On Thu, 22 Jul 2021 at 00:28, Ronan Dunklau <ronan.dunklau@aiven.io> wrote:
> The attached patch does the following:
> - verify the opfamily is shippable to keep pathkeys
> - generate a correct order by clause using the actual operator.
Thanks for writing the patch.
This is just a very superficial review. I've not spent a great deal
of time looking at postgres_fdw code, so would rather some eyes that
were more familiar with the code looked too.
1. This comment needs to be updated. It still mentions
is_foreign_expr, which you're no longer calling.
* is_foreign_expr would detect volatile expressions as well, but
* checking ec_has_volatile here saves some cycles.
*/
- if (pathkey_ec->ec_has_volatile ||
- !(em_expr = find_em_expr_for_rel(pathkey_ec, rel)) ||
- !is_foreign_expr(root, rel, em_expr))
+ if (!is_foreign_pathkey(root, rel, pathkey))
2. This is not a very easy return condition to read:
+ return (!pathkey_ec->ec_has_volatile &&
+ (em = find_em_for_rel(pathkey_ec, baserel)) &&
+ is_foreign_expr(root, baserel, em->em_expr) &&
+ is_shippable(pathkey->pk_opfamily, OperatorFamilyRelationId, fpinfo));
I think it would be nicer to break that down into something easier on
the eyes that could be commented a little more.
3. This comment is no longer true:
* Find an equivalence class member expression, all of whose Vars, come from
* the indicated relation.
*/
-Expr *
-find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
+EquivalenceMember*
+find_em_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
Also, missing space after EquivalenceMember.
The comment can just be moved down to:
+Expr *
+find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
+{
+ EquivalenceMember *em = find_em_for_rel(ec, rel);
+ return em ? em->em_expr : NULL;
+}
and you can rewrite the one for find_em_for_rel.
David
