[GitHub] [arrow-datafusion] thinkharderdev commented on a diff in pull request #2170: Handle merged schemas in parquet pruning

[GitBox <gi...@apache.org>]

thinkharderdev commented on code in PR #2170:
URL: https://github.com/apache/arrow-datafusion/pull/2170#discussion_r844308448


##########
datafusion/core/src/physical_plan/file_format/parquet.rs:
##########
@@ -878,6 +880,39 @@ mod tests {
         assert_batches_sorted_eq!(expected, &read);
     }
 
+    #[tokio::test]
+    async fn evolved_schema_intersection_filter() {
+        let c1: ArrayRef =
+            Arc::new(StringArray::from(vec![Some("Foo"), None, Some("bar")]));
+
+        let c2: ArrayRef = Arc::new(Int64Array::from(vec![Some(1), Some(2), None]));
+
+        let c3: ArrayRef = Arc::new(Int8Array::from(vec![Some(10), Some(20), None]));
+
+        // batch1: c1(string), c2(int64), c3(int8)
+        let batch1 = create_batch(vec![("c1", c1), ("c3", c3.clone())]);
+
+        // batch2: c3(int8), c2(int64), c1(string)
+        let batch2 = create_batch(vec![("c3", c3), ("c2", c2)]);
+
+        let filter = col("c2").eq(lit(0_i64));
+
+        // read/write them files:
+        let read = round_trip_to_parquet(vec![batch1, batch2], None, None, Some(filter))
+            .await
+            .unwrap();
+        let expected = vec![
+            "+-----+----+----+",
+            "| c1  | c3 | c2 |",

Review Comment:
   Yeah, this looked wrong to me as well. What I think is happening is that the min/max aren't set the pruning predicates aren't applied. In a "real" query where this predicate was pushed down from a filter stage this would still get piped into a `FilerExec`. I think we would have to special case the scenario where we fill in a null column to conform to a merged schema which may be worth doing. I can double check though and make sure there's not a bug here. 



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