django.db.models.functions.base のソースコード

"""
Classes that represent database functions.
"""
from django.db.models import Func, Transform, Value, fields


[ドキュメント]class Cast(Func): """ Coerce an expression to a new field type. """ function = 'CAST' template = '%(function)s(%(expressions)s AS %(db_type)s)' mysql_types = { fields.CharField: 'char', fields.IntegerField: 'signed integer', fields.FloatField: 'signed', } def __init__(self, expression, output_field): super(Cast, self).__init__(expression, output_field=output_field) def as_sql(self, compiler, connection, **extra_context): if 'db_type' not in extra_context: extra_context['db_type'] = self._output_field.db_type(connection) return super(Cast, self).as_sql(compiler, connection, **extra_context) def as_mysql(self, compiler, connection): extra_context = {} output_field_class = type(self._output_field) if output_field_class in self.mysql_types: extra_context['db_type'] = self.mysql_types[output_field_class] return self.as_sql(compiler, connection, **extra_context) def as_postgresql(self, compiler, connection): # CAST would be valid too, but the :: shortcut syntax is more readable. return self.as_sql(compiler, connection, template='%(expressions)s::%(db_type)s')
[ドキュメント]class Coalesce(Func): """ Chooses, from left to right, the first non-null expression and returns it. """ function = 'COALESCE' def __init__(self, *expressions, **extra): if len(expressions) < 2: raise ValueError('Coalesce must take at least two expressions') super(Coalesce, self).__init__(*expressions, **extra) def as_oracle(self, compiler, connection): # we can't mix TextField (NCLOB) and CharField (NVARCHAR), so convert # all fields to NCLOB when we expect NCLOB if self.output_field.get_internal_type() == 'TextField': class ToNCLOB(Func): function = 'TO_NCLOB' expressions = [ ToNCLOB(expression) for expression in self.get_source_expressions()] clone = self.copy() clone.set_source_expressions(expressions) return super(Coalesce, clone).as_sql(compiler, connection) return self.as_sql(compiler, connection)
class ConcatPair(Func): """ A helper class that concatenates two arguments together. This is used by `Concat` because not all backend databases support more than two arguments. """ function = 'CONCAT' def __init__(self, left, right, **extra): super(ConcatPair, self).__init__(left, right, **extra) def as_sqlite(self, compiler, connection): coalesced = self.coalesce() return super(ConcatPair, coalesced).as_sql( compiler, connection, template='%(expressions)s', arg_joiner=' || ' ) def as_mysql(self, compiler, connection): # Use CONCAT_WS with an empty separator so that NULLs are ignored. return super(ConcatPair, self).as_sql( compiler, connection, function='CONCAT_WS', template="%(function)s('', %(expressions)s)" ) def coalesce(self): # null on either side results in null for expression, wrap with coalesce c = self.copy() expressions = [ Coalesce(expression, Value('')) for expression in c.get_source_expressions() ] c.set_source_expressions(expressions) return c
[ドキュメント]class Concat(Func): """ Concatenates text fields together. Backends that result in an entire null expression when any arguments are null will wrap each argument in coalesce functions to ensure we always get a non-null result. """ function = None template = "%(expressions)s" def __init__(self, *expressions, **extra): if len(expressions) < 2: raise ValueError('Concat must take at least two expressions') paired = self._paired(expressions) super(Concat, self).__init__(paired, **extra) def _paired(self, expressions): # wrap pairs of expressions in successive concat functions # exp = [a, b, c, d] # -> ConcatPair(a, ConcatPair(b, ConcatPair(c, d)))) if len(expressions) == 2: return ConcatPair(*expressions) return ConcatPair(expressions[0], self._paired(expressions[1:]))
[ドキュメント]class Greatest(Func): """ Chooses the maximum expression and returns it. If any expression is null the return value is database-specific: On Postgres, the maximum not-null expression is returned. On MySQL, Oracle, and SQLite, if any expression is null, null is returned. """ function = 'GREATEST' def __init__(self, *expressions, **extra): if len(expressions) < 2: raise ValueError('Greatest must take at least two expressions') super(Greatest, self).__init__(*expressions, **extra) def as_sqlite(self, compiler, connection): """Use the MAX function on SQLite.""" return super(Greatest, self).as_sqlite(compiler, connection, function='MAX')
[ドキュメント]class Least(Func): """ Chooses the minimum expression and returns it. If any expression is null the return value is database-specific: On Postgres, the minimum not-null expression is returned. On MySQL, Oracle, and SQLite, if any expression is null, null is returned. """ function = 'LEAST' def __init__(self, *expressions, **extra): if len(expressions) < 2: raise ValueError('Least must take at least two expressions') super(Least, self).__init__(*expressions, **extra) def as_sqlite(self, compiler, connection): """Use the MIN function on SQLite.""" return super(Least, self).as_sqlite(compiler, connection, function='MIN')
[ドキュメント]class Length(Transform): """Returns the number of characters in the expression""" function = 'LENGTH' lookup_name = 'length' def __init__(self, expression, **extra): output_field = extra.pop('output_field', fields.IntegerField()) super(Length, self).__init__(expression, output_field=output_field, **extra) def as_mysql(self, compiler, connection): return super(Length, self).as_sql(compiler, connection, function='CHAR_LENGTH')
[ドキュメント]class Lower(Transform): function = 'LOWER' lookup_name = 'lower'
[ドキュメント]class Now(Func): template = 'CURRENT_TIMESTAMP' def __init__(self, output_field=None, **extra): if output_field is None: output_field = fields.DateTimeField() super(Now, self).__init__(output_field=output_field, **extra) def as_postgresql(self, compiler, connection): # Postgres' CURRENT_TIMESTAMP means "the time at the start of the # transaction". We use STATEMENT_TIMESTAMP to be cross-compatible with # other databases. return self.as_sql(compiler, connection, template='STATEMENT_TIMESTAMP()')
[ドキュメント]class Substr(Func): function = 'SUBSTRING' def __init__(self, expression, pos, length=None, **extra): """ expression: the name of a field, or an expression returning a string pos: an integer > 0, or an expression returning an integer length: an optional number of characters to return """ if not hasattr(pos, 'resolve_expression'): if pos < 1: raise ValueError("'pos' must be greater than 0") pos = Value(pos) expressions = [expression, pos] if length is not None: if not hasattr(length, 'resolve_expression'): length = Value(length) expressions.append(length) super(Substr, self).__init__(*expressions, **extra) def as_sqlite(self, compiler, connection): return super(Substr, self).as_sql(compiler, connection, function='SUBSTR') def as_oracle(self, compiler, connection): return super(Substr, self).as_sql(compiler, connection, function='SUBSTR')
[ドキュメント]class Upper(Transform): function = 'UPPER' lookup_name = 'upper'
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