diff options
| -rw-r--r-- | src/backend/optimizer/path/costsize.c | 111 | ||||
| -rw-r--r-- | src/include/optimizer/cost.h | 2 |
2 files changed, 72 insertions, 41 deletions
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index 458f139d7cd..a43daa744c7 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -813,7 +813,6 @@ cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel, Cost startup_cost = 0; Cost run_cost = 0; Cost indexTotalCost; - Selectivity indexSelectivity; QualCost qpqual_cost; Cost cpu_per_tuple; Cost cost_per_page; @@ -837,13 +836,12 @@ cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel, if (!enable_bitmapscan) startup_cost += disable_cost; - /* - * Fetch total cost of obtaining the bitmap, as well as its total - * selectivity. - */ - cost_bitmap_tree_node(bitmapqual, &indexTotalCost, &indexSelectivity); + pages_fetched = compute_bitmap_pages(root, baserel, bitmapqual, + loop_count, &indexTotalCost, + &tuples_fetched); startup_cost += indexTotalCost; + T = (baserel->pages > 1) ? (double) baserel->pages : 1.0; /* Fetch estimated page costs for tablespace containing table. */ get_tablespace_page_costs(baserel->reltablespace, @@ -851,41 +849,6 @@ cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel, &spc_seq_page_cost); /* - * Estimate number of main-table pages fetched. - */ - tuples_fetched = clamp_row_est(indexSelectivity * baserel->tuples); - - T = (baserel->pages > 1) ? (double) baserel->pages : 1.0; - - if (loop_count > 1) - { - /* - * For repeated bitmap scans, scale up the number of tuples fetched in - * the Mackert and Lohman formula by the number of scans, so that we - * estimate the number of pages fetched by all the scans. Then - * pro-rate for one scan. - */ - pages_fetched = index_pages_fetched(tuples_fetched * loop_count, - baserel->pages, - get_indexpath_pages(bitmapqual), - root); - pages_fetched /= loop_count; - } - else - { - /* - * For a single scan, the number of heap pages that need to be fetched - * is the same as the Mackert and Lohman formula for the case T <= b - * (ie, no re-reads needed). - */ - pages_fetched = (2.0 * T * tuples_fetched) / (2.0 * T + tuples_fetched); - } - if (pages_fetched >= T) - pages_fetched = T; - else - pages_fetched = ceil(pages_fetched); - - /* * For small numbers of pages we should charge spc_random_page_cost * apiece, while if nearly all the table's pages are being read, it's more * appropriate to charge spc_seq_page_cost apiece. The effect is @@ -4820,3 +4783,69 @@ get_parallel_divisor(Path *path) return parallel_divisor; } + +/* + * compute_bitmap_pages + * + * compute number of pages fetched from heap in bitmap heap scan. + */ +double +compute_bitmap_pages(PlannerInfo *root, RelOptInfo *baserel, Path *bitmapqual, + int loop_count, Cost *cost, double *tuple) +{ + Cost indexTotalCost; + Selectivity indexSelectivity; + double T; + double pages_fetched; + double tuples_fetched; + + /* + * Fetch total cost of obtaining the bitmap, as well as its total + * selectivity. + */ + cost_bitmap_tree_node(bitmapqual, &indexTotalCost, &indexSelectivity); + + /* + * Estimate number of main-table pages fetched. + */ + tuples_fetched = clamp_row_est(indexSelectivity * baserel->tuples); + + T = (baserel->pages > 1) ? (double) baserel->pages : 1.0; + + if (loop_count > 1) + { + /* + * For repeated bitmap scans, scale up the number of tuples fetched in + * the Mackert and Lohman formula by the number of scans, so that we + * estimate the number of pages fetched by all the scans. Then + * pro-rate for one scan. + */ + pages_fetched = index_pages_fetched(tuples_fetched * loop_count, + baserel->pages, + get_indexpath_pages(bitmapqual), + root); + pages_fetched /= loop_count; + } + else + { + /* + * For a single scan, the number of heap pages that need to be fetched + * is the same as the Mackert and Lohman formula for the case T <= b + * (ie, no re-reads needed). + */ + pages_fetched = + (2.0 * T * tuples_fetched) / (2.0 * T + tuples_fetched); + } + + if (pages_fetched >= T) + pages_fetched = T; + else + pages_fetched = ceil(pages_fetched); + + if (cost) + *cost = indexTotalCost; + if (tuple) + *tuple = tuples_fetched; + + return pages_fetched; +} diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h index 39376ec10cf..0e68264a41f 100644 --- a/src/include/optimizer/cost.h +++ b/src/include/optimizer/cost.h @@ -183,6 +183,8 @@ extern void set_cte_size_estimates(PlannerInfo *root, RelOptInfo *rel, double cte_rows); extern void set_foreign_size_estimates(PlannerInfo *root, RelOptInfo *rel); extern PathTarget *set_pathtarget_cost_width(PlannerInfo *root, PathTarget *target); +extern double compute_bitmap_pages(PlannerInfo *root, RelOptInfo *baserel, + Path *bitmapqual, int loop_count, Cost *cost, double *tuple); /* * prototypes for clausesel.c |