Github user paul-rogers commented on a diff in the pull request:
https://github.com/apache/drill/pull/1138#discussion_r171606330
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/store/avro/AvroRecordReader.java
---
@@ -154,6 +156,12 @@ public int next() {
writer.setValueCount(recordCount);
+ // adds fields which don't exist in the table but should be present
in the schema
+ if (recordCount > 0) {
+ JsonReaderUtils.ensureAtLeastOneField(writer, getColumns(), false,
--- End diff --
In general, this is a bad idea, though existing code does this. If we find
an empty file in one scanner, but a real file in another, we create an
unnecessary schema change by making up a column.
Jinfeng's changes last year are supposed to handle the "fast none" case of
a reader with no rows. There should be no reason to add a dummy column. Old
code that adds such a column should be fixed. IMHO, code that does not add
dummy columns should not begin to do so.
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