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ASF GitHub Bot commented on DRILL-5657: --------------------------------------- Github user bitblender commented on a diff in the pull request: https://github.com/apache/drill/pull/914#discussion_r137852118 --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/physical/rowSet/impl/package-info.java --- @@ -0,0 +1,295 @@ +/* + * 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. + */ + +/** + * Handles the details of the result set loader implementation. + * <p> + * The primary purpose of this loader, and the most complex to understand and + * maintain, is overflow handling. + * + * <h4>Detailed Use Cases</h4> + * + * Let's examine it by considering a number of + * use cases. + * <table style="border: 1px solid; border-collapse: collapse;"> + * <tr><th>Row</th><th>a</th><th>b</th><th>c</th><th>d</th><th>e</th><th>f</th><th>g</th><th>h</th></tr> + * <tr><td>n-2</td><td>X</td><td>X</td><td>X</td><td>X</td><td>X</td><td>X</td><td>-</td><td>-</td></tr> + * <tr><td>n-1</td><td>X</td><td>X</td><td>X</td><td>X</td><td> </td><td> </td><td>-</td><td>-</td></tr> + * <tr><td>n </td><td>X</td><td>!</td><td>O</td><td> </td><td>O</td><td> </td><td>O</td><td> </td></tr> + * </table> + * Here: + * <ul> + * <li>n-2, n-1, and n are rows. n is the overflow row.</li> + * <li>X indicates a value was written before overflow.</li> + * <li>Blank indicates no value was written in that row.</li> + * <li>! indicates the value that triggered overflow.</li> + * <li>- indicates a column that did not exist prior to overflow.</li> --- End diff -- What does an 'O' value mean in the diagram above? > Implement size-aware result set loader > -------------------------------------- > > Key: DRILL-5657 > URL: https://issues.apache.org/jira/browse/DRILL-5657 > Project: Apache Drill > Issue Type: Improvement > Affects Versions: Future > Reporter: Paul Rogers > Assignee: Paul Rogers > Fix For: Future > > > A recent extension to Drill's set of test tools created a "row set" > abstraction to allow us to create, and verify, record batches with very few > lines of code. Part of this work involved creating a set of "column > accessors" in the vector subsystem. Column readers provide a uniform API to > obtain data from columns (vectors), while column writers provide a uniform > writing interface. > DRILL-5211 discusses a set of changes to limit value vectors to 16 MB in size > (to avoid memory fragmentation due to Drill's two memory allocators.) The > column accessors have proven to be so useful that they will be the basis for > the new, size-aware writers used by Drill's record readers. > A step in that direction is to retrofit the column writers to use the > size-aware {{setScalar()}} and {{setArray()}} methods introduced in > DRILL-5517. > Since the test framework row set classes are (at present) the only consumer > of the accessors, those classes must also be updated with the changes. > This then allows us to add a new "row mutator" class that handles size-aware > vector writing, including the case in which a vector fills in the middle of a > row. -- This message was sent by Atlassian JIRA (v6.4.14#64029)