co.cask.cdap.data2.dataset2.lib.table.inmemory.InMemoryScanner.java Source code

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/*
 * Copyright  2014 Cask Data, Inc.
 *
 * Licensed 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 co.cask.cdap.data2.dataset2.lib.table.inmemory;

import co.cask.cdap.api.common.Bytes;
import co.cask.cdap.api.dataset.table.Result;
import co.cask.cdap.api.dataset.table.Row;
import co.cask.cdap.api.dataset.table.Scanner;
import co.cask.cdap.data2.dataset2.lib.table.FuzzyRowFilter;
import com.google.common.collect.Sets;

import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
import java.util.NavigableMap;
import java.util.Set;
import java.util.TreeMap;

/**
 * An in-memory implememtation of a scanner.
 */
public class InMemoryScanner implements Scanner {

    private final Iterator<Map.Entry<byte[], NavigableMap<byte[], byte[]>>> rows;
    private final Set<byte[]> columnsToInclude;
    private final FuzzyRowFilter filter;

    public InMemoryScanner(Iterator<Map.Entry<byte[], NavigableMap<byte[], byte[]>>> rows) {
        this(rows, null, null);
    }

    public InMemoryScanner(Iterator<Map.Entry<byte[], NavigableMap<byte[], byte[]>>> rows, FuzzyRowFilter filter,
            byte[][] columnsToInclude) {
        this.rows = rows;
        this.filter = filter;
        if (columnsToInclude != null) {
            this.columnsToInclude = Sets.newTreeSet(Bytes.BYTES_COMPARATOR);
            Collections.addAll(this.columnsToInclude, columnsToInclude);
        } else {
            this.columnsToInclude = null;
        }
    }

    @Override
    public Row next() {
        Map<byte[], byte[]> columns = new TreeMap<>(Bytes.BYTES_COMPARATOR);
        Map.Entry<byte[], NavigableMap<byte[], byte[]>> rowEntry = null;

        while (columns.isEmpty() && this.rows.hasNext()) {
            rowEntry = this.rows.next();
            if (filter != null) {
                FuzzyRowFilter.ReturnCode code = filter.filterRow(rowEntry.getKey());
                if (FuzzyRowFilter.ReturnCode.DONE.equals(code)) {
                    break; // no more rows can match
                } else if (!FuzzyRowFilter.ReturnCode.INCLUDE.equals(code)) {
                    continue; // this row does not match filter, move to next row
                }
            }
            //Try to read all columns for this row
            for (Map.Entry<byte[], byte[]> colEntry : rowEntry.getValue().entrySet()) {
                if (columnsToInclude == null || columnsToInclude.contains(colEntry.getKey())) {
                    columns.put(colEntry.getKey(), colEntry.getValue());
                }
            }
        }
        if (columns.size() > 0) {
            assert rowEntry != null;
            return new Result(rowEntry.getKey(), columns);
        } else {
            return null;
        }
    }

    @Override
    public void close() {
        /* no op */ }

}