How can I perform a case insensitive parse regex in Sumo Logic?

Yes, you can tell the parser to use case insensitivity by supplying the regex parameter of (?i). For example, let's say we have the following log messages:

Line1: The following exception was reported: error in log

Line2: The following exception was reported: Error in log

Line3: The following exception was reported: ERROR in log

Use the following parse regex expression to match the "error" in the logs. The (?i) tells the parser to ignore case for the trailing expression.

| parse regex "reported:\s(?<exception>(?i)error)\s"

 This would result in the following parsed fields

exception | Message 
ERROR | Line3: The following exception was reported: ERROR in log
Error | Line2: The following exception was reported: Error in log
error | Line1: The following exception was reported: error in log

When aggregating these values you may want to include these as a single result regardless of the casing. In order to do this, you will need to first normalize the strings to a common value using the toLowerCase or toUpperCase operators.