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https://issues.apache.org/jira/browse/DRILL-7442?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16973055#comment-16973055
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ASF GitHub Bot commented on DRILL-7442:
---------------------------------------
paul-rogers commented on pull request #1897: DRILL-7442: Create multi-batch row
set reader
URL: https://github.com/apache/drill/pull/1897#discussion_r345589747
##########
File path:
exec/vector/src/main/java/org/apache/drill/exec/vector/accessor/reader/AbstractTupleReader.java
##########
@@ -87,6 +87,13 @@ public void bindNullState(NullStateReader nullStateReader) {
this.nullStateReader = nullStateReader;
}
+ @Override
+ public void rebind() {
+ for (int i = 0; i < readers.length; i++) {
+ readers[i].events().rebind();
+ }
Review comment:
Generally I do use the iterator form. However, the readers and writers are
inner-loop code: old-fashioned index looping is faster and avoids creating heap
objects. The code here was specifically designed for index looping. That is why
the implementation uses an array, not a list; no method call is needed to get
the item.
Just to be clear, with an iterator, there are at least two method calls per
item:
* `hasNext()`
* `next()`
While, with an list, there is a third call:
* `get()`
With an array and old-school loop there are no method calls.
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> Create multi-batch row set reader
> ---------------------------------
>
> Key: DRILL-7442
> URL: https://issues.apache.org/jira/browse/DRILL-7442
> Project: Apache Drill
> Issue Type: Improvement
> Reporter: Paul Rogers
> Assignee: Paul Rogers
> Priority: Minor
>
> The "row set" work provided a {{RowSetWriter}} and {{RowSetReader}} to write
> to and read from a single batch. The {{ResultSetLoader}} class provided a
> writer that spans multiple batches, handling schema changes across batches
> and so on.
> This ticket introduces a reader equivalent, the {{ResultSetReader}} that
> reads an entire result set of multiple batches, handling schema changes along
> the way.
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