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2016-04-27Emit invalidations to standby for transactions without xid.Andres Freund
So far, when a transaction with pending invalidations, but without an assigned xid, committed, we simply ignored those invalidation messages. That's problematic, because those are actually sent for a reason. Known symptoms of this include that existing sessions on a hot-standby replica sometimes fail to notice new concurrently built indexes and visibility map updates. The solution is to WAL log such invalidations in transactions without an xid. We considered to alternatively force-assign an xid, but that'd be problematic for vacuum, which might be run in systems with few xids. Important: This adds a new WAL record, but as the patch has to be back-patched, we can't bump the WAL page magic. This means that standbys have to be updated before primaries; otherwise "PANIC: standby_redo: unknown op code 32" errors can be encountered. XXX: Reported-By: Васильев Дмитрий, Masahiko Sawada Discussion: CAB-SwXY6oH=9twBkXJtgR4UC1NqT-vpYAtxCseME62ADwyK5OA@mail.gmail.com CAD21AoDpZ6Xjg=gFrGPnSn4oTRRcwK1EBrWCq9OqOHuAcMMC=w@mail.gmail.com
2016-04-15Fix trivial typo.Andres Freund
2016-04-14Fix core dump in ReorderBufferRestoreChange on alignment-picky platforms.Tom Lane
When re-reading an update involving both an old tuple and a new tuple from disk, reorderbuffer.c was careless about whether the new tuple is suitably aligned for direct access --- in general, it isn't. We'd missed seeing this in the buildfarm because the contrib/test_decoding tests exercise this code path only a few times, and by chance all of those cases have old tuples with length a multiple of 4, which is usually enough to make the access to the new tuple's t_len safe. For some still-not-entirely-clear reason, however, Debian's sparc build gets a bus error, as reported by Christoph Berg; perhaps it's assuming 8-byte alignment of the pointer? The lack of previous field reports is probably because you need all of these conditions to trigger a crash: an alignment-picky platform (not Intel), a transaction large enough to spill to disk, an update within that xact that changes a primary-key field and has an odd-length old tuple, and of course logical decoding tracing the transaction. Avoid the alignment assumption by using memcpy instead of fetching t_len directly, and add a test case that exposes the crash on picky platforms. Back-patch to 9.4 where the bug was introduced. Discussion: <[email protected]>
2016-04-14Adjust signature of walrcv_receive hook.Tom Lane
Commit 314cbfc5da988eff redefined the signature of this hook as typedef int (*walrcv_receive_type) (char **buffer, int *wait_fd); But in fact the type of the "wait_fd" variable ought to be pgsocket, which is what WaitLatchOrSocket expects, and which is necessary if we want to be able to assign PGINVALID_SOCKET to it on Windows. So fix that.
2016-04-14Adjust datatype of ReplicationState.acquired_by.Tom Lane
It was declared as "pid_t", which would be fine except that none of the places that printed it in error messages took any thought for the possibility that it's not equivalent to "int". This leads to warnings on some buildfarm members, and could possibly lead to actually wrong error messages on those platforms. There doesn't seem to be any very good reason not to just make it "int"; it's only ever assigned from MyProcPid, which is int. If we want to cope with PIDs that are wider than int, this is not the place to start. Also, fix the comment, which seems to perhaps be a leftover from a time when the field was only a bool? Per buildfarm. Back-patch to 9.5 which has same issue.
2016-04-14Add required database and origin filtering for logical messages.Andres Freund
Logical messages, added in 3fe3511d05, during decoding failed to filter messages emitted in other databases and messages emitted "under" a replication origin the output plugin isn't interested in. Add tests to verify that both types of filtering actually work. While touching message.sql remove hunk obsoleted by d25379e. Bump XLOG_PAGE_MAGIC because xl_logical_message changed and because 3fe3511d05 had omitted doing so. 3fe3511d05 additionally didn't bump catversion, but 7a542700d has done so since. Author: Petr Jelinek Reported-By: Andres Freund Discussion: [email protected]
2016-04-12Remove unused function GetOldestWALSendPointer from walsender code.Fujii Masao
That unused function was introduced as a sample because synchronous replication or replication monitoring tools might need it in the future. Recently commit 989be08 added the function SyncRepGetOldestSyncRecPtr which provides almost the same functionality for multiple synchronous standbys feature. So it's time to remove that unused sample function. This commit does that.
2016-04-11Use ereport(ERROR) instead of Assert() to emit syncrep_parser error.Fujii Masao
The existing code would either Assert or generate an invalid SyncRepConfig variable, neither of which is desirable. A regular error should be thrown instead. This commit silences compiler warning in non assertion-enabled builds. Per report from Jeff Janes. Suggested fix by Tom Lane.
2016-04-06Use proper format specifier %X/%X for LSN, again.Fujii Masao
Commit cee31f5 fixed this problem, but commit 989be08 accidentally reverted the fix. Thomas Munro
2016-04-06Generic Messages for Logical DecodingSimon Riggs
API and mechanism to allow generic messages to be inserted into WAL that are intended to be read by logical decoding plugins. This commit adds an optional new callback to the logical decoding API. Messages are either text or bytea. Messages can be transactional, or not, and are identified by a prefix to allow multiple concurrent decoding plugins. (Not to be confused with Generic WAL records, which are intended to allow crash recovery of extensible objects.) Author: Petr Jelinek and Andres Freund Reviewers: Artur Zakirov, Tomas Vondra, Simon Riggs Discussion: [email protected]
2016-04-06Support multiple synchronous standby servers.Fujii Masao
Previously synchronous replication offered only the ability to confirm that all changes made by a transaction had been transferred to at most one synchronous standby server. This commit extends synchronous replication so that it supports multiple synchronous standby servers. It enables users to consider one or more standby servers as synchronous, and increase the level of transaction durability by ensuring that transaction commits wait for replies from all of those synchronous standbys. Multiple synchronous standby servers are configured in synchronous_standby_names which is extended to support new syntax of 'num_sync ( standby_name [ , ... ] )', where num_sync specifies the number of synchronous standbys that transaction commits need to wait for replies from and standby_name is the name of a standby server. The syntax of 'standby_name [ , ... ]' which was used in 9.5 or before is also still supported. It's the same as new syntax with num_sync=1. This commit doesn't include "quorum commit" feature which was discussed in pgsql-hackers. Synchronous standbys are chosen based on their priorities. synchronous_standby_names determines the priority of each standby for being chosen as a synchronous standby. The standbys whose names appear earlier in the list are given higher priority and will be considered as synchronous. Other standby servers appearing later in this list represent potential synchronous standbys. The regression test for multiple synchronous standbys is not included in this commit. It should come later. Authors: Sawada Masahiko, Beena Emerson, Michael Paquier, Fujii Masao Reviewed-By: Kyotaro Horiguchi, Amit Kapila, Robert Haas, Simon Riggs, Amit Langote, Thomas Munro, Sameer Thakur, Suraj Kharage, Abhijit Menon-Sen, Rajeev Rastogi Many thanks to the various individuals who were involved in discussing and developing this feature.
2016-04-05Implement backup API functions for non-exclusive backupsMagnus Hagander
Previously non-exclusive backups had to be done using the replication protocol and pg_basebackup. With this commit it's now possible to make them using pg_start_backup/pg_stop_backup as well, as long as the backup program can maintain a persistent connection to the database. Doing this, backup_label and tablespace_map are returned as results from pg_stop_backup() instead of being written to the data directory. This makes the server safe from a crash during an ongoing backup, which can be a problem with exclusive backups. The old syntax of the functions remain and work exactly as before, but since the new syntax is safer this should eventually be deprecated and removed. Only reference documentation is included. The main section on backup still needs to be rewritten to cover this, but since that is already scheduled for a separate large rewrite, it's not included in this patch. Reviewed by David Steele and Amit Kapila
2016-04-05Fix error message from wal_level value renamingPeter Eisentraut
found by Ian Barwick
2016-04-01Add Generic WAL interfaceTeodor Sigaev
This interface is designed to give an access to WAL for extensions which could implement new access method, for example. Previously it was impossible because restoring from custom WAL would need to access system catalog to find a redo custom function. This patch suggests generic way to describe changes on page with standart layout. Bump XLOG_PAGE_MAGIC because of new record type. Author: Alexander Korotkov with a help of Petr Jelinek, Markus Nullmeier and minor editorization by my Reviewers: Petr Jelinek, Alvaro Herrera, Teodor Sigaev, Jim Nasby, Michael Paquier
2016-03-31Fix broken variable declarationAlvaro Herrera
Author: Konstantin Knizhnik
2016-03-31Use proper format specifier %X/%X for LSN.Fujii Masao
2016-03-30Enable logical slots to follow timeline switchesAlvaro Herrera
When decoding from a logical slot, it's necessary for xlog reading to be able to read xlog from historical (i.e. not current) timelines; otherwise, decoding fails after failover, because the archives are in the historical timeline. This is required to make "failover logical slots" possible; it currently has no other use, although theoretically it could be used by an extension that creates a slot on a standby and continues to replay from the slot when the standby is promoted. This commit includes a module in src/test/modules with functions to manipulate the slots (which is not otherwise possible in SQL code) in order to enable testing, and a new test in src/test/recovery to ensure that the behavior is as expected. Author: Craig Ringer Reviewed-By: Oleksii Kliukin, Andres Freund, Petr Jelínek
2016-03-30XLogReader general code cleanupAlvaro Herrera
Some minor tweaks and comment additions, for cleanliness sake and to avoid having the upcoming timeline-following patch be polluted with unrelated cleanup. Extracted from a larger patch by Craig Ringer, reviewed by Andres Freund, with some additions by myself.
2016-03-30Add new replication mode synchronous_commit = 'remote_apply'.Robert Haas
In this mode, the master waits for the transaction to be applied on the remote side, not just written to disk. That means that you can count on a transaction started on the standby to see all commits previously acknowledged by the master. To make this work, the standby sends a reply after replaying each commit record generated with synchronous_commit >= 'remote_apply'. This introduces a small inefficiency: the extra replies will be sent even by standbys that aren't the current synchronous standby. But previously-existing synchronous_commit levels make no attempt at all to optimize which replies are sent based on what the primary cares about, so this is no worse, and at least avoids any extra replies for people not using the feature at all. Thomas Munro, reviewed by Michael Paquier and by me. Some additional tweaks by me.
2016-03-27Don't use !! but != 0/NULL to force boolean evaluation.Andres Freund
I introduced several uses of !! to force bit arithmetic to be boolean, but per discussion the project prefers != 0/NULL. Discussion: CA+TgmoZP5KakLGP6B4vUjgMBUW0woq_dJYi0paOz-My0Hwt_vQ@mail.gmail.com
2016-03-18Merge wal_level "archive" and "hot_standby" into new name "replica"Peter Eisentraut
The distinction between "archive" and "hot_standby" existed only because at the time "hot_standby" was added, there was some uncertainty about stability. This is now a long time ago. We would like to move forward with simplifying the replication configuration, but this distinction is in the way, because a primary server cannot tell (without asking a standby or predicting the future) which one of these would be the appropriate level. Pick a new name for the combined setting to make it clearer that it covers all (non-logical) backup and replication uses. The old values are still accepted but are converted internally. Reviewed-by: Michael Paquier <[email protected]> Reviewed-by: David Steele <[email protected]>
2016-03-10Provide much better wait information in pg_stat_activity.Robert Haas
When a process is waiting for a heavyweight lock, we will now indicate the type of heavyweight lock for which it is waiting. Also, you can now see when a process is waiting for a lightweight lock - in which case we will indicate the individual lock name or the tranche, as appropriate - or for a buffer pin. Amit Kapila, Ildus Kurbangaliev, reviewed by me. Lots of helpful discussion and suggestions by many others, including Alexander Korotkov, Vladimir Borodin, and many others.
2016-03-10Avoid unlikely data-loss scenarios due to rename() without fsync.Andres Freund
Renaming a file using rename(2) is not guaranteed to be durable in face of crashes. Use the previously added durable_rename()/durable_link_or_rename() in various places where we previously just renamed files. Most of the changed call sites are arguably not critical, but it seems better to err on the side of too much durability. The most prominent known case where the previously missing fsyncs could cause data loss is crashes at the end of a checkpoint. After the actual checkpoint has been performed, old WAL files are recycled. When they're filled, their contents are fdatasynced, but we did not fsync the containing directory. An OS/hardware crash in an unfortunate moment could then end up leaving that file with its old name, but new content; WAL replay would thus not replay it. Reported-By: Tomas Vondra Author: Michael Paquier, Tomas Vondra, Andres Freund Discussion: [email protected] Backpatch: All supported branches
2016-03-10Introduce durable_rename() and durable_link_or_rename().Andres Freund
Renaming a file using rename(2) is not guaranteed to be durable in face of crashes; especially on filesystems like xfs and ext4 when mounted with data=writeback. To be certain that a rename() atomically replaces the previous file contents in the face of crashes and different filesystems, one has to fsync the old filename, rename the file, fsync the new filename, fsync the containing directory. This sequence is not generally adhered to currently; which exposes us to data loss risks. To avoid having to repeat this arduous sequence, introduce durable_rename(), which wraps all that. Also add durable_link_or_rename(). Several places use link() (with a fallback to rename()) to rename a file, trying to avoid replacing the target file out of paranoia. Some of those rename sequences need to be durable as well. There seems little reason extend several copies of the same logic, so centralize the link() callers. This commit does not yet make use of the new functions; they're used in a followup commit. Author: Michael Paquier, Andres Freund Discussion: [email protected] Backpatch: All supported branches
2016-03-09Handle invalid libpq sockets in more placesPeter Eisentraut
Also, make error messages consistent. From: Michael Paquier <[email protected]>
2016-03-07Further improvements to c8f621c43.Andres Freund
Coverity and inspection for the issue addressed in fd45d16f found some questionable code. Specifically coverity noticed that the wrong length was added in ReorderBufferSerializeChange() - without immediate negative consequences as the variable isn't used afterwards. During code-review and testing I noticed that a bit of space was wasted when allocating tuple bufs in several places. Thirdly, the debug memset()s in ReorderBufferGetTupleBuf() reduce the error checking valgrind can do. Backpatch: 9.4, like c8f621c43.
2016-03-07Fix wrong allocation size in c8f621c43.Andres Freund
In c8f621c43 I forgot to account for MAXALIGN when allocating a new tuplebuf in ReorderBufferGetTupleBuf(). That happens to currently not cause active problems on a number of platforms because the affected pointer is already aligned, but others, like ppc and hppa, trigger this in the regression test, due to a debug memset clearing memory. Fix that. Backpatch: 9.4, like the previous commit.
2016-03-06logical decoding: Fix handling of large old tuples with replica identity full.Andres Freund
When decoding the old version of an UPDATE or DELETE change, and if that tuple was bigger than MaxHeapTupleSize, we either Assert'ed out, or failed in more subtle ways in non-assert builds. Normally individual tuples aren't bigger than MaxHeapTupleSize, with big datums toasted. But that's not the case for the old version of a tuple for logical decoding; the replica identity is logged as one piece. With the default replica identity btree limits that to small tuples, but that's not the case for FULL. Change the tuple buffer infrastructure to separate allocate over-large tuples, instead of always going through the slab cache. This unfortunately requires changing the ReorderBufferTupleBuf definition, we need to store the allocated size someplace. To avoid requiring output plugins to recompile, don't store HeapTupleHeaderData directly after HeapTupleData, but point to it via t_data; that leaves rooms for the allocated size. As there's no reason for an output plugin to look at ReorderBufferTupleBuf->t_data.header, remove the field. It was just a minor convenience having it directly accessible. Reported-By: Adam Dratwiński Discussion: CAKg6ypLd7773AOX4DiOGRwQk1TVOQKhNwjYiVjJnpq8Wo+i62Q@mail.gmail.com
2016-03-06logical decoding: old/newtuple in spooled UPDATE changes was switched around.Andres Freund
Somehow I managed to flip the order of restoring old & new tuples when de-spooling a change in a large transaction from disk. This happens to only take effect when a change is spooled to disk which has old/new versions of the tuple. That only is the case for UPDATEs where he primary key changed or where replica identity is changed to FULL. The tests didn't catch this because either spooled updates, or updates that changed primary keys, were tested; not both at the same time. Found while adding tests for the following commit. Backpatch: 9.4, where logical decoding was added
2016-03-06logical decoding: Tell reorderbuffer about all xids.Andres Freund
Logical decoding's reorderbuffer keeps transactions in an LSN ordered list for efficiency. To make that's efficiently possible upper-level xids are forced to be logged before nested subtransaction xids. That only works though if these records are all looked at: Unfortunately we didn't do so for e.g. row level locks, which are otherwise uninteresting for logical decoding. This could lead to errors like: "ERROR: subxact logged without previous toplevel record". It's not sufficient to just look at row locking records, the xid could appear first due to a lot of other types of records (which will trigger the transaction to be marked logged with MarkCurrentTransactionIdLoggedIfAny). So invent infrastructure to tell reorderbuffer about xids seen, when they'd otherwise not pass through reorderbuffer.c. Reported-By: Jarred Ward Bug: #13844 Discussion: [email protected] Backpatch: 9.4, where logical decoding was added
2016-03-03logical decoding: fix decoding of a commit's commit time.Andres Freund
When adding replication origins in 5aa235042, I somehow managed to set the timestamp of decoded transactions to InvalidXLogRecptr when decoding one made without a replication origin. Fix that, and the wrong type of the new commit_time variable. This didn't trigger a regression test failure because we explicitly don't show commit timestamps in the regression tests, as they obviously are variable. Add a test that checks that a decoded commit's timestamp is within minutes of NOW() from before the commit. Reported-By: Weiping Qu Diagnosed-By: Artur Zakirov Discussion: [email protected], [email protected] Backpatch: 9.5, where 5aa235042 originates.
2016-02-29Fix typosAlvaro Herrera
Author: Amit Langote
2016-02-18Improve error message about active replication slotPeter Eisentraut
The old phrasing was awkward if a replication slot is activated and deactivated repeatedly.
2016-02-12Make builtin lwlock tranche names consistent.Robert Haas
Previously, we had a mix of styles. Amit Kapila
2016-02-05Fix typo in comment.Robert Haas
Michael Paquier
2016-02-02Make all built-in lwlock tranche IDs fixed.Robert Haas
This makes the values more stable, which seems like a good thing for anybody who needs to look at at them. Alexander Korotkov and Amit Kapila
2016-02-01Fix typos in commentsMagnus Hagander
Author: Michael Paquier
2016-01-29Migrate replication slot I/O locks into a separate tranche.Robert Haas
This is following in a long train of similar changes and for the same reasons - see b319356f0e94a6482c726cf4af96597c211d8d6e and fe702a7b3f9f2bc5bf6d173166d7d55226af82c8 inter alia. Author: Amit Kapila Reviewed-by: Alexander Korotkov, Robert Haas
2016-01-21Refactor to create generic WAL page read callbackSimon Riggs
Previously we didn’t have a generic WAL page read callback function, surprisingly. Logical decoding has logical_read_local_xlog_page(), which was actually generic, so move that to xlogfunc.c and rename to read_local_xlog_page(). Maintain logical_read_local_xlog_page() so existing callers still work. As requested by Michael Paquier, Alvaro Herrera and Andres Freund
2016-01-09Clean up some lack-of-STRICT issues in the core code, too.Tom Lane
A scan for missed proisstrict markings in the core code turned up these functions: brin_summarize_new_values pg_stat_reset_single_table_counters pg_stat_reset_single_function_counters pg_create_logical_replication_slot pg_create_physical_replication_slot pg_drop_replication_slot The first three of these take OID, so a null argument will normally look like a zero to them, resulting in "ERROR: could not open relation with OID 0" for brin_summarize_new_values, and no action for the pg_stat_reset_XXX functions. The other three will dump core on a null argument, though this is mitigated by the fact that they won't do so until after checking that the caller is superuser or has rolreplication privilege. In addition, the pg_logical_slot_get/peek[_binary]_changes family was intentionally marked nonstrict, but failed to make nullness checks on all the arguments; so again a null-pointer-dereference crash is possible but only for superusers and rolreplication users. Add the missing ARGISNULL checks to the latter functions, and mark the former functions as strict in pg_proc. Make that change in the back branches too, even though we can't force initdb there, just so that installations initdb'd in future won't have the issue. Since none of these bugs rise to the level of security issues (and indeed the pg_stat_reset_XXX functions hardly misbehave at all), it seems sufficient to do this. In addition, fix some order-of-operations oddities in the slot_get_changes family, mostly cosmetic, but not the part that moves the function's last few operations into the PG_TRY block. As it stood, there was significant risk for an error to exit without clearing historical information from the system caches. The slot_get_changes bugs go back to 9.4 where that code was introduced. Back-patch appropriate subsets of the pg_proc changes into all active branches, as well.
2016-01-07pgstat: add WAL receiver status view & SRFAlvaro Herrera
This new view provides insight into the state of a running WAL receiver in a HOT standby node. The information returned includes the PID of the WAL receiver process, its status (stopped, starting, streaming, etc), start LSN and TLI, last received LSN and TLI, timestamp of last message send and receipt, latest end-of-WAL LSN and time, and the name of the slot (if any). Access to the detailed data is only granted to superusers; others only get the PID. Author: Michael Paquier Reviewer: Haribabu Kommi
2016-01-02Update copyright for 2016Bruce Momjian
Backpatch certain files through 9.1
2015-12-18Remove duplicate word.Robert Haas
Kyotaro Horiguchi
2015-12-18Fix copy-and-paste error in logical decoding callback.Robert Haas
This could result in the error context misidentifying where the error actually occurred. Craig Ringer
2015-12-13Consistently set all fields in pg_stat_replication to null instead of 0Magnus Hagander
Previously the "sent" field would be set to 0 and all other xlog pointers be set to NULL if there were no valid values (such as when in a backup sending walsender).
2015-12-13Properly initialize write, flush and replay locations in walsender slotsMagnus Hagander
These would leak random xlog positions if a walsender used for backup would a walsender slot previously used by a replication walsender. In passing also fix a couple of cases where the xlog pointer is directly compared to zero instead of using XLogRecPtrIsInvalid, noted by Michael Paquier.
2015-11-22Adopt the GNU convention for handling tar-archive members exceeding 8GB.Tom Lane
The POSIX standard for tar headers requires archive member sizes to be printed in octal with at most 11 digits, limiting the representable file size to 8GB. However, GNU tar and apparently most other modern tars support a convention in which oversized values can be stored in base-256, allowing any practical file to be a tar member. Adopt this convention to remove two limitations: * pg_dump with -Ft output format failed if the contents of any one table exceeded 8GB. * pg_basebackup failed if the data directory contained any file exceeding 8GB. (This would be a fatal problem for installations configured with a table segment size of 8GB or more, and it has also been seen to fail when large core dump files exist in the data directory.) File sizes under 8GB are still printed in octal, so that no compatibility issues are created except in cases that would have failed entirely before. In addition, this patch fixes several bugs in the same area: * In 9.3 and later, we'd defined tarCreateHeader's file-size argument as size_t, which meant that on 32-bit machines it would write a corrupt tar header for file sizes between 4GB and 8GB, even though no error was raised. This broke both "pg_dump -Ft" and pg_basebackup for such cases. * pg_restore from a tar archive would fail on tables of size between 4GB and 8GB, on machines where either "size_t" or "unsigned long" is 32 bits. This happened even with an archive file not affected by the previous bug. * pg_basebackup would fail if there were files of size between 4GB and 8GB, even on 64-bit machines. * In 9.3 and later, "pg_basebackup -Ft" failed entirely, for any file size, on 64-bit big-endian machines. In view of these potential data-loss bugs, back-patch to all supported branches, even though removal of the documented 8GB limit might otherwise be considered a new feature rather than a bug fix.
2015-11-08Set replication origin when decoding commit records.Andres Freund
By accident the replication origin was not set properly in DecodeCommit(). That's bad because the origin is passed to the output plugins origin filter, and accessible from the output plugin via ReorderBufferTXN->origin_id. Accessing the origin of individual changes worked before the fix, which is why this wasn't notices earlier. Reported-By: Craig Ringer Author: Craig Ringer Discussion: CAMsr+YFhBJLp=qfSz3-J+0P1zLkE8zNXM2otycn20QRMx380gw@mail.gmail.com Backpatch: 9.5, where replication origins where introduced
2015-10-29Message style improvementsPeter Eisentraut
Message style, plurals, quoting, spelling, consistency with similar messages
2015-10-27Measure string lengths only onceAlvaro Herrera
Bernd Helmle complained that CreateReplicationSlot() was assigning the same value to the same variable twice, so we could remove one of them. Code inspection reveals that we can actually remove both assignments: according to the author the assignment was there for beauty of the strlen line only, and another possible fix to that is to put the strlen in its own line, so do that. To be consistent within the file, refactor all duplicated strlen() calls, which is what we do elsewhere in the backend anyway. In basebackup.c, snprintf already returns the right length; no need for strlen afterwards. Backpatch to 9.4, where replication slots were introduced, to keep code identical. Some of this is older, but the patch doesn't apply cleanly and it's only of cosmetic value anyway. Discussion: http://www.postgresql.org/message-id/[email protected]