# Reindexing loses documents

**URL:** <https://discuss.elastic.co/t/reindexing-loses-documents/327673>\
**Category:** Elasticsearch\
**Tags:** language-clients\
**Created:** [March 14, 2023, 1:59pm UTC](https://discuss.elastic.co/t/reindexing-loses-documents/327673 "2023-03-14T13:59:34Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![JanGoAutonomous](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jangoautonomous/32/118375_2.png) [@JanGoAutonomous](https://discuss.elastic.co/u/JanGoAutonomous)\
**Post date:** [March 14, 2023, 1:59pm UTC](https://discuss.elastic.co/t/reindexing-loses-documents/327673/1 "2023-03-14T13:59:34Z")

</div>

With the C# NEST client (version 7.17.5), I am updating an index by copying it to a temporary index, re-creating it, and copying the data back again.

During this process, some documents get lost. For instance, starting with 1 mio. documents, the re-created index will end with 743k documents.

To my understanding, the `reindex` operation happens too quickly before all the documents are correctly indexed. However, I **do** have `.WaitForCompletion()`, so it should not be an issue.

Essentially, I do:

1. Create the temporary index with updated mappings / settings
2. Run Reindex original -\> temporary
3. Delete original index
4. Run Reindex temporary -\> original

Why do my documents go missing?

My code:

```auto
        var currentIndexName = "test-1";
        var temporaryIndexName = "test-1-reindex";

        // 1. Initialize temporary index with new mapping
        await InitializeIndex(temporaryIndexName);
 
        // 2. Do reindex to temporary mapping
        var reindexResponse = await _elasticClient.ReindexOnServerAsync(r => r
            .Source(s => s
                .Index(currentIndexName)
            )
            .Destination(d => d
                .Index(temporaryIndexName)
            )
            .WaitForCompletion()
        );
        await _elasticClient.Indices.RefreshAsync(temporaryIndexName);
        
        // 3. Delete old index
        await _elasticClient.Indices.DeleteAsync(currentIndexName);
        await _elasticClient.Indices.RefreshAsync(currentIndexName);
        
        // 4. Copy over to new index
        reindexResponse = await _elasticClient.ReindexOnServerAsync(r => r
            .Source(s => s
                .Index(temporaryIndexName)
            )
            .Destination(d => d
                .Index(currentIndexName)
            )
            .WaitForCompletion()
        );

```

---

<div class="post-metadata">

**Author:** ![carly.richmond](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/carly.richmond/32/104935_2.png) [@carly.richmond](https://discuss.elastic.co/u/carly.richmond)\
**Post date:** [March 27, 2023, 11:17am UTC](https://discuss.elastic.co/t/reindexing-loses-documents/327673/2 "2023-03-27T11:17:30Z")

</div>

Hi @JanGoAutonomous,

I'm definitely not a .NET expert, and the use of `WaitForCompletion` does look in line with the examples. Are you initializing the original index again after deletion before triggering the 2nd reindex back to the original in step 4? There is a warning in the docs that the index must exist so I wonder if that's the issue. Can you give that a try if that makes sense?

If not, I would suggest raising a GitHub issue on the client project if you think there is a potential bug so it can be investigated.

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [April 24, 2023, 11:17am UTC](https://discuss.elastic.co/t/reindexing-loses-documents/327673/3 "2023-04-24T11:17:43Z")

</div>

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