docs: examples of common mongodb migrations

[r1tsuu]

Adds some common mongodb migrations examples to the docs:

• Delete field from the database
• Synchronize indexes (which is the solution for common issues like this https://github.com/payloadcms/payload/issues/2007)
• Making field localized and vice versa

[andershermansen]

Maybe also make a note that this will not work with versioned collections?

[r1tsuu]

Maybe also make a note that this will not work with versioned collections?

You can make it work with versioned collections, you just would have to apply that migration for the versions collection. This can be noted

[DallasO]

Not necessarily related, but regarding the example for syncing indexes, should the migrateRelationshipsV2_V3 script include an option to sync all indexes?

I currently cannot run that script because I'm seeing an error that an index is missing. But the error does not list the culprit.

[DanRibbens]

@r1tsuu can you incorporate changing a collection name into this when you resolve the conflicts?

Example renaming a collection

The following example renames a collection with slug "pages" to "articles" and it includes migrating the _versions collection also.

import {
  MigrateDownArgs,
  MigrateUpArgs,
} from '@payloadcms/db-mongodb'
// import type { Db } from 'mongodb' // you will need to add this package as a devDependency in the package.json if you want db to be typed as Db

export async function up({ payload, req, session }: MigrateUpArgs): Promise<void> {
  const db = payload.db.connection.db as any

  await db.renameCollection('pages', 'articles', { session, dropTarget: true })
  await db.renameCollection('_pages_versions', '_articles_versions', { session, dropTarget: true }) // remove this line if you do not have versions enabled
}

export async function down({ payload, req, session }: MigrateDownArgs): Promise<void> {
  const db = payload.db.connection.db as any

  await db.renameCollection('articles', 'pages', { session, dropTarget: true })
  await db.renameCollection('_articles_versions', '_pages_versions', { session, dropTarget: true }) // remove this line if you do not have versions enabled
}