sql: support for SELECT with no projections

[jordanlewis]

Postgres allows this syntax to SELECT from a table with no projections.

jordan=# CREATE TABLE a (a int); INSERT INTO a VALUES(1);
CREATE TABLE
INSERT 0 1

jordan=# SELECT FROM a;
--
(1 row)

This is not supported by CockroachDB.

Jira issue: CRDB-16953

[knz]

I found that the following patch immediately delivers the functionality, without any other change:

diff --git a/pkg/sql/parser/sql.y b/pkg/sql/parser/sql.y
index 64cec45f2e..438b25f390 100644
--- a/pkg/sql/parser/sql.y
+++ b/pkg/sql/parser/sql.y
@@ -1298,7 +1298,7 @@ func (u *sqlSymUnion) asTenantClause() tree.TenantID {
 %type <*tree.Tuple> expr_tuple1_ambiguous expr_tuple_unambiguous
 %type <tree.NameList> attrs
 %type <[]string> session_var_parts
-%type <tree.SelectExprs> target_list
+%type <tree.SelectExprs> target_list opt_target_list
 %type <tree.UpdateExprs> set_clause_list
 %type <*tree.UpdateExpr> set_clause multiple_set_clause
 %type <tree.ArraySubscripts> array_subscripts
@@ -10144,7 +10144,7 @@ simple_select:
 //        [ OFFSET <expr> [ ROW | ROWS ] ]
 // %SeeAlso: WEBDOCS/select-clause.html
 simple_select_clause:
-  SELECT opt_all_clause target_list
+  SELECT opt_all_clause opt_target_list
     from_clause opt_where_clause
     group_clause having_clause window_clause
   {
@@ -10183,10 +10183,9 @@ simple_select_clause:
       Where:      tree.NewWhere(tree.AstWhere, $5.expr()),
       GroupBy:    $6.groupBy(),
       Having:     tree.NewWhere(tree.AstHaving, $7.expr()),
       Window:     $8.window(),
     }
   }
-| SELECT error // SHOW HELP: SELECT

 set_operation:
   select_clause UNION all_or_distinct select_clause
@@ -13486,6 +13485,10 @@ opt_asymmetric:
   ASYMMETRIC {}
 | /* EMPTY */ {}

+opt_target_list:
+  target_list { $$.val = $1.selExprs() }
+| /* EMPTY */ { $$.val = tree.SelectExprs{} }
+
 target_list:
   target_elem
   {

However, I am bummed out that it requires removing the SELECT error branch, which removes both error handling and the CLI interactive help.

I wasn't able to find a way to keep the error clause; I suspect (given the error with it is shift/reduce) there is something to do with a %prec clause, but I couldn't find it.

[ZhouXing19]

Hi query team, this feature is also needed by Hasura Graphql Engine. They have a workaround already, but still curious do we have a timeline for supporting this?