How to Increase index.max_regex_length in OpenSearch

The error index.max.regex_length in OpenSearch is related to the maximum length of regular expressions that can be used in index settings. This setting controls the maximum length of a regular expression used during index creation or mapping, and when a regex pattern exceeds this length, you will encounter an error.

To fix this, you can adjust the index.max.regex_length setting. Here’s how to resolve it.

Solution

• Increase the index.max.regex_length setting: If your regular expression is large, you might need to increase the allowed regex length. You can do this by adding the following setting to your OpenSearch index settings:

PUT /your_index/_settings
{
  "settings": {
    "index.max.regex_length": 10000
  }
}

In this example, the limit is set to 10,000 characters, but you can adjust this value according to the complexity of your regular expression.

• Update Index Template (for new indices): If you’re using index templates and want to apply this setting to newly created indices, you can add this setting to your index template as well.

PUT /_template/your_template
{
  "index_patterns": ["your_index_pattern*"],
  "settings": {
    "index.max.regex_length": 10000
  }
}

• Check Regular Expressions: Ensure that the regular expression you are using is not unnecessarily long or complex. Try simplifying or optimizing the regex if possible.

Example

• Check the current value:

GET /your_index/_settings

• Update the setting if needed:

PUT /your_index/_settings
{
  "settings": {
    "index.max.regex_length": 10000
  }
}

This should allow you to avoid running into the error with larger regular expressions.