During working on allowing the planner to perform GROUP BY before joining
I've noticed that cost_agg() completely ignores input_startup_cost
when aggstrategy == AGG_HASHED.
I can see at least 3 call to cost_agg() which pass aggstrategy as
AGG_HASHED that are also passing a possible non-zero startup cost.
The attached changes cost_agg() to include the startup cost, but does
nothing for the changed plans in the regression tests.
Is this really intended?
Regards
David Rowley
--
David Rowley http://www.2ndQuadrant.com/
<http://www.2ndquadrant.com/>
PostgreSQL Development, 24x7 Support, Training & Services
diff --git a/src/backend/optimizer/path/costsize.c
b/src/backend/optimizer/path/costsize.c
index 7069f60..06870a3 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -1639,7 +1639,8 @@ cost_agg(Path *path, PlannerInfo *root,
else
{
/* must be AGG_HASHED */
- startup_cost = input_total_cost;
+ startup_cost = input_startup_cost;
+ startup_cost += input_total_cost;
startup_cost += aggcosts->transCost.startup;
startup_cost += aggcosts->transCost.per_tuple * input_tuples;
startup_cost += (cpu_operator_cost * numGroupCols) *
input_tuples;
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