use pause / resume in DistributingDownstream

This eliminates the Queue from the DistributingDownstream.
Instead the StreamBuckets are used directly to save the
rows.

In addition the Broadcasting/Modulo distribution has been
decoupled from the request handling.

sql/src/main/java/io/crate/action/job/ContextPreparer.java

@@ -33,10 +33,7 @@
 import io.crate.jobs.JobExecutionContext;
 import io.crate.jobs.PageDownstreamContext;
 import io.crate.metadata.Routing;
-import io.crate.operation.NodeOperation;
-import io.crate.operation.PageDownstream;
-import io.crate.operation.PageDownstreamFactory;
-import io.crate.operation.Paging;
+import io.crate.operation.*;
 import io.crate.operation.collect.JobCollectContext;
 import io.crate.operation.collect.MapSideDataCollectOperation;
 import io.crate.operation.count.CountOperation;
@@ -150,7 +147,7 @@ public Void visitCountPhase(CountPhase phase, PreparerContext context) {
         @Override
         public Void visitMergePhase(final MergePhase phase, final PreparerContext context) {
             RamAccountingContext ramAccountingContext = RamAccountingContext.forExecutionPhase(circuitBreaker, phase);
-            ResultProvider downstream = resultProviderFactory.createDownstream(
+            RowDownstream downstream = resultProviderFactory.createDownstream(
                     context.nodeOperation,
                     phase.jobId(),
                     Paging.getWeightedPageSize(Paging.PAGE_SIZE, 1.0d / phase.executionNodes().size()));
@@ -188,10 +185,10 @@ public Void visitCollectPhase(final CollectPhase phase, final PreparerContext co
             );
             LOGGER.trace("{} setting node page size to: {}, numShards in total: {} shards on node: {}",
                     localNodeId, pageSize, numTotalShards, numShardsOnNode);
-            ResultProvider downstream = resultProviderFactory.createDownstream(context.nodeOperation, phase.jobId(), pageSize);
+            RowDownstream downstream = resultProviderFactory.createDownstream(context.nodeOperation, phase.jobId(), pageSize);
 
             if (ExecutionPhases.hasDirectResponseDownstream(context.nodeOperation.downstreamNodes())) {
-                context.directResultFuture = downstream.result();
+                context.directResultFuture = ((ResultProvider) downstream).result();
             }
             final JobCollectContext jobCollectContext = new JobCollectContext(
                     context.jobId,

sql/src/main/java/io/crate/executor/transport/distributed/BroadcastingPageBuilder.java

@@ -0,0 +1,83 @@
+/*
+ * Licensed to Crate.IO GmbH ("Crate") under one or more contributor
+ * license agreements.  See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.  Crate licenses
+ * this file to you under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.  You may
+ * obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ * However, if you have executed another commercial license agreement
+ * with Crate these terms will supersede the license and you may use the
+ * software solely pursuant to the terms of the relevant commercial agreement.
+ */
+
+package io.crate.executor.transport.distributed;
+
+import com.google.common.base.Throwables;
+import io.crate.Streamer;
+import io.crate.core.collections.Bucket;
+import io.crate.core.collections.Row;
+import io.crate.executor.transport.StreamBucket;
+
+import java.io.IOException;
+import java.util.ArrayList;
+
+/**
+ * PageBuilder that returns N buckets where N is the number of buckets specified in the constructor.
+ * Internally only one bucket is built - the same instance is returned N number of times.
+ */
+public class BroadcastingPageBuilder implements PageBuilder {
+
+    private final int numBuckets;
+    private final StreamBucket.Builder bucketBuilder;
+    private final ArrayList<Bucket> builtBuckets;
+    private volatile int size = 0;
+
+    public BroadcastingPageBuilder(Streamer<?>[] streamers, int numBuckets) {
+        this.numBuckets = numBuckets;
+        this.bucketBuilder = new StreamBucket.Builder(streamers);
+        this.builtBuckets = new ArrayList<>(numBuckets);
+    }
+
+    @Override
+    public void add(Row row) {
+        try {
+            synchronized (this) {
+                bucketBuilder.add(row);
+                size++;
+            }
+        } catch (IOException e) {
+            throw Throwables.propagate(e);
+        }
+    }
+
+    @Override
+    public int size() {
+        return size;
+    }
+
+    @Override
+    public synchronized Iterable<Bucket> buildBuckets() {
+        final Bucket bucket;
+        try {
+            bucket = bucketBuilder.build();
+            bucketBuilder.reset();
+        } catch (IOException e) {
+            throw Throwables.propagate(e);
+        }
+        builtBuckets.clear();
+        for (int i = 0; i < numBuckets; i++) {
+            builtBuckets.add(bucket);
+        }
+        size = 0;
+        return builtBuckets;
+    }
+}