Github user jinfengni commented on a diff in the pull request:
https://github.com/apache/drill/pull/906#discussion_r135424090
--- 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()) {
--- End diff --
I'm neither clear nor convinced that using internal state (such as
NO_READER) )would make the code clearer. But if you have such idea implemented
in your patch, why don't we review such idea later on?
To some degree, everything we do is "temporary"; as we continue to improve
Drill, nothing is implied to be "permanent".
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