-- data_table_links: связи между справочниками (родитель → подсправочник)
CREATE TABLE IF NOT EXISTS data_table_links (
  id SERIAL PRIMARY KEY,
  organization_id INTEGER NOT NULL REFERENCES organizations(id) ON DELETE CASCADE,
  parent_table_id INTEGER NOT NULL REFERENCES data_tables(id) ON DELETE CASCADE,
  child_table_id INTEGER NOT NULL REFERENCES data_tables(id) ON DELETE CASCADE,
  parent_column_index INTEGER NOT NULL DEFAULT 0,
  child_column_index INTEGER NOT NULL DEFAULT 0,
  parent_values JSONB NOT NULL DEFAULT '[]',
  created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
  updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
);

CREATE INDEX IF NOT EXISTS data_table_links_parent_idx ON data_table_links(parent_table_id);
CREATE INDEX IF NOT EXISTS data_table_links_child_idx ON data_table_links(child_table_id);
CREATE UNIQUE INDEX IF NOT EXISTS data_table_links_parent_child_unique
  ON data_table_links(parent_table_id, child_table_id);