From 6b6c8332c7a5740110fef58909b3a0891be3e409 Mon Sep 17 00:00:00 2001
From: Joe Portner <joseph.portner@elastic.co>
Date: Wed, 1 Jun 2022 14:12:21 -0400
Subject: [PATCH] POC

---
 .../create_or_upgrade_saved_config.ts         | 40 ++++++++++++++++++-
 .../get_upgradeable_config.ts                 | 12 +++++-
 2 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/src/core/server/ui_settings/create_or_upgrade_saved_config/create_or_upgrade_saved_config.ts b/src/core/server/ui_settings/create_or_upgrade_saved_config/create_or_upgrade_saved_config.ts
index d55a6537957cbd..3853a49d89dd8a 100644
--- a/src/core/server/ui_settings/create_or_upgrade_saved_config/create_or_upgrade_saved_config.ts
+++ b/src/core/server/ui_settings/create_or_upgrade_saved_config/create_or_upgrade_saved_config.ts
@@ -39,10 +39,46 @@ export async function createOrUpgradeSavedConfig(
     version,
   });
 
+  let defaultIndex: string | undefined;
+  let isDefaultIndexMigrated = false;
+  if (
+    upgradeableConfig?.attributes.defaultIndex &&
+    !upgradeableConfig.attributes.isDefaultIndexMigrated
+  ) {
+    defaultIndex = upgradeableConfig.attributes.defaultIndex; // Keep the existing defaultIndex attribute if the data view is not found
+    try {
+      // The defaultIndex for this config object was created prior to 8.3, and it might refer to a data view ID that is no longer valid.
+      // We should try to resolve the data view and change the defaultIndex to the new ID, if necessary.
+      const resolvedIndex = await savedObjectsClient.resolve('index-pattern', defaultIndex);
+      if (resolvedIndex.outcome === 'aliasMatch' || resolvedIndex.outcome === 'conflict') {
+        // This resolved to an aliasMatch or conflict outcome; that means we should change the defaultIndex to the data view's new ID.
+        // Note, the alias_target_id field is guaranteed to exist iff the resolve outcome is aliasMatch or conflict.
+        defaultIndex = resolvedIndex.alias_target_id!;
+        isDefaultIndexMigrated = true;
+      }
+    } catch (err) {
+      // If the defaultIndex is not found at all, it will throw a Not Found error and we should mark the defaultIndex attribute as upgraded.
+      if (SavedObjectsErrorHelpers.isNotFoundError(err)) {
+        isDefaultIndexMigrated = true;
+      }
+      // For any other error, leave it unchanged so we can try to upgrade this attribute again in the future.
+    }
+  }
+
   // default to the attributes of the upgradeableConfig if available
   const attributes = defaults(
-    { buildNum },
-    upgradeableConfig ? (upgradeableConfig.attributes as any) : {}
+    {
+      buildNum,
+      ...(isDefaultIndexMigrated && {
+        // We migrated the defaultIndex attribute for this config, make sure these two fields take precedence over any in the old config
+        defaultIndex,
+        isDefaultIndexMigrated,
+      }),
+    },
+    upgradeableConfig ?? {
+      // We didn't find an upgradeable config, so this is a fresh one; mark the defaultIndex as migrated so we don't change it later!
+      isDefaultIndexMigrated: true,
+    }
   );
 
   try {
diff --git a/src/core/server/ui_settings/create_or_upgrade_saved_config/get_upgradeable_config.ts b/src/core/server/ui_settings/create_or_upgrade_saved_config/get_upgradeable_config.ts
index 493efa518f22ba..09d7a17db7616c 100644
--- a/src/core/server/ui_settings/create_or_upgrade_saved_config/get_upgradeable_config.ts
+++ b/src/core/server/ui_settings/create_or_upgrade_saved_config/get_upgradeable_config.ts
@@ -9,6 +9,15 @@
 import { SavedObjectsClientContract } from '../../saved_objects/types';
 import { isConfigVersionUpgradeable } from './is_config_version_upgradeable';
 
+/**
+ * This contains a subset of `config` object attributes that are relevant for upgrading it.
+ */
+export interface UpgradeableConfigType {
+  buildNum: string;
+  defaultIndex: string | undefined;
+  isDefaultIndexMigrated: boolean | undefined;
+}
+
 /**
  *  Find the most recent SavedConfig that is upgradeable to the specified version
  *  @param {Object} options
@@ -24,10 +33,11 @@ export async function getUpgradeableConfig({
   version: string;
 }) {
   // attempt to find a config we can upgrade
-  const { saved_objects: savedConfigs } = await savedObjectsClient.find({
+  const { saved_objects: savedConfigs } = await savedObjectsClient.find<UpgradeableConfigType>({
     type: 'config',
     page: 1,
     perPage: 1000,
+    fields: ['buildNum', 'defaultIndex', 'isDefaultIndexMigrated'], // Optimization: we only need these type-level fields, don't return anything else
     sortField: 'buildNum',
     sortOrder: 'desc',
   });