io.druid.sql.calcite.table.DruidTables.java Source code

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Here is the source code for io.druid.sql.calcite.table.DruidTables.java

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/*
 * Licensed to Metamarkets Group Inc. (Metamarkets) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. Metamarkets 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 io.druid.sql.calcite.table;

import com.google.common.collect.Lists;
import io.druid.query.ordering.StringComparator;
import io.druid.query.ordering.StringComparators;
import io.druid.segment.column.ValueType;
import io.druid.sql.calcite.expression.RowExtraction;

import java.util.List;

public class DruidTables {
    private DruidTables() {
        // No instantiation.
    }

    /**
     * Returns the "natural" rowOrder for a Druid table. This is the order that a scan without projection would return.
     *
     * @param druidTable druid table
     *
     * @return natural row order
     */
    public static List<String> rowOrder(final DruidTable druidTable) {
        final List<String> rowOrder = Lists.newArrayListWithCapacity(druidTable.getColumnCount());
        for (int i = 0; i < druidTable.getColumnCount(); i++) {
            rowOrder.add(druidTable.getColumnName(i));
        }
        return rowOrder;
    }

    /**
     * Return the "natural" {@link StringComparator} for an extraction from a Druid table. This will be a lexicographic
     * comparator for String types and a numeric comparator for Number types.
     *
     * @param druidTable    underlying Druid table
     * @param rowExtraction extraction from the table
     *
     * @return natural comparator
     */
    public static StringComparator naturalStringComparator(final DruidTable druidTable,
            final RowExtraction rowExtraction) {
        if (rowExtraction.getExtractionFn() != null || druidTable
                .getColumnType(druidTable.getColumnNumber(rowExtraction.getColumn())) == ValueType.STRING) {
            return StringComparators.LEXICOGRAPHIC;
        } else {
            return StringComparators.NUMERIC;
        }
    }
}