Re-indexing data

Re-indexing data in Elasticsearch is a challenge when you have changed the schema or mappings of the fields. Upon changing the schema, you are either required to re-index all the documents of that field to incorporate mapping changes to previous documents stored, or to not re-index older documents, which will become useless with the change in schema.

Process of re-indexing data:

1. Create a new index with the new mappings and settings.
2. Take the documents from the old index and index it in a new index.

To minimize the effect and downtime of changing the schema and re-indexing, use the following approach.

Using aliases

Aliases are a powerful feature that can easily re-index the complete index data without any downtime. Alias can be considered as a nickname given to the index name. It can be considered as a symbolic link.

Let us see how to use aliases:

• Create an index with its mapping and settings
• Create an alias to point to the index name

After updating the schema/mappings:

• Create a new...