@Override public boolean indexAccessible(final IndexInfo ii) throws QueryException { int costs = 0; final ExprList el = new ExprList(exprs.length); for (final Expr expr : exprs) { // check if expression can be rewritten, and if access is not sequential if (!expr.indexAccessible(ii)) return false; // skip expressions without results if (ii.costs == 0) continue; costs += ii.costs; el.add(ii.expr); } // use summarized costs for estimation ii.costs = costs; // no expressions means no costs: expression will later be ignored ii.expr = el.size() == 1 ? el.get(0) : new Union(info, el.finish()); return true; }