gisserver.parsers.query module

The intermediate query result used by the various build_...() methods.

class gisserver.parsers.query.CompiledQuery(feature_types: list[FeatureType], lookups: list[Q] | None = None, typed_lookups: dict[str, list[Q]] | None = None, annotations: dict[str, Combinable | Q] | None = None)

Bases: object

Intermediate data for translating FES queries to Django.

This class effectively contains all data from the <fes:Filter> object, but using a format that can be translated to a Django QuerySet.

As the Abstract Syntax Tree of a FES-filter creates the ORM query, it fills this object with all intermediate bits. This allows building the final QuerySet object in a single round. Each build_...() method in the tree may add extra lookups and annotations.

__init__(feature_types: list[FeatureType], lookups: list[Q] | None = None, typed_lookups: dict[str, list[Q]] | None = None, annotations: dict[str, Combinable | Q] | None = None)

Parameters:

feature_types – The feature types this query uses. Typically, this is one feature unless a JOIN syntax is used.

The extra parameters of the init method ar typically used only in unit tests.

add_annotation(value: Combinable | Q) → str

Create a named-alias for a function/Q object. This alias can be used in a comparison, where expressions are used as left-hand-side.

add_distinct()

Enforce “SELECT DISTINCT” on the query, used when joining 1-N or N-M relationships.

add_extra_lookup(q_object: Q)

Temporary stash an extra lookup that the expression can’t return yet. This is used for XPath selectors that also filter on attributes, e.g. “element[@attr=..]/child”. The attribute lookup is processed as another filter.

add_lookups(q_object: Q, type_name: str | None = None)

Register an extra ‘WHERE’ clause of the query. This is used for comparisons, ID selectors and other query types.

add_ordering(ordering: list[str])

Read the desired result ordering from a <fes:SortBy> element.

apply_extra_lookups(comparison: Q) → Q

Combine stashed lookups with the provided Q object.

This is called for functions that compile a “Q” object. In case a node added extra lookups (for attributes), these are combined here with the actual comparison.

get_queryset() → QuerySet

Apply the filters and lookups to the queryset.

mark_empty()

Mark as returning no results.