echauchot commented on code in PR #3: URL: https://github.com/apache/flink-connector-cassandra/pull/3#discussion_r1089146562
########## flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/CassandraSource.java: ########## @@ -0,0 +1,162 @@ +/* + * 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.flink.connector.cassandra.source; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.annotation.PublicEvolving; +import org.apache.flink.annotation.VisibleForTesting; +import org.apache.flink.api.common.ExecutionConfig; +import org.apache.flink.api.common.typeinfo.TypeInformation; +import org.apache.flink.api.connector.source.Boundedness; +import org.apache.flink.api.connector.source.Source; +import org.apache.flink.api.connector.source.SourceReader; +import org.apache.flink.api.connector.source.SourceReaderContext; +import org.apache.flink.api.connector.source.SplitEnumerator; +import org.apache.flink.api.connector.source.SplitEnumeratorContext; +import org.apache.flink.api.java.ClosureCleaner; +import org.apache.flink.api.java.typeutils.ResultTypeQueryable; +import org.apache.flink.connector.cassandra.source.enumerator.CassandraEnumeratorState; +import org.apache.flink.connector.cassandra.source.enumerator.CassandraEnumeratorStateSerializer; +import org.apache.flink.connector.cassandra.source.enumerator.CassandraSplitEnumerator; +import org.apache.flink.connector.cassandra.source.reader.CassandraSourceReader; +import org.apache.flink.connector.cassandra.source.reader.CassandraSplitReader; +import org.apache.flink.connector.cassandra.source.split.CassandraSplit; +import org.apache.flink.connector.cassandra.source.split.CassandraSplitSerializer; +import org.apache.flink.core.io.SimpleVersionedSerializer; +import org.apache.flink.streaming.connectors.cassandra.ClusterBuilder; +import org.apache.flink.streaming.connectors.cassandra.MapperOptions; + +import static org.apache.flink.util.Preconditions.checkNotNull; +import static org.apache.flink.util.Preconditions.checkState; + +/** + * A bounded source to read from Cassandra and return a collection of entities as {@code + * DataStream<Entity>}. An entity is built by Cassandra mapper ({@code + * com.datastax.driver.mapping.EntityMapper}) based on a POJO containing annotations (as described + * in <a + * href="https://docs.datastax.com/en/developer/java-driver/3.11/manual/object_mapper/creating/";> + * Cassandra object mapper</a>). + * + * <p>To use it, do the following: + * + * <pre>{@code + * ClusterBuilder clusterBuilder = new ClusterBuilder() { + * @Override + * protected Cluster buildCluster(Cluster.Builder builder) { + * return builder.addContactPointsWithPorts(new InetSocketAddress(HOST,PORT)) + * .withQueryOptions(new QueryOptions().setConsistencyLevel(CL)) + * .withSocketOptions(new SocketOptions() + * .setConnectTimeoutMillis(CONNECT_TIMEOUT) + * .setReadTimeoutMillis(READ_TIMEOUT)) + * .build(); + * } + * }; + * Source cassandraSource = new CassandraSource(clusterBuilder, + * Pojo.class, + * "select ... from KEYSPACE.TABLE ...;", + * () -> new Mapper.Option[] {Mapper.Option.saveNullFields(true)}); + * + * DataStream<Pojo> stream = env.fromSource(cassandraSource, WatermarkStrategy.noWatermarks(), + * "CassandraSource"); + * }</pre> + */ +@PublicEvolving +public class CassandraSource<OUT> + implements Source<OUT, CassandraSplit, CassandraEnumeratorState>, ResultTypeQueryable<OUT> { + + public static final String CQL_PROHIBITTED_CLAUSES_REGEXP = + "(?i).*(AVG|COUNT|MIN|MAX|SUM|ORDER|GROUP BY).*"; + private static final long serialVersionUID = 7773196541275567433L; + + private final ClusterBuilder clusterBuilder; + private final Class<OUT> pojoClass; + private final String query; + private final MapperOptions mapperOptions; + + public CassandraSource( + ClusterBuilder clusterBuilder, + Class<OUT> pojoClass, + String query, + MapperOptions mapperOptions) { + checkNotNull(clusterBuilder, "ClusterBuilder required but not provided"); + checkNotNull(pojoClass, "POJO class required but not provided"); + checkQueryValidity(query); + this.clusterBuilder = clusterBuilder; + ClosureCleaner.clean(clusterBuilder, ExecutionConfig.ClosureCleanerLevel.RECURSIVE, true); + this.pojoClass = pojoClass; + this.query = query; + this.mapperOptions = mapperOptions; + } + + @Override + public Boundedness getBoundedness() { + return Boundedness.BOUNDED; + } + + @Internal + @Override + public SourceReader<OUT, CassandraSplit> createReader(SourceReaderContext readerContext) { + return new CassandraSourceReader<>( + readerContext, clusterBuilder, pojoClass, query, mapperOptions); + } + + @Internal + @Override + public SplitEnumerator<CassandraSplit, CassandraEnumeratorState> createEnumerator( + SplitEnumeratorContext<CassandraSplit> enumContext) { + return new CassandraSplitEnumerator(enumContext, null, clusterBuilder); + } + + @Internal + @Override + public SplitEnumerator<CassandraSplit, CassandraEnumeratorState> restoreEnumerator( + SplitEnumeratorContext<CassandraSplit> enumContext, + CassandraEnumeratorState enumCheckpoint) { + return new CassandraSplitEnumerator(enumContext, enumCheckpoint, clusterBuilder); + } + + @Internal + @Override + public SimpleVersionedSerializer<CassandraSplit> getSplitSerializer() { + return CassandraSplitSerializer.INSTANCE; + } + + @Internal + @Override + public SimpleVersionedSerializer<CassandraEnumeratorState> getEnumeratorCheckpointSerializer() { + return CassandraEnumeratorStateSerializer.INSTANCE; + } + + @Override + public TypeInformation<OUT> getProducedType() { + return TypeInformation.of(pojoClass); + } + + @VisibleForTesting + public static void checkQueryValidity(String query) { + checkNotNull(query, "query required but not provided"); + checkState( + query.matches(CassandraSplitReader.SELECT_REGEXP), + "query must be of the form select ... from keyspace.table ...;"); + checkState( + !query.matches(CQL_PROHIBITTED_CLAUSES_REGEXP), + "query must not contain aggregate or order clauses because they will be done per split. " + + "So they will be incorrect after merging the splits"); Review Comment: Ok I'll rephrase to your suggestion. Regarding pushdown I agree, it will be needed in the future but is out of the scope of the current PR. So I suggest we keep aggregates unsupported in this PR and open a ticket to keep track of this future feature. -- 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. To unsubscribe, e-mail: issues-unsubscr...@flink.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
