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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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12
src/backend/access/transam/parallel.c
View File

@ -14,6 +14,7 @@
#include "postgres.h"
#include "access/nbtree.h"
#include "access/parallel.h"
#include "access/session.h"
#include "access/xact.h"
@ -129,6 +130,9 @@ static const struct
{
{
"ParallelQueryMain", ParallelQueryMain
},
{
"_bt_parallel_build_main", _bt_parallel_build_main
}
};
@ -146,7 +150,7 @@ static void ParallelWorkerShutdown(int code, Datum arg);
*/
ParallelContext *
CreateParallelContext(const char *library_name, const char *function_name,
int nworkers)
int nworkers, bool serializable_okay)
{
MemoryContext oldcontext;
ParallelContext *pcxt;
@ -167,9 +171,11 @@ CreateParallelContext(const char *library_name, const char *function_name,
/*
* If we are running under serializable isolation, we can't use parallel
* workers, at least not until somebody enhances that mechanism to be
* parallel-aware.
* parallel-aware. Utility statement callers may ask us to ignore this
* restriction because they're always able to safely ignore the fact that
* SIREAD locks do not work with parallelism.
*/
if (IsolationIsSerializable())
if (IsolationIsSerializable() && !serializable_okay)
nworkers = 0;
/* We might be running in a short-lived memory context. */