Update README

packages/elasticsearch/docs/README.md

@@ -149,7 +149,7 @@ NOTE: Configure the `var.paths` setting to point to JSON logs.
 | log.file.path | Full path to the log file this event came from, including the file name. It should include the drive letter, when appropriate. If the event wasn't read from a log file, do not populate this field. | keyword |
 | log.offset |  | long |
 | message | For log events the message field contains the log message, optimized for viewing in a log viewer. For structured logs without an original message field, other fields can be concatenated to form a human-readable summary of the event. If multiple messages exist, they can be combined into one message. | match_only_text |
-| process.pid |  | text |
+| process.pid | Process id. | long |
 | service.type | The type of the service data is collected from. The type can be used to group and correlate logs and metrics from one service type. Example: If logs or metrics are collected from Elasticsearch, `service.type` would be `elasticsearch`. | keyword |