42 lines
1.6 KiB
PL/PgSQL
42 lines
1.6 KiB
PL/PgSQL
-- A GUI publication binds paused to its display epoch. Agent barrier changes
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-- must therefore invalidate that agent's displays in the same transaction,
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-- even when the writer does not use the API helper. Independent agents keep
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-- their epochs. This is allocation, not a Runner barrier acknowledgement.
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CREATE FUNCTION fence_agent_barrier_displays() RETURNS TRIGGER LANGUAGE plpgsql AS $$
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DECLARE
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target_bot TEXT;
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was_paused BOOLEAN := FALSE;
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is_paused BOOLEAN := FALSE;
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BEGIN
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IF TG_OP <> 'INSERT' THEN
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target_bot := OLD.bot_id;
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was_paused := OLD.paused;
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END IF;
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IF TG_OP <> 'DELETE' THEN
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target_bot := NEW.bot_id;
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is_paused := NEW.paused;
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END IF;
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-- A primary key move also removes the old bot's barrier.
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IF TG_OP='UPDATE' AND NEW.bot_id IS DISTINCT FROM OLD.bot_id THEN
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IF OLD.paused THEN
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UPDATE computer_screens SET display_epoch=display_epoch+1
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WHERE bot_id=OLD.bot_id;
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END IF;
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was_paused := FALSE;
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END IF;
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IF was_paused IS DISTINCT FROM is_paused THEN
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UPDATE computer_screens SET display_epoch=display_epoch+1
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WHERE bot_id=target_bot;
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END IF;
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RETURN NULL;
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END
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$$;
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CREATE TRIGGER agent_barrier_display_epochs
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AFTER INSERT OR UPDATE OR DELETE ON agent_mutation_barriers
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FOR EACH ROW EXECUTE FUNCTION fence_agent_barrier_displays();
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-- Existing paused rows may already have a published unpaused GUI epoch.
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UPDATE computer_screens s SET display_epoch=s.display_epoch+1
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WHERE EXISTS(SELECT 1 FROM agent_mutation_barriers b WHERE b.bot_id=s.bot_id AND b.paused);
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