[GitHub] [iceberg] zhangjun0x01 commented on a change in pull request #1822: Flink: add limit pushdown for IcebergTableSource

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

zhangjun0x01 commented on a change in pull request #1822:
URL: https://github.com/apache/iceberg/pull/1822#discussion_r535791036



##########
File path: flink/src/main/java/org/apache/iceberg/flink/IcebergTableSource.java
##########
@@ -36,25 +36,30 @@
 
 /**
  * Flink Iceberg table source.
- * TODO: Implement {@link FilterableTableSource} and {@link LimitableTableSource}.
+ * TODO: Implement {@link FilterableTableSource}
  */
-public class IcebergTableSource implements StreamTableSource<RowData>, ProjectableTableSource<RowData> {
+public class IcebergTableSource
+    implements StreamTableSource<RowData>, ProjectableTableSource<RowData>, LimitableTableSource<RowData> {
 
   private final TableLoader loader;
   private final TableSchema schema;
   private final Map<String, String> properties;
   private final int[] projectedFields;
+  private boolean isLimitPushDown = false;
+  private long limit = -1L;

Review comment:
       I also think we can judge whether to pushdown by the value of limit, but the  [LimitableTableSource](https://github.com/apache/flink/blob/release-1.11/flink-table/flink-table-common/src/main/java/org/apache/flink/table/sources/LimitableTableSource.java) interface provides two methods, `isLimitPushedDown` and `applyLimit`. From the method comments, I think the author wants to judge whether to pushdown by the `isLimitPushedDown` method.
   
   In versions after flink 1.12, a new interface [SupportsLimitPushDown](https://github.com/apache/flink/blob/release-1.12/flink-table/flink-table-common/src/main/java/org/apache/flink/table/connector/source/abilities/SupportsLimitPushDown.java) is provided. This interface only provides one method. I think we can judge pushdown by the value of limit
   
   




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