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.metadata;
  
  import org.apache.calcite.adapter.enumerable.EnumerableLimit;
  import org.apache.calcite.plan.RelOptPredicateList;
  import org.apache.calcite.plan.volcano.RelSubset;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.Aggregate;
  import org.apache.calcite.rel.core.Calc;
  import org.apache.calcite.rel.core.Exchange;
  import org.apache.calcite.rel.core.Filter;
  import org.apache.calcite.rel.core.Intersect;
  import org.apache.calcite.rel.core.Join;
  import org.apache.calcite.rel.core.Minus;
  import org.apache.calcite.rel.core.Project;
  import org.apache.calcite.rel.core.Sample;
  import org.apache.calcite.rel.core.Sort;
  import org.apache.calcite.rel.core.TableModify;
  import org.apache.calcite.rel.core.TableScan;
  import org.apache.calcite.rel.core.Union;
  import org.apache.calcite.rel.core.Values;
  import org.apache.calcite.rex.RexBuilder;
  import org.apache.calcite.rex.RexLiteral;
  import org.apache.calcite.util.Bug;
  import org.apache.calcite.util.Util;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * RelMdMaxRowCount supplies a default implementation of
   * {@link RelMetadataQuery#getMaxRowCount} for the standard logical algebra.
   */
  public class RelMdMaxRowCount
      implements MetadataHandler<BuiltInMetadata.MaxRowCount> {
    public static final RelMetadataProvider SOURCE =
        ReflectiveRelMetadataProvider.reflectiveSource(
            new RelMdMaxRowCount(), BuiltInMetadata.MaxRowCount.Handler.class);
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public MetadataDef<BuiltInMetadata.MaxRowCount> getDef() {
      return BuiltInMetadata.MaxRowCount.DEF;
    }
  
    public @Nullable Double getMaxRowCount(Union rel, RelMetadataQuery mq) {
      double rowCount = 0.0;
      for (RelNode input : rel.getInputs()) {
        Double partialRowCount = mq.getMaxRowCount(input);
        if (partialRowCount == null) {
          return null;
        }
        rowCount += partialRowCount;
      }
      return rowCount;
    }
  
    public @Nullable Double getMaxRowCount(Intersect rel, RelMetadataQuery mq) {
      // max row count is the smallest of the inputs
      Double rowCount = null;
      for (RelNode input : rel.getInputs()) {
        Double partialRowCount = mq.getMaxRowCount(input);
        if (rowCount == null
            || partialRowCount != null && partialRowCount < rowCount) {
          rowCount = partialRowCount;
        }
      }
      return rowCount;
    }
  
    public @Nullable Double getMaxRowCount(Minus rel, RelMetadataQuery mq) {
      return mq.getMaxRowCount(rel.getInput(0));
    }
  
    public @Nullable Double getMaxRowCount(Filter rel, RelMetadataQuery mq) {
      if (rel.getCondition().isAlwaysFalse()) {
        return 0D;
      }
      return mq.getMaxRowCount(rel.getInput());
    }
  
    public @Nullable Double getMaxRowCount(Calc rel, RelMetadataQuery mq) {
      return mq.getMaxRowCount(rel.getInput());
    }
  
    public @Nullable Double getMaxRowCount(Project rel, RelMetadataQuery mq) {
      return mq.getMaxRowCount(rel.getInput());
    }
  
    public @Nullable Double getMaxRowCount(Exchange rel, RelMetadataQuery mq) {
      return mq.getMaxRowCount(rel.getInput());
    }
  
    public @Nullable Double getMaxRowCount(Sample rel, RelMetadataQuery mq) {
      return mq.getMaxRowCount(rel.getInput());
    }
  
    public Double getMaxRowCount(Sort rel, RelMetadataQuery mq) {
      Double rowCount = mq.getMaxRowCount(rel.getInput());
      if (rowCount == null) {
        rowCount = Double.POSITIVE_INFINITY;
      }
  
      final long offset = rel.offset instanceof RexLiteral ? RexLiteral.longValue(rel.offset) : 0;
      rowCount = Math.max(rowCount - offset, 0D);
  
      final double limit =
          rel.fetch instanceof RexLiteral ? RexLiteral.longValue(rel.fetch) : rowCount;
      return limit < rowCount ? limit : rowCount;
    }
  
    public Double getMaxRowCount(EnumerableLimit rel, RelMetadataQuery mq) {
      Double rowCount = mq.getMaxRowCount(rel.getInput());
      if (rowCount == null) {
        rowCount = Double.POSITIVE_INFINITY;
      }
  
      final long offset = rel.offset instanceof RexLiteral ? RexLiteral.longValue(rel.offset) : 0;
      rowCount = Math.max(rowCount - offset, 0D);
  
      final double limit =
          rel.fetch instanceof RexLiteral ? RexLiteral.longValue(rel.fetch) : rowCount;
      return limit < rowCount ? limit : rowCount;
    }
  
    public @Nullable Double getMaxRowCount(Aggregate rel, RelMetadataQuery mq) {
      if (rel.getGroupSet().isEmpty()) {
        // Aggregate with no GROUP BY always returns 1 row (even on empty table).
        return 1D;
      }
  
      // Aggregate with constant GROUP BY always returns 1 row
      if (rel.getGroupType() == Aggregate.Group.SIMPLE) {
        final RelOptPredicateList predicateList =
            mq.getPulledUpPredicates(rel.getInput());
        if (!RelOptPredicateList.isEmpty(predicateList)
            && allGroupKeysAreConstant(rel, predicateList)) {
          return 1D;
        }
      }
      final Double rowCount = mq.getMaxRowCount(rel.getInput());
      if (rowCount == null) {
        return null;
      }
      return rowCount * rel.getGroupSets().size();
    }
  
    static boolean allGroupKeysAreConstant(Aggregate aggregate,
        RelOptPredicateList predicateList) {
      final RexBuilder rexBuilder = aggregate.getCluster().getRexBuilder();
      for (int key : aggregate.getGroupSet()) {
        if (!predicateList.constantMap.containsKey(
            rexBuilder.makeInputRef(aggregate.getInput(), key))) {
          return false;
        }
      }
      return true;
    }
  
    public @Nullable Double getMaxRowCount(Join rel, RelMetadataQuery mq) {
      Double left = mq.getMaxRowCount(rel.getLeft());
      Double right = mq.getMaxRowCount(rel.getRight());
      if (left == null || right == null) {
        return null;
      }
      if (left < 1D && rel.getJoinType().generatesNullsOnLeft()) {
        left = 1D;
      }
      if (right < 1D && rel.getJoinType().generatesNullsOnRight()) {
        right = 1D;
      }
      return left * right;
    }
  
    public @Nullable Double getMaxRowCount(TableScan rel, RelMetadataQuery mq) {
      final BuiltInMetadata.MaxRowCount.Handler handler =
          rel.getTable().unwrap(BuiltInMetadata.MaxRowCount.Handler.class);
      if (handler != null) {
        return handler.getMaxRowCount(rel, mq);
      }
      // For typical tables, there is no upper bound to the number of rows.
      return Double.POSITIVE_INFINITY;
    }
  
    public Double getMaxRowCount(Values values, RelMetadataQuery mq) {
      // For Values, the maximum row count is the actual row count.
      // This is especially useful if Values is empty.
      return (double) values.getTuples().size();
    }
  
    public @Nullable Double getMaxRowCount(TableModify rel, RelMetadataQuery mq) {
      return mq.getMaxRowCount(rel.getInput());
    }
  
    public Double getMaxRowCount(RelSubset rel, RelMetadataQuery mq) {
      // FIXME This is a short-term fix for [CALCITE-1018]. A complete
      // solution will come with [CALCITE-1048].
      Util.discard(Bug.CALCITE_1048_FIXED);
      for (RelNode node : rel.getRels()) {
        if (node instanceof Sort) {
          Sort sort = (Sort) node;
          if (sort.fetch instanceof RexLiteral) {
            return (double) RexLiteral.longValue(sort.fetch);
          }
        }
      }
  
      return Double.POSITIVE_INFINITY;
    }
  
    // Catch-all rule when none of the others apply.
    public @Nullable Double getMaxRowCount(RelNode rel, RelMetadataQuery mq) {
      return null;
    }
  }
  