ElasticSearch update syntax

Overwrite Update

You can use the _update API to update a single document. This method is suitable for cases where you need to overwrite the entire document.

POST /my_index/_update/1
{
  "doc": {
    "title": "Updated Title",
    "content": "Updated content."
  }
}

Partial Update

Sometimes, you only need to update certain fields of a document, rather than the entire document. Elasticsearch supports partial updates, updating only the specified fields.

Example:

POST /my_index/_update/1
{
  "doc": {
    "content": "Updated content."
  }
}

In this example, only the content field is updated, while other fields in the document remain unchanged.

Script Update

You can also use a script to update documents. This method is particularly useful for performing calculations or conditional updates on existing fields.

Example:

POST /my_index/_update/1
{
  "script": {
    "source": "ctx._source.view_count += params.count",
    "lang": "painless",
    "params": {
      "count": 1
    }
  }
}

Bulk Update

When you need to update multiple documents at once, you can use the _bulk API for bulk updates. This method can significantly improve performance.

Example:

POST /_bulk
{ "update": { "_id": "1", "_index": "my_index" } }
{ "doc": { "content": "Bulk updated content." } }
{ "update": { "_id": "2", "_index": "my_index" } }
{ "doc": { "content": "Another bulk updated content." } }

Updating Nested Fields

Updating nested fields in Elasticsearch can be complex because nested objects are essentially separate documents. Updating nested fields typically requires a script update.

Assume we have an index containing order information, with each order containing a list of nested products. Now, suppose we want to update the price of the product "Laptop" in the order with order_id 1001. We can achieve this using the following script update:

POST /orders/_update/1
{
  "script": {
    "source": """
      for (int i = 0; i < ctx._source.products.size(); i++) {
        if (ctx._source.products[i].name == params.product_name) {
          ctx._source.products[i].price = params.new_price;
        }
      }
    """,
    "lang": "painless",
    "params": {
      "product_name": "Laptop",
      "new_price": 1300
    }
  }
}

Considerations

• Concurrency Control: When multiple clients are updating the same document concurrently, conflicts may occur. Use _version or _seq_no and _primary_term to achieve concurrency control.
• Performance Optimization: Bulk updates can improve performance, but ensure you choose a reasonable bulk size to avoid memory overflow.
• Script Security: Ensure script security to prevent the execution of malicious code when using script updates.