Source code for boto3.dynamodb.conditions

# Copyright 2015, Inc. or its affiliates. All Rights Reserved.
# Licensed under the Apache License, Version 2.0 (the "License"). You
# may not use this file except in compliance with the License. A copy of
# the License is located at
# or in the "license" file accompanying this file. This file is
# ANY KIND, either express or implied. See the License for the specific
# language governing permissions and limitations under the License.
from collections import namedtuple
import re

from boto3.exceptions import DynamoDBOperationNotSupportedError
from boto3.exceptions import DynamoDBNeedsConditionError
from boto3.exceptions import DynamoDBNeedsKeyConditionError

ATTR_NAME_REGEX = re.compile(r'[^.\[\]]+(?![^\[]*\])')

class ConditionBase(object):

    expression_format = ''
    expression_operator = ''
    has_grouped_values = False

    def __init__(self, *values):
        self._values = values

    def __and__(self, other):
        if not isinstance(other, ConditionBase):
            raise DynamoDBOperationNotSupportedError('AND', other)
        return And(self, other)

    def __or__(self, other):
        if not isinstance(other, ConditionBase):
            raise DynamoDBOperationNotSupportedError('OR', other)
        return Or(self, other)

    def __invert__(self):
        return Not(self)

    def get_expression(self):
        return {'format': self.expression_format,
                'operator': self.expression_operator,
                'values': self._values}

    def __eq__(self, other):
        if isinstance(other, type(self)):
            if self._values == other._values:
                return True
        return False

    def __ne__(self, other):
        return not self.__eq__(other)

class AttributeBase(object):
    def __init__(self, name): = name

    def __and__(self, value):
        raise DynamoDBOperationNotSupportedError('AND', self)

    def __or__(self, value):
        raise DynamoDBOperationNotSupportedError('OR', self)

    def __invert__(self):
        raise DynamoDBOperationNotSupportedError('NOT', self)

    def eq(self, value):
        """Creates a condition where the attribute is equal to the value.

        :param value: The value that the attribute is equal to.
        return Equals(self, value)

    def lt(self, value):
        """Creates a condition where the attribute is less than the value.

        :param value: The value that the attribute is less than.
        return LessThan(self, value)

    def lte(self, value):
        """Creates a condition where the attribute is less than or equal to the

        :param value: The value that the attribute is less than or equal to.
        return LessThanEquals(self, value)

    def gt(self, value):
        """Creates a condition where the attribute is greater than the value.

        :param value: The value that the attribute is greater than.
        return GreaterThan(self, value)

    def gte(self, value):
        """Creates a condition where the attribute is greater than or equal to
           the value.

        :param value: The value that the attribute is greater than or equal to.
        return GreaterThanEquals(self, value)

    def begins_with(self, value):
        """Creates a condition where the attribute begins with the value.

        :param value: The value that the attribute begins with.
        return BeginsWith(self, value)

    def between(self, low_value, high_value):
        """Creates a condition where the attribute is greater than or equal
        to the low value and less than or equal to the high value.

        :param low_value: The value that the attribute is greater than or equal to.
        :param high_value: The value that the attribute is less than or equal to.
        return Between(self, low_value, high_value)

    def __eq__(self, other):
        return isinstance(other, type(self)) and ==

    def __ne__(self, other):
        return not self.__eq__(other)

class ConditionAttributeBase(ConditionBase, AttributeBase):
    """This base class is for conditions that can have attribute methods.

    One example is the Size condition. To complete a condition, you need
    to apply another AttributeBase method like eq().
    def __init__(self, *values):
        ConditionBase.__init__(self, *values)
        # This is assuming the first value to the condition is the attribute
        # in which can be used to generate its attribute base.
        AttributeBase.__init__(self, values[0].name)

    def __eq__(self, other):
        return ConditionBase.__eq__(self, other) and \
               AttributeBase.__eq__(self, other)

    def __ne__(self, other):
        return not self.__eq__(other)

class ComparisonCondition(ConditionBase):
    expression_format = '{0} {operator} {1}'

class Equals(ComparisonCondition):
    expression_operator = '='

class NotEquals(ComparisonCondition):
    expression_operator = '<>'

class LessThan(ComparisonCondition):
    expression_operator = '<'

class LessThanEquals(ComparisonCondition):
    expression_operator = '<='

class GreaterThan(ComparisonCondition):
    expression_operator = '>'

class GreaterThanEquals(ComparisonCondition):
    expression_operator = '>='

class In(ComparisonCondition):
    expression_operator = 'IN'
    has_grouped_values = True

class Between(ConditionBase):
    expression_operator = 'BETWEEN'
    expression_format = '{0} {operator} {1} AND {2}'

class BeginsWith(ConditionBase):
    expression_operator = 'begins_with'
    expression_format = '{operator}({0}, {1})'

class Contains(ConditionBase):
    expression_operator = 'contains'
    expression_format = '{operator}({0}, {1})'

class Size(ConditionAttributeBase):
    expression_operator = 'size'
    expression_format = '{operator}({0})'

class AttributeType(ConditionBase):
    expression_operator = 'attribute_type'
    expression_format = '{operator}({0}, {1})'

class AttributeExists(ConditionBase):
    expression_operator = 'attribute_exists'
    expression_format = '{operator}({0})'

class AttributeNotExists(ConditionBase):
    expression_operator = 'attribute_not_exists'
    expression_format = '{operator}({0})'

class And(ConditionBase):
    expression_operator = 'AND'
    expression_format = '({0} {operator} {1})'

class Or(ConditionBase):
    expression_operator = 'OR'
    expression_format = '({0} {operator} {1})'

class Not(ConditionBase):
    expression_operator = 'NOT'
    expression_format = '({operator} {0})'

[docs]class Key(AttributeBase): pass
[docs]class Attr(AttributeBase): """Represents an DynamoDB item's attribute."""
[docs] def ne(self, value): """Creates a condition where the attribute is not equal to the value :param value: The value that the attribute is not equal to. """ return NotEquals(self, value)
[docs] def is_in(self, value): """Creates a condition where the attribute is in the value, :type value: list :param value: The value that the attribute is in. """ return In(self, value)
[docs] def exists(self): """Creates a condition where the attribute exists.""" return AttributeExists(self)
[docs] def not_exists(self): """Creates a condition where the attribute does not exist.""" return AttributeNotExists(self)
[docs] def contains(self, value): """Creates a condition where the attribute contains the value. :param value: The value the attribute contains. """ return Contains(self, value)
[docs] def size(self): """Creates a condition for the attribute size. Note another AttributeBase method must be called on the returned size condition to be a valid DynamoDB condition. """ return Size(self)
[docs] def attribute_type(self, value): """Creates a condition for the attribute type. :param value: The type of the attribute. """ return AttributeType(self, value)
BuiltConditionExpression = namedtuple( 'BuiltConditionExpression', ['condition_expression', 'attribute_name_placeholders', 'attribute_value_placeholders'] ) class ConditionExpressionBuilder(object): """This class is used to build condition expressions with placeholders""" def __init__(self): self._name_count = 0 self._value_count = 0 self._name_placeholder = 'n' self._value_placeholder = 'v' def _get_name_placeholder(self): return '#' + self._name_placeholder + str(self._name_count) def _get_value_placeholder(self): return ':' + self._value_placeholder + str(self._value_count) def reset(self): """Resets the placeholder name and values""" self._name_count = 0 self._value_count = 0 def build_expression(self, condition, is_key_condition=False): """Builds the condition expression and the dictionary of placeholders. :type condition: ConditionBase :param condition: A condition to be built into a condition expression string with any necessary placeholders. :type is_key_condition: Boolean :param is_key_condition: True if the expression is for a KeyConditionExpression. False otherwise. :rtype: (string, dict, dict) :returns: Will return a string representing the condition with placeholders inserted where necessary, a dictionary of placeholders for attribute names, and a dictionary of placeholders for attribute values. Here is a sample return value: ('#n0 = :v0', {'#n0': 'myattribute'}, {':v1': 'myvalue'}) """ if not isinstance(condition, ConditionBase): raise DynamoDBNeedsConditionError(condition) attribute_name_placeholders = {} attribute_value_placeholders = {} condition_expression = self._build_expression( condition, attribute_name_placeholders, attribute_value_placeholders, is_key_condition=is_key_condition) return BuiltConditionExpression( condition_expression=condition_expression, attribute_name_placeholders=attribute_name_placeholders, attribute_value_placeholders=attribute_value_placeholders ) def _build_expression(self, condition, attribute_name_placeholders, attribute_value_placeholders, is_key_condition): expression_dict = condition.get_expression() replaced_values = [] for value in expression_dict['values']: # Build the necessary placeholders for that value. # Placeholders are built for both attribute names and values. replaced_value = self._build_expression_component( value, attribute_name_placeholders, attribute_value_placeholders, condition.has_grouped_values, is_key_condition) replaced_values.append(replaced_value) # Fill out the expression using the operator and the # values that have been replaced with placeholders. return expression_dict['format'].format( *replaced_values, operator=expression_dict['operator']) def _build_expression_component(self, value, attribute_name_placeholders, attribute_value_placeholders, has_grouped_values, is_key_condition): # Continue to recurse if the value is a ConditionBase in order # to extract out all parts of the expression. if isinstance(value, ConditionBase): return self._build_expression( value, attribute_name_placeholders, attribute_value_placeholders, is_key_condition) # If it is not a ConditionBase, we can recurse no further. # So we check if it is an attribute and add placeholders for # its name elif isinstance(value, AttributeBase): if is_key_condition and not isinstance(value, Key): raise DynamoDBNeedsKeyConditionError( 'Attribute object %s is of type %s. ' 'KeyConditionExpression only supports Attribute objects ' 'of type Key' % (, type(value))) return self._build_name_placeholder( value, attribute_name_placeholders) # If it is anything else, we treat it as a value and thus placeholders # are needed for the value. else: return self._build_value_placeholder( value, attribute_value_placeholders, has_grouped_values) def _build_name_placeholder(self, value, attribute_name_placeholders): attribute_name = # Figure out which parts of the attribute name that needs replacement. attribute_name_parts = ATTR_NAME_REGEX.findall(attribute_name) # Add a temporary placeholder for each of these parts. placeholder_format = ATTR_NAME_REGEX.sub('%s', attribute_name) str_format_args = [] for part in attribute_name_parts: name_placeholder = self._get_name_placeholder() self._name_count += 1 str_format_args.append(name_placeholder) # Add the placeholder and value to dictionary of name placeholders. attribute_name_placeholders[name_placeholder] = part # Replace the temporary placeholders with the designated placeholders. return placeholder_format % tuple(str_format_args) def _build_value_placeholder(self, value, attribute_value_placeholders, has_grouped_values=False): # If the values are grouped, we need to add a placeholder for # each element inside of the actual value. if has_grouped_values: placeholder_list = [] for v in value: value_placeholder = self._get_value_placeholder() self._value_count += 1 placeholder_list.append(value_placeholder) attribute_value_placeholders[value_placeholder] = v # Assuming the values are grouped by parenthesis. # IN is the currently the only one that uses this so it maybe # needed to be changed in future. return '(' + ', '.join(placeholder_list) + ')' # Otherwise, treat the value as a single value that needs only # one placeholder. else: value_placeholder = self._get_value_placeholder() self._value_count += 1 attribute_value_placeholders[value_placeholder] = value return value_placeholder