Github user sohami commented on a diff in the pull request:
https://github.com/apache/drill/pull/1223#discussion_r182628991
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/unnest/UnnestImpl.java
---
@@ -0,0 +1,137 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF 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.
+ */
+package org.apache.drill.exec.physical.impl.unnest;
+
+import com.google.common.collect.ImmutableList;
+import org.apache.drill.exec.exception.SchemaChangeException;
+import org.apache.drill.exec.ops.FragmentContext;
+import org.apache.drill.exec.physical.base.LateralContract;
+import org.apache.drill.exec.record.BatchSchema.SelectionVectorMode;
+import org.apache.drill.exec.record.RecordBatch;
+import org.apache.drill.exec.record.TransferPair;
+import org.apache.drill.exec.vector.ValueVector;
+import org.apache.drill.exec.vector.complex.RepeatedValueVector;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.List;
+
+/**
+ * Contains the actual unnest operation. Unnest is a simple transfer
operation in this impelementation.
+ * For use as a table function, we will need to change the logic of the
unnest method to operate on
+ * more than one row at a time and remove any dependence on Lateral
+ * {@link org.apache.drill.exec.physical.impl.flatten.FlattenTemplate}.
+ * This class follows the pattern of other operators that generate code at
runtime. Normally this class
+ * would be abstract and have placeholders for doSetup and doEval. Unnest
however, doesn't require code
+ * generation so we can simply implement the code in a simple class that
looks similar to the code gen
+ * templates used by other operators but does not implement the doSetup
and doEval methods.
+ */
+public class UnnestImpl implements Unnest {
+ private static final Logger logger =
LoggerFactory.getLogger(UnnestImpl.class);
+
+ private static final int OUTPUT_ROW_COUNT = ValueVector.MAX_ROW_COUNT;
+
+ private ImmutableList<TransferPair> transfers;
+ private LateralContract lateral; // corresponding lateral Join (or other
operator implementing the Lateral Contract)
+ private SelectionVectorMode svMode;
+ private RepeatedValueVector fieldToUnnest;
+ private RepeatedValueVector.RepeatedAccessor accessor;
+
+ /**
+ * The output batch limit starts at OUTPUT_ROW_COUNT, but may be
decreased
+ * if records are found to be large.
+ */
+ private int outputLimit = OUTPUT_ROW_COUNT;
+
+
+ // The index in the unnest column that is being processed.We start at
zero and continue until
+ // InnerValueCount is reached or if the batch limit is reached
+ // this allows for groups to be written between batches if we run out of
space, for cases where we have finished
+ // a batch on the boundary it will be set to 0
+ private int innerValueIndex = 0;
+
+ @Override
+ public void setUnnestField(RepeatedValueVector unnestField) {
+ this.fieldToUnnest = unnestField;
+ this.accessor =
RepeatedValueVector.RepeatedAccessor.class.cast(unnestField.getAccessor());
+ }
+
+ @Override
+ public RepeatedValueVector getUnnestField() {
+ return fieldToUnnest;
+ }
+
+ @Override
+ public void setOutputCount(int outputCount) {
+ outputLimit = outputCount;
+ }
+
+ @Override
+ public final int unnestRecords(final int recordCount) {
+ switch (svMode) {
+ case FOUR_BYTE:
+ throw new UnsupportedOperationException("Unnest does not support
selection vector inputs.");
+
+ case TWO_BYTE:
+ throw new UnsupportedOperationException("Unnest does not support
selection vector inputs.");
+
+ case NONE:
+ if (innerValueIndex == -1) {
+ innerValueIndex = 0;
+ }
+
+ // Current record being processed in the incoming record batch. We
could keep
+ // track of it ourselves, but it is better to check with the
Lateral Join and get the
+ // current record being processed thru the Lateral Join Contract.
+ final int currentRecord = lateral.getRecordIndex();
+ final int innerValueCount =
accessor.getInnerValueCountAt(currentRecord);
+ final int count = Math.min(Math.min(innerValueCount, outputLimit),
recordCount);
+
+ logger.debug("Unnest: currentRecord: {}, innerValueCount: {},
record count: {}, output limit: {}",
+ innerValueCount,
+ recordCount, outputLimit);
+ for (TransferPair t : transfers) {
+ t.splitAndTransfer(innerValueIndex, count);
+ }
+ innerValueIndex += count;
+ return count;
+
+ default:
+ throw new UnsupportedOperationException();
--- End diff --
How about adding a message in the exception "Unsupported SV mode {} found
in Unnest, svMode"?
---
