Several common ways to delete data from ElasticSearch

Preface

Deleting data in Elasticsearch is a common operation, and it can be implemented in many ways to meet different application scenarios and needs. Here are a few main ways to delete data from Elasticsearch:

1. Delete the index (Index)

Deleting indexes is the most thorough way to delete data in Elasticsearch. It deletes the structure and data of the index at the same time, similar to that in SQLDROP TABLEoperate.

Using the DELETE API: By sending a DELETE request to the index URL of Elasticsearch, the entire index and all data can be deleted. For example, to delete the namemy_indexThe following command can be executed (through the curl tool):

curl -X DELETE "localhost:9200/my_index"

Things to note：

Deleting an index is an irreversible operation, and once performed, all data and index structures will be lost.
Frequent deletion and creation of indexes can affect the performance of the Elasticsearch cluster.
You can set protection measures in Elasticsearch's configuration file to prevent error deletion of indexes.

2. Delete the document (Document)

Deleting a document means deleting only the specified data record without deleting the entire index structure. Elasticsearch provides a variety of ways to delete documents.

1. Delete according to the primary key: Delete a single document by specifying the ID of the document. For example, to delete the ID as1The following commands can be executed for the document:

curl -X DELETE "localhost:9200/my_index/_doc/1"

2. Use the Delete By Query API: If you need to delete multiple documents based on specific query conditions, you can use the Delete By Query API. This API allows users to batch delete documents based on query conditions. For example, to delete alluserThe field isjohnThe following commands can be executed for the document:

curl -X POST "localhost:9200/my_index/_delete_by_query" -H 'Content-Type: application/json' -d'  
{  
  "query": {  
    "match": {  
      "user": "john"  
    }  
  }  
}'

For deletion of large amounts of data, it is recommended to do it in batches to avoid excessive pressure on the cluster. The amount of data that is queried and deleted can be controlled by setting scroll and size parameters.

3. Precautions and best practices

Version conflict: When using the Delete By Query API, you may encounter version conflict issues. This is because the API takes a snapshot of the index before performing the deletion. If a document changes between taking the snapshot and performing the deletion, it will lead to a version conflict.
Performance impact: The deletion of large amounts of data may have an impact on the performance of the Elasticsearch cluster, especially when the index is large. Therefore, it is recommended to plan the deletion strategy reasonably to avoid large-scale deletion operations during peak periods.
Data backup: Before performing a deletion operation, be sure to make sure that important data has been backed up to prevent data loss.
Security: The deletion operation is irreversible, so you need to be cautious when performing the deletion operation to avoid accidentally deleting important data.

To sum up, deleting data from Elasticsearch can be achieved by deleting indexes or deleting documents. Which method to choose depends on the specific application scenario and requirements. During the operation, you need to pay attention to security, performance impact, and data backup.

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