Fix mis-pruned data files

Author: dentiny

src/storage/ducklake_metadata_manager.cpp

@@ -1306,13 +1306,19 @@ FilterSQLResult DuckLakeMetadataManager::ConvertFilterPushdownToSQL(const Filter
 		if (!conditions.empty()) {
 			conditions += " AND ";
 		}
+		// Files that have no stats entry for this column (i.e., written before the column was added) must
+		// NOT be pruned, we cannot determine filter satisfaction without stats.
 		if (needs_value_count_guard) {
-			conditions += StringUtil::Format("data.data_file_id IN (SELECT data_file_id FROM %s WHERE "
-			                                 "(value_count IS NULL OR value_count > 0) AND (%s(%s)))",
-			                                 cte_name, null_checks.c_str(), filter_condition.c_str());
+			conditions += StringUtil::Format(
+			    "(NOT EXISTS (SELECT 1 FROM %s s WHERE s.data_file_id = data.data_file_id) OR "
+			    "EXISTS (SELECT 1 FROM %s s WHERE s.data_file_id = data.data_file_id "
+			    "AND (value_count IS NULL OR value_count > 0) AND (%s(%s))))",
+			    cte_name, cte_name, null_checks.c_str(), filter_condition.c_str());
 		} else {
-			conditions += StringUtil::Format("data.data_file_id IN (SELECT data_file_id FROM %s WHERE %s(%s))",
-			                                 cte_name, null_checks.c_str(), filter_condition.c_str());
+			conditions += StringUtil::Format(
+			    "(NOT EXISTS (SELECT 1 FROM %s s WHERE s.data_file_id = data.data_file_id) OR "
+			    "EXISTS (SELECT 1 FROM %s s WHERE s.data_file_id = data.data_file_id AND %s(%s)))",
+			    cte_name, cte_name, null_checks.c_str(), filter_condition.c_str());
 		}
 
 		CTERequirement req(column_filter.column_field_index, referenced_stats);

test/sql/issues/issue_1135.test

@@ -0,0 +1,31 @@
+# name: test/sql/issues/issue_1135.test
+# description: Test that filter pushdown works correctly with columns added via ALTER TABLE ADD COLUMN with DEFAULT
+# group: [issues]
+
+require ducklake
+
+require parquet
+
+test-env DUCKLAKE_CONNECTION __TEST_DIR__/{UUID}.db
+
+test-env DATA_PATH __TEST_DIR__
+
+statement ok
+ATTACH 'ducklake:${DUCKLAKE_CONNECTION}' AS duck (DATA_PATH '${DATA_PATH}/issue_1135')
+
+statement ok
+CREATE TABLE duck.tbl (a INT);
+
+statement ok
+INSERT INTO duck.tbl SELECT i FROM range(10) t(i);
+
+statement ok
+CALL ducklake_flush_inlined_data('duck')
+
+statement ok
+ALTER TABLE duck.tbl ADD COLUMN b INT DEFAULT 42;
+
+query I
+SELECT count(*) FROM duck.tbl WHERE b = 42;
+----
+10