refactor(ast,analyzer): address PR review comments

Inline isSelectStarOnly into isTrivialSelectStar. And, revert
TypeSanitizer comment to match the original, and instead updated
to mention both limit and offset literals.

Refs: #2373

Author: codeaucafe

server/analyzer/type_sanitizer.go

@@ -61,10 +61,8 @@ func TypeSanitizer(ctx *sql.Context, a *analyzer.Analyzer, node sql.Node, scope
 			}
 			return expr, transform.SameTree, nil
 		case *expression.Literal:
-			// We want to leave limit and offset literals as GMS types. GMS's
-			// validateOffsetAndLimit uses IsInteger, which only recognizes its
-			// own type singletons. If we convert these to Doltgres types the
-			// validation rejects them with "invalid type: bigint".
+			// We want to leave limit literals alone, as they are expected to be GMS types when they appear in certain
+			// parts of the query (subqueries in particular)
 			// TODO: fix the limit and offset validation analysis to handle doltgres types
 			if _, isLimit := n.(*plan.Limit); isLimit {
 				break

server/ast/aliased_table_expr.go

@@ -151,24 +151,20 @@ func nodeAliasedTableExpr(ctx *Context, node *tree.AliasedTableExpr) (*vitess.Al
 // with no other clauses that would alter semantics (no WHERE, ORDER BY, LIMIT, GROUP BY,
 // HAVING, DISTINCT, or WITH).
 func isTrivialSelectStar(s *vitess.Select) bool {
-	return len(s.From) == 1 &&
-		!s.QueryOpts.Distinct &&
-		s.With == nil &&
-		s.Limit == nil &&
-		len(s.OrderBy) == 0 &&
-		s.Where == nil &&
-		len(s.GroupBy) == 0 &&
-		s.Having == nil &&
-		isSelectStarOnly(s.SelectExprs)
-}
-
-// isSelectStarOnly returns true when the SelectExprs list is exactly one
-// unqualified star expression (i.e. "SELECT *" with no table qualifier).
-func isSelectStarOnly(exprs vitess.SelectExprs) bool {
-	if len(exprs) != 1 {
+	if len(s.From) != 1 ||
+		s.QueryOpts.Distinct ||
+		s.With != nil ||
+		s.Limit != nil ||
+		len(s.OrderBy) != 0 ||
+		s.Where != nil ||
+		len(s.GroupBy) != 0 ||
+		s.Having != nil {
+		return false
+	}
+	if len(s.SelectExprs) != 1 {
 		return false
 	}
-	starExpr, ok := exprs[0].(*vitess.StarExpr)
+	starExpr, ok := s.SelectExprs[0].(*vitess.StarExpr)
 	if !ok {
 		return false
 	}