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336 lines
11 KiB
Python
336 lines
11 KiB
Python
from django.db.models.expressions import Func, Value
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from django.db.models.fields import IntegerField
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from django.db.models.functions import Coalesce
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from django.db.models.lookups import Transform
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from django.db.utils import NotSupportedError
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class BytesToCharFieldConversionMixin:
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"""
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Convert CharField results from bytes to str.
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MySQL returns long data types (bytes) instead of chars when it can't
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determine the length of the result string. For example:
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LPAD(column1, CHAR_LENGTH(column2), ' ')
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returns the LONGTEXT (bytes) instead of VARCHAR.
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"""
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def convert_value(self, value, expression, connection):
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if connection.features.db_functions_convert_bytes_to_str:
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if self.output_field.get_internal_type() == 'CharField' and isinstance(value, bytes):
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return value.decode()
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return super().convert_value(value, expression, connection)
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class MySQLSHA2Mixin:
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def as_mysql(self, compiler, connection, **extra_content):
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return super().as_sql(
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compiler,
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connection,
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template='SHA2(%%(expressions)s, %s)' % self.function[3:],
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**extra_content,
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)
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class OracleHashMixin:
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def as_oracle(self, compiler, connection, **extra_context):
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return super().as_sql(
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compiler,
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connection,
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template=(
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"LOWER(RAWTOHEX(STANDARD_HASH(UTL_I18N.STRING_TO_RAW("
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"%(expressions)s, 'AL32UTF8'), '%(function)s')))"
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),
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**extra_context,
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)
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class PostgreSQLSHAMixin:
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def as_postgresql(self, compiler, connection, **extra_content):
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return super().as_sql(
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compiler,
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connection,
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template="ENCODE(DIGEST(%(expressions)s, '%(function)s'), 'hex')",
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function=self.function.lower(),
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**extra_content,
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)
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class Chr(Transform):
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function = 'CHR'
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lookup_name = 'chr'
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def as_mysql(self, compiler, connection, **extra_context):
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return super().as_sql(
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compiler, connection, function='CHAR',
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template='%(function)s(%(expressions)s USING utf16)',
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**extra_context
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)
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def as_oracle(self, compiler, connection, **extra_context):
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return super().as_sql(
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compiler, connection,
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template='%(function)s(%(expressions)s USING NCHAR_CS)',
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**extra_context
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)
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def as_sqlite(self, compiler, connection, **extra_context):
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return super().as_sql(compiler, connection, function='CHAR', **extra_context)
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class ConcatPair(Func):
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"""
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Concatenate two arguments together. This is used by `Concat` because not
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all backend databases support more than two arguments.
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"""
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function = 'CONCAT'
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def as_sqlite(self, compiler, connection, **extra_context):
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coalesced = self.coalesce()
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return super(ConcatPair, coalesced).as_sql(
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compiler, connection, template='%(expressions)s', arg_joiner=' || ',
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**extra_context
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)
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def as_mysql(self, compiler, connection, **extra_context):
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# Use CONCAT_WS with an empty separator so that NULLs are ignored.
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return super().as_sql(
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compiler, connection, function='CONCAT_WS',
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template="%(function)s('', %(expressions)s)",
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**extra_context
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)
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def coalesce(self):
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# null on either side results in null for expression, wrap with coalesce
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c = self.copy()
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c.set_source_expressions([
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Coalesce(expression, Value('')) for expression in c.get_source_expressions()
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])
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return c
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class Concat(Func):
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"""
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Concatenate text fields together. Backends that result in an entire
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null expression when any arguments are null will wrap each argument in
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coalesce functions to ensure a non-null result.
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"""
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function = None
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template = "%(expressions)s"
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def __init__(self, *expressions, **extra):
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if len(expressions) < 2:
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raise ValueError('Concat must take at least two expressions')
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paired = self._paired(expressions)
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super().__init__(paired, **extra)
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def _paired(self, expressions):
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# wrap pairs of expressions in successive concat functions
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# exp = [a, b, c, d]
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# -> ConcatPair(a, ConcatPair(b, ConcatPair(c, d))))
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if len(expressions) == 2:
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return ConcatPair(*expressions)
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return ConcatPair(expressions[0], self._paired(expressions[1:]))
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class Left(Func):
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function = 'LEFT'
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arity = 2
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def __init__(self, expression, length, **extra):
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"""
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expression: the name of a field, or an expression returning a string
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length: the number of characters to return from the start of the string
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"""
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if not hasattr(length, 'resolve_expression'):
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if length < 1:
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raise ValueError("'length' must be greater than 0.")
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super().__init__(expression, length, **extra)
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def get_substr(self):
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return Substr(self.source_expressions[0], Value(1), self.source_expressions[1])
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def as_oracle(self, compiler, connection, **extra_context):
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return self.get_substr().as_oracle(compiler, connection, **extra_context)
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def as_sqlite(self, compiler, connection, **extra_context):
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return self.get_substr().as_sqlite(compiler, connection, **extra_context)
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class Length(Transform):
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"""Return the number of characters in the expression."""
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function = 'LENGTH'
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lookup_name = 'length'
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output_field = IntegerField()
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def as_mysql(self, compiler, connection, **extra_context):
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return super().as_sql(compiler, connection, function='CHAR_LENGTH', **extra_context)
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class Lower(Transform):
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function = 'LOWER'
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lookup_name = 'lower'
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class LPad(BytesToCharFieldConversionMixin, Func):
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function = 'LPAD'
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def __init__(self, expression, length, fill_text=Value(' '), **extra):
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if not hasattr(length, 'resolve_expression') and length is not None and length < 0:
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raise ValueError("'length' must be greater or equal to 0.")
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super().__init__(expression, length, fill_text, **extra)
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class LTrim(Transform):
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function = 'LTRIM'
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lookup_name = 'ltrim'
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class MD5(OracleHashMixin, Transform):
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function = 'MD5'
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lookup_name = 'md5'
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class Ord(Transform):
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function = 'ASCII'
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lookup_name = 'ord'
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output_field = IntegerField()
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def as_mysql(self, compiler, connection, **extra_context):
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return super().as_sql(compiler, connection, function='ORD', **extra_context)
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def as_sqlite(self, compiler, connection, **extra_context):
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return super().as_sql(compiler, connection, function='UNICODE', **extra_context)
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class Repeat(BytesToCharFieldConversionMixin, Func):
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function = 'REPEAT'
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def __init__(self, expression, number, **extra):
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if not hasattr(number, 'resolve_expression') and number is not None and number < 0:
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raise ValueError("'number' must be greater or equal to 0.")
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super().__init__(expression, number, **extra)
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def as_oracle(self, compiler, connection, **extra_context):
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expression, number = self.source_expressions
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length = None if number is None else Length(expression) * number
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rpad = RPad(expression, length, expression)
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return rpad.as_sql(compiler, connection, **extra_context)
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class Replace(Func):
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function = 'REPLACE'
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def __init__(self, expression, text, replacement=Value(''), **extra):
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super().__init__(expression, text, replacement, **extra)
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class Reverse(Transform):
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function = 'REVERSE'
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lookup_name = 'reverse'
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def as_oracle(self, compiler, connection, **extra_context):
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# REVERSE in Oracle is undocumented and doesn't support multi-byte
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# strings. Use a special subquery instead.
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return super().as_sql(
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compiler, connection,
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template=(
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'(SELECT LISTAGG(s) WITHIN GROUP (ORDER BY n DESC) FROM '
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'(SELECT LEVEL n, SUBSTR(%(expressions)s, LEVEL, 1) s '
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'FROM DUAL CONNECT BY LEVEL <= LENGTH(%(expressions)s)) '
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'GROUP BY %(expressions)s)'
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),
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**extra_context
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)
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class Right(Left):
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function = 'RIGHT'
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def get_substr(self):
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return Substr(self.source_expressions[0], self.source_expressions[1] * Value(-1))
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class RPad(LPad):
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function = 'RPAD'
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class RTrim(Transform):
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function = 'RTRIM'
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lookup_name = 'rtrim'
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class SHA1(OracleHashMixin, PostgreSQLSHAMixin, Transform):
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function = 'SHA1'
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lookup_name = 'sha1'
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class SHA224(MySQLSHA2Mixin, PostgreSQLSHAMixin, Transform):
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function = 'SHA224'
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lookup_name = 'sha224'
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def as_oracle(self, compiler, connection, **extra_context):
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raise NotSupportedError('SHA224 is not supported on Oracle.')
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class SHA256(MySQLSHA2Mixin, OracleHashMixin, PostgreSQLSHAMixin, Transform):
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function = 'SHA256'
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lookup_name = 'sha256'
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class SHA384(MySQLSHA2Mixin, OracleHashMixin, PostgreSQLSHAMixin, Transform):
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function = 'SHA384'
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lookup_name = 'sha384'
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class SHA512(MySQLSHA2Mixin, OracleHashMixin, PostgreSQLSHAMixin, Transform):
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function = 'SHA512'
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lookup_name = 'sha512'
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class StrIndex(Func):
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"""
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Return a positive integer corresponding to the 1-indexed position of the
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first occurrence of a substring inside another string, or 0 if the
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substring is not found.
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"""
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function = 'INSTR'
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arity = 2
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output_field = IntegerField()
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def as_postgresql(self, compiler, connection, **extra_context):
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return super().as_sql(compiler, connection, function='STRPOS', **extra_context)
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class Substr(Func):
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function = 'SUBSTRING'
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def __init__(self, expression, pos, length=None, **extra):
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"""
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expression: the name of a field, or an expression returning a string
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pos: an integer > 0, or an expression returning an integer
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length: an optional number of characters to return
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"""
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if not hasattr(pos, 'resolve_expression'):
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if pos < 1:
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raise ValueError("'pos' must be greater than 0")
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expressions = [expression, pos]
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if length is not None:
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expressions.append(length)
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super().__init__(*expressions, **extra)
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def as_sqlite(self, compiler, connection, **extra_context):
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return super().as_sql(compiler, connection, function='SUBSTR', **extra_context)
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def as_oracle(self, compiler, connection, **extra_context):
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return super().as_sql(compiler, connection, function='SUBSTR', **extra_context)
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class Trim(Transform):
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function = 'TRIM'
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lookup_name = 'trim'
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class Upper(Transform):
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function = 'UPPER'
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lookup_name = 'upper'
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