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from collections import namedtuple
_ColumnMetadata = namedtuple(
"ColumnMetadata", ["name", "datatype", "foreignkeys", "default", "has_default"]
)
def ColumnMetadata(name, datatype, foreignkeys=None, default=None, has_default=False):
return _ColumnMetadata(name, datatype, foreignkeys or [], default, has_default)
ForeignKey = namedtuple(
"ForeignKey",
[
"parentschema",
"parenttable",
"parentcolumn",
"childschema",
"childtable",
"childcolumn",
],
)
TableMetadata = namedtuple("TableMetadata", "name columns")
def parse_defaults(defaults_string):
"""Yields default values for a function, given the string provided by
pg_get_expr(pg_catalog.pg_proc.proargdefaults, 0)"""
if not defaults_string:
return
current = ""
in_quote = None
for char in defaults_string:
if current == "" and char == " ":
# Skip space after comma separating default expressions
continue
if char == '"' or char == "'":
if in_quote and char == in_quote:
# End quote
in_quote = None
elif not in_quote:
# Begin quote
in_quote = char
elif char == "," and not in_quote:
# End of expression
yield current
current = ""
continue
current += char
yield current
class FunctionMetadata:
def __init__(
self,
schema_name,
func_name,
arg_names,
arg_types,
arg_modes,
return_type,
is_aggregate,
is_window,
is_set_returning,
is_extension,
arg_defaults,
):
"""Class for describing a postgresql function"""
self.schema_name = schema_name
self.func_name = func_name
self.arg_modes = tuple(arg_modes) if arg_modes else None
self.arg_names = tuple(arg_names) if arg_names else None
# Be flexible in not requiring arg_types -- use None as a placeholder
# for each arg. (Used for compatibility with old versions of postgresql
# where such info is hard to get.
if arg_types:
self.arg_types = tuple(arg_types)
elif arg_modes:
self.arg_types = tuple([None] * len(arg_modes))
elif arg_names:
self.arg_types = tuple([None] * len(arg_names))
else:
self.arg_types = None
self.arg_defaults = tuple(parse_defaults(arg_defaults))
self.return_type = return_type.strip()
self.is_aggregate = is_aggregate
self.is_window = is_window
self.is_set_returning = is_set_returning
self.is_extension = bool(is_extension)
self.is_public = self.schema_name and self.schema_name == "public"
def __eq__(self, other):
return isinstance(other, self.__class__) and self.__dict__ == other.__dict__
def __ne__(self, other):
return not self.__eq__(other)
def _signature(self):
return (
self.schema_name,
self.func_name,
self.arg_names,
self.arg_types,
self.arg_modes,
self.return_type,
self.is_aggregate,
self.is_window,
self.is_set_returning,
self.is_extension,
self.arg_defaults,
)
def __hash__(self):
return hash(self._signature())
def __repr__(self):
return (
"%s(schema_name=%r, func_name=%r, arg_names=%r, "
"arg_types=%r, arg_modes=%r, return_type=%r, is_aggregate=%r, "
"is_window=%r, is_set_returning=%r, is_extension=%r, arg_defaults=%r)"
) % ((self.__class__.__name__,) + self._signature())
def has_variadic(self):
return self.arg_modes and any(arg_mode == "v" for arg_mode in self.arg_modes)
def args(self):
"""Returns a list of input-parameter ColumnMetadata namedtuples."""
if not self.arg_names:
return []
modes = self.arg_modes or ["i"] * len(self.arg_names)
args = [
(name, typ)
for name, typ, mode in zip(self.arg_names, self.arg_types, modes)
if mode in ("i", "b", "v") # IN, INOUT, VARIADIC
]
def arg(name, typ, num):
num_args = len(args)
num_defaults = len(self.arg_defaults)
has_default = num + num_defaults >= num_args
default = (
self.arg_defaults[num - num_args + num_defaults]
if has_default
else None
)
return ColumnMetadata(name, typ, [], default, has_default)
return [arg(name, typ, num) for num, (name, typ) in enumerate(args)]
def fields(self):
"""Returns a list of output-field ColumnMetadata namedtuples"""
if self.return_type.lower() == "void":
return []
elif not self.arg_modes:
# For functions without output parameters, the function name
# is used as the name of the output column.
# E.g. 'SELECT unnest FROM unnest(...);'
return [ColumnMetadata(self.func_name, self.return_type, [])]
return [
ColumnMetadata(name, typ, [])
for name, typ, mode in zip(self.arg_names, self.arg_types, self.arg_modes)
if mode in ("o", "b", "t")
] # OUT, INOUT, TABLE
|
