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Send only one FORGET_RELATION_FSYNC request when dropping a relation.

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We were sending one per fork, but a little bit of refactoring allows us
to send just one request with forknum == InvalidForkNumber.  This not only
reduces pressure on the shared-memory request queue, but saves repeated
traversals of the checkpointer's hash table.
This commit is contained in:
Tom Lane 2012-07-19 13:07:41 -04:00
parent 79c49131fa
commit 2bc30516c7
2 changed files with 33 additions and 9 deletions
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39
src/backend/storage/smgr/md.c
View File

@ -166,6 +166,8 @@ typedef enum /* behavior for mdopen & _mdfd_getseg */
} ExtensionBehavior;
/* local routines */
static void mdunlinkfork(RelFileNodeBackend rnode, ForkNumber forkNum,
bool isRedo);
static MdfdVec *mdopen(SMgrRelation reln, ForkNumber forknum,
ExtensionBehavior behavior);
static void register_dirty_segment(SMgrRelation reln, ForkNumber forknum,
@ -308,6 +310,9 @@ mdcreate(SMgrRelation reln, ForkNumber forkNum, bool isRedo)
* Note that we're passed a RelFileNodeBackend --- by the time this is called,
* there won't be an SMgrRelation hashtable entry anymore.
*
* forkNum can be a fork number to delete a specific fork, or InvalidForkNumber
* to delete all forks.
*
* For regular relations, we don't unlink the first segment file of the rel,
* but just truncate it to zero length, and record a request to unlink it after
* the next checkpoint. Additional segments can be unlinked immediately,
@ -349,17 +354,32 @@ mdcreate(SMgrRelation reln, ForkNumber forkNum, bool isRedo)
void
mdunlink(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
{
char *path;
int ret;
/*
* We have to clean out any pending fsync requests for the doomed
* relation, else the next mdsync() will fail. There can't be any such
* requests for a temp relation, though.
* requests for a temp relation, though. We can send just one request
* even when deleting multiple forks, since the fsync queuing code accepts
* the "InvalidForkNumber = all forks" convention.
*/
if (!RelFileNodeBackendIsTemp(rnode))
ForgetRelationFsyncRequests(rnode.node, forkNum);
/* Now do the per-fork work */
if (forkNum == InvalidForkNumber)
{
for (forkNum = 0; forkNum <= MAX_FORKNUM; forkNum++)
mdunlinkfork(rnode, forkNum, isRedo);
}
else
mdunlinkfork(rnode, forkNum, isRedo);
}
static void
mdunlinkfork(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
{
char *path;
int ret;
path = relpath(rnode, forkNum);
/*
@ -1340,7 +1360,8 @@ register_unlink(RelFileNodeBackend rnode)
* The range of possible segment numbers is way less than the range of
* BlockNumber, so we can reserve high values of segno for special purposes.
* We define three:
* - FORGET_RELATION_FSYNC means to cancel pending fsyncs for a relation
* - FORGET_RELATION_FSYNC means to cancel pending fsyncs for a relation,
* either for one fork, or all forks if forknum is InvalidForkNumber
* - FORGET_DATABASE_FSYNC means to cancel pending fsyncs for a whole database
* - UNLINK_RELATION_REQUEST is a request to delete the file after the next
* checkpoint.
@ -1356,7 +1377,7 @@ RememberFsyncRequest(RelFileNode rnode, ForkNumber forknum, BlockNumber segno)
if (segno == FORGET_RELATION_FSYNC)
{
/* Remove any pending requests for the entire relation */
/* Remove any pending requests for the relation (one or all forks) */
HASH_SEQ_STATUS hstat;
PendingOperationEntry *entry;
@ -1364,7 +1385,8 @@ RememberFsyncRequest(RelFileNode rnode, ForkNumber forknum, BlockNumber segno)
while ((entry = (PendingOperationEntry *) hash_seq_search(&hstat)) != NULL)
{
if (RelFileNodeEquals(entry->tag.rnode, rnode) &&
entry->tag.forknum == forknum)
(entry->tag.forknum == forknum ||
forknum == InvalidForkNumber))
{
/* Okay, cancel this entry */
entry->canceled = true;
@ -1466,6 +1488,9 @@ RememberFsyncRequest(RelFileNode rnode, ForkNumber forknum, BlockNumber segno)
/*
* ForgetRelationFsyncRequests -- forget any fsyncs for a relation fork
*
* forknum == InvalidForkNumber means all forks, although this code doesn't
* actually know that, since it's just forwarding the request elsewhere.
*/
void
ForgetRelationFsyncRequests(RelFileNode rnode, ForkNumber forknum)

3
src/backend/storage/smgr/smgr.c
View File

@ -381,8 +381,7 @@ smgrdounlink(SMgrRelation reln, bool isRedo)
* ERROR, because we've already decided to commit or abort the current
* xact.
*/
for (forknum = 0; forknum <= MAX_FORKNUM; forknum++)
(*(smgrsw[which].smgr_unlink)) (rnode, forknum, isRedo);
(*(smgrsw[which].smgr_unlink)) (rnode, InvalidForkNumber, isRedo);
}
/*