/// <summary>
/// Internal method to rebalance data across a different number of partitions.
/// </summary>
/// <param name="newPartitionCount">The target number of partitions.</param>
/// <returns>The Task object for the asynchronous execution.</returns>
private async Task <int> RepartitionData(int newPartitionCount)
{
// No-op, just delete the last collection.
if (newPartitionCount == 0)
{
return(0);
}
ManagedHashPartitionResolver currentResolver = (ManagedHashPartitionResolver)this.Client.PartitionResolvers[this.Database.SelfLink];
var nextPartitionResolver = new ManagedHashPartitionResolver(
currentResolver.PartitionKeyExtractor,
this.Client,
this.Database,
newPartitionCount);
TransitionHashPartitionResolver transitionaryResolver = new TransitionHashPartitionResolver(
currentResolver,
nextPartitionResolver,
this.ReadMode);
this.Client.PartitionResolvers[this.Database.SelfLink] = transitionaryResolver;
// Move data between partitions. Here it's one by one, but you can change this to implement inserts
// in bulk using stored procedures (bulkImport and bulkDelete), or run them in parallel. Another
// improvement to this would be push down the check for partitioning function down to the individual
// collections as a LINQ/SQL query.
int numberOfMovedDocuments = 0;
foreach (string collectionLink in currentResolver.CollectionLinks)
{
ResourceFeedReader <Document> feedReader = this.Client.CreateDocumentFeedReader(collectionLink);
while (feedReader.HasMoreResults)
{
foreach (Document document in await feedReader.ExecuteNextAsync())
{
object partitionKey = nextPartitionResolver.GetPartitionKey(document);
string newCollectionLink = nextPartitionResolver.ResolveForCreate(partitionKey);
if (newCollectionLink != collectionLink)
{
numberOfMovedDocuments++;
await this.Client.DeleteDocumentAsync(document.SelfLink);
await this.Client.CreateDocumentAsync(newCollectionLink, document);
}
}
}
}
this.Client.PartitionResolvers[this.Database.SelfLink] = nextPartitionResolver;
return(numberOfMovedDocuments);
}
