Source code for django.db.models.functions.text
from django.db import NotSupportedError
from django.db.models.expressions import Func, Value
from django.db.models.fields import CharField, IntegerField
from django.db.models.functions import Coalesce
from django.db.models.lookups import Transform
class MySQLSHA2Mixin:
def as_mysql(self, compiler, connection, **extra_content):
return super().as_sql(
compiler,
connection,
template='SHA2(%%(expressions)s, %s)' % self.function[3:],
**extra_content,
)
class OracleHashMixin:
def as_oracle(self, compiler, connection, **extra_context):
return super().as_sql(
compiler,
connection,
template=(
"LOWER(RAWTOHEX(STANDARD_HASH(UTL_I18N.STRING_TO_RAW("
"%(expressions)s, 'AL32UTF8'), '%(function)s')))"
),
**extra_context,
)
class PostgreSQLSHAMixin:
def as_postgresql(self, compiler, connection, **extra_content):
return super().as_sql(
compiler,
connection,
template="ENCODE(DIGEST(%(expressions)s, '%(function)s'), 'hex')",
function=self.function.lower(),
**extra_content,
)
[docs]class Chr(Transform):
function = 'CHR'
lookup_name = 'chr'
def as_mysql(self, compiler, connection, **extra_context):
return super().as_sql(
compiler, connection, function='CHAR',
template='%(function)s(%(expressions)s USING utf16)',
**extra_context
)
def as_oracle(self, compiler, connection, **extra_context):
return super().as_sql(
compiler, connection,
template='%(function)s(%(expressions)s USING NCHAR_CS)',
**extra_context
)
def as_sqlite(self, compiler, connection, **extra_context):
return super().as_sql(compiler, connection, function='CHAR', **extra_context)
class ConcatPair(Func):
"""
Concatenate two arguments together. This is used by `Concat` because not
all backend databases support more than two arguments.
"""
function = 'CONCAT'
def as_sqlite(self, compiler, connection, **extra_context):
coalesced = self.coalesce()
return super(ConcatPair, coalesced).as_sql(
compiler, connection, template='%(expressions)s', arg_joiner=' || ',
**extra_context
)
def as_mysql(self, compiler, connection, **extra_context):
# Use CONCAT_WS with an empty separator so that NULLs are ignored.
return super().as_sql(
compiler, connection, function='CONCAT_WS',
template="%(function)s('', %(expressions)s)",
**extra_context
)
def coalesce(self):
# null on either side results in null for expression, wrap with coalesce
c = self.copy()
c.set_source_expressions([
Coalesce(expression, Value('')) for expression in c.get_source_expressions()
])
return c
[docs]class Concat(Func):
"""
Concatenate 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 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().__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:]))
[docs]class Left(Func):
function = 'LEFT'
arity = 2
output_field = CharField()
def __init__(self, expression, length, **extra):
"""
expression: the name of a field, or an expression returning a string
length: the number of characters to return from the start of the string
"""
if not hasattr(length, 'resolve_expression'):
if length < 1:
raise ValueError("'length' must be greater than 0.")
super().__init__(expression, length, **extra)
def get_substr(self):
return Substr(self.source_expressions[0], Value(1), self.source_expressions[1])
def as_oracle(self, compiler, connection, **extra_context):
return self.get_substr().as_oracle(compiler, connection, **extra_context)
def as_sqlite(self, compiler, connection, **extra_context):
return self.get_substr().as_sqlite(compiler, connection, **extra_context)
[docs]class Length(Transform):
"""Return the number of characters in the expression."""
function = 'LENGTH'
lookup_name = 'length'
output_field = IntegerField()
def as_mysql(self, compiler, connection, **extra_context):
return super().as_sql(compiler, connection, function='CHAR_LENGTH', **extra_context)
[docs]class LPad(Func):
function = 'LPAD'
output_field = CharField()
def __init__(self, expression, length, fill_text=Value(' '), **extra):
if not hasattr(length, 'resolve_expression') and length is not None and length < 0:
raise ValueError("'length' must be greater or equal to 0.")
super().__init__(expression, length, fill_text, **extra)
[docs]class Ord(Transform):
function = 'ASCII'
lookup_name = 'ord'
output_field = IntegerField()
def as_mysql(self, compiler, connection, **extra_context):
return super().as_sql(compiler, connection, function='ORD', **extra_context)
def as_sqlite(self, compiler, connection, **extra_context):
return super().as_sql(compiler, connection, function='UNICODE', **extra_context)
[docs]class Repeat(Func):
function = 'REPEAT'
output_field = CharField()
def __init__(self, expression, number, **extra):
if not hasattr(number, 'resolve_expression') and number is not None and number < 0:
raise ValueError("'number' must be greater or equal to 0.")
super().__init__(expression, number, **extra)
def as_oracle(self, compiler, connection, **extra_context):
expression, number = self.source_expressions
length = None if number is None else Length(expression) * number
rpad = RPad(expression, length, expression)
return rpad.as_sql(compiler, connection, **extra_context)
[docs]class Replace(Func):
function = 'REPLACE'
def __init__(self, expression, text, replacement=Value(''), **extra):
super().__init__(expression, text, replacement, **extra)
[docs]class Reverse(Transform):
function = 'REVERSE'
lookup_name = 'reverse'
def as_oracle(self, compiler, connection, **extra_context):
# REVERSE in Oracle is undocumented and doesn't support multi-byte
# strings. Use a special subquery instead.
return super().as_sql(
compiler, connection,
template=(
'(SELECT LISTAGG(s) WITHIN GROUP (ORDER BY n DESC) FROM '
'(SELECT LEVEL n, SUBSTR(%(expressions)s, LEVEL, 1) s '
'FROM DUAL CONNECT BY LEVEL <= LENGTH(%(expressions)s)) '
'GROUP BY %(expressions)s)'
),
**extra_context
)
[docs]class Right(Left):
function = 'RIGHT'
def get_substr(self):
return Substr(self.source_expressions[0], self.source_expressions[1] * Value(-1))
[docs]class SHA1(OracleHashMixin, PostgreSQLSHAMixin, Transform):
function = 'SHA1'
lookup_name = 'sha1'
[docs]class SHA224(MySQLSHA2Mixin, PostgreSQLSHAMixin, Transform):
function = 'SHA224'
lookup_name = 'sha224'
def as_oracle(self, compiler, connection, **extra_context):
raise NotSupportedError('SHA224 is not supported on Oracle.')
[docs]class SHA256(MySQLSHA2Mixin, OracleHashMixin, PostgreSQLSHAMixin, Transform):
function = 'SHA256'
lookup_name = 'sha256'
[docs]class SHA384(MySQLSHA2Mixin, OracleHashMixin, PostgreSQLSHAMixin, Transform):
function = 'SHA384'
lookup_name = 'sha384'
[docs]class SHA512(MySQLSHA2Mixin, OracleHashMixin, PostgreSQLSHAMixin, Transform):
function = 'SHA512'
lookup_name = 'sha512'
[docs]class StrIndex(Func):
"""
Return a positive integer corresponding to the 1-indexed position of the
first occurrence of a substring inside another string, or 0 if the
substring is not found.
"""
function = 'INSTR'
arity = 2
output_field = IntegerField()
def as_postgresql(self, compiler, connection, **extra_context):
return super().as_sql(compiler, connection, function='STRPOS', **extra_context)
[docs]class Substr(Func):
function = 'SUBSTRING'
output_field = CharField()
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")
expressions = [expression, pos]
if length is not None:
expressions.append(length)
super().__init__(*expressions, **extra)
def as_sqlite(self, compiler, connection, **extra_context):
return super().as_sql(compiler, connection, function='SUBSTR', **extra_context)
def as_oracle(self, compiler, connection, **extra_context):
return super().as_sql(compiler, connection, function='SUBSTR', **extra_context)
