Github user jinfengni commented on a diff in the pull request:
https://github.com/apache/drill/pull/906#discussion_r135709915
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/ScanBatch.java
---
@@ -252,14 +235,28 @@ public IterOutcome next() {
}
}
+ private void releaseAssets() {
+ container.zeroVectors();
+ }
+
+ private void clearFieldVectorMap() {
+ for (final ValueVector v : mutator.fieldVectorMap().values()) {
+ v.clear();
+ }
+ }
+
+ private void advanceNextReader() throws ExecutionSetupException {
+ currentReader = readers.next();
+ implicitValues = implicitColumns.hasNext() ? implicitColumns.next() :
null;
+ currentReader.setup(oContext, mutator);
--- End diff --
Nice catch. You are right we should not advance to next reader if we need
pass a batch to downstream, since `reader.setup()` for new reader could modify
both mutator and container. This seems to be true for original ScanBatch code
as well.
In the revised batch, I remove the code to get next reader in constructor,
and put the code to get next reader in the beginning of loop when needed. In
case of return a `OK_NEW_SCHEMA`, we will only get next reader in the next
`next()` method call after `OK_NEW_SCHEMA` is returned.
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