org.apache.calcite.materialize.SqlLatticeStatisticProvider.java Source code

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Here is the source code for org.apache.calcite.materialize.SqlLatticeStatisticProvider.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.calcite.materialize;

import org.apache.calcite.schema.ScannableTable;
import org.apache.calcite.schema.Table;
import org.apache.calcite.util.ImmutableBitSet;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;

/**
 * Implementation of {@link LatticeStatisticProvider} that gets statistics by
 * executing "SELECT COUNT(DISTINCT ...) ..." SQL queries.
 */
class SqlLatticeStatisticProvider implements LatticeStatisticProvider {
    static final SqlLatticeStatisticProvider INSTANCE = new SqlLatticeStatisticProvider();

    /** Creates an SqlLatticeStatisticProvider. */
    private SqlLatticeStatisticProvider() {
    }

    @Override
    public int cardinality(Lattice lattice, Lattice.Column column) {
        final String sql = lattice.countSql(ImmutableBitSet.of(column.ordinal));
        final Table table = new MaterializationService.DefaultTableFactory().createTable(lattice.rootSchema, sql,
                ImmutableList.<String>of());
        final Object[] values = Iterables.getOnlyElement(((ScannableTable) table).scan(null));
        return ((Number) values[0]).intValue();
    }
}

// End SqlLatticeStatisticProvider.java