* Routines copied from PostgreSQL core distribution.
*
* src/backend/optimizer/path/allpaths.c
- * standard_join_search()
* set_plain_rel_pathlist()
* set_append_rel_pathlist()
* accumulate_append_subpath()
* set_dummy_rel_pathlist()
+ * standard_join_search()
*
* src/backend/optimizer/path/joinrels.c
* join_search_one_level()
*/
/*
- * standard_join_search
- * Find possible joinpaths for a query by successively finding ways
- * to join component relations into join relations.
- *
- * 'levels_needed' is the number of iterations needed, ie, the number of
- * independent jointree items in the query. This is > 1.
- *
- * 'initial_rels' is a list of RelOptInfo nodes for each independent
- * jointree item. These are the components to be joined together.
- * Note that levels_needed == list_length(initial_rels).
- *
- * Returns the final level of join relations, i.e., the relation that is
- * the result of joining all the original relations together.
- * At least one implementation path must be provided for this relation and
- * all required sub-relations.
- *
- * To support loadable plugins that modify planner behavior by changing the
- * join searching algorithm, we provide a hook variable that lets a plugin
- * replace or supplement this function. Any such hook must return the same
- * final join relation as the standard code would, but it might have a
- * different set of implementation paths attached, and only the sub-joinrels
- * needed for these paths need have been instantiated.
- *
- * Note to plugin authors: the functions invoked during standard_join_search()
- * modify root->join_rel_list and root->join_rel_hash. If you want to do more
- * than one join-order search, you'll probably need to save and restore the
- * original states of those data structures. See geqo_eval() for an example.
- */
-RelOptInfo *
-standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
-{
- int lev;
- RelOptInfo *rel;
-
- /*
- * This function cannot be invoked recursively within any one planning
- * problem, so join_rel_level[] can't be in use already.
- */
- Assert(root->join_rel_level == NULL);
-
- /*
- * We employ a simple "dynamic programming" algorithm: we first find all
- * ways to build joins of two jointree items, then all ways to build joins
- * of three items (from two-item joins and single items), then four-item
- * joins, and so on until we have considered all ways to join all the
- * items into one rel.
- *
- * root->join_rel_level[j] is a list of all the j-item rels. Initially we
- * set root->join_rel_level[1] to represent all the single-jointree-item
- * relations.
- */
- root->join_rel_level = (List **) palloc0((levels_needed + 1) * sizeof(List *));
-
- root->join_rel_level[1] = initial_rels;
-
- for (lev = 2; lev <= levels_needed; lev++)
- {
- ListCell *lc;
-
- /*
- * Determine all possible pairs of relations to be joined at this
- * level, and build paths for making each one from every available
- * pair of lower-level relations.
- */
- join_search_one_level(root, lev);
-
- /*
- * Do cleanup work on each just-processed rel.
- */
- foreach(lc, root->join_rel_level[lev])
- {
- rel = (RelOptInfo *) lfirst(lc);
-
- /* Find and save the cheapest paths for this rel */
- set_cheapest(rel);
-
-#ifdef OPTIMIZER_DEBUG
- debug_print_rel(root, rel);
-#endif
- }
- }
-
- /*
- * We should have a single rel at the final level.
- */
- if (root->join_rel_level[levels_needed] == NIL)
- elog(ERROR, "failed to build any %d-way joins", levels_needed);
- Assert(list_length(root->join_rel_level[levels_needed]) == 1);
-
- rel = (RelOptInfo *) linitial(root->join_rel_level[levels_needed]);
-
- root->join_rel_level = NULL;
-
- return rel;
-}
-
-/*
* set_plain_rel_pathlist
* Build access paths for a plain relation (no subquery, no inheritance)
*/
}
/*
+ * standard_join_search
+ * Find possible joinpaths for a query by successively finding ways
+ * to join component relations into join relations.
+ *
+ * 'levels_needed' is the number of iterations needed, ie, the number of
+ * independent jointree items in the query. This is > 1.
+ *
+ * 'initial_rels' is a list of RelOptInfo nodes for each independent
+ * jointree item. These are the components to be joined together.
+ * Note that levels_needed == list_length(initial_rels).
+ *
+ * Returns the final level of join relations, i.e., the relation that is
+ * the result of joining all the original relations together.
+ * At least one implementation path must be provided for this relation and
+ * all required sub-relations.
+ *
+ * To support loadable plugins that modify planner behavior by changing the
+ * join searching algorithm, we provide a hook variable that lets a plugin
+ * replace or supplement this function. Any such hook must return the same
+ * final join relation as the standard code would, but it might have a
+ * different set of implementation paths attached, and only the sub-joinrels
+ * needed for these paths need have been instantiated.
+ *
+ * Note to plugin authors: the functions invoked during standard_join_search()
+ * modify root->join_rel_list and root->join_rel_hash. If you want to do more
+ * than one join-order search, you'll probably need to save and restore the
+ * original states of those data structures. See geqo_eval() for an example.
+ */
+RelOptInfo *
+standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
+{
+ int lev;
+ RelOptInfo *rel;
+
+ /*
+ * This function cannot be invoked recursively within any one planning
+ * problem, so join_rel_level[] can't be in use already.
+ */
+ Assert(root->join_rel_level == NULL);
+
+ /*
+ * We employ a simple "dynamic programming" algorithm: we first find all
+ * ways to build joins of two jointree items, then all ways to build joins
+ * of three items (from two-item joins and single items), then four-item
+ * joins, and so on until we have considered all ways to join all the
+ * items into one rel.
+ *
+ * root->join_rel_level[j] is a list of all the j-item rels. Initially we
+ * set root->join_rel_level[1] to represent all the single-jointree-item
+ * relations.
+ */
+ root->join_rel_level = (List **) palloc0((levels_needed + 1) * sizeof(List *));
+
+ root->join_rel_level[1] = initial_rels;
+
+ for (lev = 2; lev <= levels_needed; lev++)
+ {
+ ListCell *lc;
+
+ /*
+ * Determine all possible pairs of relations to be joined at this
+ * level, and build paths for making each one from every available
+ * pair of lower-level relations.
+ */
+ join_search_one_level(root, lev);
+
+ /*
+ * Do cleanup work on each just-processed rel.
+ */
+ foreach(lc, root->join_rel_level[lev])
+ {
+ rel = (RelOptInfo *) lfirst(lc);
+
+ /* Find and save the cheapest paths for this rel */
+ set_cheapest(rel);
+
+#ifdef OPTIMIZER_DEBUG
+ debug_print_rel(root, rel);
+#endif
+ }
+ }
+
+ /*
+ * We should have a single rel at the final level.
+ */
+ if (root->join_rel_level[levels_needed] == NIL)
+ elog(ERROR, "failed to build any %d-way joins", levels_needed);
+ Assert(list_length(root->join_rel_level[levels_needed]) == 1);
+
+ rel = (RelOptInfo *) linitial(root->join_rel_level[levels_needed]);
+
+ root->join_rel_level = NULL;
+
+ return rel;
+}
+
+/*
* join_search_one_level
* Consider ways to produce join relations containing exactly 'level'
* jointree items. (This is one step of the dynamic-programming method
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