Rewrite executemany() to batch args for performance.

Now `Bind` and `Execute` pairs are batched into 4 x 32KB buffers to take
advantage of `writelines()`. A single `Sync` is sent at last, so that
all args live in the same transaction.

Closes: #289

asyncpg/connection.py

@@ -331,6 +331,13 @@ async def executemany(self, command: str, args, *, timeout: float=None):
 
         .. versionchanged:: 0.11.0
            `timeout` became a keyword-only parameter.
+
+        .. versionchanged:: 0.22.0
+           The execution was changed to be in an implicit transaction if there
+           was no explicit transaction, so that it will no longer end up with
+           partial success. If you still need the previous behavior to
+           progressively execute many args, please use a loop with prepared
+           statement instead.
         """
         self._check_open()
         return await self._executemany(command, args, timeout)
@@ -1010,6 +1017,9 @@ async def _copy_in(self, copy_stmt, source, timeout):
             f = source
         elif isinstance(source, collections.abc.AsyncIterable):
             # assuming calling output returns an awaitable.
+            # copy_in() is designed to handle very large amounts of data, and
+            # the source async iterable is allowed to return an arbitrary
+            # amount of data on every iteration.
             reader = source
         else:
             # assuming source is an instance supporting the buffer protocol.

asyncpg/prepared_stmt.py

@@ -202,11 +202,24 @@ async def fetchrow(self, *args, timeout=None):
             return None
         return data[0]
 
-    async def __bind_execute(self, args, limit, timeout):
+    @connresource.guarded
+    async def executemany(self, args, *, timeout: float=None):
+        """Execute the statement for each sequence of arguments in *args*.
+
+        :param args: An iterable containing sequences of arguments.
+        :param float timeout: Optional timeout value in seconds.
+        :return None: This method discards the results of the operations.
+
+        .. versionadded:: 0.22.0
+        """
+        return await self.__do_execute(
+            lambda protocol: protocol.bind_execute_many(
+                self._state, args, '', timeout))
+
+    async def __do_execute(self, executor):
         protocol = self._connection._protocol
         try:
-            data, status, _ = await protocol.bind_execute(
-                self._state, args, '', limit, True, timeout)
+            return await executor(protocol)
         except exceptions.OutdatedSchemaCacheError:
             await self._connection.reload_schema_state()
             # We can not find all manually created prepared statements, so just
@@ -215,6 +228,11 @@ async def __bind_execute(self, args, limit, timeout):
             # invalidate themselves (unfortunately, clearing caches again).
             self._state.mark_closed()
             raise
+
+    async def __bind_execute(self, args, limit, timeout):
+        data, status, _ = await self.__do_execute(
+            lambda protocol: protocol.bind_execute(
+                self._state, args, '', limit, True, timeout))
         self._last_status = status
         return data
 

asyncpg/protocol/consts.pxi

@@ -8,3 +8,5 @@
 DEF _MAXINT32 = 2**31 - 1
 DEF _COPY_BUFFER_SIZE = 524288
 DEF _COPY_SIGNATURE = b"PGCOPY\n\377\r\n\0"
+DEF _EXECUTE_MANY_BUF_NUM = 4
+DEF _EXECUTE_MANY_BUF_SIZE = 32768

asyncpg/protocol/coreproto.pxd

@@ -114,6 +114,7 @@ cdef class CoreProtocol:
         # True - completed, False - suspended
         bint result_execute_completed
 
+    cpdef is_in_transaction(self)
     cdef _process__auth(self, char mtype)
     cdef _process__prepare(self, char mtype)
     cdef _process__bind_execute(self, char mtype)
@@ -146,6 +147,7 @@ cdef class CoreProtocol:
     cdef _auth_password_message_sasl_continue(self, bytes server_response)
 
     cdef _write(self, buf)
+    cdef _writelines(self, list buffers)
 
     cdef _read_server_messages(self)
 
@@ -155,9 +157,13 @@ cdef class CoreProtocol:
 
     cdef _ensure_connected(self)
 
+    cdef WriteBuffer _build_parse_message(self, str stmt_name, str query)
     cdef WriteBuffer _build_bind_message(self, str portal_name,
                                          str stmt_name,
                                          WriteBuffer bind_data)
+    cdef WriteBuffer _build_empty_bind_data(self)
+    cdef WriteBuffer _build_execute_message(self, str portal_name,
+                                            int32_t limit)
 
 
     cdef _connect(self)
@@ -166,8 +172,9 @@ cdef class CoreProtocol:
                             WriteBuffer bind_data, int32_t limit)
     cdef _bind_execute(self, str portal_name, str stmt_name,
                        WriteBuffer bind_data, int32_t limit)
-    cdef _bind_execute_many(self, str portal_name, str stmt_name,
-                            object bind_data)
+    cdef bint _bind_execute_many(self, str portal_name, str stmt_name,
+                                 object bind_data)
+    cdef bint _bind_execute_many_more(self, bint first=*)
     cdef _bind(self, str portal_name, str stmt_name,
                WriteBuffer bind_data)
     cdef _execute(self, str portal_name, int32_t limit)

asyncpg/protocol/coreproto.pyx

@@ -34,6 +34,11 @@ cdef class CoreProtocol:
 
         self._reset_result()
 
+    cpdef is_in_transaction(self):
+        # PQTRANS_INTRANS = idle, within transaction block
+        # PQTRANS_INERROR = idle, within failed transaction
+        return self.xact_status in (PQTRANS_INTRANS, PQTRANS_INERROR)
+
     cdef _read_server_messages(self):
         cdef:
             char mtype
@@ -263,27 +268,16 @@ cdef class CoreProtocol:
         elif mtype == b'Z':
             # ReadyForQuery
             self._parse_msg_ready_for_query()
-            if self.result_type == RESULT_FAILED:
-                self._push_result()
-            else:
-                try:
-                    buf = <WriteBuffer>next(self._execute_iter)
-                except StopIteration:
-                    self._push_result()
-                except Exception as e:
-                    self.result_type = RESULT_FAILED
-                    self.result = e
-                    self._push_result()
-                else:
-                    # Next iteration over the executemany() arg sequence
-                    self._send_bind_message(
-                        self._execute_portal_name, self._execute_stmt_name,
-                        buf, 0)
+            self._push_result()
 
         elif mtype == b'I':
             # EmptyQueryResponse
             self.buffer.discard_message()
 
+        elif mtype == b'1':
+            # ParseComplete
+            self.buffer.discard_message()
+
     cdef _process__bind(self, char mtype):
         if mtype == b'E':
             # ErrorResponse
@@ -780,6 +774,17 @@ cdef class CoreProtocol:
         if self.con_status != CONNECTION_OK:
             raise apg_exc.InternalClientError('not connected')
 
+    cdef WriteBuffer _build_parse_message(self, str stmt_name, str query):
+        cdef WriteBuffer buf
+
+        buf = WriteBuffer.new_message(b'P')
+        buf.write_str(stmt_name, self.encoding)
+        buf.write_str(query, self.encoding)
+        buf.write_int16(0)
+
+        buf.end_message()
+        return buf
+
     cdef WriteBuffer _build_bind_message(self, str portal_name,
                                          str stmt_name,
                                          WriteBuffer bind_data):
@@ -795,6 +800,25 @@ cdef class CoreProtocol:
         buf.end_message()
         return buf
 
+    cdef WriteBuffer _build_empty_bind_data(self):
+        cdef WriteBuffer buf
+        buf = WriteBuffer.new()
+        buf.write_int16(0)  # The number of parameter format codes
+        buf.write_int16(0)  # The number of parameter values
+        buf.write_int16(0)  # The number of result-column format codes
+        return buf
+
+    cdef WriteBuffer _build_execute_message(self, str portal_name,
+                                            int32_t limit):
+        cdef WriteBuffer buf
+
+        buf = WriteBuffer.new_message(b'E')
+        buf.write_str(portal_name, self.encoding)  # name of the portal
+        buf.write_int32(limit)  # number of rows to return; 0 - all
+
+        buf.end_message()
+        return buf
+
     # API for subclasses
 
     cdef _connect(self):
@@ -845,12 +869,7 @@ cdef class CoreProtocol:
         self._ensure_connected()
         self._set_state(PROTOCOL_PREPARE)
 
-        buf = WriteBuffer.new_message(b'P')
-        buf.write_str(stmt_name, self.encoding)
-        buf.write_str(query, self.encoding)
-        buf.write_int16(0)
-        buf.end_message()
-        packet = buf
+        packet = self._build_parse_message(stmt_name, query)
 
         buf = WriteBuffer.new_message(b'D')
         buf.write_byte(b'S')
@@ -872,10 +891,7 @@ cdef class CoreProtocol:
         buf = self._build_bind_message(portal_name, stmt_name, bind_data)
         packet = buf
 
-        buf = WriteBuffer.new_message(b'E')
-        buf.write_str(portal_name, self.encoding)  # name of the portal
-        buf.write_int32(limit)  # number of rows to return; 0 - all
-        buf.end_message()
+        buf = self._build_execute_message(portal_name, limit)
         packet.write_buffer(buf)
 
         packet.write_bytes(SYNC_MESSAGE)
@@ -894,11 +910,8 @@ cdef class CoreProtocol:
 
         self._send_bind_message(portal_name, stmt_name, bind_data, limit)
 
-    cdef _bind_execute_many(self, str portal_name, str stmt_name,
-                            object bind_data):
-
-        cdef WriteBuffer buf
-
+    cdef bint _bind_execute_many(self, str portal_name, str stmt_name,
+                                 object bind_data):
         self._ensure_connected()
         self._set_state(PROTOCOL_BIND_EXECUTE_MANY)
 
@@ -907,17 +920,88 @@ cdef class CoreProtocol:
         self._execute_iter = bind_data
         self._execute_portal_name = portal_name
         self._execute_stmt_name = stmt_name
+        return self._bind_execute_many_more(True)
 
-        try:
-            buf = <WriteBuffer>next(bind_data)
-        except StopIteration:
-            self._push_result()
-        except Exception as e:
-            self.result_type = RESULT_FAILED
-            self.result = e
-            self._push_result()
-        else:
-            self._send_bind_message(portal_name, stmt_name, buf, 0)
+    cdef bint _bind_execute_many_more(self, bint first=False):
+        cdef:
+            WriteBuffer packet
+            WriteBuffer buf
+            list buffers = []
+
+        # as we keep sending, the server may return an error early
+        if self.result_type == RESULT_FAILED:
+            self._write(SYNC_MESSAGE)
+            return False
+
+        # collect up to four 32KB buffers to send
+        # https://github.com/MagicStack/asyncpg/pull/289#issuecomment-391215051
+        while len(buffers) < _EXECUTE_MANY_BUF_NUM:
+            packet = WriteBuffer.new()
+
+            # fill one 32KB buffer
+            while packet.len() < _EXECUTE_MANY_BUF_SIZE:
+                try:
+                    # grab one item from the input
+                    buf = <WriteBuffer>next(self._execute_iter)
+
+                # reached the end of the input
+                except StopIteration:
+                    if first:
+                        # if we never send anything, simply set the result
+                        self._push_result()
+                    else:
+                        # otherwise, append SYNC and send the buffers
+                        packet.write_bytes(SYNC_MESSAGE)
+                        buffers.append(packet)
+                        self._writelines(buffers)
+                    return False
+
+                # error in input, give up the buffers and cleanup
+                except Exception as ex:
+                    self.result_type = RESULT_FAILED
+                    self.result = ex
+                    if first:
+                        self._push_result()
+                    elif self.is_in_transaction():
+                        # we're in an explicit transaction, just SYNC
+                        self._write(SYNC_MESSAGE)
+                    else:
+                        # In an implicit transaction, if `ignore_till_sync`,
+                        # `ROLLBACK` will be ignored and `Sync` will restore
+                        # the state; or the transaction will be rolled back
+                        # with a warning saying that there was no transaction,
+                        # but rollback is done anyway, so we could safely
+                        # ignore this warning.
+                        # GOTCHA: simple query message will be ignored if
+                        # `ignore_till_sync` is set.
+                        buf = self._build_parse_message('', 'ROLLBACK')
+                        buf.write_buffer(self._build_bind_message(
+                            '', '', self._build_empty_bind_data()))
+                        buf.write_buffer(self._build_execute_message('', 0))
+                        buf.write_bytes(SYNC_MESSAGE)
+                        self._write(buf)
+                    return False
+
+                # all good, write to the buffer
+                first = False
+                packet.write_buffer(
+                    self._build_bind_message(
+                        self._execute_portal_name,
+                        self._execute_stmt_name,
+                        buf,
+                    )
+                )
+                packet.write_buffer(
+                    self._build_execute_message(self._execute_portal_name, 0,
+                    )
+                )
+
+            # collected one buffer
+            buffers.append(packet)
+
+        # write to the wire, and signal the caller for more to send
+        self._writelines(buffers)
+        return True
 
     cdef _execute(self, str portal_name, int32_t limit):
         cdef WriteBuffer buf
@@ -927,10 +1011,7 @@ cdef class CoreProtocol:
 
         self.result = []
 
-        buf = WriteBuffer.new_message(b'E')
-        buf.write_str(portal_name, self.encoding)  # name of the portal
-        buf.write_int32(limit)  # number of rows to return; 0 - all
-        buf.end_message()
+        buf = self._build_execute_message(portal_name, limit)
 
         buf.write_bytes(SYNC_MESSAGE)
 
@@ -1013,6 +1094,9 @@ cdef class CoreProtocol:
     cdef _write(self, buf):
         raise NotImplementedError
 
+    cdef _writelines(self, list buffers):
+        raise NotImplementedError
+
     cdef _decode_row(self, const char* buf, ssize_t buf_len):
         pass