We don't actually need a lock to set PGPROC->statusFlags itself; what we
do need is a shared lock on either XidGenLock or ProcArrayLock in order to
ensure MyProc->pgxactoff keeps still while we modify the mirror array in
ProcGlobal->statusFlags. Some places were using an exclusive lock for
that, which is excessive. Relax those to use shared lock only.
procarray.c has a couple of places with somewhat brittle assumptions
about PGPROC changes: ProcArrayEndTransaction uses only shared lock, so
it's permissible to change MyProc only. On the other hand,
ProcArrayEndTransactionInternal also changes other procs, so it must
hold exclusive lock. Add asserts to ensure those assumptions continue
to hold.
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/20201117155501.GA13805@alvherre.pgsql
This adds the statistics about transactions streamed to the decoding
output plugin from ReorderBuffer. Users can query the
pg_stat_replication_slots view to check these stats and call
pg_stat_reset_replication_slot to reset the stats of a particular slot.
Users can pass NULL in pg_stat_reset_replication_slot to reset stats of
all the slots.
Commit 9868167500 has added the basic infrastructure to capture the stats
of slot and this commit extends the statistics collector to track
additional information about slots.
Bump the catversion as we have added new columns in the catalog entry.
Author: Ajin Cherian and Amit Kapila
Reviewed-by: Sawada Masahiko and Dilip Kumar
Discussion: https://postgr.es/m/CAA4eK1+chpEomLzgSoky-D31qev19AmECNiEAietPQUGEFhtVA@mail.gmail.com
This adds the statistics about transactions spilled to disk from
ReorderBuffer. Users can query the pg_stat_replication_slots view to check
these stats and call pg_stat_reset_replication_slot to reset the stats of
a particular slot. Users can pass NULL in pg_stat_reset_replication_slot
to reset stats of all the slots.
This commit extends the statistics collector to track this information
about slots.
Author: Sawada Masahiko and Amit Kapila
Reviewed-by: Amit Kapila and Dilip Kumar
Discussion: https://postgr.es/m/CA+fd4k5_pPAYRTDrO2PbtTOe0eHQpBvuqmCr8ic39uTNmR49Eg@mail.gmail.com
Similar to the previous commit this increases the chance that data
frequently needed by GetSnapshotData() stays in l2 cache. As we now
take care to not unnecessarily write to ProcGlobal->vacuumFlags, there
should be very few modifications to the ProcGlobal->vacuumFlags array.
Author: Andres Freund <andres@anarazel.de>
Reviewed-By: Robert Haas <robertmhaas@gmail.com>
Reviewed-By: Thomas Munro <thomas.munro@gmail.com>
Reviewed-By: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/20200301083601.ews6hz5dduc3w2se@alap3.anarazel.de
They are equivalent, except that StrNCpy() zero-fills the entire
destination buffer instead of providing just one trailing zero. For
all but a tiny number of callers, that's just overhead rather than
being desirable.
Remove StrNCpy() as it is now unused.
In some cases, namestrcpy() is the more appropriate function to use.
While we're here, simplify the API of namestrcpy(): Remove the return
value, don't check for NULL input. Nothing was using that anyway.
Also, remove a few unused name-related functions.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/44f5e198-36f6-6cdb-7fa9-60e34784daae%402ndquadrant.com
Instead of serializing the transaction to disk after reaching the
logical_decoding_work_mem limit in memory, we consume the changes we have
in memory and invoke stream API methods added by commit 45fdc9738b.
However, sometimes if we have incomplete toast or speculative insert we
spill to the disk because we can't generate the complete tuple and stream.
And, as soon as we get the complete tuple we stream the transaction
including the serialized changes.
We can do this incremental processing thanks to having assignments
(associating subxact with toplevel xacts) in WAL right away, and
thanks to logging the invalidation messages at each command end. These
features are added by commits 0bead9af48 and c55040ccd0 respectively.
Now that we can stream in-progress transactions, the concurrent aborts
may cause failures when the output plugin consults catalogs (both system
and user-defined).
We handle such failures by returning ERRCODE_TRANSACTION_ROLLBACK
sqlerrcode from system table scan APIs to the backend or WALSender
decoding a specific uncommitted transaction. The decoding logic on the
receipt of such a sqlerrcode aborts the decoding of the current
transaction and continue with the decoding of other transactions.
We have ReorderBufferTXN pointer in each ReorderBufferChange by which we
know which xact it belongs to. The output plugin can use this to decide
which changes to discard in case of stream_abort_cb (e.g. when a subxact
gets discarded).
We also provide a new option via SQL APIs to fetch the changes being
streamed.
Author: Dilip Kumar, Tomas Vondra, Amit Kapila, Nikhil Sontakke
Reviewed-by: Amit Kapila, Kuntal Ghosh, Ajin Cherian
Tested-by: Neha Sharma, Mahendra Singh Thalor and Ajin Cherian
Discussion: https://postgr.es/m/688b0b7f-2f6c-d827-c27b-216a8e3ea700@2ndquadrant.com
This adds seven methods to the output plugin API, adding support for
streaming changes of large in-progress transactions.
* stream_start
* stream_stop
* stream_abort
* stream_commit
* stream_change
* stream_message
* stream_truncate
Most of this is a simple extension of the existing methods, with
the semantic difference that the transaction (or subtransaction)
is incomplete and may be aborted later (which is something the
regular API does not really need to deal with).
This also extends the 'test_decoding' plugin, implementing these
new stream methods.
The stream_start/start_stop are used to demarcate a chunk of changes
streamed for a particular toplevel transaction.
This commit simply adds these new APIs and the upcoming patch to "allow
the streaming mode in ReorderBuffer" will use these APIs.
Author: Tomas Vondra, Dilip Kumar, Amit Kapila
Reviewed-by: Amit Kapila
Tested-by: Neha Sharma and Mahendra Singh Thalor
Discussion: https://postgr.es/m/688b0b7f-2f6c-d827-c27b-216a8e3ea700@2ndquadrant.com
Code review for 0dc8ead46363, prompted by a bug closed by 91c40548d5f7.
XLogReader's system for opening and closing segments had gotten too
complicated, with callbacks being passed at both the XLogReaderAllocate
level (read_page) as well as at the WALRead level (segment_open). This
was confusing and hard to follow, so restructure things so that these
callbacks are passed together at XLogReaderAllocate time, and add
another callback to the set (segment_close) to make it a coherent whole.
Also, ensure XLogReaderState is an argument to all the callbacks, so
that they can grab at the ->private data if necessary.
Document the whole arrangement more clearly.
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://postgr.es/m/20200422175754.GA19858@alvherre.pgsql
Commit 9f06d79ef831's replication slot copying failed to
properly reserve the WAL that the slot is expecting to see
during DecodingContextFindStartpoint (to set the confirmed_flush
LSN), so concurrent activity could remove that WAL and cause the
copy process to error out. But it doesn't actually *need* that
WAL anyway: instead of running decode to find confirmed_flush, it
can be copied from the source slot. Fix this by rearranging things
to avoid DecodingContextFindStartpoint() (leaving the target slot's
confirmed_flush_lsn to invalid), and set that up afterwards by copying
from the target slot's value.
Also ensure the source slot's confirmed_flush_lsn is valid.
Reported-by: Arseny Sher
Author: Masahiko Sawada, Arseny Sher
Discussion: https://postgr.es/m/871rr3ohbo.fsf@ars-thinkpad
The signature of XLogReadRecord() required the caller to pass the starting
WAL position as argument, or InvalidXLogRecPtr to continue reading at the
end of previous record. That's slightly awkward to the callers, as most
of them don't want to randomly jump around in the WAL stream, but start
reading at one position and then read everything from that point onwards.
Remove the 'RecPtr' argument and add a new function XLogBeginRead() to
specify the starting position instead. That's more convenient for the
callers. Also, xlogreader holds state that is reset when you change the
starting position, so having a separate function for doing that feels like
a more natural fit.
This changes XLogFindNextRecord() function so that it doesn't reset the
xlogreader's state to what it was before the call anymore. Instead, it
positions the xlogreader to the found record, like XLogBeginRead().
Reviewed-by: Kyotaro Horiguchi, Alvaro Herrera
Discussion: https://www.postgresql.org/message-id/5382a7a3-debe-be31-c860-cb810c08f366%40iki.fi
Similar to commits 7e735035f2 and dddf4cdc33, this commit makes the order
of header file inclusion consistent for backend modules.
In the passing, removed a couple of duplicate inclusions.
Author: Vignesh C
Reviewed-by: Kuntal Ghosh and Amit Kapila
Discussion: https://postgr.es/m/CALDaNm2Sznv8RR6Ex-iJO6xAdsxgWhCoETkaYX=+9DW3q0QCfA@mail.gmail.com
The state-tracking of WAL reading in various places was pretty messy,
mostly because the ancient physical-replication WAL reading code wasn't
using the XLogReader abstraction. This led to some untidy code. Make
it prettier by creating two additional supporting structs,
WALSegmentContext and WALOpenSegment which keep track of WAL-reading
state. This makes code cleaner, as well as supports more future
cleanup.
Author: Antonin Houska
Reviewed-by: Álvaro Herrera and (older versions) Robert Haas
Discussion: https://postgr.es/m/14984.1554998742@spoje.net
This allows the user to create duplicates of existing replication slots,
either logical or physical, and even changing properties such as whether
they are temporary or the output plugin used.
There are multiple uses for this, such as initializing multiple replicas
using the slot for one base backup; when doing investigation of logical
replication issues; and to select a different output plugins.
Author: Masahiko Sawada
Reviewed-by: Michael Paquier, Andres Freund, Petr Jelinek
Discussion: https://postgr.es/m/CAD21AoAm7XX8y_tOPP6j4Nzzch12FvA1wPqiO690RCk+uYVstg@mail.gmail.com
Previously it was possible to create a slot, change wal_level, and
restart, even if the new wal_level was insufficient for the
slot. That's a problem for both logical and physical slots, because
the necessary WAL records are not generated.
This removes a few tests in newer versions that, somewhat
inexplicably, whether restarting with a too low wal_level worked (a
buggy behaviour!).
Reported-By: Joshua D. Drake
Author: Andres Freund
Discussion: https://postgr.es/m/20181029191304.lbsmhshkyymhw22w@alap3.anarazel.de
Backpatch: 9.4-, where replication slots where introduced
This was broken in commit 9c7d06d60680, which inadvertently gave the
wrong value to fast_forward in one StartupDecodingContext call. Fix by
flipping the value. Add a test for the obvious error, namely trying to
initialize a replication slot with an nonexistent output plugin.
While at it, move the CreateDecodingContext call earlier, so that any
errors are reported before sending the CopyBoth message.
Author: Dave Cramer <davecramer@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CADK3HHLVkeRe1v4P02-5hj55H3_yJg3AEtpXyEY5T3wuzO2jSg@mail.gmail.com
The code added by 9c7d06d60680 was a bit obscure; clarify that by
rewriting the comments. Lack of clarity has already caused bugs, so
it's a worthy goal.
Co-authored-by: Arseny Sher <a.sher@postgrespro.ru>
Co-authored-by: Michaël Paquier <michael@paquier.xyz>
Co-authored-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Petr Jelínek <petr.jelinek@2ndquadrant.com>
Discussion: https://postgr.es/m/87y3fgoyrn.fsf@ars-thinkpad
While debugging issues on HEAD for the new slot forwarding feature of
Postgres 11, some monitoring of the code surrounding in-memory slot data
has proved that the lock handling may cause inconsistent data to be read
by read-only callers of slot functions, particularly
pg_get_replication_slots() which fetches data for the system view
pg_replication_slots, or modules looking directly at slot information.
The code paths involved in those problems concern logical decoding
initialization (down to 9.4) and WAL reservation for slots (new as of
10).
A set of comments documenting all the lock handlings, particularly the
dependency with LW locks for slots and the in_use flag as well as the
internal mutex lock is added, based on a suggested by Simon Riggs.
Some of the fixed code exists down to 9.4 where WAL decoding has been
introduced, but as those race conditions are really unlikely going to
happen as those concern code paths for slot and decoding creation, just
fix the problem on HEAD.
Author: Michael Paquier
Discussion: https://postgr.es/m/20180528085747.GA27845@paquier.xyz
Add a new WAL record type for TRUNCATE, which is only used when
wal_level >= logical. (For physical replication, TRUNCATE is already
replicated via SMGR records.) Add new callback for logical decoding
output plugins to receive TRUNCATE actions.
Author: Simon Riggs <simon@2ndquadrant.com>
Author: Marco Nenciarini <marco.nenciarini@2ndquadrant.it>
Author: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Reviewed-by: Petr Jelinek <petr.jelinek@2ndquadrant.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Per the project style guide, details and hints should have leading
capitalization and end with a period. On the other hand, errcontext should
not be capitalized and should not end with a period. To support well
formatted error contexts in dblink, extend dblink_res_error() to take a
format+arguments rather than a hardcoded string.
Daniel Gustafsson
Discussion: https://postgr.es/m/B3C002C8-21A0-4F53-A06E-8CAB29FCF295@yesql.se
Logical decoding should not publish anything about tables created as
part of a heap rewrite during DDL. Those tables don't exist externally,
so consumers of logical decoding cannot do anything sensible with that
information. In ab28feae2bd3d4629bd73ae3548e671c57d785f0, we worked
around this for built-in logical replication, but that was hack.
This is a more proper fix: We mark such transient heaps using the new
field pg_class.relwrite, linking to the original relation OID. By
default, we ignore them in logical decoding before they get to the
output plugin. Optionally, a plugin can register their interest in
getting such changes, if they handle DDL specially, in which case the
new field will help them get information about the actual table.
Reviewed-by: Craig Ringer <craig@2ndquadrant.com>
Ability to advance both physical and logical replication slots using a
new user function pg_replication_slot_advance().
For logical advance that means records are consumed as fast as possible
and changes are not given to output plugin for sending. Makes 2nd phase
(after we reached SNAPBUILD_FULL_SNAPSHOT) of replication slot creation
faster, especially when there are big transactions as the reorder buffer
does not have to deal with data changes and does not have to spill to
disk.
Author: Petr Jelinek
Reviewed-by: Simon Riggs
For performance reasons a larger segment size than the default 16MB
can be useful. A larger segment size has two main benefits: Firstly,
in setups using archiving, it makes it easier to write scripts that
can keep up with higher amounts of WAL, secondly, the WAL has to be
written and synced to disk less frequently.
But at the same time large segment size are disadvantageous for
smaller databases. So far the segment size had to be configured at
compile time, often making it unrealistic to choose one fitting to a
particularly load. Therefore change it to a initdb time setting.
This includes a breaking changes to the xlogreader.h API, which now
requires the current segment size to be configured. For that and
similar reasons a number of binaries had to be taught how to recognize
the current segment size.
Author: Beena Emerson, editorialized by Andres Freund
Reviewed-By: Andres Freund, David Steele, Kuntal Ghosh, Michael
Paquier, Peter Eisentraut, Robert Hass, Tushar Ahuja
Discussion: https://postgr.es/m/CAOG9ApEAcQ--1ieKbhFzXSQPw_YLmepaa4hNdnY5+ZULpt81Mw@mail.gmail.com
The callers for GetOldestSafeDecodingTransactionId() all inverted the
argument for the argument introduced in 2bef06d516460. Luckily this
appears to be inconsequential for the moment, as we wait for
concurrent in-progress transaction when assembling a
snapshot. Additionally this could only make a difference when adding a
second logical slot, because only a pre-existing slot could cause an
issue by lowering the returned xid dangerously much.
Reported-By: Antonin Houska
Discussion: https://postgr.es/m/32704.1496993134@localhost
Backport: 9.4-, where 2bef06d516460 was backpatched to.
Don't move parenthesized lines to the left, even if that means they
flow past the right margin.
By default, BSD indent lines up statement continuation lines that are
within parentheses so that they start just to the right of the preceding
left parenthesis. However, traditionally, if that resulted in the
continuation line extending to the right of the desired right margin,
then indent would push it left just far enough to not overrun the margin,
if it could do so without making the continuation line start to the left of
the current statement indent. That makes for a weird mix of indentations
unless one has been completely rigid about never violating the 80-column
limit.
This behavior has been pretty universally panned by Postgres developers.
Hence, disable it with indent's new -lpl switch, so that parenthesized
lines are always lined up with the preceding left paren.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
Change pg_bsd_indent to follow upstream rules for placement of comments
to the right of code, and remove pgindent hack that caused comments
following #endif to not obey the general rule.
Commit e3860ffa4dd0dad0dd9eea4be9cc1412373a8c89 wasn't actually using
the published version of pg_bsd_indent, but a hacked-up version that
tried to minimize the amount of movement of comments to the right of
code. The situation of interest is where such a comment has to be
moved to the right of its default placement at column 33 because there's
code there. BSD indent has always moved right in units of tab stops
in such cases --- but in the previous incarnation, indent was working
in 8-space tab stops, while now it knows we use 4-space tabs. So the
net result is that in about half the cases, such comments are placed
one tab stop left of before. This is better all around: it leaves
more room on the line for comment text, and it means that in such
cases the comment uniformly starts at the next 4-space tab stop after
the code, rather than sometimes one and sometimes two tabs after.
Also, ensure that comments following #endif are indented the same
as comments following other preprocessor commands such as #else.
That inconsistency turns out to have been self-inflicted damage
from a poorly-thought-through post-indent "fixup" in pgindent.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
Lag tracking is called for each commit, but we introduce
a pacing delay to ensure we don't swamp the lag tracker.
Author: Petr Jelinek, with minor pacing delay code from me
Logical decoding stores historical snapshots on disk, so that logical
decoding can restart without having to reconstruct a snapshot from
scratch (for which the resources are not guaranteed to be present
anymore). These serialized snapshots were also used when creating a
new slot via the walsender interface, which can export a "full"
snapshot (i.e. one that can read all tables, not just catalog ones).
The problem is that the serialized snapshots are only useful for
catalogs and not for normal user tables. Thus the use of such a
serialized snapshot could result in an inconsistent snapshot being
exported, which could lead to queries returning wrong data. This
would only happen if logical slots are created while another logical
slot already exists.
Author: Petr Jelinek
Reviewed-By: Andres Freund
Discussion: https://postgr.es/m/f37e975c-908f-858e-707f-058d3b1eb214@2ndquadrant.com
Backport: 9.4, where logical decoding was introduced.
The logical decoding machinery already preserved all the required
catalog tuples, which is sufficient in the course of normal logical
decoding, but did not guarantee that non-catalog tuples were preserved
during computation of the initial snapshot when creating a slot over
the replication protocol.
This could cause a corrupted initial snapshot being exported. The
time window for issues is usually not terribly large, but on a busy
server it's perfectly possible to it hit it. Ongoing decoding is not
affected by this bug.
To avoid increased overhead for the SQL API, only retain additional
tuples when a logical slot is being created over the replication
protocol. To do so this commit changes the signature of
CreateInitDecodingContext(), but it seems unlikely that it's being
used in an extension, so that's probably ok.
In a drive-by fix, fix handling of
ReplicationSlotsComputeRequiredXmin's already_locked argument, which
should only apply to ProcArrayLock, not ReplicationSlotControlLock.
Reported-By: Erik Rijkers
Analyzed-By: Petr Jelinek
Author: Petr Jelinek, heavily editorialized by Andres Freund
Reviewed-By: Andres Freund
Discussion: https://postgr.es/m/9a897b86-46e1-9915-ee4c-da02e4ff6a95@2ndquadrant.com
Backport: 9.4, where logical decoding was introduced.
I found that half a dozen (nearly 5%) of our AllocSetContextCreate calls
had typos in the context-sizing parameters. While none of these led to
especially significant problems, they did create minor inefficiencies,
and it's now clear that expecting people to copy-and-paste those calls
accurately is not a great idea. Let's reduce the risk of future errors
by introducing single macros that encapsulate the common use-cases.
Three such macros are enough to cover all but two special-purpose contexts;
those two calls can be left as-is, I think.
While this patch doesn't in itself improve matters for third-party
extensions, it doesn't break anything for them either, and they can
gradually adopt the simplified notation over time.
In passing, change TopMemoryContext to use the default allocation
parameters. Formerly it could only be extended 8K at a time. That was
probably reasonable when this code was written; but nowadays we create
many more contexts than we did then, so that it's not unusual to have a
couple hundred K in TopMemoryContext, even without considering various
dubious code that sticks other things there. There seems no good reason
not to let it use growing blocks like most other contexts.
Back-patch to 9.6, mostly because that's still close enough to HEAD that
it's easy to do so, and keeping the branches in sync can be expected to
avoid some future back-patching pain. The bugs fixed by these changes
don't seem to be significant enough to justify fixing them further back.
Discussion: <21072.1472321324@sss.pgh.pa.us>
Back in 3b02ea4f0780 I added some comments in various places to explain
how logical decoding and other things worked. Not all of the changes
were welcome, because they were misleading or wrong. This changes them
a little bit to make them more accurate.
Some other comments are also changed to be more accurate. Also, fix a
bunch of typos.
Author: Álvaro Herrera, Craig Ringer
Andres Freund reviewed some parts of this.
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: 5685F999.6010202@2ndquadrant.com
