putIndexPolicy

Creates or updates a field index policy for the specified log group. Only log groups in the Standard log class support field index policies. For more information about log classes, see Log classes.

You can use field index policies to create field indexes on fields found in log events in the log group. Creating field indexes speeds up and lowers the costs for CloudWatch Logs Insights queries that reference those field indexes, because these queries attempt to skip the processing of log events that are known to not match the indexed field. Good fields to index are fields that you often need to query for and fields or values that match only a small fraction of the total log events. Common examples of indexes include request ID, session ID, userID, and instance IDs. For more information, see Create field indexes to improve query performance and reduce costs.

To find the fields that are in your log group events, use the GetLogGroupFields operation.

For example, suppose you have created a field index for requestId. Then, any CloudWatch Logs Insights query on that log group that includes requestId = <i>value</i> or requestId IN [<i>value</i>, <i>value</i>, ...] will process fewer log events to reduce costs, and have improved performance.

Each index policy has the following quotas and restrictions:

• As many as 20 fields can be included in the policy.

• Each field name can include as many as 100 characters.

Matches of log events to the names of indexed fields are case-sensitive. For example, a field index of RequestId won't match a log event containing requestId.

Log group-level field index policies created with PutIndexPolicy override account-level field index policies created with PutAccountPolicy. If you use PutIndexPolicy to create a field index policy for a log group, that log group uses only that policy. The log group ignores any account-wide field index policy that you might have created.