
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_lengthsetting: 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.
The post How to Increase index.max_regex_length in OpenSearch appeared first on SOC Prime.
