Filters

There are some ways to filter data in order to find the desired records in a model: filter and search methods. The method first operates in a way similar to filter, while the method count simply returns the records count.

To filter the data the filters argument for the previous methods must be specified as a list combined of:

• some BooleanOperator objects to apply to the next values in the filters list. The NOT operator applies to the next Filter object, while AND and OR operators apply to next two Filter objects.
• some Filter objects

You can define a filters list using a Python list combining both BooleanOperator and Filter objects.

If no operators are specified an implicit AND will be applied to all the Filter objects.

Single field filters list

To create a filters list for a single field you can use the following:

filters = [
  Filter('field1', CompareType.EQUAL, 'value1'),
]

Two fields filters list

To create a filters list with two fields you can use the following:

filters = [
  BooleanOperator.AND,
  Filter('field1', CompareType.EQUAL, 'value1'),
  Filter('field2', CompareType.EQUAL, 'value2'),
]

Multiple fields filters list

To create a filters list with three fields you have to specify two operators: the former for combining the first Filter object with the result of the operation between the second operator with the second and the third Filter objects:

filters = [
  BooleanOperator.AND,
  Filter('field1', CompareType.EQUAL, 'value1'),  # A
  BooleanOperator.OR,
  Filter('field2', CompareType.EQUAL, 'value2'),  # B
  Filter('field3', CompareType.EQUAL, 'value3'),  # C
]

The previous expression will match the record having field1 = 'value1' and those having either field2 = 'value2' or field3 = 'value3'. In Python code this would be described as A and (B or C) which equals to:

field1 == 'value1' and (field2 == 'value2' or field3 == 'value3')

If you need to create a filters list combining the first two filters or another filter, you have to change the order BooleanOperator objects:

filters = [
  BooleanOperator.AND,
  BooleanOperator.OR,
  Filter('field1', CompareType.EQUAL, 'value1'),  # A
  Filter('field2', CompareType.EQUAL, 'value2'),  # B
  Filter('field3', CompareType.EQUAL, 'value3'),  # C
]

The previous filters list will translate to (A or B) and C which equals to:

(field1 == 'value1' or field2 == 'value2') and field3 == 'value3'

You can combine multiple BooleanOperator object with multiple Filter object as you need.

Negate a filter object

You can negate a Filter object using BooleanOperator.NOT applied to the next filter or expression like the following example:

filters = [
  BooleanOperator.AND,
  Filter('field1', CompareType.EQUAL, 'value1'),
  BooleanOperator.NOT,
  Filter('field2', CompareType.EQUAL, 'value2'),
]