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From Josh Wills <jwi...@cloudera.com>
Subject Re: map side ("replicated") joins in Crunch
Date Thu, 05 Jul 2012 22:11:53 GMT
FYI: https://issues.apache.org/jira/browse/CRUNCH-3 to track this.

Gabriel, is your feeling that this is ready to go in? I'm debating whether
or not to check this in before/after I do the massive com.cloudera ->
org.apache renaming. What do you think?

On Tue, Jul 3, 2012 at 1:25 PM, Gabriel Reid <gabriel.reid@gmail.com> wrote:

> Hi Joe,
>
> Looking forward to hearing your feedback! This is still just a patch and
> not committed yet, and there's still definitely room for help (i.e. ideas
> on how to improve it, or do it totally differently), so certainly let me
> know if you've got some ideas.
>
> - Gabriel
>
>
> On Tuesday 3 July 2012 at 18:01, Joseph Adler wrote:
>
> > Awesome! Will give this a try soon... wish I could have helped with this
> one...
> >
> > On Tue, Jul 3, 2012 at 1:53 AM, Gabriel Reid <gabriel.reid@gmail.com(mailto:
> gabriel.reid@gmail.com)> wrote:
> > > Thanks for pointing that out Chris. I'm guessing the mailing list is
> > > stripping out attachments(?). Once the JIRA is up and running then
> > > that will be taken care of I guess.
> > >
> > > The mime type on the last attempt was application/octet-stream, so
> > > I've renamed this to a .txt file to try to ensure that it'll get a
> > > text/plain mime type (although I don't know if that'll make a
> > > difference). I've also pasted it inline below, hopefully one of those
> > > solutions works.
> > >
> > > - Gabriel
> > >
> > >
> > > diff --git src/main/java/com/cloudera/crunch/impl/mr/MRPipeline.java
> > > src/main/java/com/cloudera/crunch/impl/mr/MRPipeline.java
> > > index 420e8dc..c8ba596 100644
> > > --- src/main/java/com/cloudera/crunch/impl/mr/MRPipeline.java
> > > +++ src/main/java/com/cloudera/crunch/impl/mr/MRPipeline.java
> > > @@ -59,9 +59,9 @@ import com.google.common.collect.Sets;
> > > public class MRPipeline implements Pipeline {
> > >
> > > private static final Log LOG = LogFactory.getLog(MRPipeline.class);
> > > -
> > > +
> > > private static final Random RANDOM = new Random();
> > > -
> > > +
> > > private final Class<?> jarClass;
> > > private final String name;
> > > private final Map<PCollectionImpl<?>, Set<Target>> outputTargets;
> > > @@ -75,15 +75,15 @@ public class MRPipeline implements Pipeline {
> > > public MRPipeline(Class<?> jarClass) throws IOException {
> > > this(jarClass, new Configuration());
> > > }
> > > -
> > > - public MRPipeline(Class<?> jarClass, String name){
> > > +
> > > + public MRPipeline(Class<?> jarClass, String name) {
> > > this(jarClass, name, new Configuration());
> > > }
> > > -
> > > +
> > > public MRPipeline(Class<?> jarClass, Configuration conf) {
> > > - this(jarClass, jarClass.getName(), conf);
> > > + this(jarClass, jarClass.getName(), conf);
> > > }
> > > -
> > > +
> > > public MRPipeline(Class<?> jarClass, String name, Configuration conf)
{
> > > this.jarClass = jarClass;
> > > this.name (http://this.name) = name;
> > > @@ -102,9 +102,9 @@ public class MRPipeline implements Pipeline {
> > >
> > > @Override
> > > public void setConfiguration(Configuration conf) {
> > > - this.conf = conf;
> > > + this.conf = conf;
> > > }
> > > -
> > > +
> > > @Override
> > > public PipelineResult run() {
> > > MSCRPlanner planner = new MSCRPlanner(this, outputTargets);
> > > @@ -125,8 +125,8 @@ public class MRPipeline implements Pipeline {
> > > boolean materialized = false;
> > > for (Target t : outputTargets.get(c)) {
> > > if (!materialized && t instanceof Source) {
> > > - c.materializeAt((SourceTarget) t);
> > > - materialized = true;
> > > + c.materializeAt((SourceTarget) t);
> > > + materialized = true;
> > > }
> > > }
> > > }
> > > @@ -144,7 +144,7 @@ public class MRPipeline implements Pipeline {
> > > cleanup();
> > > return res;
> > > }
> > > -
> > > +
> > > public <S> PCollection<S> read(Source<S> source) {
> > > return new InputCollection<S>(source, this);
> > > }
> > > @@ -160,85 +160,120 @@ public class MRPipeline implements Pipeline {
> > > @SuppressWarnings("unchecked")
> > > public void write(PCollection<?> pcollection, Target target) {
> > > if (pcollection instanceof PGroupedTableImpl) {
> > > - pcollection = ((PGroupedTableImpl<?,?>) pcollection).ungroup();
> > > + pcollection = ((PGroupedTableImpl<?, ?>) pcollection).ungroup();
> > > } else if (pcollection instanceof UnionCollection || pcollection
> > > instanceof UnionTable) {
> > > - pcollection = pcollection.parallelDo("UnionCollectionWrapper",
> > > - (MapFn)IdentityFn.<Object>getInstance(), pcollection.getPType());
> > > + pcollection = pcollection.parallelDo("UnionCollectionWrapper",
> > > + (MapFn) IdentityFn.<Object> getInstance(), pcollection.getPType());
> > > }
> > > addOutput((PCollectionImpl<?>) pcollection, target);
> > > }
> > >
> > > private void addOutput(PCollectionImpl<?> impl, Target target) {
> > > if (!outputTargets.containsKey(impl)) {
> > > - outputTargets.put(impl, Sets.<Target>newHashSet());
> > > + outputTargets.put(impl, Sets.<Target> newHashSet());
> > > }
> > > outputTargets.get(impl).add(target);
> > > }
> > > -
> > > +
> > > @Override
> > > public <T> Iterable<T> materialize(PCollection<T> pcollection)
{
> > > -
> > > - if (pcollection instanceof UnionCollection) {
> > > - pcollection = pcollection.parallelDo("UnionCollectionWrapper",
> > > - (MapFn)IdentityFn.<Object>getInstance(), pcollection.getPType());
> > > - }
> > > - PCollectionImpl<T> impl = (PCollectionImpl<T>) pcollection;
> > > +
> > > + PCollectionImpl<T> pcollectionImpl = toPcollectionImpl(pcollection);
> > > + ReadableSourceTarget<T> srcTarget =
> > > getMaterializeSourceTarget(pcollectionImpl);
> > > +
> > > + MaterializableIterable<T> c = new MaterializableIterable<T>(this,
> > > srcTarget);
> > > + if (!outputTargetsToMaterialize.containsKey(pcollectionImpl)) {
> > > + outputTargetsToMaterialize.put(pcollectionImpl, c);
> > > + }
> > > + return c;
> > > + }
> > > +
> > > + /**
> > > + * Retrieve a ReadableSourceTarget that provides access to the
> contents of a
> > > + * {@link PCollection}. This is primarily intended as a helper method
> to
> > > + * {@link #materialize(PCollection)}. The underlying data of the
> > > + * ReadableSourceTarget may not be actually present until the
> > > pipeline is run.
> > > + *
> > > + * @param pcollection
> > > + * The collection for which the ReadableSourceTarget is to be
> > > + * retrieved
> > > + * @return The ReadableSourceTarget
> > > + * @throws IllegalArgumentException
> > > + * If no ReadableSourceTarget can be retrieved for the given
> > > + * PCollection
> > > + */
> > > + public <T> ReadableSourceTarget<T>
> > > getMaterializeSourceTarget(PCollection<T> pcollection) {
> > > + PCollectionImpl<T> impl = toPcollectionImpl(pcollection);
> > > SourceTarget<T> matTarget = impl.getMaterializedAt();
> > > if (matTarget != null && matTarget instanceof ReadableSourceTarget)
{
> > > - return new MaterializableIterable<T>(this,
> > > (ReadableSourceTarget<T>) matTarget);
> > > + return (ReadableSourceTarget<T>) matTarget;
> > > + }
> > > +
> > > + ReadableSourceTarget<T> srcTarget = null;
> > > + if (outputTargets.containsKey(pcollection)) {
> > > + for (Target target : outputTargets.get(impl)) {
> > > + if (target instanceof ReadableSourceTarget) {
> > > + srcTarget = (ReadableSourceTarget<T>) target;
> > > + break;
> > > + }
> > > + }
> > > }
> > > -
> > > - ReadableSourceTarget<T> srcTarget = null;
> > > - if (outputTargets.containsKey(pcollection)) {
> > > - for (Target target : outputTargets.get(impl)) {
> > > - if (target instanceof ReadableSourceTarget) {
> > > - srcTarget = (ReadableSourceTarget) target;
> > > - break;
> > > - }
> > > - }
> > > - }
> > > -
> > > - if (srcTarget == null) {
> > > - SourceTarget<T> st =
> createIntermediateOutput(pcollection.getPType());
> > > - if (!(st instanceof ReadableSourceTarget)) {
> > > - throw new IllegalArgumentException("The PType for the given
> > > PCollection is not readable"
> > > - + " and cannot be materialized");
> > > - } else {
> > > - srcTarget = (ReadableSourceTarget) st;
> > > - addOutput(impl, srcTarget);
> > > - }
> > > - }
> > > -
> > > - MaterializableIterable<T> c = new MaterializableIterable<T>(this,
> srcTarget);
> > > - outputTargetsToMaterialize.put(impl, c);
> > > - return c;
> > > +
> > > + if (srcTarget == null) {
> > > + SourceTarget<T> st =
> createIntermediateOutput(pcollection.getPType());
> > > + if (!(st instanceof ReadableSourceTarget)) {
> > > + throw new IllegalArgumentException("The PType for the given
> > > PCollection is not readable"
> > > + + " and cannot be materialized");
> > > + } else {
> > > + srcTarget = (ReadableSourceTarget<T>) st;
> > > + addOutput(impl, srcTarget);
> > > + }
> > > + }
> > > +
> > > + return srcTarget;
> > > + }
> > > +
> > > + /**
> > > + * Safely cast a PCollection into a PCollectionImpl, including
> > > handling the case of UnionCollections.
> > > + * @param pcollection The PCollection to be cast/transformed
> > > + * @return The PCollectionImpl representation
> > > + */
> > > + private <T> PCollectionImpl<T> toPcollectionImpl(PCollection<T>
> > > pcollection) {
> > > + PCollectionImpl<T> pcollectionImpl = null;
> > > + if (pcollection instanceof UnionCollection) {
> > > + pcollectionImpl = (PCollectionImpl<T>)
> > > pcollection.parallelDo("UnionCollectionWrapper",
> > > + (MapFn) IdentityFn.<Object> getInstance(), pcollection.getPType());
> > > + } else {
> > > + pcollectionImpl = (PCollectionImpl<T>) pcollection;
> > > + }
> > > + return pcollectionImpl;
> > > }
> > >
> > > public <T> SourceTarget<T> createIntermediateOutput(PType<T>
ptype) {
> > > - return ptype.getDefaultFileSource(createTempPath());
> > > + return ptype.getDefaultFileSource(createTempPath());
> > > }
> > >
> > > public Path createTempPath() {
> > > tempFileIndex++;
> > > return new Path(tempDirectory, "p" + tempFileIndex);
> > > }
> > > -
> > > +
> > > private static Path createTempDirectory(Configuration conf) {
> > > Path dir = new Path("/tmp/crunch" + RANDOM.nextInt());
> > > - try {
> > > - FileSystem.get(conf).mkdirs(dir);
> > > - } catch (IOException e) {
> > > - LOG.error("Exception creating job output directory", e);
> > > - throw new RuntimeException(e);
> > > - }
> > > + try {
> > > + FileSystem.get(conf).mkdirs(dir);
> > > + } catch (IOException e) {
> > > + LOG.error("Exception creating job output directory", e);
> > > + throw new RuntimeException(e);
> > > + }
> > > return dir;
> > > }
> > > -
> > > +
> > > @Override
> > > public <T> void writeTextFile(PCollection<T> pcollection, String
> pathName) {
> > > // Ensure that this is a writable pcollection instance.
> > > - pcollection = pcollection.parallelDo("asText",
> IdentityFn.<T>getInstance(),
> > > - WritableTypeFamily.getInstance().as(pcollection.getPType()));
> > > + pcollection = pcollection.parallelDo("asText", IdentityFn.<T>
> > > getInstance(), WritableTypeFamily
> > > + .getInstance().as(pcollection.getPType()));
> > > write(pcollection, At.textFile(pathName));
> > > }
> > >
> > > @@ -256,7 +291,7 @@ public class MRPipeline implements Pipeline {
> > > LOG.info (http://LOG.info)("Exception during cleanup", e);
> > > }
> > > }
> > > -
> > > +
> > > public int getNextAnonymousStageId() {
> > > return nextAnonymousStageId++;
> > > }
> > > @@ -265,7 +300,7 @@ public class MRPipeline implements Pipeline {
> > > public void enableDebug() {
> > > // Turn on Crunch runtime error catching.
> > > getConfiguration().setBoolean(RuntimeParameters.DEBUG, true);
> > > -
> > > +
> > > // Write Hadoop's WARN logs to the console.
> > > Logger crunchInfoLogger = LogManager.getLogger("com.cloudera.crunch");
> > > Appender console = crunchInfoLogger.getAppender("A");
> > > @@ -277,9 +312,9 @@ public class MRPipeline implements Pipeline {
> > > LOG.warn("Could not find console appender named 'A' for writing
> > > Hadoop warning logs");
> > > }
> > > }
> > > -
> > > +
> > > @Override
> > > public String getName() {
> > > - return name;
> > > + return name;
> > > }
> > > }
> > > diff --git
> src/main/java/com/cloudera/crunch/impl/mr/run/CrunchRuntimeException.java
> > >
> src/main/java/com/cloudera/crunch/impl/mr/run/CrunchRuntimeException.java
> > > index d41a52e..68ef054 100644
> > > ---
> src/main/java/com/cloudera/crunch/impl/mr/run/CrunchRuntimeException.java
> > > +++
> src/main/java/com/cloudera/crunch/impl/mr/run/CrunchRuntimeException.java
> > > @@ -12,6 +12,10 @@ public class CrunchRuntimeException extends
> > > RuntimeException {
> > > super(e);
> > > }
> > >
> > > + public CrunchRuntimeException(String msg, Exception e) {
> > > + super(msg, e);
> > > + }
> > > +
> > > public boolean wasLogged() {
> > > return logged;
> > > }
> > > diff --git
> src/main/java/com/cloudera/crunch/io/avro/AvroFileSource.java
> > > src/main/java/com/cloudera/crunch/io/avro/AvroFileSource.java
> > > index 1122d62..4debfeb 100644
> > > --- src/main/java/com/cloudera/crunch/io/avro/AvroFileSource.java
> > > +++ src/main/java/com/cloudera/crunch/io/avro/AvroFileSource.java
> > > @@ -45,7 +45,8 @@ public class AvroFileSource<T> extends
> > > FileSourceImpl<T> implements ReadableSour
> > >
> > > @Override
> > > public Iterable<T> read(Configuration conf) throws IOException {
> > > - return CompositePathIterable.create(FileSystem.get(conf), path,
> > > new AvroFileReaderFactory<T>(
> > > + FileSystem fs = FileSystem.get(path.toUri(), conf);
> > > + return CompositePathIterable.create(fs, path, new
> AvroFileReaderFactory<T>(
> > > (AvroType<T>) ptype, conf));
> > > }
> > > }
> > > diff --git src/main/java/com/cloudera/crunch/io/seq/SeqFileSource.java
> > > src/main/java/com/cloudera/crunch/io/seq/SeqFileSource.java
> > > index 24dec2d..462ef93 100644
> > > --- src/main/java/com/cloudera/crunch/io/seq/SeqFileSource.java
> > > +++ src/main/java/com/cloudera/crunch/io/seq/SeqFileSource.java
> > > @@ -26,18 +26,16 @@ import com.cloudera.crunch.io.ReadableSource;
> > > import com.cloudera.crunch.io.impl.FileSourceImpl;
> > > import com.cloudera.crunch.types.PType;
> > >
> > > -public class SeqFileSource<T> extends FileSourceImpl<T> implements
> > > - ReadableSource<T> {
> > > +public class SeqFileSource<T> extends FileSourceImpl<T> implements
> > > ReadableSource<T> {
> > >
> > > public SeqFileSource(Path path, PType<T> ptype) {
> > > - super(path, ptype, SequenceFileInputFormat.class);
> > > + super(path, ptype, SequenceFileInputFormat.class);
> > > }
> > > -
> > > +
> > > @Override
> > > public Iterable<T> read(Configuration conf) throws IOException {
> > > - FileSystem fs = FileSystem.get(conf);
> > > - return CompositePathIterable.create(fs, path,
> > > - new SeqFileReaderFactory<T>(ptype, conf));
> > > + FileSystem fs = FileSystem.get(path.toUri(), conf);
> > > + return CompositePathIterable.create(fs, path, new
> > > SeqFileReaderFactory<T>(ptype, conf));
> > > }
> > >
> > > @Override
> > > diff --git
> src/main/java/com/cloudera/crunch/io/seq/SeqFileTableSource.java
> > > src/main/java/com/cloudera/crunch/io/seq/SeqFileTableSource.java
> > > index 69ca12b..4db6658 100644
> > > --- src/main/java/com/cloudera/crunch/io/seq/SeqFileTableSource.java
> > > +++ src/main/java/com/cloudera/crunch/io/seq/SeqFileTableSource.java
> > > @@ -42,7 +42,7 @@ public class SeqFileTableSource<K, V> extends
> > > FileTableSourceImpl<K, V> implemen
> > >
> > > @Override
> > > public Iterable<Pair<K, V>> read(Configuration conf) throws
> IOException {
> > > - FileSystem fs = FileSystem.get(conf);
> > > + FileSystem fs = FileSystem.get(path.toUri(), conf);
> > > return CompositePathIterable.create(fs, path,
> > > new SeqFileTableReaderFactory<K, V>((PTableType<K, V>) ptype, conf));
> > > }
> > > diff --git
> src/main/java/com/cloudera/crunch/io/text/TextFileSource.java
> > > src/main/java/com/cloudera/crunch/io/text/TextFileSource.java
> > > index a876843..e0dbe68 100644
> > > --- src/main/java/com/cloudera/crunch/io/text/TextFileSource.java
> > > +++ src/main/java/com/cloudera/crunch/io/text/TextFileSource.java
> > > @@ -67,7 +67,7 @@ public class TextFileSource<T> extends
> > > FileSourceImpl<T> implements
> > >
> > > @Override
> > > public Iterable<T> read(Configuration conf) throws IOException {
> > > - return CompositePathIterable.create(FileSystem.get(conf), path,
> > > - new TextFileReaderFactory<T>(ptype, conf));
> > > + return CompositePathIterable.create(FileSystem.get(path.toUri(),
> > > conf), path,
> > > + new TextFileReaderFactory<T>(ptype, conf));
> > > }
> > > }
> > > diff --git src/main/java/com/cloudera/crunch/lib/join/MapsideJoin.java
> > > src/main/java/com/cloudera/crunch/lib/join/MapsideJoin.java
> > > new file mode 100644
> > > index 0000000..8072e07
> > > --- /dev/null
> > > +++ src/main/java/com/cloudera/crunch/lib/join/MapsideJoin.java
> > > @@ -0,0 +1,143 @@
> > > +package com.cloudera.crunch.lib.join;
> > > +
> > > +import java.io.IOException;
> > > +
> > > +import org.apache.hadoop.filecache.DistributedCache;
> > > +import org.apache.hadoop.fs.FileSystem;
> > > +import org.apache.hadoop.fs.Path;
> > > +
> > > +import com.cloudera.crunch.DoFn;
> > > +import com.cloudera.crunch.Emitter;
> > > +import com.cloudera.crunch.PTable;
> > > +import com.cloudera.crunch.Pair;
> > > +import com.cloudera.crunch.impl.mr.MRPipeline;
> > > +import com.cloudera.crunch.impl.mr.run.CrunchRuntimeException;
> > > +import com.cloudera.crunch.io.ReadableSourceTarget;
> > > +import com.cloudera.crunch.io.impl.SourcePathTargetImpl;
> > > +import com.cloudera.crunch.types.PType;
> > > +import com.cloudera.crunch.types.PTypeFamily;
> > > +import com.google.common.collect.ArrayListMultimap;
> > > +import com.google.common.collect.Multimap;
> > > +
> > > +/**
> > > + * Utility for doing map side joins on a common key between two
> > > {@link PTable}s.
> > > + * <p>
> > > + * A map side join is an optimized join which doesn't use a reducer;
> instead,
> > > + * the right side of the join is loaded into memory and the join is
> > > performed in
> > > + * a mapper. This style of join has the important implication that
> > > the output of
> > > + * the join is not sorted, which is the case with a conventional
> > > (reducer-based)
> > > + * join.
> > > + * <p>
> > > + * <b>Note:</b>This utility is only supported when running with
a
> > > + * {@link MRPipeline} as the pipeline.
> > > + */
> > > +public class MapsideJoin {
> > > +
> > > + /**
> > > + * Join two tables using a map side join. The right-side table will
> be loaded
> > > + * fully in memory, so this method should only be used if the right
> side
> > > + * table's contents can fit in the memory allocated to mappers. The
> join
> > > + * performed by this method is an inner join.
> > > + *
> > > + * @param left
> > > + * The left-side table of the join
> > > + * @param right
> > > + * The right-side table of the join, whose contents will be fully
> > > + * read into memory
> > > + * @return A table keyed on the join key, containing pairs of joined
> values
> > > + */
> > > + public static <K, U, V> PTable<K, Pair<U, V>> join(PTable<K,
U>
> > > left, PTable<K, V> right) {
> > > +
> > > + if (!(right.getPipeline() instanceof MRPipeline)) {
> > > + throw new CrunchRuntimeException("Map-side join is only
> > > supported within a MapReduce context");
> > > + }
> > > +
> > > + MRPipeline pipeline = (MRPipeline) right.getPipeline();
> > > + pipeline.materialize(right);
> > > +
> > > + // TODO Move necessary logic to MRPipeline so that we can
> theoretically
> > > + // optimize his by running the setup of multiple map-side joins
> > > concurrently
> > > + pipeline.run();
> > > +
> > > + ReadableSourceTarget<Pair<K, V>> readableSourceTarget = pipeline
> > > + .getMaterializeSourceTarget(right);
> > > + if (!(readableSourceTarget instanceof SourcePathTargetImpl)) {
> > > + throw new CrunchRuntimeException("Right-side contents can't be
> > > read from a path");
> > > + }
> > > +
> > > + // Suppress warnings because we've just checked this cast via
> instanceof
> > > + @SuppressWarnings("unchecked")
> > > + SourcePathTargetImpl<Pair<K, V>> sourcePathTarget =
> > > (SourcePathTargetImpl<Pair<K, V>>) readableSourceTarget;
> > > +
> > > + Path path = sourcePathTarget.getPath();
> > > + DistributedCache.addCacheFile(path.toUri(),
> pipeline.getConfiguration());
> > > +
> > > + MapsideJoinDoFn<K, U, V> mapJoinDoFn = new MapsideJoinDoFn<K, U,
> > > V>(path.toString(),
> > > + right.getPType());
> > > + PTypeFamily typeFamily = left.getTypeFamily();
> > > + return left.parallelDo(
> > > + "mapjoin",
> > > + mapJoinDoFn,
> > > + typeFamily.tableOf(left.getKeyType(),
> > > + typeFamily.pairs(left.getValueType(), right.getValueType())));
> > > +
> > > + }
> > > +
> > > + static class MapsideJoinDoFn<K, U, V> extends DoFn<Pair<K, U>,
> > > Pair<K, Pair<U, V>>> {
> > > +
> > > + private String inputPath;
> > > + private PType<Pair<K, V>> ptype;
> > > + private Multimap<K, V> joinMap;
> > > +
> > > + public MapsideJoinDoFn(String inputPath, PType<Pair<K, V>> ptype)
{
> > > + this.inputPath = inputPath;
> > > + this.ptype = ptype;
> > > + }
> > > +
> > > + private Path getCacheFilePath() {
> > > + try {
> > > + for (Path localPath :
> > > DistributedCache.getLocalCacheFiles(getConfiguration())) {
> > > + if (localPath.toString().endsWith(inputPath)) {
> > > + return
> > > localPath.makeQualified(FileSystem.getLocal(getConfiguration()));
> > > +
> > > + }
> > > + }
> > > + } catch (IOException e) {
> > > + throw new CrunchRuntimeException(e);
> > > + }
> > > +
> > > + throw new CrunchRuntimeException("Can't find local cache file
> > > for '" + inputPath + "'");
> > > + }
> > > +
> > > + @Override
> > > + public void initialize() {
> > > + super.initialize();
> > > +
> > > + ReadableSourceTarget<Pair<K, V>> sourceTarget =
> > > (ReadableSourceTarget<Pair<K, V>>) ptype
> > > + .getDefaultFileSource(getCacheFilePath());
> > > + Iterable<Pair<K, V>> iterable = null;
> > > + try {
> > > + iterable = sourceTarget.read(getConfiguration());
> > > + } catch (IOException e) {
> > > + throw new CrunchRuntimeException("Error reading right-side of
> > > map side join: ", e);
> > > + }
> > > +
> > > + joinMap = ArrayListMultimap.create();
> > > + for (Pair<K, V> joinPair : iterable) {
> > > + joinMap.put(joinPair.first(), joinPair.second());
> > > + }
> > > + }
> > > +
> > > + @Override
> > > + public void process(Pair<K, U> input, Emitter<Pair<K, Pair<U,
> > > V>>> emitter) {
> > > + K key = input.first();
> > > + U value = input.second();
> > > + for (V joinValue : joinMap.get(key)) {
> > > + Pair<U, V> valuePair = Pair.of(value, joinValue);
> > > + emitter.emit(Pair.of(key, valuePair));
> > > + }
> > > + }
> > > +
> > > + }
> > > +
> > > +}
> > > diff --git src/main/java/com/cloudera/crunch/types/PType.java
> > > src/main/java/com/cloudera/crunch/types/PType.java
> > > index af4ef1b..ae480aa 100644
> > > --- src/main/java/com/cloudera/crunch/types/PType.java
> > > +++ src/main/java/com/cloudera/crunch/types/PType.java
> > > @@ -15,6 +15,7 @@
> > >
> > > package com.cloudera.crunch.types;
> > >
> > > +import java.io.Serializable;
> > > import java.util.List;
> > >
> > > import org.apache.hadoop.fs.Path;
> > > @@ -31,7 +32,7 @@ import com.cloudera.crunch.SourceTarget;
> > > * {@code PCollection}.
> > > *
> > > */
> > > -public interface PType<T> {
> > > +public interface PType<T> extends Serializable {
> > > /**
> > > * Returns the Java type represented by this {@code PType}.
> > > */
> > > diff --git src/main/java/com/cloudera/crunch/types/avro/AvroType.java
> > > src/main/java/com/cloudera/crunch/types/avro/AvroType.java
> > > index 3db00c0..29af9fb 100644
> > > --- src/main/java/com/cloudera/crunch/types/avro/AvroType.java
> > > +++ src/main/java/com/cloudera/crunch/types/avro/AvroType.java
> > > @@ -14,6 +14,7 @@
> > > */
> > > package com.cloudera.crunch.types.avro;
> > >
> > > +import java.io.Serializable;
> > > import java.util.List;
> > >
> > > import org.apache.avro.Schema;
> > > @@ -41,7 +42,8 @@ public class AvroType<T> implements PType<T>
{
> > > private static final Converter AVRO_CONVERTER = new AvroKeyConverter();
> > >
> > > private final Class<T> typeClass;
> > > - private final Schema schema;
> > > + private final String schemaString;
> > > + private transient Schema schema;
> > > private final MapFn baseInputMapFn;
> > > private final MapFn baseOutputMapFn;
> > > private final List<PType> subTypes;
> > > @@ -55,6 +57,7 @@ public class AvroType<T> implements PType<T>
{
> > > MapFn outputMapFn, PType... ptypes) {
> > > this.typeClass = typeClass;
> > > this.schema = Preconditions.checkNotNull(schema);
> > > + this.schemaString = schema.toString();
> > > this.baseInputMapFn = inputMapFn;
> > > this.baseOutputMapFn = outputMapFn;
> > > this.subTypes = ImmutableList.<PType> builder().add(ptypes).build();
> > > @@ -76,6 +79,9 @@ public class AvroType<T> implements PType<T>
{
> > > }
> > >
> > > public Schema getSchema() {
> > > + if (schema == null){
> > > + schema = new Schema.Parser().parse(schemaString);
> > > + }
> > > return schema;
> > > }
> > >
> > > diff --git
> src/test/java/com/cloudera/crunch/impl/mr/MRPipelineTest.java
> > > src/test/java/com/cloudera/crunch/impl/mr/MRPipelineTest.java
> > > new file mode 100644
> > > index 0000000..f265460
> > > --- /dev/null
> > > +++ src/test/java/com/cloudera/crunch/impl/mr/MRPipelineTest.java
> > > @@ -0,0 +1,60 @@
> > > +package com.cloudera.crunch.impl.mr;
> > > +
> > > +import static org.junit.Assert.assertEquals;
> > > +import static org.mockito.Mockito.doReturn;
> > > +import static org.mockito.Mockito.mock;
> > > +import static org.mockito.Mockito.spy;
> > > +import static org.mockito.Mockito.when;
> > > +
> > > +import java.io.IOException;
> > > +
> > > +import org.junit.Before;
> > > +import org.junit.Test;
> > > +
> > > +import com.cloudera.crunch.SourceTarget;
> > > +import com.cloudera.crunch.impl.mr.collect.PCollectionImpl;
> > > +import com.cloudera.crunch.io.ReadableSourceTarget;
> > > +import com.cloudera.crunch.types.avro.Avros;
> > > +
> > > +public class MRPipelineTest {
> > > +
> > > + private MRPipeline pipeline;
> > > +
> > > + @Before
> > > + public void setUp() throws IOException {
> > > + pipeline = spy(new MRPipeline(MRPipelineTest.class));
> > > + }
> > > +
> > > + @Test
> > > + public void testGetMaterializeSourceTarget_AlreadyMaterialized() {
> > > + PCollectionImpl<String> materializedPcollection =
> > > mock(PCollectionImpl.class);
> > > + ReadableSourceTarget<String> readableSourceTarget =
> > > mock(ReadableSourceTarget.class);
> > > +
> when(materializedPcollection.getMaterializedAt()).thenReturn(readableSourceTarget);
> > > +
> > > + assertEquals(readableSourceTarget,
> > > pipeline.getMaterializeSourceTarget(materializedPcollection));
> > > + }
> > > +
> > > + @Test
> > > + public void
> testGetMaterializeSourceTarget_NotMaterialized_HasOutput() {
> > > +
> > > + PCollectionImpl<String> pcollection = mock(PCollectionImpl.class);
> > > + ReadableSourceTarget<String> readableSourceTarget =
> > > mock(ReadableSourceTarget.class);
> > > + when(pcollection.getPType()).thenReturn(Avros.strings());
> > > +
> doReturn(readableSourceTarget).when(pipeline).createIntermediateOutput(Avros.strings());
> > > + when(pcollection.getMaterializedAt()).thenReturn(null);
> > > +
> > > + assertEquals(readableSourceTarget,
> > > pipeline.getMaterializeSourceTarget(pcollection));
> > > + }
> > > +
> > > + @Test(expected = IllegalArgumentException.class)
> > > + public void
> testGetMaterializeSourceTarget_NotMaterialized_NotReadableSourceTarget()
> > > {
> > > + PCollectionImpl<String> pcollection = mock(PCollectionImpl.class);
> > > + SourceTarget<String> nonReadableSourceTarget =
> mock(SourceTarget.class);
> > > + when(pcollection.getPType()).thenReturn(Avros.strings());
> > > +
> doReturn(nonReadableSourceTarget).when(pipeline).createIntermediateOutput(Avros.strings());
> > > + when(pcollection.getMaterializedAt()).thenReturn(null);
> > > +
> > > + pipeline.getMaterializeSourceTarget(pcollection);
> > > + }
> > > +
> > > +}
> > > diff --git
> src/test/java/com/cloudera/crunch/lib/join/MapsideJoinTest.java
> > > src/test/java/com/cloudera/crunch/lib/join/MapsideJoinTest.java
> > > new file mode 100644
> > > index 0000000..97e0c63
> > > --- /dev/null
> > > +++ src/test/java/com/cloudera/crunch/lib/join/MapsideJoinTest.java
> > > @@ -0,0 +1,102 @@
> > > +package com.cloudera.crunch.lib.join;
> > > +
> > > +import static org.junit.Assert.assertEquals;
> > > +import static org.junit.Assert.assertTrue;
> > > +
> > > +import java.io.IOException;
> > > +import java.util.Collections;
> > > +import java.util.List;
> > > +
> > > +import org.junit.Test;
> > > +
> > > +import com.cloudera.crunch.FilterFn;
> > > +import com.cloudera.crunch.MapFn;
> > > +import com.cloudera.crunch.PTable;
> > > +import com.cloudera.crunch.Pair;
> > > +import com.cloudera.crunch.Pipeline;
> > > +import com.cloudera.crunch.impl.mem.MemPipeline;
> > > +import com.cloudera.crunch.impl.mr.MRPipeline;
> > > +import com.cloudera.crunch.impl.mr.run.CrunchRuntimeException;
> > > +import com.cloudera.crunch.test.FileHelper;
> > > +import com.cloudera.crunch.types.writable.Writables;
> > > +import com.google.common.collect.Lists;
> > > +
> > > +public class MapsideJoinTest {
> > > +
> > > + private static class LineSplitter extends MapFn<String,
> > > Pair<Integer, String>> {
> > > +
> > > + @Override
> > > + public Pair<Integer, String> map(String input) {
> > > + String[] fields = input.split("\\|");
> > > + return Pair.of(Integer.parseInt(fields[0]), fields[1]);
> > > + }
> > > +
> > > + }
> > > +
> > > + private static class NegativeFilter extends FilterFn<Pair<Integer,
> String>> {
> > > +
> > > + @Override
> > > + public boolean accept(Pair<Integer, String> input) {
> > > + return false;
> > > + }
> > > +
> > > + }
> > > +
> > > + @Test(expected = CrunchRuntimeException.class)
> > > + public void testNonMapReducePipeline() {
> > > + runMapsideJoin(MemPipeline.getInstance());
> > > + }
> > > +
> > > + @Test
> > > + public void testMapsideJoin_RightSideIsEmpty() throws IOException {
> > > + MRPipeline pipeline = new MRPipeline(MapsideJoinTest.class);
> > > + PTable<Integer, String> customerTable = readTable(pipeline,
> > > "customers.txt");
> > > + PTable<Integer, String> orderTable = readTable(pipeline,
> "orders.txt");
> > > +
> > > + PTable<Integer, String> filteredOrderTable =
> > > orderTable.parallelDo(new NegativeFilter(),
> > > + orderTable.getPTableType());
> > > +
> > > + PTable<Integer, Pair<String, String>> joined =
> > > MapsideJoin.join(customerTable,
> > > + filteredOrderTable);
> > > +
> > > + List<Pair<Integer, Pair<String, String>>> materializedJoin
=
> > > Lists.newArrayList(joined
> > > + .materialize());
> > > +
> > > + assertTrue(materializedJoin.isEmpty());
> > > +
> > > + }
> > > +
> > > + @Test
> > > + public void testMapsideJoin() throws IOException {
> > > + runMapsideJoin(new MRPipeline(MapsideJoinTest.class));
> > > + }
> > > +
> > > + private void runMapsideJoin(Pipeline pipeline) {
> > > + PTable<Integer, String> customerTable = readTable(pipeline,
> > > "customers.txt");
> > > + PTable<Integer, String> orderTable = readTable(pipeline,
> "orders.txt");
> > > +
> > > + PTable<Integer, Pair<String, String>> joined =
> > > MapsideJoin.join(customerTable, orderTable);
> > > +
> > > + List<Pair<Integer, Pair<String, String>>> expectedJoinResult
=
> > > Lists.newArrayList();
> > > + expectedJoinResult.add(Pair.of(111, Pair.of("John Doe", "Corn
> flakes")));
> > > + expectedJoinResult.add(Pair.of(222, Pair.of("Jane Doe", "Toilet
> paper")));
> > > + expectedJoinResult.add(Pair.of(222, Pair.of("Jane Doe", "Toilet
> > > plunger")));
> > > + expectedJoinResult.add(Pair.of(333, Pair.of("Someone Else",
> > > "Toilet brush")));
> > > +
> > > + List<Pair<Integer, Pair<String, String>>> joinedResultList
=
> > > Lists.newArrayList(joined
> > > + .materialize());
> > > + Collections.sort(joinedResultList);
> > > +
> > > + assertEquals(expectedJoinResult, joinedResultList);
> > > + }
> > > +
> > > + private static PTable<Integer, String> readTable(Pipeline pipeline,
> > > String filename) {
> > > + try {
> > > + return
> pipeline.readTextFile(FileHelper.createTempCopyOf(filename)).parallelDo("asTable",
> > > + new LineSplitter(), Writables.tableOf(Writables.ints(),
> > > Writables.strings()));
> > > + } catch (IOException e) {
> > > + throw new RuntimeException(e);
> > > + }
> > > + }
> > > +
> > > +}
> > > diff --git src/test/java/com/cloudera/crunch/types/avro/AvrosTest.java
> > > src/test/java/com/cloudera/crunch/types/avro/AvrosTest.java
> > > index 74e2ad3..c6a0b46 100644
> > > --- src/test/java/com/cloudera/crunch/types/avro/AvrosTest.java
> > > +++ src/test/java/com/cloudera/crunch/types/avro/AvrosTest.java
> > > @@ -25,6 +25,7 @@ import org.apache.avro.Schema.Type;
> > > import org.apache.avro.generic.GenericData;
> > > import org.apache.avro.util.Utf8;
> > > import org.apache.hadoop.io.LongWritable;
> > > +import org.junit.Ignore;
> > > import org.junit.Test;
> > >
> > > import com.cloudera.crunch.Pair;
> > > @@ -103,6 +104,7 @@ public class AvrosTest {
> > > }
> > >
> > > @Test
> > > + @Ignore("This test creates an invalid schema that causes
> > > Schema#toString to fail")
> > > public void testNestedTables() throws Exception {
> > > PTableType<Long, Long> pll = Avros.tableOf(Avros.longs(),
> Avros.longs());
> > > PTableType<Pair<Long, Long>, String> nest = Avros.tableOf(pll,
> > > Avros.strings());
> > > diff --git src/test/resources/customers.txt
> src/test/resources/customers.txt
> > > new file mode 100644
> > > index 0000000..98f3f3d
> > > --- /dev/null
> > > +++ src/test/resources/customers.txt
> > > @@ -0,0 +1,4 @@
> > > +111|John Doe
> > > +222|Jane Doe
> > > +333|Someone Else
> > > +444|Has No Orders
> > > \ No newline at end of file
> > > diff --git src/test/resources/orders.txt src/test/resources/orders.txt
> > > new file mode 100644
> > > index 0000000..2f1383f
> > > --- /dev/null
> > > +++ src/test/resources/orders.txt
> > > @@ -0,0 +1,4 @@
> > > +222|Toilet plunger
> > > +333|Toilet brush
> > > +222|Toilet paper
> > > +111|Corn flakes
> > > \ No newline at end of file
> > >
> > >
> > >
> > > On Tue, Jul 3, 2012 at 10:42 AM, Christian Tzolov
> > > <christian.tzolov@gmail.com (mailto:christian.tzolov@gmail.com)>
> wrote:
> > > > Hi Gabriel,
> > > >
> > > > Seems like the attachment is missing.
> > > >
> > > > Cheers,
> > > > Chris
> > > >
> > > > On Tue, Jul 3, 2012 at 9:23 AM, Gabriel Reid <gabriel.reid@gmail.com(mailto:
> gabriel.reid@gmail.com)> wrote:
> > > >
> > > > > Hi guys,
> > > > >
> > > > > Attached (hopefully) is a patch for an initial implementation of
> map
> > > > > side joins. It's currently implemented as a static method in a
> class
> > > > > called MapsideJoin, with the same interface as the existing Join
> class
> > > > > (with only inner joins being implemented for now). The way it
> works is
> > > > > that the right-side PTable of the join is put in the distributed
> cache
> > > > > and then read by the join function at runtime.
> > > > >
> > > > > There's one spot that I can see for a potentially interesting
> > > > > optimization -- MRPipeline#run is called once for each map side
> join
> > > > > that is set up, but if the setup of the joins was done within
> > > > > MRPipeline, then we could set up multiple map side joins in
> parallel
> > > > > with a single call to MRPipeline#run. OTOH, a whole bunch of map
> side
> > > > > joins in parallel probably isn't that common of an operation.
> > > > >
> > > > > If anyone feels like taking a look at the patch, any feedback is
> > > > > appreciated. If nobody sees something that needs serious changes
in
> > > > > the patch, I'll commit it.
> > > > >
> > > > > - Gabriel
> > > > >
> > > > >
> > > > > On Thu, Jun 21, 2012 at 9:09 AM, Gabriel Reid <
> gabriel.reid@gmail.com (mailto:gabriel.reid@gmail.com)>
> > > > > wrote:
> > > > > > Replying to all...
> > > > > >
> > > > > > On Thu, Jun 21, 2012 at 8:40 AM, Josh Wills <jwills@cloudera.com(mailto:
> jwills@cloudera.com)> wrote:
> > > > > > >
> > > > > > > So there's a philosophical issue here: should Crunch ever
make
> > > > > > > decisions about how to do something itself based on its
> estimates of
> > > > > > > the size of the data sets, or should it always do exactly
what
> the
> > > > > > > developer indicates?
> > > > > > >
> > > > > > > I can make a case either way, but I think that no matter
what,
> we
> > > > > > > would want to have explicit functions for performing a
join
> that reads
> > > > > > > one data set into memory, so I think we can proceed w/the
> > > > > > > implementation while folks weigh in on what their preferences
> are for
> > > > > > > the default join() behavior (e.g., just do a reduce-side
join,
> or try
> > > > > > > to figure out the best join given information about the
input
> data and
> > > > > > > some configuration parameters.)
> > > > > >
> > > > > >
> > > > > >
> > > > > > I definitely agree on needing to have an explicit way to invoke
> one or
> > > > > > the other -- and in general I don't like having magic behind
the
> > > > > > scenes to decide on behaviour (especially considering Crunch
is
> > > > > > generally intended to be closer to the metal than Pig and Hive).
> I'm
> > > > > > not sure if the runtime decision is something specific to some
> of my
> > > > > > use cases or if it could be useful to a wider audience.
> > > > > >
> > > > > > The ability to dynamically decide at runtime whether a map side
> join
> > > > > > should be used can also easily be tacked on outside of Crunch,
> and
> > > > > > won't impact the underlying implementation (as you pointed out),
> so I
> > > > > > definitely also agree on focusing on the underlying
> implementation
> > > > > > first, and we can worry about the options used for exposing
it
> later
> > > > > > on.
> > > > > >
> > > > > > - Gabriel
>
>
>


-- 
Director of Data Science
Cloudera <http://www.cloudera.com>
Twitter: @josh_wills <http://twitter.com/josh_wills>

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