diff options
| -rw-r--r-- | src/backend/optimizer/path/costsize.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index 104e779f6ac..f39e6a9f80d 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -2416,6 +2416,7 @@ cost_agg(Path *path, PlannerInfo *root, double pages; double pages_written = 0.0; double pages_read = 0.0; + double spill_cost; double hashentrysize; double nbatches; Size mem_limit; @@ -2453,9 +2454,21 @@ cost_agg(Path *path, PlannerInfo *root, pages = relation_byte_size(input_tuples, input_width) / BLCKSZ; pages_written = pages_read = pages * depth; + /* + * HashAgg has somewhat worse IO behavior than Sort on typical + * hardware/OS combinations. Account for this with a generic penalty. + */ + pages_read *= 2.0; + pages_written *= 2.0; + startup_cost += pages_written * random_page_cost; total_cost += pages_written * random_page_cost; total_cost += pages_read * seq_page_cost; + + /* account for CPU cost of spilling a tuple and reading it back */ + spill_cost = depth * input_tuples * 2.0 * cpu_tuple_cost; + startup_cost += spill_cost; + total_cost += spill_cost; } /* |