paul-rogers commented on a change in pull request #2060: DRILL-7706: Implement Drill RDBMS Metastore for Tables component URL: https://github.com/apache/drill/pull/2060#discussion_r410834619
########## File path: metastore/rdbms-metastore/src/main/java/org/apache/drill/metastore/rdbms/operate/RdbmsRead.java ########## @@ -0,0 +1,146 @@ +/* + * 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.drill.metastore.rdbms.operate; + +import org.apache.drill.metastore.operate.AbstractRead; +import org.apache.drill.metastore.operate.MetadataTypeValidator; +import org.apache.drill.metastore.operate.Read; +import org.apache.drill.metastore.rdbms.RdbmsMetastoreContext; +import org.apache.drill.metastore.rdbms.exception.RdbmsMetastoreException; +import org.apache.drill.metastore.rdbms.transform.MetadataMapper; +import org.jooq.Condition; +import org.jooq.DSLContext; +import org.jooq.Field; +import org.jooq.Record; +import org.jooq.Result; +import org.jooq.exception.DataAccessException; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.util.ArrayList; +import java.util.Arrays; +import java.util.Collections; +import java.util.List; +import java.util.Set; +import java.util.stream.Collectors; +import java.util.stream.IntStream; + +/** + * Implementation of {@link Read} interface based on {@link AbstractRead} parent class. + * Reads information from RDBMS tables based on given filter expression. + * Supports reading information for specific columns. + * + * @param <T> Metastore component unit type + */ +public class RdbmsRead<T> extends AbstractRead<T> { Review comment: Very painful experience with Impala tells us that, when Drill is used under load, there must be some form of metadata cache or either a) performance suffers, or b) the DB becomes a bottleneck. Does this design lend itself to caching? How will we know, without flushing and reloading, that metadata for some data item changed? ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
