presto-main/src/main/java/io/prestosql/sql/planner/optimizations/IndexJoinOptimizer.java/IndexJoinOptimizer/createEquiJoinClause
class IndexJoinOptimizer:        private static List<IndexJoinNode.EquiJoinClause> createEquiJoinClause(List<Symbol> probeSymbols, List<Symbol> indexSymbols)
        {
            checkArgument(probeSymbols.size() == indexSymbols.size());
            ImmutableList.Builder<IndexJoinNode.EquiJoinClause> builder = ImmutableList.builder();
            for (int i = 0; i < probeSymbols.size(); i++) {
                builder.add(new IndexJoinNode.EquiJoinClause(probeSymbols.get(i), indexSymbols.get(i)));
            }
            return builder.build();
        }