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.hadoop.hive.metastore; import java.io.IOException; import java.nio.ByteBuffer; import java.util.List; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.hive.metastore.api.FileMetadataExprType; import org.apache.hadoop.hive.metastore.hbase.MetadataStore; /** * The base implementation of a file metadata handler for a specific file type. * There are currently two classes for each file type (of 1), this one, which is very simple due * to the fact that it just calls the proxy class for most calls; and the proxy class, that * contains the actual implementation that depends on some stuff in QL (for ORC). */ public abstract class FileMetadataHandler { protected static final Log LOG = LogFactory.getLog(FileMetadataHandler.class); private Configuration conf; private PartitionExpressionProxy expressionProxy; private FileFormatProxy fileFormatProxy; private MetadataStore store; /** * Same as RawStore.getFileMetadataByExpr. */ public abstract void getFileMetadataByExpr(List<Long> fileIds, byte[] expr, ByteBuffer[] metadatas, ByteBuffer[] results, boolean[] eliminated) throws IOException; protected abstract FileMetadataExprType getType(); protected PartitionExpressionProxy getExpressionProxy() { return expressionProxy; } protected FileFormatProxy getFileFormatProxy() { return fileFormatProxy; } protected MetadataStore getStore() { return store; } /** * Configures the handler. Called once before use. * @param conf Config. * @param expressionProxy Expression proxy to access ql stuff. * @param store Storage interface to manipulate the metadata. */ public void configure(Configuration conf, PartitionExpressionProxy expressionProxy, MetadataStore store) { this.conf = conf; this.expressionProxy = expressionProxy; this.store = store; this.fileFormatProxy = expressionProxy.getFileFormatProxy(getType()); } /** * Caches the file metadata for a particular file. * @param fileId File id. * @param fs The filesystem of the file. * @param path Path to the file. */ public void cacheFileMetadata(long fileId, FileSystem fs, Path path) throws IOException, InterruptedException { // ORC is in ql, so we cannot do anything here. For now, all the logic is in the proxy. ByteBuffer[] cols = fileFormatProxy.getAddedColumnsToCache(); ByteBuffer[] vals = (cols == null) ? null : new ByteBuffer[cols.length]; ByteBuffer metadata = fileFormatProxy.getMetadataToCache(fs, path, vals); LOG.info("Caching file metadata for " + path + ", size " + metadata.remaining()); store.storeFileMetadata(fileId, metadata, cols, vals); } /** * @return the added column names to be cached in metastore with the metadata for this type. */ public ByteBuffer[] createAddedCols() { return fileFormatProxy.getAddedColumnsToCache(); } /** * @return the values for the added columns returned by createAddedCols for respective metadatas. */ public ByteBuffer[][] createAddedColVals(List<ByteBuffer> metadata) { return fileFormatProxy.getAddedValuesToCache(metadata); } }