Java tutorial
/* * 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.hbase.index.covered.data; import java.io.IOException; import java.util.ArrayList; import java.util.Collection; import java.util.Collections; import java.util.List; import org.apache.hadoop.hbase.Cell; import org.apache.hadoop.hbase.client.Mutation; import org.apache.hadoop.hbase.client.Result; import org.apache.hadoop.hbase.client.Scan; import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment; import org.apache.hadoop.hbase.regionserver.Region; import org.apache.hadoop.hbase.regionserver.RegionScanner; import org.apache.phoenix.hbase.index.covered.update.ColumnReference; import org.apache.phoenix.hbase.index.util.IndexManagementUtil; import com.google.common.collect.Iterables; import com.google.common.collect.Ordering; import com.google.common.primitives.Longs; /** * Wrapper around a lazily instantiated, local HTable. * <p> * Previously, we had used various row and batch caches. However, this ends up being very * complicated when attempting manage updating and invalidating the cache with no real gain as any * row accessed multiple times will likely be in HBase's block cache, invalidating any extra caching * we are doing here. In the end, its simpler and about as efficient to just get the current state * of the row from HBase and let HBase manage caching the row from disk on its own. */ public class LocalTable implements LocalHBaseState { private RegionCoprocessorEnvironment env; public LocalTable(RegionCoprocessorEnvironment env) { this.env = env; } @Override public Result getCurrentRowState(Mutation m, Collection<? extends ColumnReference> columns, boolean ignoreNewerMutations) throws IOException { byte[] row = m.getRow(); // need to use a scan here so we can get raw state, which Get doesn't provide. Scan s = IndexManagementUtil.newLocalStateScan(Collections.singletonList(columns)); s.setStartRow(row); s.setStopRow(row); if (ignoreNewerMutations) { // Provides a means of client indicating that newer cells should not be considered, // enabling mutations to be replayed to partially rebuild the index when a write fails. // When replaying mutations we want the oldest timestamp (as anything newer we be replayed) long ts = getOldestTimestamp(m.getFamilyCellMap().values()); s.setTimeRange(0, ts); } Region region = this.env.getRegion(); RegionScanner scanner = region.getScanner(s); List<Cell> kvs = new ArrayList<Cell>(1); boolean more = scanner.next(kvs); assert !more : "Got more than one result when scanning" + " a single row in the primary table!"; Result r = Result.create(kvs); scanner.close(); return r; } // Returns the smallest timestamp in the given cell lists. // It is assumed that the lists have cells ordered from largest to smallest timestamp protected long getOldestTimestamp(Collection<List<Cell>> cellLists) { Ordering<List<Cell>> cellListOrdering = new Ordering<List<Cell>>() { @Override public int compare(List<Cell> left, List<Cell> right) { // compare the last element of each list, since that is the smallest in that list return Longs.compare(Iterables.getLast(left).getTimestamp(), Iterables.getLast(right).getTimestamp()); } }; List<Cell> minList = cellListOrdering.min(cellLists); return Iterables.getLast(minList).getTimestamp(); } }