Fix singleton array column sample extraction - #3231

cpp/heimdall_common/array_column_view.hpp (1)

123-123: 🎯 Functional Correctness | 🔵 Trivial | ⚡ Quick win

Add a one-sample regression test through table_data.

The existing tests do not cover this boundary. The DuckDB scan calls request_range(), not request_sample(). The PostgreSQL table_scan path calls table_data::get_column_value(), but the existing fixtures contain multiple rows, so the old samples_count() == 1 branch is not taken.

Add a one-row array test with pg_deeplake.use_deeplake_executor disabled. Assert that the returned value is [1, 2, 3], not a nested one-sample array.

Suggested fix

+@pytest.mark.asyncio
+async def test_one_sample_array_uses_sample_index(db_conn: asyncpg.Connection):
+    table_name = "array_one_sample_test"
+
+    try:
+        await db_conn.execute("SET pg_deeplake.use_deeplake_executor = off")
+        await db_conn.execute(f"""
+            CREATE TABLE {table_name} (
+                array_1d int4[]
+            ) USING deeplake
+        """)
+        await db_conn.execute(
+            f"INSERT INTO {table_name} (array_1d) VALUES (ARRAY[1, 2, 3]::int4[])"
+        )
+
+        row = await db_conn.fetchrow(f"SELECT array_1d FROM {table_name}")
+        assert row["array_1d"] == [1, 2, 3]
+    finally:
+        await db_conn.execute("RESET pg_deeplake.use_deeplake_executor")
+        await db_conn.execute(f"DROP TABLE IF EXISTS {table_name} CASCADE")

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Review comment at @cpp/heimdall_common/array_column_view.hpp at line 123:
Add a PostgreSQL regression test through table_data for a one-row array, using
the existing test conventions and disabling pg_deeplake.use_deeplake_executor
during the scan. Assert the fetched value is [1, 2, 3], and restore the setting
and clean up the table afterward.

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