Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/11846#discussion_r56909402
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
---
@@ -620,24 +627,26 @@ class Analyzer(
}
}
- /**
- * In many dialects of SQL it is valid to sort by attributes that are
not present in the SELECT
- * clause. This rule detects such queries and adds the required
attributes to the original
- * projection, so that they will be available during sorting. Another
projection is added to
- * remove these attributes after sorting.
- *
- * This rule also resolves the position number in sort references. This
support is introduced
- * in Spark 2.0. Before Spark 2.0, the integers in Order By has no
effect on output sorting.
- * - When the sort references are not integer but foldable expressions,
ignore them.
- * - When spark.sql.orderByOrdinal is set to false, ignore the position
numbers too.
- */
- object ResolveSortReferences extends Rule[LogicalPlan] {
+ /**
+ * In many dialects of SQL it is valid to use ordinal positions in
order/sort by and group by
+ * clauses. This rule is to convert ordinal positions to the
corresponding expressions in the
+ * select list. This support is introduced in Spark 2.0.
+ *
+ * - When the sort references or group by expressions are not integer but
foldable expressions,
+ * just ignore them.
+ * - When spark.sql.orderByOrdinal/spark.sql.groupByOrdinal is set to
false, ignore the position
+ * numbers too.
+ *
+ * Before the release of Spark 2.0, the literals in order/sort by and
group by clauses
+ * have no effect on the results.
+ */
+ object ResolveOrdinal extends Rule[LogicalPlan] {
--- End diff --
Sure, will do. Thanks!
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