--On 1. Mai 2015 11:30:51 -0700 Tom Lane wrote:
> No. The non-parameterized paths for a given relation must all have the
> same rowcount estimates; otherwise the path comparison logic fails
> fundamentally. Another way to look at it is that every correct path
> will yield the same number of r
Bernd Helmle writes:
> While looking into a customer performance problem, i saw this in
> costsize.c, cost_index() (9.3.6, but it looks the same in HEAD):
> ...
> What i'm wondering is the else branch, where the baserel row estimate is
> assigned to the
> IndexPath. However, it occurs to me that i
While looking into a customer performance problem, i saw this in
costsize.c, cost_index() (9.3.6, but it looks the same in HEAD):
/* Mark the path with the correct row estimate */
if (path->path.param_info)
{
path->path.rows = path->path.param_info->ppi_rows
No. Costs for touching the index were computed by the amcostestimate
function; this code is solely about estimating costs for touching the
heap.
I see. Thank you.
--
Teodor Sigaev E-mail: teo...@sigaev.ru
WWW:
Teodor Sigaev writes:
> if (indexonly)
> pages_fetched = ceil(pages_fetched * (1.0 -
> baserel->allvisfrac));
> As I understand the code, index_pages_fetched() returns summary of page's
> read
> for index and heap together.
No. Costs for touching the index were computed
Hi!
Some fragment of code (src/backend/optimizer/path/costsize.c, lineno ~400):
/*
* Normal case: apply the Mackert and Lohman formula, and then
* interpolate between that and the correlation-derived result.
*/
pages_fetched = index_pages_fetched(tuples_
