Function join

src/runtime/join.ts:866–888

(multiIndex: MultiIndex, providers : ProposalProvider[], vars : Variable[], prefix: any[] = [], options: JoinOptions = {})

// to determine how may rounds of generic join we need to do. Since we solve
// for one variable each round, it's the number of vars in the query.
export function join(multiIndex: MultiIndex, providers : ProposalProvider[], vars : Variable[], prefix: any[] = [], options: JoinOptions = {}) {
  let rows = options.rows || [];
  let {presolved, accepted} = preJoinAccept(multiIndex, providers, vars, prefix);
  if(!accepted) return rows;
  let rounds = 0;
  for(let variable of vars) {
    if(variable !== undefined) rounds++;
  }
  rounds = rounds - presolved;
  if(presolved > 0 && rounds === 0) {
    rows.push(prefix.slice());
  } else if(rounds === 0) {
    for(let provider of providers) {
      if(!provider.accept(multiIndex, prefix, null, true)) {
        return rows;
      }
    }
    rows.push(prefix.slice());
  } else {
    joinRound(multiIndex, providers, prefix, rounds, rows, options);
  }
  return rows;
}