Github user jinfengni commented on a diff in the pull request:
https://github.com/apache/drill/pull/906#discussion_r135708467
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/ScanBatch.java
---
@@ -152,97 +157,75 @@ public void kill(boolean sendUpstream) {
}
}
- private void releaseAssets() {
- container.zeroVectors();
- }
-
- private void clearFieldVectorMap() {
- for (final ValueVector v : mutator.fieldVectorMap().values()) {
- v.clear();
- }
- }
-
@Override
public IterOutcome next() {
if (done) {
return IterOutcome.NONE;
}
oContext.getStats().startProcessing();
try {
- try {
- injector.injectChecked(context.getExecutionControls(),
"next-allocate", OutOfMemoryException.class);
-
- currentReader.allocate(mutator.fieldVectorMap());
- } catch (OutOfMemoryException e) {
- clearFieldVectorMap();
- throw UserException.memoryError(e).build(logger);
- }
- while ((recordCount = currentReader.next()) == 0) {
+ while (true) {
try {
- if (!readers.hasNext()) {
- // We're on the last reader, and it has no (more) rows.
- currentReader.close();
- releaseAssets();
- done = true; // have any future call to next() return NONE
-
- if (mutator.isNewSchema()) {
- // This last reader has a new schema (e.g., we have a
zero-row
- // file or other source). (Note that some sources have a
non-
- // null/non-trivial schema even when there are no rows.)
+ injector.injectChecked(context.getExecutionControls(),
"next-allocate", OutOfMemoryException.class);
+ currentReader.allocate(mutator.fieldVectorMap());
+ } catch (OutOfMemoryException e) {
+ clearFieldVectorMap();
+ throw UserException.memoryError(e).build(logger);
+ }
- container.buildSchema(SelectionVectorMode.NONE);
- schema = container.getSchema();
+ recordCount = currentReader.next();
+ Preconditions.checkArgument(recordCount >= 0,
+ "recordCount from RecordReader.next() should not be negative");
- return IterOutcome.OK_NEW_SCHEMA;
- }
- return IterOutcome.NONE;
- }
- // At this point, the reader that hit its end is not the last
reader.
+ boolean isNewRegularSchema = mutator.isNewSchema();
+ // We should skip the reader, when recordCount = 0 && !
isNewRegularSchema.
+ // Add/set implicit column vectors, only when reader gets > 0 row,
or
+ // when reader gets 0 row but with a schema with new field added
+ if (recordCount > 0 || isNewRegularSchema) {
+ addImplicitVectors();
+ populateImplicitVectors();
+ }
- // If all the files we have read so far are just empty, the
schema is not useful
- if (! hasReadNonEmptyFile) {
- container.clear();
- clearFieldVectorMap();
- mutator.clear();
- }
+ boolean isNewImplicitSchema = mutator.isNewSchema();
+ for (VectorWrapper<?> w : container) {
+ w.getValueVector().getMutator().setValueCount(recordCount);
+ }
+ final boolean isNewSchema = isNewRegularSchema ||
isNewImplicitSchema;
+ oContext.getStats().batchReceived(0, recordCount, isNewSchema);
+ if (recordCount == 0) {
currentReader.close();
- currentReader = readers.next();
- implicitValues = implicitColumns.hasNext() ?
implicitColumns.next() : null;
- currentReader.setup(oContext, mutator);
- try {
- currentReader.allocate(mutator.fieldVectorMap());
- } catch (OutOfMemoryException e) {
- clearFieldVectorMap();
- throw UserException.memoryError(e).build(logger);
+ if (isNewSchema) {
+ // current reader presents a new schema in mutator even though
it has 0 row.
+ // This could happen when data sources have a non-trivial
schema with 0 row.
+ container.buildSchema(SelectionVectorMode.NONE);
+ schema = container.getSchema();
+ if (readers.hasNext()) {
+ advanceNextReader();
+ } else {
+ done = true; // indicates the follow-up next() call will
return IterOutcome.NONE.
+ }
+ return IterOutcome.OK_NEW_SCHEMA;
+ } else { // not a new schema
+ if (readers.hasNext()) {
+ advanceNextReader();
+ continue; // skip reader returning 0 row and having same
schema.
+ // Skip to next loop iteration with next available
reader.
+ } else {
+ releaseAssets(); // All data has been read. Release resource.
+ return IterOutcome.NONE;
+ }
+ }
+ } else { // recordCount > 0
+ if (isNewSchema) {
--- End diff --
Removed one copy of shared code to handle two different cases in revised
patch, though I did not use the idea of state. Hopefully, the new code looks
cleaner.
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