query/mogrify broken when named parameters are used more than once

[wolph]

The issue is with the dump function that automatically converts all parameters into tuples but doesn't take into consideration that some parameters might be used more than once.

psycopg/psycopg/psycopg/_queries.py

Lines 131 to 144 in 8a44473

	def dump(self, vars: Optional[Params]) -> None:
	"""
	Process a new set of variables on the query processed by `convert()`.
	This method updates `params` and `types`.
	"""
	if vars is not None:
	params = _validate_and_reorder_params(self._parts, vars, self._order)
	self.params = tuple(
	self._tx.as_literal(p) if p is not None else b"NULL" for p in params
	)
	self.query = self.template % self.params
	else:
	self.params = None

The traceback:

Traceback (most recent call last):
  File "psycopg/client_cursor.py", line 40, in mogrify
    pgq = self._convert_query(query, params)
  File "psycopg/client_cursor.py", line 79, in _convert_query
    pgq.convert(query, params)
  File "psycopg/_queries.py", line 129, in convert
    self.dump(vars)
  File "psycopg/_queries.py", line 142, in dump
    self.query = self.template % self.params
TypeError: not enough arguments for format string

To reproduce:

query = '''
SELECT *
FROM some_table
WHERE some_column = %(some_value)s
AND some_other_column = %(some_value)s
'''
params = dict(some_value=1)

with psycopg.connect() as connection:
    cursor = psycopg.ClientCursor(connection)
    cursor.mogrify(query, params)

[wolph]

As a "fix" it works to replace this line:

psycopg/psycopg/psycopg/_queries.py

Line 273 in 8a44473

return [vars[item] for item in order or ()] # type: ignore[call-overload]

With this:

return [vars[part.item] for part in parts[:-1]]

However... this breaks the execution of the query in some cases so it needs to be specific to this dump() call

[dvarrazzo]

Querying is broken too, not only mogrify. A fix is on the way.