brkyvz commented on a change in pull request #28027:
URL: https://github.com/apache/spark/pull/28027#discussion_r525389190
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File path:
sql/catalyst/src/main/java/org/apache/spark/sql/connector/catalog/SupportsMetadataColumns.java
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@@ -0,0 +1,29 @@
+package org.apache.spark.sql.connector.catalog;
+
+import org.apache.spark.annotation.Evolving;
+import org.apache.spark.sql.connector.read.SupportsPushDownRequiredColumns;
+import org.apache.spark.sql.types.StructField;
+import org.apache.spark.sql.types.StructType;
+
+/**
+ * An interface for exposing data columns for a table that are not in the
table schema. For example,
+ * a file source could expose a "file" column that contains the path of the
file that contained each
+ * row.
+ * <p>
Review comment:
Should we talk about the behavior of reserving names for metadata
columns or the behavior that will happen during name collisions here (data
columns will be selected over metadata)?
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