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Recent versions of the Linux system header files cause xlogdefs.h to
believe that open_datasync should be the default sync method, whereas
formerly fdatasync was the default on Linux. open_datasync is a bad
choice, first because it doesn't actually outperform fdatasync (in fact
the reverse), and second because we try to use O_DIRECT with it, causing
failures on certain filesystems (e.g., ext4 with data=journal option).
This part of the patch is largely per a proposal from Marti Raudsepp.
More extensive changes are likely to follow in HEAD, but this is as much
change as we want to back-patch.
Also clean up confusing code and incorrect documentation surrounding the
fsync_writethrough option. Those changes shouldn't result in any actual
behavioral change, but I chose to back-patch them anyway to keep the
branches looking similar in this area.
In 9.0 and HEAD, also do some copy-editing on the WAL Reliability
documentation section.
Back-patch to all supported branches, since any of them might get used
on modern Linux versions.
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location read from backup label file can be found: wasShutdown was set
incorrectly when a backup label file was found.
Jeff Davis, with a little tweaking by me.
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that WAL file containing the checkpoint redo-location can be found. This
avoids making the cluster irrecoverable if the redo location is in an earlie
WAL file than the checkpoint record.
Report, analysis and patch by Jeff Davis, with small changes by me.
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Backpatch to 8.0.
Andres Freund, with cleanup and adjustment for older branches by me.
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segment of XLOG_BACKUP_END record even if the the record is placed
at a segment boundary. Furthermore the previous implementation could
return nonexistent segment file name when the boundary is in segments
that has "FE" suffix; We never use segments with "FF" suffix.
Backpatch to 8.0, where hot backup was introduced.
Reported by Fujii Masao.
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AbortTransaction or AbortSubTransaction, when trying to clean up after an
error that prevented (sub)transaction start from completing:
* access to TopTransactionResourceOwner that might not exist
* assert failure in AtEOXact_GUC, if AtStart_GUC not called yet
* assert failure or core dump in AfterTriggerEndSubXact, if
AfterTriggerBeginSubXact not called yet
Per testing by injecting elog(ERROR) at successive steps in StartTransaction
and StartSubTransaction. It's not clear whether all of these cases could
really occur in the field, but at least one of them is easily exposed by
simple stress testing, as per my accidental discovery yesterday.
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an allegedly immutable index function. It was previously recognized that
we had to prevent such a function from executing SET/RESET ROLE/SESSION
AUTHORIZATION, or it could trivially obtain the privileges of the session
user. However, since there is in general no privilege checking for changes
of session-local state, it is also possible for such a function to change
settings in a way that might subvert later operations in the same session.
Examples include changing search_path to cause an unexpected function to
be called, or replacing an existing prepared statement with another one
that will execute a function of the attacker's choosing.
The present patch secures VACUUM, ANALYZE, and CREATE INDEX/REINDEX against
these threats, which are the same places previously deemed to need protection
against the SET ROLE issue. GUC changes are still allowed, since there are
many useful cases for that, but we prevent security problems by forcing a
rollback of any GUC change after completing the operation. Other cases are
handled by throwing an error if any change is attempted; these include temp
table creation, closing a cursor, and creating or deleting a prepared
statement. (In 7.4, the infrastructure to roll back GUC changes doesn't
exist, so we settle for rejecting changes of "search_path" in these contexts.)
Original report and patch by Gurjeet Singh, additional analysis by
Tom Lane.
Security: CVE-2009-4136
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be part of multixacts, so allocate a slot for each prepared transaction in
the "oldest member" array in multixact.c. On PREPARE TRANSACTION, transfer
the oldest member value from the current backends slot to the prepared xact
slot. Also save and recover the value from the 2pc state file.
The symptom of the bug was that after a transaction prepared, a shared lock
still held by the prepared transaction was sometimes ignored by other
transactions.
Fix back to 8.1, where both 2PC and multixact were introduced.
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of checkpoint. Although the checkpoint has been written to WAL at that point
already, so that all data is safe, and we'll retry removing the WAL segment at
the next checkpoint, if such a failure persists we won't be able to remove any
other old WAL segments either and will eventually run out of disk space. It's
better to treat the failure as non-fatal, and move on to clean any other WAL
segment and continue with any other end-of-checkpoint cleanup.
We don't normally expect any such failures, but on Windows it can happen with
some anti-virus or backup software that lock files without FILE_SHARE_DELETE
flag.
Also, the loop in pgrename() to retry when the file is locked was broken. If a
file is locked on Windows, you get ERROR_SHARE_VIOLATION, not
ERROR_ACCESS_DENIED, at least on modern versions. Fix that, although I left
the check for ERROR_ACCESS_DENIED in there as well (presumably it was correct
in some environment), and added ERROR_LOCK_VIOLATION to be consistent with
similar checks in pgwin32_open(). Reduce the timeout on the loop from 30s to
10s, on the grounds that since it's been broken, we've effectively had a
timeout of 0s and no-one has complained, so a smaller timeout is actually
closer to the old behavior. A longer timeout would mean that if recycling a
WAL file fails because it's locked for some reason, InstallXLogFileSegment()
will hold ControlFileLock for longer, potentially blocking other backends, so
a long timeout isn't totally harmless.
While we're at it, set errno correctly in pgrename().
Backpatch to 8.2, which is the oldest version supported on Windows. The xlog.c
changes would make sense on other platforms and thus on older versions as
well, but since there's no such locking issues on other platforms, it's not
worth it.
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file handle on it, the file goes into "pending deletion" state where it
still shows up in directory listing, but isn't accessible otherwise. That
confuses RemoveOldXLogFiles(), making it think that the file hasn't been
archived yet, while it actually was, and it was deleted along with the .done
file.
Fix that by renaming the file with ".deleted" extension before deleting it.
Also check the return value of rename() and unlink(), so that if the removal
fails for any reason (e.g another process is holding the file locked), we
don't delete the .done file until the WAL file is really gone.
Backpatch to 8.2, which is the oldest version supported on Windows.
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you can end up with an unrecoverable backup if you start a new base backup
right after finishing archive recovery. In that scenario, the redo pointer of
the checkpoint that pg_start_backup() writes points to the XLOG segment where
the timeline-changing end-of-archive-recovery checkpoint is. The beginning
of that segment contains pages with the old timeline ID, and we don't accept
that in recovery unless we find a history file covering the old timeline ID.
If you omit pg_xlog from the base backup and clear the archive directory
before starting the backup, there will be no such history file available.
The bug is present in all versions since PITR was introduced in 8.0, but I'm
back-patching only back to 8.2. Earlier versions didn't have XLOG switch
records, making this fix unfeasible. Given the lack of reports until now,
it doesn't seem worthwhile to spend more effort to fix 8.0 and 8.1.
Per report and suggestion by Mikael Krantz
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to go beoynd 10MB, as demonstrated by Gavin Sharry's example of dropping a
schema with ~25000 objects. The really bogus thing about the limit was that
it was enforced when a state file file was read in, not when it was written,
so you would end up with a prepared transaction that you can't commit or
abort, and the only recourse was to shut down the server and remove the file
by hand.
Raise the limit to MaxAllocSize, and enforce it also when a state file is
written. We could've removed the limit altogether, but reading in a file
larger than MaxAllocSize would fail anyway because we read it into a
palloc'd buffer.
Backpatch down to 8.1, where 2PC and this issue was introduced.
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crashes on certain platforms. In particular, the MSVC runtime is known
to do this.
Fixes bug #4162, reported and diagnosed by Javier Pimas
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corrupted. (Neither is very important if SIGTERM is used to shut down the
whole database cluster together, but there's a problem if someone tries to
SIGTERM individual backends.) To do this, introduce new infrastructure
macros PG_ENSURE_ERROR_CLEANUP/PG_END_ENSURE_ERROR_CLEANUP that take care
of transiently pushing an on_shmem_exit cleanup hook. Also use this method
for createdb cleanup --- that wasn't a shared-memory-corruption problem,
but SIGTERM abort of createdb could leave orphaned files lying around.
Backpatch as far as 8.2. The shmem corruption cases don't exist in 8.1,
and the createdb usage doesn't seem important enough to risk backpatching
further.
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temporary table; we can't support that because there's no way to clean up the
source backend's internal state if the eventual COMMIT PREPARED is done by
another backend. This was checked correctly in 8.1 but I broke it in 8.2 :-(.
Patch by Heikki Linnakangas, original trouble report by John Smith.
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and CLUSTER) execute as the table owner rather than the calling user, using
the same privilege-switching mechanism already used for SECURITY DEFINER
functions. The purpose of this change is to ensure that user-defined
functions used in index definitions cannot acquire the privileges of a
superuser account that is performing routine maintenance. While a function
used in an index is supposed to be IMMUTABLE and thus not able to do anything
very interesting, there are several easy ways around that restriction; and
even if we could plug them all, there would remain a risk of reading sensitive
information and broadcasting it through a covert channel such as CPU usage.
To prevent bypassing this security measure, execution of SET SESSION
AUTHORIZATION and SET ROLE is now forbidden within a SECURITY DEFINER context.
Thanks to Itagaki Takahiro for reporting this vulnerability.
Security: CVE-2007-6600
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recovery stop time was used. This avoids a corner-case risk of trying to
overwrite an existing archived copy of the last WAL segment, and seems
simpler and cleaner all around than the original definition. Per example
from Jon Colverson and subsequent analysis by Simon.
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on Windows. This is yet another manifestation of the problem that Windows
returns time zone names that may be in a different encoding than we are using.
I've put a better solution in HEAD, but the back branches need a simple patch.
Per report from Hiroshi Saito.
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fail when used in a deferred trigger. Bug goes back to 8.0; no doubt the
reason it hadn't been noticed is that we've been discouraging use of
user-defined constraint triggers. Per report from Frank van Vugt.
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is in progress on the same hashtable. This seems the least invasive way to
fix the recently-recognized problem that a split could cause the scan to
visit entries twice or (with much lower probability) miss them entirely.
The only field-reported problem caused by this is the "failed to re-find
shared lock object" PANIC in COMMIT PREPARED reported by Michel Dorochevsky,
which was caused by multiply visited entries. However, it seems certain
that mdsync() is vulnerable to missing required fsync's due to missed
entries, and I am fearful that RelationCacheInitializePhase2() might be at
risk as well. Because of that and the generalized hazard presented by this
bug, back-patch all the supported branches.
Along the way, fix pg_prepared_statement() and pg_cursor() to not assume
that the hashtables they are examining will stay static between calls.
This is risky regardless of the newly noted dynahash problem, because
hash_seq_search() has never promised to cope with deletion of table entries
other than the just-returned one. There may be no bug here because the only
supported way to call these functions is via ExecMakeTableFunctionResult()
which will cycle them to completion before doing anything very interesting,
but it seems best to get rid of the assumption. This affects 8.2 and HEAD
only, since those functions weren't there earlier.
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it was executed in. Someday it might be nice to allow cross-DB commits, but
work would be needed in NOTIFY and perhaps other places. Per Heikki.
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StartupXLOG and ShutdownXLOG no longer need to be critical sections, because
in all contexts where they are invoked, elog(ERROR) would be translated to
elog(FATAL) anyway. (One change in bgwriter.c is needed to make this true:
set ExitOnAnyError before trying to exit. This is a good fix anyway since
the existing code would have gone into an infinite loop on elog(ERROR) during
shutdown.) That avoids a misleading report of PANIC during semi-orderly
failures. Modify the postmaster to include the startup process in the set of
processes that get SIGTERM when a fast shutdown is requested, and also fix it
to not try to restart the bgwriter if the bgwriter fails while trying to write
the shutdown checkpoint. Net result is that "pg_ctl stop -m fast" does
something reasonable for a system in warm standby mode, and so should Unix
system shutdown (ie, universal SIGTERM). Per gripe from Stephen Harris and
some corner-case testing of my own.
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AbortTransaction, which would lead to recursion and eventual PANIC exit
as illustrated in recent report from Jeff Davis. First, in xact.c create
a special dedicated memory context for AbortTransaction to run in. This
solves the problem as long as AbortTransaction doesn't need more than 32K
(or whatever other size we create the context with). But in corner cases
it might. Second, in trigger.c arrange to keep pending after-trigger event
records in separate contexts that can be freed near the beginning of
AbortTransaction, rather than having them persist until CleanupTransaction
as before. Third, in portalmem.c arrange to free executor state data
earlier as well. These two changes should result in backing off the
out-of-memory condition before AbortTransaction needs any significant
amount of memory, at least in typical cases such as memory overrun due
to too many trigger events or too big an executor hash table. And all
the same for subtransaction abort too, of course.
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Windows), arrange for each postmaster child process to be its own process
group leader, and deliver signals SIGINT, SIGTERM, SIGQUIT to the whole
process group not only the direct child process. This provides saner behavior
for archive and recovery scripts; in particular, it's possible to shut down a
warm-standby recovery server using "pg_ctl stop -m immediate", since delivery
of SIGQUIT to the startup subprocess will result in killing the waiting
recovery_command. Also, this makes Query Cancel and statement_timeout apply
to scripts being run from backends via system(). (There is no support in the
core backend for that, but it's widely done using untrusted PLs.) Per gripe
from Stephen Harris and subsequent discussion.
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cases where we already hold the desired lock "indirectly", either via
membership in a MultiXact or because the lock was originally taken by a
different subtransaction of the current transaction. These cases must be
accounted for to avoid needless deadlocks and/or inappropriate replacement of
an exclusive lock with a shared lock. Per report from Clarence Gardner and
subsequent investigation.
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30 seconds instead of retrying forever. Also modify xlog.c so that if
it fails to rename an old xlog segment up to a future slot, it will
unlink the segment instead. Per discussion of bug #2712, in which it
became apparent that Windows can handle unlinking a file that's being
held open, but not renaming it.
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in PITR scenarios. We now WAL-log the replacement of old XIDs with
FrozenTransactionId, so that such replacement is guaranteed to propagate to
PITR slave databases. Also, rather than relying on hint-bit updates to be
preserved, pg_clog is not truncated until all instances of an XID are known to
have been replaced by FrozenTransactionId. Add new GUC variables and
pg_autovacuum columns to allow management of the freezing policy, so that
users can trade off the size of pg_clog against the amount of freezing work
done. Revise the already-existing code that forces autovacuum of tables
approaching the wraparound point to make it more bulletproof; also, revise the
autovacuum logic so that anti-wraparound vacuuming is done per-table rather
than per-database. initdb forced because of changes in pg_class, pg_database,
and pg_autovacuum catalogs. Heikki Linnakangas, Simon Riggs, and Tom Lane.
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that conflict with the OID that we want to use for the new database.
This avoids the risk of trying to remove files that maybe we shouldn't
remove. Per gripe from Jon Lapham and subsequent discussion of 27-Sep.
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Euler Taveira de Oliveira
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discussion.
Patch from Simon Riggs.
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PGPROC array into snapshots, and use this information to avoid visits
to pg_subtrans in HeapTupleSatisfiesSnapshot. This appears to solve
the pg_subtrans-related context swap storm problem that's been reported
by several people for 8.1. While at it, modify GetSnapshotData to not
take an exclusive lock on ProcArrayLock, as closer analysis shows that
shared lock is always sufficient.
Itagaki Takahiro and Tom Lane
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Needed because lock.c is now going to use the same type of list.
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of the transaction ID counter. Nothing is done with the epoch except to
store it in checkpoint records, but this provides a foundation with which
add-on code can pretend that XIDs never wrap around. This is a severely
trimmed and rewritten version of the xxid patch submitted by Marko Kreen.
Per discussion, the epoch counter seems the only part of xxid that really
needs to be in the core server.
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than N seconds apart. This allows a simple, if not very high performance,
means of guaranteeing that a PITR archive is no more than N seconds behind
real time. Also make pg_current_xlog_location return the WAL Write pointer,
add pg_current_xlog_insert_location to return the Insert pointer, and fix
pg_xlogfile_name_offset to return its results as a two-element record instead
of a smashed-together string, as per recent discussion.
Simon Riggs
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operation every so often. This improves the usefulness of PITR log
shipping for hot standby: formerly, if the standby server crashed, it
was necessary to restart it from the last base backup and replay all
the WAL since then. Now it will only need to reread about the same
amount of WAL as the master server would. The behavior might also
come in handy during a long PITR replay sequence. Simon Riggs,
with some editorialization by Tom Lane.
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to happen automatically during pg_stop_backup(). Add some functions for
interrogating the current xlog insertion point and for easily extracting
WAL filenames from the hex WAL locations displayed by pg_stop_backup
and friends. Simon Riggs with some editorialization by Tom Lane.
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vacuums. This allows a OLTP-like system with big tables to continue
regular vacuuming on small-but-frequently-updated tables while the
big tables are being vacuumed.
Original patch from Hannu Krossing, rewritten by Tom Lane and updated
by me.
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by Robert Lor
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recovery. In the first place, it doesn't work because slru's
latest_page_number isn't set up yet (this is why we've been hearing reports
of strange "apparent wraparound" log messages during crash recovery, but
only from people who'd managed to advance their next-mxact counters some
considerable distance from 0). In the second place, it seems a bit unwise
to be throwing away data during crash recovery anwyway. This latter
consideration convinces me to just disable truncation during recovery,
rather than computing latest_page_number and pushing ahead.
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Strip unused include files out unused include files, and add needed
includes to C files.
The next step is to remove unused include files in C files.
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To this end, add a couple of columns to pg_class, relminxid and relvacuumxid,
based on which we calculate the pg_database columns after each vacuum.
We now force all databases to be vacuumed, even template ones. A backend
noticing too old a database (meaning pg_database.datminxid is in danger of
falling behind Xid wraparound) will signal the postmaster, which in turn will
start an autovacuum iteration to process the offending database. In principle
this is only there to cope with frozen (non-connectable) databases without
forcing users to set them to connectable, but it could force regular user
database to go through a database-wide vacuum at any time. Maybe we should
warn users about this somehow. Of course the real solution will be to use
autovacuum all the time ;-)
There are some additional improvements we could have in this area: for example
the vacuum code could be smarter about not updating pg_database for each table
when called by autovacuum, and do it only once the whole autovacuum iteration
is done.
I updated the system catalogs documentation, but I didn't modify the
maintenance section. Also having some regression tests for this would be nice
but it's not really a very straightforward thing to do.
Catalog version bumped due to system catalog changes.
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discussion (including making def_arg allow reserved words), add missed
opt_definition for UNIQUE case. Put the reloptions support code in a less
random place (I chose to make a new file access/common/reloptions.c).
Eliminate header inclusion creep. Make the index options functions safely
user-callable (seems like client apps might like to be able to test validity
of options before trying to make an index). Reduce overhead for normal case
with no options by allowing rd_options to be NULL. Fix some unmaintainably
klugy code, including getting rid of Natts_pg_class_fixed at long last.
Some stylistic cleanup too, and pay attention to keeping comments in sync
with code.
Documentation still needs work, though I did fix the omissions in
catalogs.sgml and indexam.sgml.
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ITAGAKI Takahiro
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