ASF GitHub Bot commented on DRILL-5657:

Github user bitblender commented on a diff in the pull request:

    --- Diff: 
    @@ -0,0 +1,91 @@
    + * 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.
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    + */
    +package org.apache.drill.exec.physical.rowSet;
    +import org.apache.drill.exec.physical.rowSet.impl.MaterializedSchema;
    +import org.apache.drill.exec.record.BatchSchema;
    +import org.apache.drill.exec.record.MaterializedField;
    + * Defines the schema of a tuple: either the top-level row or a nested
    + * "map" (really structure). A schema is a collection of columns (backed
    + * by vectors in the loader itself.) Columns are accessible by name or
    + * index. New columns may be added at any time; the new column takes the
    + * next available index.
    + */
    +public interface TupleSchema {
    +  public interface TupleColumnSchema {
    +    MaterializedField schema();
    +    /**
    +     * Report if a column is selected.
    +     * @param colIndex index of the column to check
    +     * @return true if the column is selected (data is collected),
    +     * false if the column is unselected (data is discarded)
    +     */
    +    boolean isSelected();
    --- End diff --
    What does it mean for a  column to be selected? Selected in the query?

> 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.

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