double input_tuples, int width, Cost comparison_cost, int sort_mem,
double limit_tuples)
{
- Cost startup_cost = 0,
- run_cost = 0,
+ Cost startup_cost,
+ run_cost,
input_run_cost = input_total_cost - input_startup_cost;
double group_tuples,
input_groups;
group_input_run_cost;
List *presortedExprs = NIL;
ListCell *l;
- int i = 0;
bool unknown_varno = false;
- Assert(presorted_keys != 0);
+ Assert(presorted_keys > 0 && presorted_keys < list_length(pathkeys));
/*
* We want to be sure the cost of a sort is never estimated as zero, even
/* expression not containing any Vars with "varno 0" */
presortedExprs = lappend(presortedExprs, member->em_expr);
- i++;
- if (i >= presorted_keys)
+ if (foreach_current_index(l) + 1 >= presorted_keys)
break;
}
- /* Estimate number of groups with equal presorted keys. */
+ /* Estimate the number of groups with equal presorted keys. */
if (!unknown_varno)
input_groups = estimate_num_groups(root, presortedExprs, input_tuples,
NULL, NULL);
group_input_run_cost = input_run_cost / input_groups;
/*
- * Estimate average cost of sorting of one group where presorted keys are
- * equal. Incremental sort is sensitive to distribution of tuples to the
- * groups, where we're relying on quite rough assumptions. Thus, we're
- * pessimistic about incremental sort performance and increase its average
- * group size by half.
+ * Estimate the average cost of sorting of one group where presorted keys
+ * are equal.
*/
cost_tuplesort(&group_startup_cost, &group_run_cost,
- 1.5 * group_tuples, width, comparison_cost, sort_mem,
+ group_tuples, width, comparison_cost, sort_mem,
limit_tuples);
/*
* Startup cost of incremental sort is the startup cost of its first group
* plus the cost of its input.
*/
- startup_cost += group_startup_cost
- + input_startup_cost + group_input_run_cost;
+ startup_cost = group_startup_cost + input_startup_cost +
+ group_input_run_cost;
/*
* After we started producing tuples from the first group, the cost of
* group, plus the total cost to process the remaining groups, plus the
* remaining cost of input.
*/
- run_cost += group_run_cost
- + (group_run_cost + group_startup_cost) * (input_groups - 1)
- + group_input_run_cost * (input_groups - 1);
+ run_cost = group_run_cost + (group_run_cost + group_startup_cost) *
+ (input_groups - 1) + group_input_run_cost * (input_groups - 1);
/*
* Incremental sort adds some overhead by itself. Firstly, it has to
* detect the sort groups. This is roughly equal to one extra copy and
- * comparison per tuple. Secondly, it has to reset the tuplesort context
- * for every group.
+ * comparison per tuple.
*/
run_cost += (cpu_tuple_cost + comparison_cost) * input_tuples;
+
+ /*
+ * Additionally, we charge double cpu_tuple_cost for each input group to
+ * account for the tuplesort_reset that's performed after each group.
+ */
run_cost += 2.0 * cpu_tuple_cost * input_groups;
path->rows = input_tuples;
foreach(lc, input_rel->pathlist)
{
Path *input_path = (Path *) lfirst(lc);
- Path *sorted_path = input_path;
+ Path *sorted_path;
bool is_sorted;
int presorted_keys;
input_path->pathkeys, &presorted_keys);
if (is_sorted)
- {
- /* Use the input path as is, but add a projection step if needed */
- if (sorted_path->pathtarget != target)
- sorted_path = apply_projection_to_path(root, ordered_rel,
- sorted_path, target);
-
- add_path(ordered_rel, sorted_path);
- }
+ sorted_path = input_path;
else
{
/*
- * Try adding an explicit sort, but only to the cheapest total
- * path since a full sort should generally add the same cost to
- * all paths.
+ * Try at least sorting the cheapest path and also try
+ * incrementally sorting any path which is partially sorted
+ * already (no need to deal with paths which have presorted keys
+ * when incremental sort is disabled unless it's the cheapest
+ * input path).
*/
- if (input_path == cheapest_input_path)
- {
- /*
- * Sort the cheapest input path. An explicit sort here can
- * take advantage of LIMIT.
- */
+ if (input_path != cheapest_input_path &&
+ (presorted_keys == 0 || !enable_incremental_sort))
+ continue;
+
+ /*
+ * We've no need to consider both a sort and incremental sort.
+ * We'll just do a sort if there are no presorted keys and an
+ * incremental sort when there are presorted keys.
+ */
+ if (presorted_keys == 0 || !enable_incremental_sort)
sorted_path = (Path *) create_sort_path(root,
ordered_rel,
input_path,
root->sort_pathkeys,
limit_tuples);
- /* Add projection step if needed */
- if (sorted_path->pathtarget != target)
- sorted_path = apply_projection_to_path(root, ordered_rel,
- sorted_path, target);
-
- add_path(ordered_rel, sorted_path);
- }
-
- /*
- * If incremental sort is enabled, then try it as well. Unlike
- * with regular sorts, we can't just look at the cheapest path,
- * because the cost of incremental sort depends on how well
- * presorted the path is. Additionally incremental sort may enable
- * a cheaper startup path to win out despite higher total cost.
- */
- if (!enable_incremental_sort)
- continue;
-
- /* Likewise, if the path can't be used for incremental sort. */
- if (!presorted_keys)
- continue;
-
- /* Also consider incremental sort. */
- sorted_path = (Path *) create_incremental_sort_path(root,
- ordered_rel,
- input_path,
- root->sort_pathkeys,
- presorted_keys,
- limit_tuples);
+ else
+ sorted_path = (Path *) create_incremental_sort_path(root,
+ ordered_rel,
+ input_path,
+ root->sort_pathkeys,
+ presorted_keys,
+ limit_tuples);
+ }
- /* Add projection step if needed */
- if (sorted_path->pathtarget != target)
- sorted_path = apply_projection_to_path(root, ordered_rel,
- sorted_path, target);
+ /* Add projection step if needed */
+ if (sorted_path->pathtarget != target)
+ sorted_path = apply_projection_to_path(root, ordered_rel,
+ sorted_path, target);
- add_path(ordered_rel, sorted_path);
- }
+ add_path(ordered_rel, sorted_path);
}
/*
{
/*
* Use any available suitably-sorted path as input, and also consider
- * sorting the cheapest-total path.
+ * sorting the cheapest-total path and incremental sort on any paths
+ * with presorted keys.
*/
foreach(lc, input_rel->pathlist)
{
Path *path = (Path *) lfirst(lc);
- Path *path_original = path;
bool is_sorted;
int presorted_keys;
path->pathkeys,
&presorted_keys);
- if (path == cheapest_path || is_sorted)
+ if (!is_sorted)
{
- /* Sort the cheapest-total path if it isn't already sorted */
- if (!is_sorted)
+ /*
+ * Try at least sorting the cheapest path and also try
+ * incrementally sorting any path which is partially sorted
+ * already (no need to deal with paths which have presorted
+ * keys when incremental sort is disabled unless it's the
+ * cheapest input path).
+ */
+ if (path != cheapest_path &&
+ (presorted_keys == 0 || !enable_incremental_sort))
+ continue;
+
+ /*
+ * We've no need to consider both a sort and incremental sort.
+ * We'll just do a sort if there are no presorted keys and an
+ * incremental sort when there are presorted keys.
+ */
+ if (presorted_keys == 0 || !enable_incremental_sort)
path = (Path *) create_sort_path(root,
grouped_rel,
path,
root->group_pathkeys,
-1.0);
-
- /* Now decide what to stick atop it */
- if (parse->groupingSets)
- {
- consider_groupingsets_paths(root, grouped_rel,
- path, true, can_hash,
- gd, agg_costs, dNumGroups);
- }
- else if (parse->hasAggs)
- {
- /*
- * We have aggregation, possibly with plain GROUP BY. Make
- * an AggPath.
- */
- add_path(grouped_rel, (Path *)
- create_agg_path(root,
- grouped_rel,
- path,
- grouped_rel->reltarget,
- parse->groupClause ? AGG_SORTED : AGG_PLAIN,
- AGGSPLIT_SIMPLE,
- parse->groupClause,
- havingQual,
- agg_costs,
- dNumGroups));
- }
- else if (parse->groupClause)
- {
- /*
- * We have GROUP BY without aggregation or grouping sets.
- * Make a GroupPath.
- */
- add_path(grouped_rel, (Path *)
- create_group_path(root,
- grouped_rel,
- path,
- parse->groupClause,
- havingQual,
- dNumGroups));
- }
else
- {
- /* Other cases should have been handled above */
- Assert(false);
- }
+ path = (Path *) create_incremental_sort_path(root,
+ grouped_rel,
+ path,
+ root->group_pathkeys,
+ presorted_keys,
+ -1.0);
}
- /*
- * Now we may consider incremental sort on this path, but only
- * when the path is not already sorted and when incremental sort
- * is enabled.
- */
- if (is_sorted || !enable_incremental_sort)
- continue;
-
- /* Restore the input path (we might have added Sort on top). */
- path = path_original;
-
- /* no shared prefix, no point in building incremental sort */
- if (presorted_keys == 0)
- continue;
-
- /*
- * We should have already excluded pathkeys of length 1 because
- * then presorted_keys > 0 would imply is_sorted was true.
- */
- Assert(list_length(root->group_pathkeys) != 1);
-
- path = (Path *) create_incremental_sort_path(root,
- grouped_rel,
- path,
- root->group_pathkeys,
- presorted_keys,
- -1.0);
-
/* Now decide what to stick atop it */
if (parse->groupingSets)
{
foreach(lc, partially_grouped_rel->pathlist)
{
Path *path = (Path *) lfirst(lc);
- Path *path_original = path;
bool is_sorted;
int presorted_keys;
path->pathkeys,
&presorted_keys);
- /*
- * Insert a Sort node, if required. But there's no point in
- * sorting anything but the cheapest path.
- */
if (!is_sorted)
{
- if (path != partially_grouped_rel->cheapest_total_path)
+ /*
+ * Try at least sorting the cheapest path and also try
+ * incrementally sorting any path which is partially
+ * sorted already (no need to deal with paths which have
+ * presorted keys when incremental sort is disabled unless
+ * it's the cheapest input path).
+ */
+ if (path != partially_grouped_rel->cheapest_total_path &&
+ (presorted_keys == 0 || !enable_incremental_sort))
continue;
- path = (Path *) create_sort_path(root,
- grouped_rel,
- path,
- root->group_pathkeys,
- -1.0);
+
+ /*
+ * We've no need to consider both a sort and incremental
+ * sort. We'll just do a sort if there are no pre-sorted
+ * keys and an incremental sort when there are presorted
+ * keys.
+ */
+ if (presorted_keys == 0 || !enable_incremental_sort)
+ path = (Path *) create_sort_path(root,
+ grouped_rel,
+ path,
+ root->group_pathkeys,
+ -1.0);
+ else
+ path = (Path *) create_incremental_sort_path(root,
+ grouped_rel,
+ path,
+ root->group_pathkeys,
+ presorted_keys,
+ -1.0);
}
if (parse->hasAggs)
havingQual,
dNumGroups));
- /*
- * Now we may consider incremental sort on this path, but only
- * when the path is not already sorted and when incremental
- * sort is enabled.
- */
- if (is_sorted || !enable_incremental_sort)
- continue;
-
- /* Restore the input path (we might have added Sort on top). */
- path = path_original;
-
- /* no shared prefix, not point in building incremental sort */
- if (presorted_keys == 0)
- continue;
-
- /*
- * We should have already excluded pathkeys of length 1
- * because then presorted_keys > 0 would imply is_sorted was
- * true.
- */
- Assert(list_length(root->group_pathkeys) != 1);
-
- path = (Path *) create_incremental_sort_path(root,
- grouped_rel,
- path,
- root->group_pathkeys,
- presorted_keys,
- -1.0);
-
- if (parse->hasAggs)
- add_path(grouped_rel, (Path *)
- create_agg_path(root,
- grouped_rel,
- path,
- grouped_rel->reltarget,
- parse->groupClause ? AGG_SORTED : AGG_PLAIN,
- AGGSPLIT_FINAL_DESERIAL,
- parse->groupClause,
- havingQual,
- agg_final_costs,
- dNumGroups));
- else
- add_path(grouped_rel, (Path *)
- create_group_path(root,
- grouped_rel,
- path,
- parse->groupClause,
- havingQual,
- dNumGroups));
}
}
}
{
Path *path = (Path *) lfirst(lc);
bool is_sorted;
+ int presorted_keys;
- is_sorted = pathkeys_contained_in(root->group_pathkeys,
- path->pathkeys);
- if (path == cheapest_total_path || is_sorted)
+ is_sorted = pathkeys_count_contained_in(root->group_pathkeys,
+ path->pathkeys,
+ &presorted_keys);
+ if (!is_sorted)
{
- /* Sort the cheapest partial path, if it isn't already */
- if (!is_sorted)
+ /*
+ * Try at least sorting the cheapest path and also try
+ * incrementally sorting any path which is partially sorted
+ * already (no need to deal with paths which have presorted
+ * keys when incremental sort is disabled unless it's the
+ * cheapest input path).
+ */
+ if (path != cheapest_total_path &&
+ (presorted_keys == 0 || !enable_incremental_sort))
+ continue;
+
+ /*
+ * We've no need to consider both a sort and incremental sort.
+ * We'll just do a sort if there are no presorted keys and an
+ * incremental sort when there are presorted keys.
+ */
+ if (presorted_keys == 0 || !enable_incremental_sort)
path = (Path *) create_sort_path(root,
partially_grouped_rel,
path,
root->group_pathkeys,
-1.0);
-
- if (parse->hasAggs)
- add_path(partially_grouped_rel, (Path *)
- create_agg_path(root,
- partially_grouped_rel,
- path,
- partially_grouped_rel->reltarget,
- parse->groupClause ? AGG_SORTED : AGG_PLAIN,
- AGGSPLIT_INITIAL_SERIAL,
- parse->groupClause,
- NIL,
- agg_partial_costs,
- dNumPartialGroups));
else
- add_path(partially_grouped_rel, (Path *)
- create_group_path(root,
- partially_grouped_rel,
- path,
- parse->groupClause,
- NIL,
- dNumPartialGroups));
+ path = (Path *) create_incremental_sort_path(root,
+ partially_grouped_rel,
+ path,
+ root->group_pathkeys,
+ presorted_keys,
+ -1.0);
}
- }
-
- /*
- * Consider incremental sort on all partial paths, if enabled.
- *
- * We can also skip the entire loop when we only have a single-item
- * group_pathkeys because then we can't possibly have a presorted
- * prefix of the list without having the list be fully sorted.
- */
- if (enable_incremental_sort && list_length(root->group_pathkeys) > 1)
- {
- foreach(lc, input_rel->pathlist)
- {
- Path *path = (Path *) lfirst(lc);
- bool is_sorted;
- int presorted_keys;
-
- is_sorted = pathkeys_count_contained_in(root->group_pathkeys,
- path->pathkeys,
- &presorted_keys);
-
- /* Ignore already sorted paths */
- if (is_sorted)
- continue;
-
- if (presorted_keys == 0)
- continue;
- /* Since we have presorted keys, consider incremental sort. */
- path = (Path *) create_incremental_sort_path(root,
- partially_grouped_rel,
- path,
- root->group_pathkeys,
- presorted_keys,
- -1.0);
-
- if (parse->hasAggs)
- add_path(partially_grouped_rel, (Path *)
- create_agg_path(root,
- partially_grouped_rel,
- path,
- partially_grouped_rel->reltarget,
- parse->groupClause ? AGG_SORTED : AGG_PLAIN,
- AGGSPLIT_INITIAL_SERIAL,
- parse->groupClause,
- NIL,
- agg_partial_costs,
- dNumPartialGroups));
- else
- add_path(partially_grouped_rel, (Path *)
- create_group_path(root,
- partially_grouped_rel,
- path,
- parse->groupClause,
- NIL,
- dNumPartialGroups));
- }
+ if (parse->hasAggs)
+ add_path(partially_grouped_rel, (Path *)
+ create_agg_path(root,
+ partially_grouped_rel,
+ path,
+ partially_grouped_rel->reltarget,
+ parse->groupClause ? AGG_SORTED : AGG_PLAIN,
+ AGGSPLIT_INITIAL_SERIAL,
+ parse->groupClause,
+ NIL,
+ agg_partial_costs,
+ dNumPartialGroups));
+ else
+ add_path(partially_grouped_rel, (Path *)
+ create_group_path(root,
+ partially_grouped_rel,
+ path,
+ parse->groupClause,
+ NIL,
+ dNumPartialGroups));
}
}
foreach(lc, input_rel->partial_pathlist)
{
Path *path = (Path *) lfirst(lc);
- Path *path_original = path;
bool is_sorted;
int presorted_keys;
path->pathkeys,
&presorted_keys);
- if (path == cheapest_partial_path || is_sorted)
+ if (!is_sorted)
{
- /* Sort the cheapest partial path, if it isn't already */
- if (!is_sorted)
+ /*
+ * Try at least sorting the cheapest path and also try
+ * incrementally sorting any path which is partially sorted
+ * already (no need to deal with paths which have presorted
+ * keys when incremental sort is disabled unless it's the
+ * cheapest input path).
+ */
+ if (path != cheapest_partial_path &&
+ (presorted_keys == 0 || !enable_incremental_sort))
+ continue;
+
+ /*
+ * We've no need to consider both a sort and incremental sort.
+ * We'll just do a sort if there are no presorted keys and an
+ * incremental sort when there are presorted keys.
+ */
+ if (presorted_keys == 0 || !enable_incremental_sort)
path = (Path *) create_sort_path(root,
partially_grouped_rel,
path,
root->group_pathkeys,
-1.0);
-
- if (parse->hasAggs)
- add_partial_path(partially_grouped_rel, (Path *)
- create_agg_path(root,
- partially_grouped_rel,
- path,
- partially_grouped_rel->reltarget,
- parse->groupClause ? AGG_SORTED : AGG_PLAIN,
- AGGSPLIT_INITIAL_SERIAL,
- parse->groupClause,
- NIL,
- agg_partial_costs,
- dNumPartialPartialGroups));
else
- add_partial_path(partially_grouped_rel, (Path *)
- create_group_path(root,
- partially_grouped_rel,
- path,
- parse->groupClause,
- NIL,
- dNumPartialPartialGroups));
+ path = (Path *) create_incremental_sort_path(root,
+ partially_grouped_rel,
+ path,
+ root->group_pathkeys,
+ presorted_keys,
+ -1.0);
}
- /*
- * Now we may consider incremental sort on this path, but only
- * when the path is not already sorted and when incremental sort
- * is enabled.
- */
- if (is_sorted || !enable_incremental_sort)
- continue;
-
- /* Restore the input path (we might have added Sort on top). */
- path = path_original;
-
- /* no shared prefix, not point in building incremental sort */
- if (presorted_keys == 0)
- continue;
-
- /*
- * We should have already excluded pathkeys of length 1 because
- * then presorted_keys > 0 would imply is_sorted was true.
- */
- Assert(list_length(root->group_pathkeys) != 1);
-
- path = (Path *) create_incremental_sort_path(root,
- partially_grouped_rel,
- path,
- root->group_pathkeys,
- presorted_keys,
- -1.0);
-
if (parse->hasAggs)
add_partial_path(partially_grouped_rel, (Path *)
create_agg_path(root,
projects / users / gsingh / postgres.git / commitdiff