[GitHub] HanumathRao commented on a change in pull request #1441: DRILL-6703: Query with complex expressions in lateral and unnest fails with CannotPlanException

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HanumathRao commented on a change in pull request #1441: DRILL-6703: Query with complex expressions in lateral and unnest fails with CannotPlanException
URL: https://github.com/apache/drill/pull/1441#discussion_r212391730
 
 

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 File path: exec/java-exec/src/main/java/org/apache/drill/exec/planner/sql/handlers/ComplexUnnestVisitor.java
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+/*
+ * 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.planner.sql.handlers;
+
+import com.google.common.collect.ImmutableList;
+import org.apache.calcite.plan.RelOptUtil;
+import org.apache.calcite.rel.RelNode;
+import org.apache.calcite.rel.RelShuttleImpl;
+import org.apache.calcite.rel.core.Correlate;
+import org.apache.calcite.rel.core.CorrelationId;
+import org.apache.calcite.rel.core.Project;
+import org.apache.calcite.rel.core.Uncollect;
+import org.apache.calcite.rel.logical.LogicalCorrelate;
+import org.apache.calcite.rel.type.RelDataTypeField;
+import org.apache.calcite.rex.RexBuilder;
+import org.apache.calcite.rex.RexFieldAccess;
+import org.apache.calcite.rex.RexNode;
+import org.apache.calcite.rex.RexShuttle;
+import org.apache.calcite.sql.SqlKind;
+import org.apache.calcite.tools.RelBuilder;
+import org.apache.calcite.util.ImmutableBitSet;
+import org.apache.drill.exec.planner.logical.DrillRelFactories;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+/**
+ * Visitor that moves non-{@link RexFieldAccess} rex node from project below {@link Uncollect}
+ * to the left side of the {@link Correlate}.
+ */
+public class ComplexUnnestVisitor extends RelShuttleImpl {
+  private static final String COMPLEX_FIELD_NAME = "$COMPLEX_FIELD_NAME";
+
+  private final Map<CorrelationId, RelNode> leftInputs = new HashMap<>();
+  private final Map<CorrelationId, CorrelationId> updatedCorrelationIds = new HashMap<>();
+
+  private ComplexUnnestVisitor() {
+  }
+
+  @Override
+  public RelNode visit(LogicalCorrelate correlate) {
+    RelNode left = correlate.getLeft().accept(this);
+    leftInputs.put(correlate.getCorrelationId(), left);
+
+    RelNode right = correlate.getRight().accept(this);
+    // if right input wasn't changed or left input wasn't changed
+    // after rewriting right input, no need to create Correlate with new CorrelationId
+    if (correlate.getRight() == right
+        || left == leftInputs.get(correlate.getCorrelationId())) {
+      if (correlate.getLeft() == left) {
+        return correlate;
+      }
+      // changed only inputs, but CorrelationId left the same
+      return correlate.copy(correlate.getTraitSet(), Arrays.asList(left, right));
+    }
+
+    Correlate newCorrelate = correlate.copy(correlate.getTraitSet(),
+        leftInputs.get(correlate.getCorrelationId()), right,
+        updatedCorrelationIds.get(correlate.getCorrelationId()),
+        ImmutableBitSet.of(left.getRowType().getFieldCount()), correlate.getJoinType());
+
+    RelBuilder builder = DrillRelFactories.LOGICAL_BUILDER.create(correlate.getCluster(), null);
+    builder.push(newCorrelate);
+
+    List<RexNode> topProjectExpressions = left.getRowType().getFieldList().stream()
+        .map(field -> builder.getRexBuilder().makeInputRef(left, field.getIndex()))
+        .collect(Collectors.toList());
+
+    switch (correlate.getJoinType()) {
+      case LEFT:
+      case INNER:
+        // adds field from the right input of correlate to the top project
+        topProjectExpressions.add(
+            builder.getRexBuilder().makeInputRef(newCorrelate, topProjectExpressions.size() + 1));
+        // fall through
+      case ANTI:
+      case SEMI:
+        builder.project(topProjectExpressions, correlate.getRowType().getFieldNames());
+    }
+    return builder.build();
+  }
+
+  @Override
+  public RelNode visit(RelNode other) {
+    if (other instanceof Uncollect) {
+      return visit((Uncollect) other);
+    }
+    return super.visit(other);
+  }
+
+  public RelNode visit(Uncollect uncollect) {
+    RelBuilder builder = DrillRelFactories.LOGICAL_BUILDER.create(uncollect.getCluster(), null);
+    RexBuilder rexBuilder = builder.getRexBuilder();
+
+    assert uncollect.getInput() instanceof Project : "Uncollect should have Project input";
+
+    Project project = (Project) uncollect.getInput();
+    // If project below uncollect contains only field references, no need to rewrite it
+    if (project.getChildExps().iterator().next().getKind() == SqlKind.FIELD_ACCESS) {
+      return uncollect;
+    }
+
+    // Collects CorrelationId instances used in current rel node
+    RelOptUtil.VariableUsedVisitor variableUsedVisitor = new RelOptUtil.VariableUsedVisitor(null);
+    project.accept(variableUsedVisitor);
+
+    assert variableUsedVisitor.variables.size() == 1 : "Uncollect supports only single correlated reference";
+
+    CorrelationId oldCorrId = variableUsedVisitor.variables.iterator().next();
+    RelNode left = leftInputs.get(oldCorrId);
+
+    // Creates new project to be placed on top of the left input of correlate
+    List<RexNode> leftProjExprs = new ArrayList<>();
+
+    List<String> fieldNames = new ArrayList<>();
+    for (RelDataTypeField field : left.getRowType().getFieldList()) {
+      leftProjExprs.add(rexBuilder.makeInputRef(left, field.getIndex()));
+      fieldNames.add(field.getName());
+    }
+    fieldNames.add(COMPLEX_FIELD_NAME);
+
+    builder.push(left);
+
+    // Adds complex expression with replaced correlation
+    // to the projected list from the left
+    leftProjExprs.addAll(new RexFieldAccessReplacer(builder).apply(project.getChildExps()));
 
 Review comment:
   Assuming that only one project expression is present at this point, Is it better to have an assert here to make sure that only one proj expression is added?

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