Reindexing using NEST V5.4 - ElasticSearch

Question

I'm quite new to ElasticSearch. I'm trying to reindex a index in order to rename it. I'm using NEST API v5.4. I saw this example:

var reindex =
    elasticClient.Reindex<Customer>(r =>
        r.FromIndex("customers-v1")
            .ToIndex("customers-v2")
            .Query(q => q.MatchAll())
            .Scroll("10s")
            .CreateIndex(i =>
                i.AddMapping<Customer>(m =>
                    m.Properties(p =>
                        p.String(n => n.Name(name => name.Zipcode).Index(FieldIndexOption.not_analyzed))))));

Source: http://thomasardal.com/elasticsearch-migrations-with-c-and-nest/

However, I can't reproduce this using NEST 5.4. I think that is to version 2.4. I check the breaking changes of ElasticSearch and try reindexing using this:

Source: https://www.elastic.co/guide/en/elasticsearch/client/net-api/current/nest-breaking-changes.html

public method Nest.ReindexDescriptor..ctor Declaration changed (Breaking)
2.x: public .ctor(IndexName from, IndexName to) 5.x: public .ctor()

var reindex = new client.Reindex(oldIndexName, newIndexName);

But this did not work too. I also search for documentation but i didn't find any code on c#, just JSON Source: https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-reindex.html)

Can someone give me a example how to reindex using NEST 5.4 on C#?

Thanks in advance! :slight_smile:

Answer 1

After search for 2 long days I found out the solution to reindex a index. In order to solve future problems, I'll provide my solution.

Nest Version - 5.4

var reindex = client.Reindex<object>(r => r
              .BackPressureFactor(10)
              // ScrollAll - Scroll all the documents of the index and store it for 1minute 
              .ScrollAll("1m", 2, s => s
                  .Search(ss => ss
                      .Index(oldIndexName)
                          .AllTypes())
                      // there needs to be some degree of parallelism for this to work
                      .MaxDegreeOfParallelism(4))
              .CreateIndex(c => c
                  // New index here
                  .Index(newIndexName)
                  .Settings(
                      // settings goes here)
                  .Mappings(
                      // mappings goes here))
              .BulkAll(b => b
                  // New index here!
                  .Index(newIndexName)
                  .Size(100)
                  .MaxDegreeOfParallelism(2)
                  .RefreshOnCompleted()));

the ReIndex method returns a cold IObservable on which you have to call .Subscribe() to kick off everything.

So, you need to add it to your code:

var o = new ReindexObserver(
            onError: (e) => { //do something },
            onCompleted: () => { //do something });
reindex.Subscribe(o);

Useful links to check this are:

Documentation

Issue 2660 on GitHub

Issue 2771 on GitHub