diff options
Diffstat (limited to 'src/backend/storage/smgr/smgr.c')
| -rw-r--r-- | src/backend/storage/smgr/smgr.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/src/backend/storage/smgr/smgr.c b/src/backend/storage/smgr/smgr.c index 7b9fa103eff..925728eb6c1 100644 --- a/src/backend/storage/smgr/smgr.c +++ b/src/backend/storage/smgr/smgr.c @@ -88,6 +88,8 @@ typedef struct f_smgr BlockNumber blocknum, int nblocks, bool skipFsync); bool (*smgr_prefetch) (SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, int nblocks); + uint32 (*smgr_maxcombine) (SMgrRelation reln, ForkNumber forknum, + BlockNumber blocknum); void (*smgr_readv) (SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, void **buffers, BlockNumber nblocks); @@ -117,6 +119,7 @@ static const f_smgr smgrsw[] = { .smgr_extend = mdextend, .smgr_zeroextend = mdzeroextend, .smgr_prefetch = mdprefetch, + .smgr_maxcombine = mdmaxcombine, .smgr_readv = mdreadv, .smgr_writev = mdwritev, .smgr_writeback = mdwriteback, @@ -589,12 +592,28 @@ smgrprefetch(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, } /* + * smgrmaxcombine() - Return the maximum number of total blocks that can be + * combined with an IO starting at blocknum. + * + * The returned value includes the IO for blocknum itself. + */ +uint32 +smgrmaxcombine(SMgrRelation reln, ForkNumber forknum, + BlockNumber blocknum) +{ + return smgrsw[reln->smgr_which].smgr_maxcombine(reln, forknum, blocknum); +} + +/* * smgrreadv() -- read a particular block range from a relation into the * supplied buffers. * * This routine is called from the buffer manager in order to * instantiate pages in the shared buffer cache. All storage managers * return pages in the format that POSTGRES expects. + * + * If more than one block is intended to be read, callers need to use + * smgrmaxcombine() to check how many blocks can be combined into one IO. */ void smgrreadv(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, @@ -626,6 +645,9 @@ smgrreadv(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, * skipFsync indicates that the caller will make other provisions to * fsync the relation, so we needn't bother. Temporary relations also * do not require fsync. + * + * If more than one block is intended to be read, callers need to use + * smgrmaxcombine() to check how many blocks can be combined into one IO. */ void smgrwritev(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, |