(improvement)Optimize column_encryption_policy checks in Cython's unpack_row() function

Very similar to the native Python code, separate the two cases, if column encryption (CE) policy
is not enabled, the code is substantially simplified. If it is, it's slightly more elaborate.

Decided to have two loops in two functions, one for each case, for performance reasons, even if readability-wise it's
not as great. AI agreed with me:
Recommendation: Keep it as is. In high-performance Cython code like this, duplicating a small block of code

Fixes: #639
Signed-off-by: Yaniv Kaul <yaniv.kaul@scylladb.com>

Author: mykaul

cassandra/obj_parser.pyx

@@ -31,7 +31,10 @@ cdef class ListParser(ColumnParser):
         cdef Py_ssize_t i, rowcount
         rowcount = read_int(reader)
         cdef RowParser rowparser = TupleRowParser()
-        return [rowparser.unpack_row(reader, desc) for i in range(rowcount)]
+        if desc.column_encryption_policy:
+            return [rowparser.unpack_ce_row(reader, desc) for i in range(rowcount)]
+        else:
+            return [rowparser.unpack_row(reader, desc) for i in range(rowcount)]
 
 
 cdef class LazyParser(ColumnParser):
@@ -47,17 +50,22 @@ def parse_rows_lazy(BytesIOReader reader, ParseDesc desc):
     cdef Py_ssize_t i, rowcount
     rowcount = read_int(reader)
     cdef RowParser rowparser = TupleRowParser()
-    return (rowparser.unpack_row(reader, desc) for i in range(rowcount))
+    if desc.column_encryption_policy:
+        return (rowparser.unpack_ce_row(reader, desc) for i in range(rowcount))
+    else:
+        return (rowparser.unpack_row(reader, desc) for i in range(rowcount))
 
 
 cdef class TupleRowParser(RowParser):
     """
     Parse a single returned row into a tuple of objects:
 
         (obj1, ..., objN)
+    If CE (Column encryption) policy is enabled - use unpack_ce_row(),
+    otherwsise use unpack_row()
     """
 
-    cpdef unpack_row(self, BytesIOReader reader, ParseDesc desc):
+    cpdef unpack_ce_row(self, BytesIOReader reader, ParseDesc desc):
         assert desc.rowsize >= 0
 
         cdef Buffer buf
@@ -73,9 +81,9 @@ cdef class TupleRowParser(RowParser):
 
             # Deserialize bytes to python object
             deserializer = desc.deserializers[i]
-            coldesc = desc.coldescs[i]
-            uses_ce = ce_policy and ce_policy.contains_column(coldesc)
             try:
+                coldesc = desc.coldescs[i]
+                uses_ce = ce_policy.contains_column(coldesc)
                 if uses_ce:
                     col_type = ce_policy.column_type(coldesc)
                     decrypted_bytes = ce_policy.decrypt(coldesc, to_bytes(&buf))
@@ -84,11 +92,36 @@ cdef class TupleRowParser(RowParser):
                     val = from_binary(deserializer, &newbuf, desc.protocol_version)
                 else:
                     val = from_binary(deserializer, &buf, desc.protocol_version)
+                # Insert new object into tuple
+                tuple_set(res, i, val)
+            except Exception as e:
+                raise DriverException('Failed decoding result column "%s" of type %s: %s' % (desc.colnames[i],
+                                                                                             desc.coltypes[i].cql_parameterized_type(),
+                                                                                             str(e)))
+
+        return res
+
+    cpdef unpack_row(self, BytesIOReader reader, ParseDesc desc):
+        assert desc.rowsize >= 0
+
+        cdef Buffer buf
+        cdef Py_ssize_t i, rowsize = desc.rowsize
+        cdef Deserializer deserializer
+        cdef tuple res = tuple_new(desc.rowsize)
+
+        for i in range(rowsize):
+            # Read the next few bytes
+            get_buf(reader, &buf)
+
+            # Deserialize bytes to python object
+            deserializer = desc.deserializers[i]
+            try:
+                val = from_binary(deserializer, &buf, desc.protocol_version)
+                # Insert new object into tuple
+                tuple_set(res, i, val)
             except Exception as e:
                 raise DriverException('Failed decoding result column "%s" of type %s: %s' % (desc.colnames[i],
                                                                                              desc.coltypes[i].cql_parameterized_type(),
                                                                                              str(e)))
-            # Insert new object into tuple
-            tuple_set(res, i, val)
 
         return res

cassandra/row_parser.pyx

@@ -44,7 +44,11 @@ def make_recv_results_rows(ColumnParser colparser):
             reader.buf_ptr = reader.buf
             reader.pos = 0
             rowcount = read_int(reader)
-            for i in range(rowcount):
-                rowparser.unpack_row(reader, desc)
+            if desc.column_encryption_policy:
+                for i in range(rowcount):
+                    rowparser.unpack_ce_row(reader, desc)
+            else:
+                for i in range(rowcount):
+                    rowparser.unpack_row(reader, desc)
 
     return recv_results_rows