org.apache.hadoop.hive.ql.metadata.TableIterable Maven / Gradle / Ivy
/**
* 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.ql.metadata;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.apache.hadoop.hive.metastore.IMetaStoreClient;
import org.apache.hadoop.hive.metastore.api.Table;
import org.apache.thrift.TException;
/**
* Use this to get Table objects for a table list. It provides an iterator to
* on the resulting Table objects. It batches the calls to
* IMetaStoreClient.getTableObjectsByName to avoid OOM issues in HS2 (with
* embedded metastore) or MetaStore server (if HS2 is using remote metastore).
*
*/
public class TableIterable implements Iterable {
@Override
public Iterator iterator() {
return new Iterator() {
private final Iterator tableNamesIter = tableNames.iterator();
private Iterator batchIter = null;
@Override
public boolean hasNext() {
return ((batchIter != null) && batchIter.hasNext()) || tableNamesIter.hasNext();
}
@Override
public Table next() {
if ((batchIter == null) || !batchIter.hasNext()) {
getNextBatch();
}
return batchIter.next();
}
private void getNextBatch() {
// get next batch of table names in this list
List nameBatch = new ArrayList();
int batch_counter = 0;
while (batch_counter < batch_size && tableNamesIter.hasNext()) {
nameBatch.add(tableNamesIter.next());
batch_counter++;
}
// get the Table objects for this batch of table names and get iterator
// on it
try {
try {
batchIter = msc.getTableObjectsByName(dbname, nameBatch).iterator();
} catch (TException e) {
throw new HiveException(e);
}
} catch (HiveException e) {
throw new RuntimeException(e);
}
}
@Override
public void remove() {
throw new IllegalStateException(
"TableIterable is a read-only iterable and remove() is unsupported");
}
};
}
private final IMetaStoreClient msc;
private final String dbname;
private final List tableNames;
private final int batch_size;
/**
* Primary constructor that fetches all tables in a given msc, given a Hive
* object,a db name and a table name list
*/
public TableIterable(IMetaStoreClient msc, String dbname, List tableNames, int batch_size)
throws TException {
this.msc = msc;
this.dbname = dbname;
this.tableNames = tableNames;
this.batch_size = batch_size;
}
}
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