bool target_parallel_safe,
const AggClauseCosts *agg_costs,
grouping_sets_data *gd);
+static bool is_degenerate_grouping(PlannerInfo *root);
+static void create_degenerate_grouping_paths(PlannerInfo *root,
+ RelOptInfo *input_rel,
+ PathTarget *target, RelOptInfo *grouped_rel);
+static void create_ordinary_grouping_paths(PlannerInfo *root,
+ RelOptInfo *input_rel,
+ PathTarget *target, RelOptInfo *grouped_rel,
+ RelOptInfo *partially_grouped_rel,
+ const AggClauseCosts *agg_costs,
+ grouping_sets_data *gd);
static void consider_groupingsets_paths(PlannerInfo *root,
RelOptInfo *grouped_rel,
Path *path,
*
* Note: all Paths in input_rel are expected to return the target computed
* by make_group_input_target.
- *
- * We need to consider sorted and hashed aggregation in the same function,
- * because otherwise (1) it would be harder to throw an appropriate error
- * message if neither way works, and (2) we should not allow hashtable size
- * considerations to dissuade us from using hashing if sorting is not possible.
*/
static RelOptInfo *
create_grouping_paths(PlannerInfo *root,
grouping_sets_data *gd)
{
Query *parse = root->parse;
- Path *cheapest_path = input_rel->cheapest_total_path;
RelOptInfo *grouped_rel;
RelOptInfo *partially_grouped_rel;
- AggClauseCosts agg_partial_costs; /* parallel only */
- AggClauseCosts agg_final_costs; /* parallel only */
- double dNumGroups;
- bool can_hash;
- bool can_sort;
- bool try_parallel_aggregation;
/*
* For now, all aggregated paths are added to the (GROUP_AGG, NULL)
partially_grouped_rel->fdwroutine = input_rel->fdwroutine;
/*
- * Check for degenerate grouping.
+ * Create either paths for a degenerate grouping or paths for ordinary
+ * grouping, as appropriate.
*/
- if ((root->hasHavingQual || parse->groupingSets) &&
- !parse->hasAggs && parse->groupClause == NIL)
+ if (is_degenerate_grouping(root))
+ create_degenerate_grouping_paths(root, input_rel, target, grouped_rel);
+ else
+ create_ordinary_grouping_paths(root, input_rel, target, grouped_rel,
+ partially_grouped_rel, agg_costs, gd);
+
+ set_cheapest(grouped_rel);
+ return grouped_rel;
+}
+
+/*
+ * is_degenerate_grouping
+ *
+ * A degenerate grouping is one in which the query has a HAVING qual and/or
+ * grouping sets, but no aggregates and no GROUP BY (which implies that the
+ * grouping sets are all empty).
+ */
+static bool
+is_degenerate_grouping(PlannerInfo *root)
+{
+ Query *parse = root->parse;
+
+ return (root->hasHavingQual || parse->groupingSets) &&
+ !parse->hasAggs && parse->groupClause == NIL;
+}
+
+/*
+ * create_degenerate_grouping_paths
+ *
+ * When the grouping is degenerate (see is_degenerate_grouping), we are
+ * supposed to emit either zero or one row for each grouping set depending on
+ * whether HAVING succeeds. Furthermore, there cannot be any variables in
+ * either HAVING or the targetlist, so we actually do not need the FROM table
+ * at all! We can just throw away the plan-so-far and generate a Result node.
+ * This is a sufficiently unusual corner case that it's not worth contorting
+ * the structure of this module to avoid having to generate the earlier paths
+ * in the first place.
+ */
+static void
+create_degenerate_grouping_paths(PlannerInfo *root, RelOptInfo *input_rel,
+ PathTarget *target, RelOptInfo *grouped_rel)
+{
+ Query *parse = root->parse;
+ int nrows;
+ Path *path;
+
+ nrows = list_length(parse->groupingSets);
+ if (nrows > 1)
{
/*
- * We have a HAVING qual and/or grouping sets, but no aggregates and
- * no GROUP BY (which implies that the grouping sets are all empty).
- *
- * This is a degenerate case in which we are supposed to emit either
- * zero or one row for each grouping set depending on whether HAVING
- * succeeds. Furthermore, there cannot be any variables in either
- * HAVING or the targetlist, so we actually do not need the FROM table
- * at all! We can just throw away the plan-so-far and generate a
- * Result node. This is a sufficiently unusual corner case that it's
- * not worth contorting the structure of this module to avoid having
- * to generate the earlier paths in the first place.
+ * Doesn't seem worthwhile writing code to cons up a generate_series
+ * or a values scan to emit multiple rows. Instead just make N clones
+ * and append them. (With a volatile HAVING clause, this means you
+ * might get between 0 and N output rows. Offhand I think that's
+ * desired.)
*/
- int nrows = list_length(parse->groupingSets);
- Path *path;
+ List *paths = NIL;
- if (nrows > 1)
+ while (--nrows >= 0)
{
- /*
- * Doesn't seem worthwhile writing code to cons up a
- * generate_series or a values scan to emit multiple rows. Instead
- * just make N clones and append them. (With a volatile HAVING
- * clause, this means you might get between 0 and N output rows.
- * Offhand I think that's desired.)
- */
- List *paths = NIL;
-
- while (--nrows >= 0)
- {
- path = (Path *)
- create_result_path(root, grouped_rel,
- target,
- (List *) parse->havingQual);
- paths = lappend(paths, path);
- }
- path = (Path *)
- create_append_path(grouped_rel,
- paths,
- NIL,
- NULL,
- 0,
- false,
- NIL,
- -1);
- path->pathtarget = target;
- }
- else
- {
- /* No grouping sets, or just one, so one output row */
path = (Path *)
create_result_path(root, grouped_rel,
target,
(List *) parse->havingQual);
+ paths = lappend(paths, path);
}
+ path = (Path *)
+ create_append_path(grouped_rel,
+ paths,
+ NIL,
+ NULL,
+ 0,
+ false,
+ NIL,
+ -1);
+ path->pathtarget = target;
+ }
+ else
+ {
+ /* No grouping sets, or just one, so one output row */
+ path = (Path *)
+ create_result_path(root, grouped_rel,
+ target,
+ (List *) parse->havingQual);
+ }
- add_path(grouped_rel, path);
-
- /* No need to consider any other alternatives. */
- set_cheapest(grouped_rel);
+ add_path(grouped_rel, path);
+}
- return grouped_rel;
- }
+/*
+ * create_ordinary_grouping_paths
+ *
+ * Create grouping paths for the ordinary (that is, non-degenerate) case.
+ *
+ * We need to consider sorted and hashed aggregation in the same function,
+ * because otherwise (1) it would be harder to throw an appropriate error
+ * message if neither way works, and (2) we should not allow hashtable size
+ * considerations to dissuade us from using hashing if sorting is not possible.
+ */
+static void
+create_ordinary_grouping_paths(PlannerInfo *root, RelOptInfo *input_rel,
+ PathTarget *target, RelOptInfo *grouped_rel,
+ RelOptInfo *partially_grouped_rel,
+ const AggClauseCosts *agg_costs,
+ grouping_sets_data *gd)
+{
+ Query *parse = root->parse;
+ Path *cheapest_path = input_rel->cheapest_total_path;
+ AggClauseCosts agg_partial_costs; /* parallel only */
+ AggClauseCosts agg_final_costs; /* parallel only */
+ double dNumGroups;
+ bool can_hash;
+ bool can_sort;
+ bool try_parallel_aggregation;
/*
* Estimate number of groups.
if (create_upper_paths_hook)
(*create_upper_paths_hook) (root, UPPERREL_GROUP_AGG,
input_rel, grouped_rel);
-
- /* Now choose the best path(s) */
- set_cheapest(grouped_rel);
-
- return grouped_rel;
}
-
/*
* For a given input path, consider the possible ways of doing grouping sets on
* it, by combinations of hashing and sorting. This can be called multiple
projects / users / gsingh / postgres.git / commitdiff