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Report the current queries of all backends involved in a deadlock

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(if they'd be visible to the current user in pg_stat_activity).

This might look like it's subject to race conditions, but it's actually
pretty safe because at the time DeadLockReport() is constructing the
report, we haven't yet aborted our transaction and so we can expect that
everyone else involved in the deadlock is still blocked on some lock.
(There are corner cases where that might not be true, such as a statement
timeout triggering in another backend before we finish reporting; but at
worst we'd report a misleading activity string, so it seems acceptable
considering the usefulness of reporting the queries.)

Original patch by Itagaki Takahiro, heavily modified by me.
This commit is contained in:
Tom Lane
2008-03-21 21:08:31 +00:00
parent df812e91ad
commit 4b7ae4afae
3 changed files with 104 additions and 16 deletions
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41
src/backend/storage/lmgr/deadlock.c
View File

@@ -12,7 +12,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/lmgr/deadlock.c,v 1.51 2008/01/01 19:45:52 momjian Exp $
* $PostgreSQL: pgsql/src/backend/storage/lmgr/deadlock.c,v 1.52 2008/03/21 21:08:31 tgl Exp $
*
* Interface:
*
@@ -26,6 +26,7 @@
#include "postgres.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "storage/lmgr.h"
#include "storage/proc.h"
#include "utils/memutils.h"
@@ -878,12 +879,14 @@ PrintLockQueue(LOCK *lock, const char *info)
void
DeadLockReport(void)
{
StringInfoData buf;
StringInfoData buf2;
StringInfoData detailbuf;
StringInfoData contextbuf;
StringInfoData locktagbuf;
int i;
initStringInfo(&buf);
initStringInfo(&buf2);
initStringInfo(&detailbuf);
initStringInfo(&contextbuf);
initStringInfo(&locktagbuf);
for (i = 0; i < nDeadlockDetails; i++)
{
@@ -896,26 +899,36 @@ DeadLockReport(void)
else
nextpid = deadlockDetails[0].pid;
/* reset locktagbuf to hold next object description */
resetStringInfo(&locktagbuf);
DescribeLockTag(&locktagbuf, &info->locktag);
if (i > 0)
appendStringInfoChar(&buf, '\n');
appendStringInfoChar(&detailbuf, '\n');
/* reset buf2 to hold next object description */
resetStringInfo(&buf2);
DescribeLockTag(&buf2, &info->locktag);
appendStringInfo(&buf,
appendStringInfo(&detailbuf,
_("Process %d waits for %s on %s; blocked by process %d."),
info->pid,
GetLockmodeName(info->locktag.locktag_lockmethodid,
info->lockmode),
buf2.data,
locktagbuf.data,
nextpid);
if (i > 0)
appendStringInfoChar(&contextbuf, '\n');
appendStringInfo(&contextbuf,
_("Process %d: %s"),
info->pid,
pgstat_get_backend_current_activity(info->pid));
}
ereport(ERROR,
(errcode(ERRCODE_T_R_DEADLOCK_DETECTED),
errmsg("deadlock detected"),
errdetail("%s", buf.data)));
errdetail("%s", detailbuf.data),
errcontext("%s", contextbuf.data)));
}
/*