  console.log('updating private threads');
+  await updateThreads(threadTypes.PRIVATE);
+}
+
+async function updateSidebars() {
+  console.log('updating sidebars');
+  await updateThreads(threadTypes.SIDEBAR);
+}
+
+const batchSize = 10;
+
+async function updateThreads(threadType: ThreadType) {
+  const fetchThreads = SQL`
+    SELECT id FROM threads WHERE type = ${threadType}
+  `;
+  const [result] = await dbQuery(fetchThreads);
+  const threadIDs = result.map((row) => row.id.toString());
+
+  const viewer = createScriptViewer(bots.squadbot.userID);
+  while (threadIDs.length > 0) {
+    const batch = threadIDs.splice(0, batchSize);
+    const membershipRows = [];
+    const relationshipChangeset = new RelationshipChangeset();
+    await Promise.all(
+      batch.map(async (threadID) => {
+        console.log(`updating roles for ${threadID}`);
+        await updateRoles(viewer, threadID, threadType);
+        console.log(`recalculating permissions for ${threadID}`);
+        const {
+          membershipRows: threadMembershipRows,
+          relationshipChangeset: threadRelationshipChangeset,
+        } = await recalculateThreadPermissions(threadID, threadType);
+        membershipRows.push(...threadMembershipRows);
+        relationshipChangeset.addAll(threadRelationshipChangeset);
+      }),
+    );
+    console.log(`committing batch ${JSON.stringify(batch)}`);
+    await commitMembershipChangeset(viewer, {
+      membershipRows,
+      relationshipChangeset,
+    });
+  }
+}
+
+// This migration is supposed to update the database to reflect
+// https://phabricator.ashoat.com/D1020. There are two changes there:
+// (1) Changes to SIDEBAR so membership no longer automatically confers KNOW_OF
+// (2) Changes to PRIVATE so all of its children have KNOW_OF
+// We want to apply the changes to PRIVATE first so that when we recalculate
+// the permissions for any of a PRIVATE thread's SIDEBARs, the parent has
+// already been updated.
+main([updatePrivateThreads, updateSidebars]);