planner: support index_join_first() hint to prefer index join

Author: fixdb

pkg/parser/ast/misc.go

@@ -4102,7 +4102,7 @@ func (n *TableOptimizerHint) Restore(ctx *format.RestoreCtx) error {
 	}
 	// Hints without args except query block.
 	switch n.HintName.L {
-	case "mpp_1phase_agg", "mpp_2phase_agg", "hash_agg", "stream_agg", "agg_to_cop", "read_consistent_replica", "no_index_merge", "ignore_plan_cache", "limit_to_cop", "straight_join", "merge", "no_decorrelate":
+	case "mpp_1phase_agg", "mpp_2phase_agg", "hash_agg", "stream_agg", "agg_to_cop", "read_consistent_replica", "no_index_merge", "ignore_plan_cache", "limit_to_cop", "straight_join", "merge", "no_decorrelate", "index_join_first":
 		ctx.WritePlain(")")
 		return nil
 	}