test: DH-18259: Add empty-table test for Iceberg (#6678)

extensions/iceberg/src/test/java/io/deephaven/iceberg/Pyiceberg2Test.java

@@ -35,6 +35,7 @@
 class Pyiceberg2Test {
     private static final Namespace NAMESPACE = Namespace.of("trading");
     private static final TableIdentifier TRADING_DATA = TableIdentifier.of(NAMESPACE, "data");
+    private static final TableIdentifier EMPTY_DATA = TableIdentifier.of(NAMESPACE, "data_empty");
 
     // This will need to be updated if the data is regenerated
     private static final long SNAPSHOT_1_ID = 2806418501596315192L;
@@ -55,7 +56,7 @@ void setUp() throws URISyntaxException {
     @Test
     void catalogInfo() {
         assertThat(catalogAdapter.listNamespaces()).containsExactly(NAMESPACE);
-        assertThat(catalogAdapter.listTables(NAMESPACE)).containsExactly(TRADING_DATA);
+        assertThat(catalogAdapter.listTables(NAMESPACE)).containsExactly(TRADING_DATA, EMPTY_DATA);
 
         final IcebergTableAdapter tableAdapter = catalogAdapter.loadTable(TRADING_DATA);
         final List<Snapshot> snapshots = tableAdapter.listSnapshots();
@@ -105,4 +106,17 @@ void testData() {
         TstUtils.assertTableEquals(expectedData.sort("datetime", "symbol"),
                 fromIceberg.sort("datetime", "symbol"));
     }
+
+    @Test
+    void testEmpty() {
+        final IcebergTableAdapter tableAdapter = catalogAdapter.loadTable(EMPTY_DATA);
+        final Table fromIceberg = tableAdapter.table();
+        assertThat(fromIceberg.size()).isEqualTo(0);
+        final Table expectedData = TableTools.newTable(TABLE_DEFINITION,
+                TableTools.col("datetime", new LocalDateTime[0]),
+                TableTools.stringCol("symbol"),
+                TableTools.doubleCol("bid"),
+                TableTools.doubleCol("ask"));
+        TstUtils.assertTableEquals(expectedData, fromIceberg);
+    }
 }

extensions/iceberg/src/test/resources/io/deephaven/iceberg/sqlite/db_resource/catalogs/pyiceberg-2/trading.db/data_empty/metadata/00000-ba9e11f2-a7b1-43bb-9cac-7d9081820b06.metadata.json

@@ -0,0 +1 @@
+{"location":"catalogs/pyiceberg-2/trading.db/data_empty","table-uuid":"c6d40ecb-6228-4ce8-b5a9-b7d27c965fb2","last-updated-ms":1740686637766,"last-column-id":4,"schemas":[{"type":"struct","fields":[{"id":1,"name":"datetime","type":"timestamp","required":false},{"id":2,"name":"symbol","type":"string","required":false},{"id":3,"name":"bid","type":"double","required":false},{"id":4,"name":"ask","type":"double","required":false}],"schema-id":0,"identifier-field-ids":[]}],"current-schema-id":0,"partition-specs":[{"spec-id":0,"fields":[{"source-id":1,"field-id":1000,"transform":"day","name":"datetime_day"},{"source-id":2,"field-id":1001,"transform":"identity","name":"symbol"}]}],"default-spec-id":0,"last-partition-id":1001,"properties":{},"snapshots":[],"snapshot-log":[],"metadata-log":[],"sort-orders":[{"order-id":0,"fields":[]}],"default-sort-order-id":0,"refs":{},"format-version":2,"last-sequence-number":0}

extensions/iceberg/src/test/resources/io/deephaven/iceberg/sqlite/db_resource/generate-pyiceberg-2.py

@@ -56,3 +56,11 @@
 
 # Append the table to the Iceberg table
 tbl.append(table)
+
+######## Empty table testing ########
+
+tbl_empty = catalog.create_table(
+    identifier="trading.data_empty",
+    schema=schema,
+    partition_spec=partition_spec,
+)