diff options
| -rw-r--r-- | doc/src/sgml/custom-scan.sgml | 5 | ||||
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 27 |
2 files changed, 19 insertions, 13 deletions
diff --git a/doc/src/sgml/custom-scan.sgml b/doc/src/sgml/custom-scan.sgml index 9d1ca7bfe16..5e440d2d154 100644 --- a/doc/src/sgml/custom-scan.sgml +++ b/doc/src/sgml/custom-scan.sgml @@ -37,8 +37,9 @@ <para> A custom scan provider will typically add paths for a base relation by setting the following hook, which is called after the core code has - generated what it believes to be the complete and correct set of access - paths for the relation. + generated all the access paths it can for the relation (except for + Gather paths, which are made after this call so that they can use + partial paths added by the hook): <programlisting> typedef void (*set_rel_pathlist_hook_type) (PlannerInfo *root, RelOptInfo *rel, diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index d9a2f9bf695..2aa8837880c 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -479,23 +479,28 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, } /* - * If this is a baserel, consider gathering any partial paths we may have - * created for it. (If we tried to gather inheritance children, we could - * end up with a very large number of gather nodes, each trying to grab - * its own pool of workers, so don't do this for otherrels. Instead, - * we'll consider gathering partial paths for the parent appendrel.) - */ - if (rel->reloptkind == RELOPT_BASEREL) - generate_gather_paths(root, rel); - - /* * Allow a plugin to editorialize on the set of Paths for this base * relation. It could add new paths (such as CustomPaths) by calling - * add_path(), or delete or modify paths added by the core code. + * add_path(), or add_partial_path() if parallel aware. It could also + * delete or modify paths added by the core code. */ if (set_rel_pathlist_hook) (*set_rel_pathlist_hook) (root, rel, rti, rte); + /* + * If this is a baserel, we should normally consider gathering any partial + * paths we may have created for it. We have to do this after calling the + * set_rel_pathlist_hook, else it cannot add partial paths to be included + * here. + * + * However, if this is an inheritance child, skip it. Otherwise, we could + * end up with a very large number of gather nodes, each trying to grab + * its own pool of workers. Instead, we'll consider gathering partial + * paths for the parent appendrel. + */ + if (rel->reloptkind == RELOPT_BASEREL) + generate_gather_paths(root, rel); + /* Now find the cheapest of the paths for this rel */ set_cheapest(rel); |