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https://issues.apache.org/jira/browse/BEAM-9008?focusedWorklogId=440999&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-440999
]
ASF GitHub Bot logged work on BEAM-9008:
----------------------------------------
Author: ASF GitHub Bot
Created on: 03/Jun/20 21:33
Start Date: 03/Jun/20 21:33
Worklog Time Spent: 10m
Work Description: vmarquez commented on a change in pull request #10546:
URL: https://github.com/apache/beam/pull/10546#discussion_r434870508
##########
File path:
sdks/java/io/cassandra/src/main/java/org/apache/beam/sdk/io/cassandra/CassandraIO.java
##########
@@ -1170,4 +898,44 @@ private void waitForFuturesToFinish() throws
ExecutionException, InterruptedExce
}
}
}
+
+ /**
+ * A {@link PTransform} to read data from Apache Cassandra. See {@link
CassandraIO} for more
+ * information on usage and configuration.
+ */
+ @AutoValue
+ public abstract static class ReadAll<T> extends
PTransform<PCollection<Read<T>>, PCollection<T>> {
+
+ @Nullable
+ abstract Coder<T> coder();
+
+ abstract ReadAll.Builder<T> builder();
+
+ /** Specify the {@link Coder} used to serialize the entity in the {@link
PCollection}. */
+ public ReadAll<T> withCoder(Coder<T> coder) {
Review comment:
I think we do, but am not sure. You have to call `setCoder` on the
PCollection itself, so we don't have access to the `Read<T>` at a point when we
also have access to a single `Read<T>` (they are only supplied in the `ReadFn`
which can't call `setCoder` on the returned PTransform). Is my thinking
correct? I could be unaware of a different way to do this.
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Issue Time Tracking
-------------------
Worklog Id: (was: 440999)
Time Spent: 13h 20m (was: 13h 10m)
> Add readAll() method to CassandraIO
> -----------------------------------
>
> Key: BEAM-9008
> URL: https://issues.apache.org/jira/browse/BEAM-9008
> Project: Beam
> Issue Type: New Feature
> Components: io-java-cassandra
> Affects Versions: 2.16.0
> Reporter: vincent marquez
> Assignee: vincent marquez
> Priority: P3
> Time Spent: 13h 20m
> Remaining Estimate: 0h
>
> When querying a large cassandra database, it's often *much* more useful to
> programatically generate the queries needed to to be run rather than reading
> all partitions and attempting some filtering.
> As an example:
> {code:java}
> public class Event {
> @PartitionKey(0) public UUID accountId;
> @PartitionKey(1)public String yearMonthDay;
> @ClusteringKey public UUID eventId;
> //other data...
> }{code}
> If there is ten years worth of data, you may want to only query one year's
> worth. Here each token range would represent one 'token' but all events for
> the day.
> {code:java}
> Set<UUID> accounts = getRelevantAccounts();
> Set<String> dateRange = generateDateRange("2018-01-01", "2019-01-01");
> PCollection<TokenRange> tokens = generateTokens(accounts, dateRange);
> {code}
>
> I propose an additional _readAll()_ PTransform that can take a PCollection
> of token ranges and can return a PCollection<T> of what the query would
> return.
> *Question: How much code should be in common between both methods?*
> Currently the read connector already groups all partitions into a List of
> Token Ranges, so it would be simple to refactor the current read() based
> method to a 'ParDo' based one and have them both share the same function.
> Reasons against sharing code between read and readAll
> * Not having the read based method return a BoundedSource connector would
> mean losing the ability to know the size of the data returned
> * Currently the CassandraReader executes all the grouped TokenRange queries
> *asynchronously* which is (maybe?) fine when all that's happening is
> splitting up all the partition ranges but terrible for executing potentially
> millions of queries.
> Reasons _for_ sharing code would be simplified code base and that both of
> the above issues would most likely have a negligable performance impact.
>
>
>
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