Thanks, for suggestions.
On Sun 02. 07. 2023 at 10:18 Richard Guo <[email protected]> wrote:
> 1. For comment "On success, the result list is ordered by pathkeys.", I
> think it'd be more accurate if we say something like "On success, the
> result list is ordered by pathkeys or a prefix list of pathkeys."
> considering the possibility of incremental sort.
>
> 2. The comment below is not true anymore.
>
> /*
> * Note: for any failure to match, we just return NIL immediately.
> * There is no value in matching just some of the pathkeys.
> */
> We should either remove it or change it to emphasize that we may return
> a prefix of the pathkeys for incremental sort.
Comments are updated now.
> BTW, would you please add the patch to the CF to not lose track of it?
Submitted <https://commitfest.postgresql.org/43/4433/>
--
Best regards
Miroslav
diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index 0065c8992b..a1daa31d07 100644
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -978,10 +978,8 @@ build_index_paths(PlannerInfo *root, RelOptInfo *rel,
match_pathkeys_to_index(index, root->query_pathkeys,
&orderbyclauses,
&orderbyclausecols);
- if (orderbyclauses)
- useful_pathkeys = root->query_pathkeys;
- else
- useful_pathkeys = NIL;
+ useful_pathkeys = list_copy_head(root->query_pathkeys,
+ list_length(orderbyclauses));
}
else
{
@@ -3059,16 +3057,14 @@ expand_indexqual_rowcompare(PlannerInfo *root,
* index column numbers (zero based) that each clause would be used with.
* NIL lists are returned if the ordering is not achievable this way.
*
- * On success, the result list is ordered by pathkeys, and in fact is
- * one-to-one with the requested pathkeys.
+ * On success, the result list is ordered by pathkeys or a prefix list of
+ * pathkeys. Result can be shorter than pathkeys on partial prefix match.
*/
static void
match_pathkeys_to_index(IndexOptInfo *index, List *pathkeys,
List **orderby_clauses_p,
List **clause_columns_p)
{
- List *orderby_clauses = NIL;
- List *clause_columns = NIL;
ListCell *lc1;
*orderby_clauses_p = NIL; /* set default results */
@@ -3085,8 +3081,8 @@ match_pathkeys_to_index(IndexOptInfo *index, List *pathkeys,
ListCell *lc2;
/*
- * Note: for any failure to match, we just return NIL immediately.
- * There is no value in matching just some of the pathkeys.
+ * Note: for any failure to match, we just stop matching. Current
+ * longest match is already accumulated.
*/
/* Pathkey must request default sort order for the target opfamily */
@@ -3133,8 +3129,8 @@ match_pathkeys_to_index(IndexOptInfo *index, List *pathkeys,
pathkey->pk_opfamily);
if (expr)
{
- orderby_clauses = lappend(orderby_clauses, expr);
- clause_columns = lappend_int(clause_columns, indexcol);
+ *orderby_clauses_p = lappend(*orderby_clauses_p, expr);
+ *clause_columns_p = lappend_int(*clause_columns_p, indexcol);
found = true;
break;
}
@@ -3144,12 +3140,9 @@ match_pathkeys_to_index(IndexOptInfo *index, List *pathkeys,
break;
}
- if (!found) /* fail if no match for this pathkey */
+ if (!found) /* end after first not matching expression */
return;
}
-
- *orderby_clauses_p = orderby_clauses; /* success! */
- *clause_columns_p = clause_columns;
}
/*
diff --git a/src/test/regress/expected/incremental_sort.out b/src/test/regress/expected/incremental_sort.out
index 0c3433f8e5..41c62e0268 100644
--- a/src/test/regress/expected/incremental_sort.out
+++ b/src/test/regress/expected/incremental_sort.out
@@ -1660,3 +1660,33 @@ order by 1, 2;
-> Function Scan on generate_series
(7 rows)
+-- Incremental sort for not ordered indexes, but with AM order operator
+set enable_incremental_sort = on;
+-- table with GiST index supports closest points retrieval,
+-- but has not sorted index
+create table t (a point, b int);
+create index on t using gist(a);
+insert into t select point(mod(i, 7), mod(i, 11)), i from generate_series(1, 1000) s(i);
+analyze t;
+explain (costs off) select a, b, a <-> point(5, 5) dist from t order by dist, b limit 1;
+ QUERY PLAN
+-------------------------------------------------
+ Limit
+ -> Incremental Sort
+ Sort Key: ((a <-> '(5,5)'::point)), b
+ Presorted Key: ((a <-> '(5,5)'::point))
+ -> Index Scan using t_a_idx on t
+ Order By: (a <-> '(5,5)'::point)
+(6 rows)
+
+explain (costs off) select a, b, a <-> point(5, 5) dist from t order by dist, b desc limit 1;
+ QUERY PLAN
+----------------------------------------------------
+ Limit
+ -> Incremental Sort
+ Sort Key: ((a <-> '(5,5)'::point)), b DESC
+ Presorted Key: ((a <-> '(5,5)'::point))
+ -> Index Scan using t_a_idx on t
+ Order By: (a <-> '(5,5)'::point)
+(6 rows)
+
diff --git a/src/test/regress/sql/incremental_sort.sql b/src/test/regress/sql/incremental_sort.sql
index 071f8a5268..c89e8e7409 100644
--- a/src/test/regress/sql/incremental_sort.sql
+++ b/src/test/regress/sql/incremental_sort.sql
@@ -276,3 +276,14 @@ from tenk1, lateral (select tenk1.unique1 from generate_series(1, 1000)) as sub;
explain (costs off) select sub.unique1, stringu1 || random()::text
from tenk1, lateral (select tenk1.unique1 from generate_series(1, 1000)) as sub
order by 1, 2;
+
+-- Incremental sort for not ordered indexes, but with AM order operator
+set enable_incremental_sort = on;
+-- table with GiST index supports closest points retrieval,
+-- but has not sorted index
+create table t (a point, b int);
+create index on t using gist(a);
+insert into t select point(mod(i, 7), mod(i, 11)), i from generate_series(1, 1000) s(i);
+analyze t;
+explain (costs off) select a, b, a <-> point(5, 5) dist from t order by dist, b limit 1;
+explain (costs off) select a, b, a <-> point(5, 5) dist from t order by dist, b desc limit 1;
