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    schema-upgrade

    0.3.0 • Public • Published

    schema-upgrade

    Database-agnostic schema upgrading library.

    Usage

    async function main() {
      const Schema = require('schema-upgrade')
     
      // connect to mongodb
      const { MongoClient } = require('mongodb')
      const mongoClient = await new MongoClient('mongodb://localhost:27017').connect()
      const db = await mongoClient.db('mydb')
     
      // get current schema version
      const collection = db.collection('appInfo')
      let appInfo = await collection.findOne({ key: 'appInfo' })
     
      // appInfo doesn't exist, this is the first time we run the app
      // initialize appInfo struct
      if (!appInfo) {
        appInfo = {
          key: 'appInfo',
          version: 0, // set initial version to 0
          upgrading: false
        }
     
        await collection.createIndex({ key: 1 }, { unique: true })
        await collection.insertOne(appInfo)
      }
     
      // create a schema object, provide current db's schema version
      const schema = new Schema(appInfo.version, db)
     
      // version 1
      schema.version(1, async db => {
        console.log('Upgrading to v1...')
        await db.collection('users').createIndex({ userId: 1 }, { unique: true })
        console.log('Upgraded to v1')
      })
     
      // version 2
      schema.version(2, async db => {
        console.log('Upgrading to v2...')
        await db.collection('users').crateIndex({ openId: 1 }, { unique: true })
        console.log('Upgraded to v2')
      })
     
      // get the latest version
      const latest = schema.latest()
     
      // if db's schema version is the latest
      // no upgrade is needed
      if (latest === appInfo.version) {
        return
      }
     
      // else we upgrade the schema
      // set 'upgrading' to true to lock the db
      const result = await collection.updateOne({
        key: 'appInfo',
        version: appInfo.version,
        upgrading: false
      }, {
        $set: {
          upgrading: true
        }
      })
     
      // if 'upgrading' is already true
      // the other server is performing the upgrading
      if (!result.modifiedCount) {
        throw new Error('Other process is upgrading the database. Please wait.')
      }
     
      // upgrade
      console.log(`Upgrading from version ${appInfo.version} to ${latest}`)
      await schema.upgrade()
     
      // unlock db
      await collection.updateOne({
        key: 'appInfo',
        version: appInfo.version,
        upgrading: true
      }, {
        $set: {
          version: latest,
          upgrading: false
        }
      })
     
      // finished
    }
     
    main()

    APIs

    new Schema(currentVersion, ...args)

    Create a schema object.

    currentVersion

    Number. Current schema version.

    ...args

    Any. The arguments passed to upgradeFunction.

    schema.version(versionNumber, upgradeFunction)

    Defines a version.

    versionNumber

    Number. The version number.

    upgradeFunction(...args)

    Function. The upgrade function. It should return a Promise.

    schema.latest()

    Returns the latest version number, or null if no version is defined.

    schema.upgrade()

    Run the upgrade operations. It will run the upgradeFunction from the next version to the latest version.

    Returns: Promise. Resolves to true when upgrade is completed. Rejects if any error occurred.

    LICENSE

    MIT

    Install

    npm i schema-upgrade

    DownloadsWeekly Downloads

    3

    Version

    0.3.0

    License

    MIT

    Unpacked Size

    5.72 kB

    Total Files

    4

    Last publish

    Collaborators

    • jiangfengming