Syntax

import { replacePrefix } from 'dexie';

db.files
  .where('filePath')
  .startsWith('foo/')
  .modify({
    filePath: replacePrefix('foo/', 'bar/')
  });

Description

Performs a sync-consistent replacement of the leading parts of a string. The operation can be performed in order to consistently move sub trees when syncing data using Dexie Cloud.

Consistency use cases

Client A and Client B shares a copy of a Dexie Cloud database with a tree structure. The tree structure is defined using the indexed filePath property. A network outage happens for both clients. At the time of the network outage both clients have identical copies of the tree:

foo/
    item1
    item2
    item3

Now both clients are off-line for a while and while they are offline they perform different actions:

• Client A adds item4 with filePath foo/.
• Client B renames filepath foo/ to bar/ using replacePrefix() the same way as in the sample from syntax above.

Network is then repaired for both clients.

If Client A syncs first:

1. Client A syncs. The canonical data is now:

   foo/
       item1
       item2
       item3
       item4
   

2. Client B syncs. The consistent replacePrefix operation is executed server-side. Result:

   bar/
       item1
       item2
       item3
       item4
   

If instead Client B would have synced first:

1. Client B syncs. The consistent replacePrefix operation is executed server-side and also persisted in the change log, in case another client based on previous revision will sync things later.

   bar/
       item1
       item2
       item3
   

2. Client A syncs the addition of {filePath: 'foo/', name: 'item4'} (based on an earlier state of the data). Since the base revision number is part of the sync request, server detects that a consistent operation has to be executed onto the data that client A wants to add to the database. The new object {filePath: 'foo/', name: 'item4'} is therefore transformed into {filePath: 'bar/', name: 'item4'}. Result:

   bar/
       item1
       item2
       item3
       item4
   

See Also

add()

remove()