paul-rogers commented on a change in pull request #1618: DRILL-6950: Row set-based scan framework URL: https://github.com/apache/drill/pull/1618#discussion_r251218457
########## File path: exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/scan/columns/ColumnsArrayParser.java ########## @@ -0,0 +1,173 @@ +/* + * 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.columns; + +import org.apache.drill.common.exceptions.UserException; +import org.apache.drill.exec.physical.impl.scan.project.ColumnProjection; +import org.apache.drill.exec.physical.impl.scan.project.ScanLevelProjection; +import org.apache.drill.exec.physical.impl.scan.project.ScanLevelProjection.ScanProjectionParser; +import org.apache.drill.exec.physical.impl.scan.project.UnresolvedColumn; +import org.apache.drill.exec.physical.rowSet.project.RequestedColumnImpl; +import org.apache.drill.exec.physical.rowSet.project.RequestedTuple.RequestedColumn; +import org.apache.drill.exec.store.easy.text.compliant.RepeatedVarCharOutput; + +/** + * Parses the `columns` array. Doing so is surprisingly complex. + * <ul> + * <li>Depending on what is known about the input file, the `columns` + * array may be required or optional.</li> + * <li>If the columns array is required, then the wildcard (`*`) + * expands to `columns`.</li> + * <li>If the columns array appears, then no other table columns + * can appear.</li> + * <li>If the columns array appears, then the wildcard cannot also + * appear, unless that wildcard expanded to be `columns` as + * described above.</li> + * <li>The query can select specific elements such as `columns`[2]. + * In this case, only array elements can appear, not the unindexed + * `columns` column.</li> + * </ul> + * <p> + * It falls to this parser to detect a not-uncommon user error, a + * query such as the following:<pre><code> + * SELECT max(columns[1]) AS col1 + * FROM cp.`textinput/input1.csv` + * WHERE col1 IS NOT NULL + * </code></pre> + * In standard SQL, column aliases are not allowed in the WHERE + * clause. So, Drill will push two columns down to the scan operator: + * `columns`[1] and `col1`. This parser will detect the "extra" + * columns and must provide a message that helps the user identify + * the likely original problem. + */ + +public class ColumnsArrayParser implements ScanProjectionParser { + static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(ColumnsArrayParser.class); + + // Config + + private final boolean requireColumnsArray; + + // Internals + + private ScanLevelProjection builder; + + // Output + + private UnresolvedColumnsArrayColumn columnsArrayCol; + + public ColumnsArrayParser(boolean requireColumnsArray) { + this.requireColumnsArray = requireColumnsArray; + } + + @Override + public void bind(ScanLevelProjection builder) { + this.builder = builder; + } + + @Override + public boolean parse(RequestedColumn inCol) { + if (requireColumnsArray && inCol.isWildcard()) { + expandWildcard(); + return true; + } + if (! inCol.nameEquals(ColumnsArrayManager.COLUMNS_COL)) { + return false; + } + + // The columns column cannot be a map. That is, the following is + // not allowed: columns.foo. + + if (inCol.isTuple()) { + throw UserException + .validationError() + .message("{} has mep elements, but cannot be a map", inCol.name()) Review comment: Done. Shows you are reading carefully... ---------------------------------------------------------------- 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: us...@infra.apache.org With regards, Apache Git Services
