content: /*
   * 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.calcite.rel.logical;
  
  import org.apache.calcite.linq4j.Ord;
  import org.apache.calcite.plan.RelOptCluster;
  import org.apache.calcite.plan.RelOptUtil;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.RelCollation;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.Window;
  import org.apache.calcite.rel.hint.RelHint;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rex.RexInputRef;
  import org.apache.calcite.rex.RexLiteral;
  import org.apache.calcite.rex.RexLocalRef;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.rex.RexOver;
  import org.apache.calcite.rex.RexProgram;
  import org.apache.calcite.rex.RexShuttle;
  import org.apache.calcite.rex.RexWindow;
  import org.apache.calcite.rex.RexWindowBound;
  import org.apache.calcite.rex.RexWindowExclusion;
  import org.apache.calcite.tools.RelBuilder;
  import org.apache.calcite.util.ImmutableBitSet;
  import org.apache.calcite.util.Litmus;
  import org.apache.calcite.util.Pair;
  import org.apache.calcite.util.Util;
  
  import com.google.common.collect.LinkedListMultimap;
  import com.google.common.collect.Lists;
  import com.google.common.collect.Multimap;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.AbstractList;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.IdentityHashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Sub-class of {@link org.apache.calcite.rel.core.Window}
   * not targeted at any particular engine or calling convention.
   */
  public final class LogicalWindow extends Window {
    /**
     * Creates a LogicalWindow.
     *
     * <p>Use {@link #create} unless you know what you're doing.
     *
     * @param cluster Cluster
     * @param traitSet Trait set
     * @param hints Hints for this node
     * @param input Input relational expression
     * @param constants List of constants that are additional inputs
     * @param rowType Output row type
     * @param groups Window groups
     */
    public LogicalWindow(RelOptCluster cluster, RelTraitSet traitSet,
        List<RelHint> hints, RelNode input, List<RexLiteral> constants,
        RelDataType rowType, List<Group> groups) {
      super(cluster, traitSet, hints, input, constants, rowType, groups);
    }
  
    /**
     * Creates a LogicalWindow.
     *
     * <p>Use {@link #create} unless you know what you're doing.
     *
     * @param cluster Cluster
     * @param traitSet Trait set
     * @param input   Input relational expression
     * @param constants List of constants that are additional inputs
     * @param rowType Output row type
     * @param groups Window groups
     */
    public LogicalWindow(RelOptCluster cluster, RelTraitSet traitSet, RelNode input,
        List<RexLiteral> constants, RelDataType rowType, List<Group> groups) {
      this(cluster, traitSet, Collections.emptyList(), input, constants, rowType, groups);
    }
  
    @Override public LogicalWindow copy(RelTraitSet traitSet,
        List<RelNode> inputs) {
      return new LogicalWindow(getCluster(), traitSet, sole(inputs), constants,
        getRowType(), groups);
    }
  
    @Override public Window copy(List<RexLiteral> constants) {
      return new LogicalWindow(getCluster(), getTraitSet(), getInput(),
          constants, getRowType(), groups);
    }
  
    /**
     * Creates a LogicalWindow.
     *
     * @param input   Input relational expression
     * @param traitSet Trait set
     * @param constants List of constants that are additional inputs
     * @param rowType Output row type
     * @param groups Window groups
     */
    public static LogicalWindow create(RelTraitSet traitSet, RelNode input,
        List<RexLiteral> constants, RelDataType rowType, List<Group> groups) {
      return new LogicalWindow(input.getCluster(), traitSet, input, constants,
          rowType, groups);
    }
  
    /**
     * Creates a LogicalWindow by parsing a {@link RexProgram}.
     */
    public static RelNode create(RelOptCluster cluster,
        RelTraitSet traitSet, RelBuilder relBuilder, RelNode child,
        final RexProgram program) {
      final RelDataType outRowType = program.getOutputRowType();
      // Build a list of distinct groups, partitions and aggregate
      // functions.
      final Multimap<WindowKey, RexOver> windowMap =
          LinkedListMultimap.create();
  
      final int inputFieldCount = child.getRowType().getFieldCount();
  
      final Map<RexLiteral, RexInputRef> constantPool = new HashMap<>();
      final List<RexLiteral> constants = new ArrayList<>();
  
      // Identify constants in the expression tree and replace them with
      // references to newly generated constant pool.
      RexShuttle replaceConstants = new RexShuttle() {
        @Override public RexNode visitLiteral(RexLiteral literal) {
          RexInputRef ref = constantPool.get(literal);
          if (ref != null) {
            return ref;
          }
          constants.add(literal);
          ref =
              new RexInputRef(constantPool.size() + inputFieldCount,
                  literal.getType());
          constantPool.put(literal, ref);
          return ref;
        }
      };
  
      // Build a list of groups, partitions, and aggregate functions. Each
      // aggregate function will add its arguments as outputs of the input
      // program.
      final IdentityHashMap<RexOver, RexOver> origToNewOver = new IdentityHashMap<>();
      for (RexNode agg : program.getExprList()) {
        if (agg instanceof RexOver) {
          final RexOver origOver = (RexOver) agg;
          final RexOver newOver = (RexOver) origOver.accept(replaceConstants);
          origToNewOver.put(origOver, newOver);
          addWindows(windowMap, newOver, inputFieldCount);
        }
      }
  
      final Map<RexOver, Window.RexWinAggCall> aggMap = new HashMap<>();
      List<Group> groups = new ArrayList<>();
      for (Map.Entry<WindowKey, Collection<RexOver>> entry
          : windowMap.asMap().entrySet()) {
        final WindowKey windowKey = entry.getKey();
        final List<RexWinAggCall> aggCalls = new ArrayList<>();
        for (RexOver over : entry.getValue()) {
          final RexWinAggCall aggCall =
              new RexWinAggCall(
                  over.getAggOperator(),
                  over.getType(),
                  toInputRefs(over.operands),
                  aggMap.size(),
                  over.isDistinct(),
                  over.ignoreNulls());
          aggCalls.add(aggCall);
          aggMap.put(over, aggCall);
        }
        RexShuttle toInputRefs = new RexShuttle() {
          @Override public RexNode visitLocalRef(RexLocalRef localRef) {
            return new RexInputRef(localRef.getIndex(), localRef.getType());
          }
        };
        groups.add(
            new Group(
                windowKey.groupSet,
                windowKey.isRows,
                windowKey.lowerBound.accept(toInputRefs),
                windowKey.upperBound.accept(toInputRefs),
                windowKey.exclude,
                windowKey.orderKeys,
                aggCalls));
      }
  
      // Figure out the type of the inputs to the output program.
      // They are: the inputs to this rel, followed by the outputs of
      // each window.
      final List<Window.RexWinAggCall> flattenedAggCallList = new ArrayList<>();
      final List<Map.Entry<String, RelDataType>> fieldList =
          new ArrayList<>(child.getRowType().getFieldList());
      final int offset = fieldList.size();
  
      // Use better field names for agg calls that are projected.
      final Map<Integer, String> fieldNames = new HashMap<>();
      for (Ord<RexLocalRef> ref : Ord.zip(program.getProjectList())) {
        final int index = ref.e.getIndex();
        if (index >= offset) {
          fieldNames.put(
              index - offset, outRowType.getFieldNames().get(ref.i));
        }
      }
  
      for (Ord<Group> window : Ord.zip(groups)) {
        for (Ord<RexWinAggCall> over : Ord.zip(window.e.aggCalls)) {
          // Add the k-th over expression of
          // the i-th window to the output of the program.
          String name = fieldNames.get(over.i);
          if (name == null || name.startsWith("$")) {
            name = "w" + window.i + "$o" + over.i;
          }
          fieldList.add(Pair.of(name, over.e.getType()));
          flattenedAggCallList.add(over.e);
        }
      }
      final RelDataType intermediateRowType =
          cluster.getTypeFactory().createStructType(fieldList);
  
      // The output program is the windowed agg's program, combined with
      // the output calc (if it exists).
      RexShuttle shuttle =
          new RexShuttle() {
            @Override public RexNode visitOver(RexOver over) {
              // Look up the aggCall which this expr was translated to.
              final Window.RexWinAggCall aggCall =
                  requireNonNull(aggMap.get(origToNewOver.get(over)));
              assert RelOptUtil.eq(
                  "over",
                  over.getType(),
                  "aggCall",
                  aggCall.getType(),
                  Litmus.THROW);
  
              // Find the index of the aggCall among all partitions of all
              // groups.
              final int aggCallIndex =
                  flattenedAggCallList.indexOf(aggCall);
              assert aggCallIndex >= 0;
  
              // Replace expression with a reference to the window slot.
              final int index = inputFieldCount + aggCallIndex;
              assert RelOptUtil.eq(
                  "over",
                  over.getType(),
                  "intermed",
                  intermediateRowType.getFieldList().get(index).getType(),
                  Litmus.THROW);
              return new RexInputRef(
                  index,
                  over.getType());
            }
  
            @Override public RexNode visitLocalRef(RexLocalRef localRef) {
              final int index = localRef.getIndex();
              if (index < inputFieldCount) {
                // Reference to input field.
                return localRef;
              }
              return new RexLocalRef(
                  flattenedAggCallList.size() + index,
                  localRef.getType());
            }
          };
  
      final LogicalWindow window =
          LogicalWindow.create(traitSet, child, constants, intermediateRowType,
              groups);
  
      // The order that the "over" calls occur in the groups and
      // partitions may not match the order in which they occurred in the
      // original expression.
      // Add a project to permute them.
      final List<RexNode> refToWindow =
          toInputRefs(shuttle.visitList(program.getExprList()));
  
      final List<RexNode> projectList = new ArrayList<>();
      for (RexLocalRef inputRef : program.getProjectList()) {
        final int index = inputRef.getIndex();
        final RexInputRef ref = (RexInputRef) refToWindow.get(index);
        projectList.add(ref);
      }
  
      return relBuilder.push(window)
          .project(projectList, outRowType.getFieldNames())
          .build();
    }
  
    private static List<RexNode> toInputRefs(
        final List<? extends RexNode> operands) {
      return new AbstractList<RexNode>() {
        @Override public int size() {
          return operands.size();
        }
  
        @Override public RexNode get(int index) {
          final RexNode operand = operands.get(index);
          if (operand instanceof RexInputRef) {
            return operand;
          }
          assert operand instanceof RexLocalRef;
          final RexLocalRef ref = (RexLocalRef) operand;
          return new RexInputRef(ref.getIndex(), ref.getType());
        }
      };
    }
  
    /** Group specification. All windowed aggregates over the same window
     * (regardless of how it is specified, in terms of a named window or specified
     * attribute by attribute) will end up with the same window key. */
    private static class WindowKey {
      private final ImmutableBitSet groupSet;
      private final RelCollation orderKeys;
      private final boolean isRows;
      private final RexWindowBound lowerBound;
      private final RexWindowBound upperBound;
      private final RexWindowExclusion exclude;
  
      WindowKey(
          ImmutableBitSet groupSet,
          RelCollation orderKeys,
          boolean isRows,
          RexWindowBound lowerBound,
          RexWindowBound upperBound,
          RexWindowExclusion exclude) {
        this.groupSet = groupSet;
        this.orderKeys = orderKeys;
        this.isRows = isRows;
        this.lowerBound = lowerBound;
        this.upperBound = upperBound;
        this.exclude = exclude;
      }
  
      @Override public int hashCode() {
        return Objects.hash(groupSet, orderKeys, isRows, lowerBound, upperBound, exclude);
      }
  
      @Override public boolean equals(@Nullable Object obj) {
        return obj == this
            || obj instanceof WindowKey
            && groupSet.equals(((WindowKey) obj).groupSet)
            && orderKeys.equals(((WindowKey) obj).orderKeys)
            && Objects.equals(lowerBound, ((WindowKey) obj).lowerBound)
            && Objects.equals(upperBound, ((WindowKey) obj).upperBound)
            && exclude == ((WindowKey) obj).exclude
            && isRows == ((WindowKey) obj).isRows;
      }
    }
  
    private static void addWindows(
        Multimap<WindowKey, RexOver> windowMap,
        RexOver over, final int inputFieldCount) {
      final RexWindow aggWindow = over.getWindow();
  
      // Look up or create a window.
      RelCollation orderKeys =
          getCollation(
              Lists.newArrayList(
                  Util.filter(aggWindow.orderKeys,
                      rexFieldCollation ->
                          // If ORDER BY references constant (i.e. RexInputRef),
                          // then we can ignore such ORDER BY key.
                          rexFieldCollation.left instanceof RexLocalRef)));
      ImmutableBitSet groupSet =
          ImmutableBitSet.of(getProjectOrdinals(aggWindow.partitionKeys));
      final int groupLength = groupSet.length();
      if (inputFieldCount < groupLength) {
        // If PARTITION BY references constant, we can ignore such partition key.
        // All the inputs after inputFieldCount are literals, thus we can clear.
        groupSet =
            groupSet.except(ImmutableBitSet.range(inputFieldCount, groupLength));
      }
  
      WindowKey windowKey =
          new WindowKey(
              groupSet, orderKeys, aggWindow.isRows(),
              aggWindow.getLowerBound(), aggWindow.getUpperBound(), aggWindow.getExclude());
      windowMap.put(windowKey, over);
    }
  
    @Override public RelNode withHints(List<RelHint> hintList) {
      return new LogicalWindow(getCluster(), traitSet, hintList,
          input, constants, getRowType(), groups);
    }
  }
  