CREATE TABLE entity_facts (
    entity_id uuid NOT NULL REFERENCES entities(id) ON DELETE CASCADE,
    field_name text NOT NULL,
    source_id uuid NOT NULL REFERENCES data_sources(id) ON DELETE CASCADE,
    value jsonb NOT NULL,
    observed_at timestamptz NOT NULL,
    confidence numeric(5,4) NOT NULL CHECK (confidence >= 0 AND confidence <= 1),
    valid_until timestamptz,
    PRIMARY KEY (entity_id, field_name, source_id)
);

CREATE TABLE entity_overrides (
    entity_id uuid NOT NULL REFERENCES entities(id) ON DELETE CASCADE,
    field_name text NOT NULL,
    value jsonb NOT NULL,
    user_id uuid REFERENCES users(id) ON DELETE SET NULL,
    updated_at timestamptz NOT NULL DEFAULT now(),
    PRIMARY KEY (entity_id, field_name)
);

CREATE TABLE entity_relations (
    id uuid PRIMARY KEY,
    source_entity_id uuid NOT NULL REFERENCES entities(id) ON DELETE CASCADE,
    relation_type text NOT NULL,
    target_entity_id uuid NOT NULL REFERENCES entities(id) ON DELETE CASCADE,
    source_id uuid NOT NULL REFERENCES data_sources(id) ON DELETE CASCADE,
    confidence numeric(5,4) NOT NULL CHECK (confidence >= 0 AND confidence <= 1),
    confirmed boolean NOT NULL DEFAULT false,
    first_seen_at timestamptz NOT NULL,
    last_seen_at timestamptz,
    tombstoned_at timestamptz,
    UNIQUE (source_entity_id, relation_type, target_entity_id, source_id)
);

CREATE INDEX entity_facts_source_observed_idx ON entity_facts (source_id, observed_at DESC);
CREATE INDEX entity_relations_source_idx ON entity_relations (source_id, last_seen_at DESC);