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55 lines
1.9 KiB
Python
55 lines
1.9 KiB
Python
"""
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Queryset helpers that resolve effective Channel field values.
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Each Channel can optionally have a related ChannelOverride row carrying user
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edits to any subset of its user-facing fields. Sync never touches the override
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row; provider metadata flows directly into Channel.* and the override table
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sits alongside with a nullable value per field. The helpers here coalesce the
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two sources into `effective_*` annotations so output querysets can sort,
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filter, and emit values correctly at SQL level (avoiding 23+ Python-side
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resolutions across the codebase).
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"""
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from django.db.models.functions import Coalesce
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OVERRIDABLE_FIELDS = (
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"name",
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"channel_number",
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"channel_group_id",
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"logo_id",
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"tvg_id",
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"tvc_guide_stationid",
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"epg_data_id",
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"stream_profile_id",
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)
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def with_effective_values(queryset, select_related_fks=False):
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"""
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Annotate the channels queryset with `effective_*` columns that resolve to
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the override value when set, otherwise fall back to the channel's own
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value. Always eagerly loads the override one-to-one to avoid N+1 when the
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caller reads annotated attributes and then the related override.
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Pass `select_related_fks=True` when the output path will access FK objects
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through the `effective_*_obj` Channel properties; this pulls the override's
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logo, channel_group, epg_data, and stream_profile in the same query so
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those accessors do not trigger per-row lookups.
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"""
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annotations = {
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f"effective_{field}": Coalesce(
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f"override__{field}",
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field,
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)
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for field in OVERRIDABLE_FIELDS
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}
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qs = queryset.select_related("override").annotate(**annotations)
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if select_related_fks:
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qs = qs.select_related(
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"override__logo",
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"override__channel_group",
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"override__epg_data",
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"override__stream_profile",
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)
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return qs
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