Introduction
Elasticsearch types, introduced in earlier versions, allowed users to store different types of documents within the same index. However, with the introduction of Elasticsearch 6.x, the concept of types was deprecated, and since Elasticsearch 7.x, only a single type per index is allowed. In this article, we will discuss the reasons behind this change and provide a guide for migrating from multiple types to single types.
Reasons for Deprecating Elasticsearch Types
1. Performance Issues: Having multiple types in a single index can lead to performance problems, as it requires Elasticsearch to maintain separate mappings for each type. This increases the overhead and can slow down search and indexing operations.
2. Sparse Data: Storing different types of documents in the same index can lead to sparse data, where many fields are empty for a given document. This can negatively impact storage efficiency and search performance.
3. Conflicting Mappings: When using multiple types, there is a risk of having conflicting mappings for fields with the same name but different data types. This can lead to unexpected search results and indexing errors
Migrating from Multiple Types to Single Types
1. Create a New Index for Each Type: The first step in migrating from multiple types to single types is to create a new index for each type. This can be done using the Create Index API. For example, if you have an index called “my_index” with types “type1” and “type2”, you would create two new indices called “my_index_type1” and “my_index_type2”.
2. Reindex Data: After creating the new indices, you need to reindex the data from the old index to the new indices. This can be done using the Reindex API. For example, to reindex data from “my_index” to “my_index_type1” and “my_index_type2”, you would run the following commands:
POST _reindex
{
"source": {
"index": "my_index",
"type": "type1"
},
"dest": {
"index": "my_index_type1"
}
}
POST _reindex
{
"source": {
"index": "my_index",
"type": "type2"
},
"dest": {
"index": "my_index_type2"
}
}
3. Update Application Code: Once the data has been reindexed, you need to update your application code to use the new indices instead of the old index with multiple types. This may involve updating index names and removing references to types in your queries and indexing operations.
4. Delete Old Index: After verifying that the new indices are working correctly, you can delete the old index using the Delete Index API:
DELETE my_index
Conclusion
By following these steps, you can successfully migrate from using multiple types in Elasticsearch to using single types, improving performance and avoiding potential mapping conflicts.
