Github user ottobackwards commented on a diff in the pull request:
https://github.com/apache/metron/pull/861#discussion_r155664254
--- Diff: metron-platform/metron-parsers/README.md ---
@@ -216,6 +216,23 @@ whenever `field2` exists and whose corresponding equal
to 'foo':
}
```
+* `SELECT`: This transformation filters the fields in the message to
include only the configured output fields, and drops any not explicitly
included.
+
+For example:
+```
+{
+...
+ "fieldTransformations" : [
+ {
+ "output" : ["field1", "field2" ]
+ , "transformation" : "SELECT"
+ }
+ ]
+}
+```
+
+when applied to a message containing keys field1, field2 and field3, will
only output the first two.
+
--- End diff --
It should be documented then in the readme
---
