What is the cause of Storage data disappearance?

Question

Storage in the application which was used normally so far, all the data has disappeared in the update. There is no change in @ ionic / storage version or ionic version.

Also, the data created after the data disappears is newly saved normally. What are the conditions under which Storaage data is initialized?

"@ionic/storage": "2.0.0"


--- Ionic Info ---

Ionic:

   ionic (Ionic CLI)  : 4.0.1 (C:\Users\xxxxx\AppData\Roaming\npm\node_modules\ionic)
   Ionic Framework    : ionic-angular 3.9.2
   @ionic/app-scripts : 3.1.11

Cordova:

   cordova (Cordova CLI) : not installed
   Cordova Platforms     : android 6.3.0, ios 4.5.4

System:

   Android SDK Tools : 26.1.1
   NodeJS            : v8.11.3 (C:\Program Files\nodejs\node.exe)
   npm               : 6.2.0
   OS                : Windows 7

Environment:

   ANDROID_HOME : C:\Users\xxxxx\AppData\Local\Android\Sdk

Answer 1

Ionic Storage is a "wrapper" of localForage library which wraps different persistence solutions under the hood (via "drivers"). The only "guaranteed" persistence is SQLite if ionic storage runs on a device as hybrid (cordova app). The other browser based drivers (indexeddb or websql) persist data according to particular browser allowance. And such browser based persistence is not truly "guaranteed" since it is subject to:

• browser quotation (how much disk space browser allows a web site to store for)
• browser mode (like privacy mode that can block localStorage etc)
• browser need to use space for another site (and it can start removing data from your app for instance)

So overall unless you use SQLite - treat this Ionic Storage as persistent cache of some sort...

Also keep in mind that Ionic Storage can use one type of storage available to it at one point and then switch to another if conditions changed thus making your data still available in websql but not accessible since your app could have switched to indexeddb. To avoid that its best to strictly control available drivers and their order of preference / initialization