/*
 * 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.phoenix.iterate;

import java.sql.SQLException;
import java.util.List;
import org.apache.hadoop.hbase.HRegionLocation;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.phoenix.compile.QueryPlan;
import org.apache.phoenix.compile.StatementContext;
import org.apache.phoenix.schema.PTable;
import org.apache.phoenix.schema.PTable.IndexType;
import org.apache.phoenix.schema.SaltingUtil;
import org.apache.phoenix.util.ScanUtil;

/**
 * Default implementation that creates a scan group if a plan is row key ordered (which requires a
 * merge sort), or if a scan crosses a region boundary and the table is salted or a local index.
 */
public class DefaultParallelScanGrouper implements ParallelScanGrouper {

  private static DefaultParallelScanGrouper INSTANCE = new DefaultParallelScanGrouper();

  public DefaultParallelScanGrouper() {
  }

  public static DefaultParallelScanGrouper getInstance() {
    return INSTANCE;
  }

  /**
   * Returns true if the scan with the startKey is to be the first of a new batch
   */
  @Override
  public boolean shouldStartNewScan(QueryPlan plan, Scan lastScan, byte[] startKey,
    boolean crossesRegionBoundary) {
    PTable table = plan.getTableRef().getTable();
    if (lastScan == null) {
      return false;
    } else if (!plan.isRowKeyOrdered()) {
      return true;
    } else if (crossesRegionBoundary && table.getIndexType() == IndexType.LOCAL) {
      return true;
    } else if (table.getBucketNum() != null) {
      return crossesRegionBoundary || ScanUtil.crossesPrefixBoundary(startKey,
        ScanUtil.getPrefix(lastScan.getStartRow(), SaltingUtil.NUM_SALTING_BYTES),
        SaltingUtil.NUM_SALTING_BYTES);
    } else {
      return false;
    }
  }

  @Override
  public List<HRegionLocation> getRegionBoundaries(StatementContext context, byte[] tableName)
    throws SQLException {
    return context.getConnection().getQueryServices().getAllTableRegions(tableName,
      context.getStatement().getQueryTimeoutInMillis());
  }

  /**
   * {@inheritDoc}.
   */
  @Override
  public List<HRegionLocation> getRegionBoundaries(StatementContext context, byte[] tableName,
    byte[] startRegionBoundaryKey, byte[] stopRegionBoundaryKey) throws SQLException {
    return context.getConnection().getQueryServices().getTableRegions(tableName,
      startRegionBoundaryKey, stopRegionBoundaryKey,
      context.getStatement().getQueryTimeoutInMillis());
  }
}
