arina-ielchiieva commented on a change in pull request #1501: DRILL-6791: Scan projection framework URL: https://github.com/apache/drill/pull/1501#discussion_r233450250
########## File path: exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/scan/project/MetadataManager.java ########## @@ -0,0 +1,73 @@ +/* + * 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.exec.physical.impl.scan.project; + +import org.apache.drill.exec.physical.impl.scan.project.ScanLevelProjection.ScanProjectionParser; +import org.apache.drill.exec.physical.impl.scan.project.SchemaLevelProjection.SchemaProjectionResolver; +import org.apache.drill.exec.physical.rowSet.ResultVectorCache; + +/** + * Queries can contain a wildcard (*), table columns, or special + * system-defined columns (the file metadata columns AKA implicit + * columns, the `columns` column of CSV, etc.). + * <p> + * This class provides a generalized way of handling such extended + * columns. That is, this handles metadata for columns defined by + * the scan or file; columns defined by the table (the actual + * data metadata) is handled elsewhere. + * <p> + * Objects of this interface are driven by the projection processing + * framework which provides a vector cache from which to obtain + * materialized columns. The implementation must provide a projection + * parser to pick out the columns which this object handles. + * <p> + * A better name might be ImplicitMetadataManager to signify that Review comment: Agree, let's rename to avoid the confusion in future. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on 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
