test: Add Spark interop test for Puffin DV reader

Verify pyiceberg's PuffinFile reader can parse deletion vectors written
by Spark. Uses coalesce(1) to force Spark to create DVs instead of COW.

tests/integration/test_puffin_spark_interop.py

@@ -0,0 +1,93 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+import pytest
+from pyspark.sql import SparkSession
+
+from pyiceberg.catalog.rest import RestCatalog
+from pyiceberg.manifest import ManifestContent
+from pyiceberg.table.puffin import PuffinFile
+
+
+def run_spark_commands(spark: SparkSession, sqls: list[str]) -> None:
+    for sql in sqls:
+        spark.sql(sql)
+
+
+@pytest.mark.integration
+def test_read_spark_written_puffin_dv(spark: SparkSession, session_catalog: RestCatalog) -> None:
+    """Verify pyiceberg can read Puffin DVs written by Spark."""
+    identifier = "default.spark_puffin_format_test"
+
+    run_spark_commands(spark, [f"DROP TABLE IF EXISTS {identifier}"])
+    run_spark_commands(
+        spark,
+        [
+            f"""
+            CREATE TABLE {identifier} (id BIGINT)
+            USING iceberg
+            TBLPROPERTIES (
+                'format-version' = '3',
+                'write.delete.mode' = 'merge-on-read'
+            )
+            """,
+        ],
+    )
+
+    df = spark.range(1, 51)
+    df.coalesce(1).writeTo(identifier).append()
+
+    files_before = spark.sql(f"SELECT * FROM {identifier}.files").collect()
+    assert len(files_before) == 1, f"Expected 1 file, got {len(files_before)}"
+
+    run_spark_commands(spark, [f"DELETE FROM {identifier} WHERE id IN (10, 20, 30, 40)"])
+
+    table = session_catalog.load_table(identifier)
+    current_snapshot = table.current_snapshot()
+    assert current_snapshot is not None
+
+    manifests = current_snapshot.manifests(table.io)
+    delete_manifests = [m for m in manifests if m.content == ManifestContent.DELETES]
+    assert len(delete_manifests) > 0, "Expected delete manifest with DVs"
+
+    delete_manifest = delete_manifests[0]
+    entries = list(delete_manifest.fetch_manifest_entry(table.io))
+    assert len(entries) > 0, "Expected at least one delete file entry"
+
+    delete_entry = entries[0]
+    puffin_path = delete_entry.data_file.file_path
+    assert puffin_path.endswith(".puffin"), f"Expected Puffin file, got: {puffin_path}"
+
+    input_file = table.io.new_input(puffin_path)
+    with input_file.open() as f:
+        puffin_bytes = f.read()
+
+    puffin = PuffinFile(puffin_bytes)
+
+    assert len(puffin.footer.blobs) == 1, "Expected exactly one blob"
+
+    blob = puffin.footer.blobs[0]
+    assert blob.type == "deletion-vector-v1"
+    assert "referenced-data-file" in blob.properties
+    assert blob.properties["cardinality"] == "4"
+
+    dv_dict = puffin.to_vector()
+    assert len(dv_dict) == 1, "Expected one data file's deletions"
+
+    for data_file_path, chunked_array in dv_dict.items():
+        positions = chunked_array.to_pylist()
+        assert len(positions) == 4, f"Expected 4 deleted positions, got {len(positions)}"
+        assert sorted(positions) == [9, 19, 29, 39], f"Unexpected positions: {positions}"