jaketf commented on a change in pull request #11596:
URL: https://github.com/apache/beam/pull/11596#discussion_r427641350
##########
File path:
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/healthcare/HL7v2IO.java
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@@ -415,10 +423,29 @@ private Message fetchMessage(HealthcareApiClient client,
String msgId)
}
}
- /** List HL7v2 messages in HL7v2 Stores with optional filter. */
+ /**
+ * List HL7v2 messages in HL7v2 Stores with optional filter.
+ *
+ * <p>This transform is optimized for dynamic splitting of message.list
calls for large batches of
+ * historical data and assumes rather continuous stream of sendTimes. It
will dynamically
+ * rebalance resources to handle "peak traffic times" but will waste
resources if there are large
+ * durations (days) of the sendTime dimension without data.
+ *
+ * <p>Implementation includes overhead for: 1. two api calls to determine
the min/max sendTime of
+ * the HL7v2 store at invocation time. 2. initial splitting into
non-overlapping time ranges
+ * (default daily) to achieve parallelization in separate messages.list
calls.
+ *
+ * <p>This will make more queries than necessary when used with very small
data sets. (or very
+ * sparse data sets in the sendTime dimension).
+ *
+ * <p>If you have large but sparse data (e.g. hours between consecutive
message sendTimes) and
+ * know something about the time ranges where you have no data, consider
using multiple instances
+ * of this transform specifying sendTime filters to omit the ranges where
there is no data.
Review comment:
That's great to know! will remove this guidance as it will lead to
unnecessary complexity.
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