Module query_utils

Factored out from django.db.models.query to avoid making the main module very
large and/or so that they can be used by other modules without getting into
circular import difficulties.

Classes

• class DeferredAttribute
  A wrapper for a deferred-loading field. When the value is read from this object the first time, the query is executed.
• class FilteredRelation
  Specify custom filtering in the ON clause of SQL joins.
• class InvalidQuery
• class InvalidQueryType
• class Q
  Encapsulate filters as objects that can then be combined logically (using `&` and `|`).
• class RegisterLookupMixin

Functions

• ▶ def check_rel_lookup_compatibility(model, target_opts, field)

  Check that self.model is compatible with target_opts. Compatibility

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  is OK if:
    1) model and opts match (where proxy inheritance is removed)
    2) model is parent of opts' model or the other way around

  Reexports

  • Imported in django.db.models.sql.query.
• ▶ def refs_expression(lookup_parts, annotations)

  Check if the lookup_parts contains references to the given annotations set. Because the LOOKUP_SEP is contained in the default annotation names, check each prefix of the lookup_parts for a match.

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  Reexports

  • Imported in django.db.models.sql.query.
• ▶ def select_related_descend(field, restricted, requested, load_fields, reverse=False)

  Return True if this field should be used to descend deeper for

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  select_related() purposes. Used by both the query construction code
  (sql.query.fill_related_selections()) and the model instance creation code
  (query.get_klass_info()).
  
  Arguments:
   * field - the field to be checked
   * restricted - a boolean field, indicating if the field list has been
     manually restricted using a requested clause)
   * requested - The select_related() dictionary.
   * load_fields - the set of fields to be loaded on this model
   * reverse - boolean, True if we are checking a reverse select related

  Reexports

  • Imported in django.db.models.sql.compiler.
• ▷ def subclasses(cls)

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