This will get you started:
(index="*tech*" AND (sourcetype="technical_rproxy_access" OR sourcetype="technical_mule_api") AND NOT statusCode="0") OR
(index="*" AND sourcetype="technical_rproxy_access")
| rex field=source "/appvol/(?<api_name_A>[\w\/]+)/logs.*"
| rex field=api_name "api\/(?<api_name_B>[\w\-]+)*"
| eval api_name_joiner = coalesce(api_name_A, api_name_B)
| eval MULE = coalesce(MULE, "null")
| stats count(api_name_A) AS GWcount count(api_name_B) AS RPCount values(api_name_A) AS APIatGW values(api_name_B) AS APIatRproxy values(statusCode) AS StatusatGW BY MULE
Then you might do something like:
... | eval api_name_joiner = coalesce(api_name_A, api_name_B)
| stats Some Stuff Here BY api_name_joiner
... View more