vvysotskyi commented on a change in pull request #1839: DRILL-4517: Support
reading empty Parquet files
URL: https://github.com/apache/drill/pull/1839#discussion_r312738641
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File path:
exec/java-exec/src/main/java/org/apache/drill/exec/expr/IsPredicate.java
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@@ -121,15 +121,28 @@ static boolean hasNoNulls(ColumnStatistics stat) {
}
/**
- * Checks that column chunk's statistics has only nulls
+ * Checks that column chunk's statistics has only nulls.
+ * <p/>
+ * Besides comparing number of nulls, we need to check
+ * if min and max values are also nulls to cover use cases for arrays,
+ * since array can hold N number of elements and nulls statistics
+ * is collected for all elements, thus number of nulls may be greater
+ * or equal to the number of rows.
+ * <p/>
+ * Two rows: [null, {"id": 1}], [null, {"id": 2]]
Review comment:
```suggestion
* Two rows: [null, {"id": 1}], [null, {"id": 2}]
```
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