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https://issues.apache.org/jira/browse/BEAM-9008?focusedWorklogId=374654&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-374654
]
ASF GitHub Bot logged work on BEAM-9008:
----------------------------------------
Author: ASF GitHub Bot
Created on: 20/Jan/20 16:36
Start Date: 20/Jan/20 16:36
Worklog Time Spent: 10m
Work Description: iemejia commented on pull request #10546: [BEAM-9008]
add CassandraIO readAll method
URL: https://github.com/apache/beam/pull/10546#discussion_r368623996
##########
File path:
sdks/java/io/cassandra/src/main/java/org/apache/beam/sdk/io/cassandra/CassandraIO.java
##########
@@ -608,121 +470,32 @@ static double getRingFraction(List<TokenRange>
tokenRanges) {
return ringFraction;
}
- /**
- * Check if the current partitioner is the Murmur3 (default in Cassandra
version newer than 2).
- */
- @VisibleForTesting
- static boolean isMurmur3Partitioner(Cluster cluster) {
- return MURMUR3PARTITIONER.equals(cluster.getMetadata().getPartitioner());
- }
-
/** Measure distance between two tokens. */
@VisibleForTesting
static BigInteger distance(BigInteger left, BigInteger right) {
return (right.compareTo(left) > 0)
? right.subtract(left)
:
right.subtract(left).add(SplitGenerator.getRangeSize(MURMUR3PARTITIONER));
}
+ }
- /**
- * Represent a token range in Cassandra instance, wrapping the partition
count, size and token
- * range.
- */
- @VisibleForTesting
- static class TokenRange {
- private final long partitionCount;
- private final long meanPartitionSize;
- private final BigInteger rangeStart;
- private final BigInteger rangeEnd;
-
- TokenRange(
- long partitionCount, long meanPartitionSize, BigInteger rangeStart,
BigInteger rangeEnd) {
- this.partitionCount = partitionCount;
- this.meanPartitionSize = meanPartitionSize;
- this.rangeStart = rangeStart;
- this.rangeEnd = rangeEnd;
- }
- }
-
- private class CassandraReader extends BoundedSource.BoundedReader<T> {
- private final CassandraIO.CassandraSource<T> source;
- private Cluster cluster;
- private Session session;
- private Iterator<T> iterator;
- private T current;
-
- CassandraReader(CassandraSource<T> source) {
- this.source = source;
- }
-
- @Override
- public boolean start() {
- LOG.debug("Starting Cassandra reader");
- cluster =
- getCluster(
- source.spec.hosts(),
- source.spec.port(),
- source.spec.username(),
- source.spec.password(),
- source.spec.localDc(),
- source.spec.consistencyLevel());
- session = cluster.connect(source.spec.keyspace().get());
- LOG.debug("Queries: " + source.splitQueries);
- List<ResultSetFuture> futures = new ArrayList<>();
- for (String query : source.splitQueries) {
- futures.add(session.executeAsync(query));
- }
-
- final Mapper<T> mapper = getMapper(session, source.spec.entity());
-
- for (ResultSetFuture result : futures) {
- if (iterator == null) {
- iterator = mapper.map(result.getUninterruptibly());
- } else {
- iterator = Iterators.concat(iterator,
mapper.map(result.getUninterruptibly()));
- }
- }
-
- return advance();
- }
-
- @Override
- public boolean advance() {
- if (iterator.hasNext()) {
- current = iterator.next();
- return true;
- }
- current = null;
- return false;
- }
-
- @Override
- public void close() {
- LOG.debug("Closing Cassandra reader");
- if (session != null) {
- session.close();
- }
- if (cluster != null) {
- cluster.close();
- }
- }
-
- @Override
- public T getCurrent() throws NoSuchElementException {
- if (current == null) {
- throw new NoSuchElementException();
- }
- return current;
- }
-
- @Override
- public CassandraIO.CassandraSource<T> getCurrentSource() {
- return source;
- }
-
- private Mapper<T> getMapper(Session session, Class<T> enitity) {
- return source.spec.mapperFactoryFn().apply(session);
- }
+ /**
+ * Represent a token range in Cassandra instance, wrapping the partition
count, size and token
+ * range.
+ */
+ @VisibleForTesting
+ static class TokenRange {
Review comment:
We don't need this one anymore I think we can remove this class now as well
as: `CassandraIO.getRingFraction` and `CassandraIOTest.testRingFraction`. Can
you remove these too please.
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Issue Time Tracking
-------------------
Worklog Id: (was: 374654)
Time Spent: 1h 40m (was: 1.5h)
> 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: Minor
> Time Spent: 1h 40m
> 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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