Github user jinfengni commented on a diff in the pull request: https://github.com/apache/drill/pull/906#discussion_r135974310 --- 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)) { --- End diff -- This code has been removed in revised patch.
--- 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. ---