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Support parallel btree index builds.

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To make this work, tuplesort.c and logtape.c must also support
parallelism, so this patch adds that infrastructure and then applies
it to the particular case of parallel btree index builds.  Testing
to date shows that this can often be 2-3x faster than a serial
index build.

The model for deciding how many workers to use is fairly primitive
at present, but it's better than not having the feature.  We can
refine it as we get more experience.

Peter Geoghegan with some help from Rushabh Lathia.  While Heikki
Linnakangas is not an author of this patch, he wrote other patches
without which this feature would not have been possible, and
therefore the release notes should possibly credit him as an author
of this feature.  Reviewed by Claudio Freire, Heikki Linnakangas,
Thomas Munro, Tels, Amit Kapila, me.

Discussion: http://postgr.es/m/CAM3SWZQKM=Pzc=CAHzRixKjp2eO5Q0Jg1SoFQqeXFQ647JiwqQ@mail.gmail.com
Discussion: http://postgr.es/m/CAH2-Wz=AxWqDoVvGU7dq856S4r6sJAj6DBn7VMtigkB33N5eyg@mail.gmail.com
This commit is contained in:
Robert Haas
2018-02-02 13:25:55 -05:00
parent 9aef173163
commit 9da0cc3528
51 changed files with 2238 additions and 362 deletions
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18
src/backend/optimizer/path/allpaths.c
View File

@ -720,7 +720,8 @@ create_plain_partial_paths(PlannerInfo *root, RelOptInfo *rel)
{
int parallel_workers;
parallel_workers = compute_parallel_worker(rel, rel->pages, -1);
parallel_workers = compute_parallel_worker(rel, rel->pages, -1,
max_parallel_workers_per_gather);
/* If any limit was set to zero, the user doesn't want a parallel scan. */
if (parallel_workers <= 0)
@ -3299,7 +3300,8 @@ create_partial_bitmap_paths(PlannerInfo *root, RelOptInfo *rel,
pages_fetched = compute_bitmap_pages(root, rel, bitmapqual, 1.0,
NULL, NULL);
parallel_workers = compute_parallel_worker(rel, pages_fetched, -1);
parallel_workers = compute_parallel_worker(rel, pages_fetched, -1,
max_parallel_workers_per_gather);
if (parallel_workers <= 0)
return;
@ -3319,9 +3321,13 @@ create_partial_bitmap_paths(PlannerInfo *root, RelOptInfo *rel,
*
* "index_pages" is the number of pages from the index that we expect to scan, or
* -1 if we don't expect to scan any.
*
* "max_workers" is caller's limit on the number of workers. This typically
* comes from a GUC.
*/
int
compute_parallel_worker(RelOptInfo *rel, double heap_pages, double index_pages)
compute_parallel_worker(RelOptInfo *rel, double heap_pages, double index_pages,
int max_workers)
{
int parallel_workers = 0;
@ -3392,10 +3398,8 @@ compute_parallel_worker(RelOptInfo *rel, double heap_pages, double index_pages)
}
}
/*
* In no case use more than max_parallel_workers_per_gather workers.
*/
parallel_workers = Min(parallel_workers, max_parallel_workers_per_gather);
/* In no case use more than caller supplied maximum number of workers */
parallel_workers = Min(parallel_workers, max_workers);
return parallel_workers;
}

4
src/backend/optimizer/path/costsize.c
View File

@ -682,7 +682,9 @@ cost_index(IndexPath *path, PlannerInfo *root, double loop_count,
* order.
*/
path->path.parallel_workers = compute_parallel_worker(baserel,
rand_heap_pages, index_pages);
rand_heap_pages,
index_pages,
max_parallel_workers_per_gather);
/*
* Fall out if workers can't be assigned for parallel scan, because in