Github user paul-rogers commented on a diff in the pull request:
https://github.com/apache/drill/pull/906#discussion_r134628593
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/project/ProjectRecordBatch.java
---
@@ -768,4 +765,73 @@ else if (exprHasPrefix && refHasPrefix) {
}
}
}
+
+ /**
+ * handle FAST NONE specially when Project for query output. This
happens when input returns a
+ * FAST NONE directly ( input does not return any batch with
schema/data).
+ *
+ * Project operator has to return a batch with schema derived using the
following 3 rules:
+ * Case 1: * ==> expand into an empty list of columns.
+ * Case 2: regular column reference ==> treat as nullable-int column
+ * Case 3: expressions => Call ExpressionTreeMaterialization over an
empty vector contain.
+ * Once the expression is materialized without error, use the
output type of materialized
+ * expression.
+ * The batch is constructed with the above rules, and recordCount = 0.
+ * Returned with OK_NEW_SCHEMA to down-stream operator.
+ */
+ @Override
+ protected IterOutcome handleFastNone() {
+ if (! popConfig.isOutputProj()) {
+ return super.handleFastNone();
+ }
+
+ allocationVectors = new ArrayList<>();
+ final List<NamedExpression> exprs = getExpressionList();
+ final ErrorCollector collector = new ErrorCollectorImpl();
+ VectorContainer fakedIncomingVC = new VectorContainer();
+
+ for (NamedExpression namedExpression : exprs) {
+ if (namedExpression.getExpr() instanceof SchemaPath) {
+ final NameSegment expr = ((SchemaPath)
namedExpression.getExpr()).getRootSegment();
+ if (expr.getPath().contains(StarColumnHelper.STAR_COLUMN)) {
+ continue; // * would expand into an empty list.
+ } else {
+ final TypeProtos.MajorType majorType =
TypeProtos.MajorType.newBuilder()
+ .setMinorType(MinorType.INT)
+ .setMode(TypeProtos.DataMode.OPTIONAL)
+ .build();
+
+ MaterializedField outputField =
MaterializedField.create(namedExpression.getRef().getRootSegment().getPath(),
majorType);
+ final ValueVector vv = container.addOrGet(outputField, callBack);
--- End diff --
Does this code handle map columns? `map1.nestedMap.col`?
Does this code handle references to arrays, such as `columns[2]` for a CSV
file?
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---
