[GitHub] [iceberg] JingsongLi commented on a change in pull request #1353: Core: check that cannot project schema when selected columns is specified

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

JingsongLi commented on a change in pull request #1353:
URL: https://github.com/apache/iceberg/pull/1353#discussion_r472661716



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File path: core/src/main/java/org/apache/iceberg/BaseTableScan.java
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@@ -159,6 +159,10 @@ public TableScan option(String property, String value) {
 
   @Override
   public TableScan project(Schema projectedSchema) {
+    if (context.selectedColumns() != null) {
+      throw new IllegalStateException("Cannot project schema when selected columns is specified.");
+    }

Review comment:
       Another thing is: `BaseTableScan.lazyColumnProjection` looks weird. It looks only work for `DataTableScan`. Because other table scan like `MetadataTableScan`, the file/expected scan schema is different from `table.schema()`. But in `BaseTableScan.lazyColumnProjection`, it use `table.schema()` to select. And for `rowFilter`, it looks only works for `DataTableScan` selection, should not affect `MetadataTableScan`s selection.
   
   In other words, we may need to implement different selections for various scans.




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