fix(c/driver/postgresql): prevent crash when server terminates connection

c/driver/postgresql/error.h

@@ -99,7 +99,9 @@ Status MakeStatus(PGresult* result, const char* format_string, Args&&... args) {
   }
 
   Status status(code, message);
-  status.SetSqlState(sqlstate);
+  if (sqlstate) {
+    status.SetSqlState(sqlstate);
+  }
   for (const auto& field : kDetailFields) {
     const char* value = PQresultErrorField(result, field.code);
     if (value) {

python/adbc_driver_postgresql/tests/test_dbapi.py

@@ -557,3 +557,32 @@ def test_connect_conn_kwargs_db_schema(postgres_uri: str, postgres: dbapi.Connec
     with dbapi.connect(postgres_uri, conn_kwargs={schema_key: schema_name}) as conn:
         option_value = conn.adbc_connection.get_option(schema_key)
         assert option_value == schema_name
+
+
+def test_server_terminates_connection(postgres_uri: str) -> None:
+    """Test that driver handles server terminating the connection gracefully.
+
+    Reproduces: https://github.com/apache/arrow-adbc/issues/3878
+    When the server terminates a connection, the driver should return an error
+    instead of crashing with a segfault.
+    """
+    with dbapi.connect(postgres_uri) as conn1:
+        with dbapi.connect(postgres_uri) as conn2:
+            # Get the backend PID of conn2
+            with conn2.cursor() as cur:
+                cur.execute("SELECT pg_backend_pid()")
+                row = cur.fetchone()
+                assert row is not None
+                backend_pid = row[0]
+            conn2.commit()
+
+            # simulate a server side termination of a connection2
+            with conn1.cursor() as cur:
+                cur.execute(f"SELECT pg_terminate_backend({backend_pid})")
+            conn1.commit()
+
+            # Try to execute a query on the terminated connection
+            # This should raise an exception, NOT crash with a segfault
+            with pytest.raises(Exception):
+                with conn2.cursor() as cur:
+                    cur.execute("SELECT 1")