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Commitfd3a75d

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committed
Free disk space for dropped relations on commit.
When committing a transaction that dropped a relation, we previouslytruncated only the first segment file to free up disk space (the onethat won't be unlinked until the next checkpoint).Truncate higher numbered segments too, even though we unlink them oncommit. This frees the disk space immediately, even if other backendshave open file descriptors and might take a long time to get around tohandling shared invalidation events and closing them. Also extend thesame behavior to the first segment, in recovery.Back-patch to all supported releases.Bug: #16663Reported-by: Denis Patron <denis.patron@previnet.it>Reviewed-by: Pavel Borisov <pashkin.elfe@gmail.com>Reviewed-by: Neil Chen <carpenter.nail.cz@gmail.com>Reviewed-by: David Zhang <david.zhang@highgo.ca>Discussion:https://postgr.es/m/16663-fe97ccf9932fc800%40postgresql.org
1 parenta095e04 commitfd3a75d

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1 file changed

+69
-31
lines changed
  • src/backend/storage/smgr

1 file changed

+69
-31
lines changed

‎src/backend/storage/smgr/md.c

Lines changed: 69 additions & 31 deletions
Original file line numberDiff line numberDiff line change
@@ -286,6 +286,41 @@ mdunlink(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
286286
mdunlinkfork(rnode,forkNum,isRedo);
287287
}
288288

289+
/*
290+
* Truncate a file to release disk space.
291+
*/
292+
staticint
293+
do_truncate(constchar*path)
294+
{
295+
intsave_errno;
296+
intret;
297+
intfd;
298+
299+
/* truncate(2) would be easier here, but Windows hasn't got it */
300+
fd=OpenTransientFile(path,O_RDWR |PG_BINARY);
301+
if (fd >=0)
302+
{
303+
ret=ftruncate(fd,0);
304+
save_errno=errno;
305+
CloseTransientFile(fd);
306+
errno=save_errno;
307+
}
308+
else
309+
ret=-1;
310+
311+
/* Log a warning here to avoid repetition in callers. */
312+
if (ret<0&&errno!=ENOENT)
313+
{
314+
save_errno=errno;
315+
ereport(WARNING,
316+
(errcode_for_file_access(),
317+
errmsg("could not truncate file \"%s\": %m",path)));
318+
errno=save_errno;
319+
}
320+
321+
returnret;
322+
}
323+
289324
staticvoid
290325
mdunlinkfork(RelFileNodeBackendrnode,ForkNumberforkNum,boolisRedo)
291326
{
@@ -299,38 +334,31 @@ mdunlinkfork(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
299334
*/
300335
if (isRedo||forkNum!=MAIN_FORKNUM||RelFileNodeBackendIsTemp(rnode))
301336
{
302-
/* First, forget any pending sync requests for the first segment */
303337
if (!RelFileNodeBackendIsTemp(rnode))
338+
{
339+
/* Prevent other backends' fds from holding on to the disk space */
340+
ret=do_truncate(path);
341+
342+
/* Forget any pending sync requests for the first segment */
304343
register_forget_request(rnode,forkNum,0/* first seg */ );
344+
}
345+
else
346+
ret=0;
305347

306-
/* Next unlink the file */
307-
ret=unlink(path);
308-
if (ret<0&&errno!=ENOENT)
309-
ereport(WARNING,
310-
(errcode_for_file_access(),
311-
errmsg("could not remove file \"%s\": %m",path)));
348+
/* Next unlink the file, unless it was already found to be missing */
349+
if (ret==0||errno!=ENOENT)
350+
{
351+
ret=unlink(path);
352+
if (ret<0&&errno!=ENOENT)
353+
ereport(WARNING,
354+
(errcode_for_file_access(),
355+
errmsg("could not remove file \"%s\": %m",path)));
356+
}
312357
}
313358
else
314359
{
315-
/* truncate(2) would be easier here, but Windows hasn't got it */
316-
intfd;
317-
318-
fd=OpenTransientFile(path,O_RDWR |PG_BINARY);
319-
if (fd >=0)
320-
{
321-
intsave_errno;
322-
323-
ret=ftruncate(fd,0);
324-
save_errno=errno;
325-
CloseTransientFile(fd);
326-
errno=save_errno;
327-
}
328-
else
329-
ret=-1;
330-
if (ret<0&&errno!=ENOENT)
331-
ereport(WARNING,
332-
(errcode_for_file_access(),
333-
errmsg("could not truncate file \"%s\": %m",path)));
360+
/* Prevent other backends' fds from holding on to the disk space */
361+
ret=do_truncate(path);
334362

335363
/* Register request to unlink first segment later */
336364
register_unlink_segment(rnode,forkNum,0/* first seg */ );
@@ -350,14 +378,24 @@ mdunlinkfork(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
350378
*/
351379
for (segno=1;;segno++)
352380
{
353-
/*
354-
* Forget any pending sync requests for this segment before we try
355-
* to unlink.
356-
*/
381+
sprintf(segpath,"%s.%u",path,segno);
382+
357383
if (!RelFileNodeBackendIsTemp(rnode))
384+
{
385+
/*
386+
* Prevent other backends' fds from holding on to the disk
387+
* space.
388+
*/
389+
if (do_truncate(segpath)<0&&errno==ENOENT)
390+
break;
391+
392+
/*
393+
* Forget any pending sync requests for this segment before we
394+
* try to unlink.
395+
*/
358396
register_forget_request(rnode,forkNum,segno);
397+
}
359398

360-
sprintf(segpath,"%s.%u",path,segno);
361399
if (unlink(segpath)<0)
362400
{
363401
/* ENOENT is expected after the last segment... */

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