On Sun, Apr 16, 2023 at 1:20 AM Miroslav Bendik <miroslav.ben...@gmail.com> wrote:
> Postgres allows incremental sort only for ordered indexes. Function > build_index_paths dont build partial order paths for access methods > with order support. My patch adds support for incremental ordering > with access method. I think this is a meaningful optimization. I reviewed the patch and here are the comments from me. * I understand the new param 'match_pathkeys_length_p' is used to tell how many presorted keys are useful. I think list_length(orderbyclauses) will do the same. So there is no need to add the new param, thus we can reduce the code diffs. * Now that match_pathkeys_to_index() returns a prefix of the pathkeys rather than returns NIL immediately when there is a failure to match, it seems the two local variables 'orderby_clauses' and 'clause_columns' are not necessary any more. I think we can instead lappend the matched 'expr' and 'indexcol' to '*orderby_clauses_p' and '*clause_columns_p' directly. In this way we can still call 'return' when we come to a failure to match. * In build_index_paths(), I think the diff can be reduced to - if (orderbyclauses) - useful_pathkeys = root->query_pathkeys; - else - useful_pathkeys = NIL; + useful_pathkeys = list_truncate(list_copy(root->query_pathkeys), + list_length(orderbyclauses)); * Several comments in match_pathkeys_to_index() are out of date. We need to revise them to cope with the change. * I think it's better to provide a test case. Thanks Richard
