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Implement prefetching via posix_fadvise() for bitmap index scans. A new

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GUC variable effective_io_concurrency controls how many concurrent block
prefetch requests will be issued.

(The best way to handle this for plain index scans is still under debate,
so that part is not applied yet --- tgl)

Greg Stark
This commit is contained in:
Tom Lane
2009-01-12 05:10:45 +00:00
parent 1a37056a74
commit b7b8f0b609
15 changed files with 422 additions and 17 deletions
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22
src/backend/storage/smgr/md.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/smgr/md.c,v 1.143 2009/01/01 17:23:48 momjian Exp $
* $PostgreSQL: pgsql/src/backend/storage/smgr/md.c,v 1.144 2009/01/12 05:10:44 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -550,6 +550,26 @@ mdclose(SMgrRelation reln, ForkNumber forknum)
}
}
/*
* mdprefetch() -- Initiate asynchronous read of the specified block of a relation
*/
void
mdprefetch(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum)
{
#ifdef USE_PREFETCH
off_t seekpos;
MdfdVec *v;
v = _mdfd_getseg(reln, forknum, blocknum, false, EXTENSION_FAIL);
seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
Assert(seekpos < (off_t) BLCKSZ * RELSEG_SIZE);
(void) FilePrefetch(v->mdfd_vfd, seekpos, BLCKSZ);
#endif /* USE_PREFETCH */
}
/*
* mdread() -- Read the specified block from a relation.
*/