Neon doesn't have seqscan detection of its own, so stop read_stream from
trying to utilize that readahead, and instead make it issue readahead of
its own.
## Problem
@knizhnik noticed that we didn't issue smgrprefetch[v] calls for
seqscans in PG17 due to the move to the read_stream API, which assumes
that the underlying IO facilities do seqscan detection for readahead.
That is a wrong assumption when Neon is involved, so let's remove the
code that applies that assumption.
## Summary of changes
Remove the cases where seqscans are detected and prefetch is disabled as
a consequence, and instead don't do that detection.
PG PR: https://github.com/neondatabase/postgres/pull/532
## Problem
I have made a mistake in merging Postgre PRs
## Summary of changes
Restore consistency of submodule referenced.
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
The community decided to make a new off-schedule release due to ABI
breakage in last week's release. We're not affected by the ABI
breakage because we rebuild all extensions in our docker images, but
let's stay up-to-date. There were a few other fixes in the release
too.
The PostgreSQL 17 vendor module is now based on postgres/postgres @
d7ec59a63d745ba74fba0e280bbf85dc6d1caa3e, presumably the final code
change before the V17 tag.
We can't FlushOneBuffer when we're in redo-only mode on PageServer, so
make execution of that function conditional on us not running in
pageserver walredo mode.
If the primary is started at an LSN within the first of a 16 MB WAL
segment, the "long XLOG page header" at the beginning of the segment was
not initialized correctly. That has gone unnnoticed, because under
normal circumstances, nothing looks at the page header. The WAL that is
streamed to the safekeepers starts at the new record's LSN, not at the
beginning of the page, so that bogus page header didn't propagate
elsewhere, and a primary server doesn't normally read the WAL its
written. Which is good because the contents of the page would be bogus
anyway, as it wouldn't contain any of the records before the LSN where
the new record is written.
Except that in the following cases a primary does read its own WAL:
1. When there are two-phase transactions in prepared state at
checkpoint. The checkpointer reads the two-phase state from the
XLOG_XACT_PREPARE record, and writes it to a file in pg_twophase/.
2. Logical decoding reads the WAL starting from the replication slot's
restart LSN.
This PR fixes the problem with two-phase transactions. For that, it's
sufficient to initialize the page header correctly. The checkpointer
only needs to read XLOG_XACT_PREPARE records that were generated after
the server startup, so it's still OK that older WAL is missing / bogus.
I have not investigated if we have a problem with logical decoding,
however. Let's deal with that separately.
Special thanks to @Lzjing-1997, who independently found the same bug
and opened a PR to fix it, although I did not use that PR.
This adds preliminary PG17 support to Neon, based on RC1 / 2024-09-04
07b828e9d4
NOTICE: The data produced by the included version of the PostgreSQL fork
may not be compatible with the future full release of PostgreSQL 17 due to
expected or unexpected future changes in magic numbers and internals.
DO NOT EXPECT DATA IN V17-TENANTS TO BE COMPATIBLE WITH THE 17.0
RELEASE!
Co-authored-by: Anastasia Lubennikova <anastasia@neon.tech>
Co-authored-by: Alexander Bayandin <alexander@neon.tech>
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
There was a confusion on the REL_14_STABLE_neon branch. PR
https://github.com/neondatabase/postgres/pull/471 was merged ot the
branch, but the corresponding PRs on the other REL_15_STABLE_neon and
REL_16_STABLE_neon branches were not merged. Also, the submodule
reference in the neon repository was never updated, so even though the
REL_14_STABLE_neon branch contained the commit, it was never used.
That PR https://github.com/neondatabase/postgres/pull/471 was a few
bricks shy of a load (no tests, some differences between the different
branches), so to get us to a good state, revert that change from the
REL_14_STABLE_neon branch. This PR in the neon repository updates the
submodule reference past two commites on the REL_14_STABLE_neon branch:
first the commit from PR
https://github.com/neondatabase/postgres/pull/471, and immediately after
that the revert of the same commit. This brings us back to square one,
but now the submodule reference matches the tip of the
REL_14_STABLE_neon branch again.
Commit cfa45ff5ee (PR #8860) updated the vendor/postgres submodules, but
didn't use the same commit SHAs that were pushed as the corresponding
REL_*_STABLE_neon branches in the postgres repository. The contents were
the same, but the REL_*_STABLE_neon branches pointed to squashed
versions of the commits, whereas the SHAs used in the submodules
referred to the pre-squash revisions.
Note: The vendor/postgres-v14 submodule still doesn't match with the tip
of REL_14_STABLE_neon branch, because there has been one more commit on
that branch since then. That's another confusion which we should fix,
but let's do that separately. This commit doesn't change the code that
gets built in any way, only changes the submodule references to point to
the correct SHAs in the REL_*_STABLE_neon branch histories, rather than
some detached commits.
## Problem
See #8620
## Summary of changes
Remove walloping of replorigin file because it is reconstructed by PS
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
## Problem
See https://github.com/neondatabase/neon/issues/8499
## Summary of changes
Save HEAP_COMBOCID flag in WAL and do not clear it in redo handlers.
Related Postgres PRs:
https://github.com/neondatabase/postgres/pull/457https://github.com/neondatabase/postgres/pull/458https://github.com/neondatabase/postgres/pull/459
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
It should take syncrep flush_lsn into account because WAL before it on endpoint
restart is lost, which makes replication miss some data if slot had already been
advanced too far. This commit adds test reproducing the issue and bumps
vendor/postgres to commit with the actual fix.
## Problem
PR #7992 was merged without correspondent changes in Postgres submodules
and this is why test_oid_overflow.py is failed now.
## Summary of changes
Bump Postgres versions
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
## Problem
Postgres is using `access()` function in `GetNewRelFileNumber` to check
if assigned relfilenumber is not used for any other relation. This check
will not work in Neon, because we do not have all files in local
storage.
## Summary of changes
Use smgrexists() instead which will check at page server if such
relfilenode is used.
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
We have one pretty serious MVCC visibility bug with hot standby
replicas. We incorrectly treat any transactions that are in progress
in the primary, when the standby is started, as aborted. That can
break MVCC for queries running concurrently in the standby. It can
also lead to hint bits being set incorrectly, and that damage can last
until the replica is restarted.
The fundamental bug was that we treated any replica start as starting
from a shut down server. The fix for that is straightforward: we need
to set 'wasShutdown = false' in InitWalRecovery() (see changes in the
postgres repo).
However, that introduces a new problem: with wasShutdown = false, the
standby will not open up for queries until it receives a running-xacts
WAL record from the primary. That's correct, and that's how Postgres
hot standby always works. But it's a problem for Neon, because:
* It changes the historical behavior for existing users. Currently,
the standby immediately opens up for queries, so if they now need to
wait, we can breka existing use cases that were working fine
(assuming you don't hit the MVCC issues).
* The problem is much worse for Neon than it is for standalone
PostgreSQL, because in Neon, we can start a replica from an
arbitrary LSN. In standalone PostgreSQL, the replica always starts
WAL replay from a checkpoint record, and the primary arranges things
so that there is always a running-xacts record soon after each
checkpoint record. You can still hit this issue with PostgreSQL if
you have a transaction with lots of subtransactions running in the
primary, but it's pretty rare in practice.
To mitigate that, we introduce another way to collect the
running-xacts information at startup, without waiting for the
running-xacts WAL record: We can the CLOG for XIDs that haven't been
marked as committed or aborted. It has limitations with
subtransactions too, but should mitigate the problem for most users.
See https://github.com/neondatabase/neon/issues/7236.
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
We did not recover the subtransaction IDs of prepared transactions when
starting a hot standby from a shutdown checkpoint. As a result, such
subtransactions were considered as aborted, rather than in-progress.
That would lead to hint bits being set incorrectly, and the
subtransactions suddenly becoming visible to old snapshots when the
prepared transaction was committed.
To fix, update pg_subtrans with prepared transactions's subxids when
starting hot standby from a shutdown checkpoint. The snapshots taken
from that state need to be marked as "suboverflowed", so that we also
check the pg_subtrans.
Discussion:
https://www.postgresql.org/message-id/6b852e98-2d49-4ca1-9e95-db419a2696e0%40iki.fi
NEON: cherry-picked from the upstream thread ahead of time, to unblock
https://github.com/neondatabase/neon/pull/7288. I expect this to be
committed to upstream in the next few days, superseding this. NOTE: I
did not include the new regression test on v15 and v14 branches, because
the test would need some adapting, and we don't run the perl tests on
Neon anyway.
## Problem
See https://github.com/neondatabase/cloud/issues/10845
## Summary of changes
Do not report error if GIN page is not restored
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Using InvalidateBuffer is wrong, because if the page is concurrently
dirtied, it will throw away the dirty page without calling
smgwrite(). In Neon, that means that the last-written LSN update for
the page is missed.
In v16, use the new InvalidateVictimBuffer() function that does what
we need. In v15 and v14, backport the InvalidateVictimBuffer()
function.
Fixes issue https://github.com/neondatabase/neon/issues/7802
## Problem
Ref https://neondb.slack.com/archives/C036U0GRMRB/p1688122168477729
## Summary of changes
- Add sha from postgres repo into postgres version string (via
`--with-extra-version`)
- Add a test that Postgres version matches the expected one
- Remove build-time hard check and allow only related tests to fail
## Problem
See https://neondb.slack.com/archives/C03QLRH7PPD/p1712529369520409
In case of statements CREATE TABLE AS SELECT... or INSERT FROM SELECT...
we are fetching data from source table and storing it in destination
table. It cause problems with prefetch last-written-lsn is known for the
pages of source table
(which for example happens after compute restart). In this case we get
get global value of last-written-lsn which is changed frequently as far
as we are writing pages of destination table. As a result request-isn
for the prefetch and request-let when this page is actually needed are
different and we got exported prefetch request. So it actually disarms
prefetch.
## Summary of changes
Proposed simple patch stores last-written LSN for the page when it is
not found. So next time we will request last-written LSN for this page,
we will get the same value (certainly if the page was not changed).
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
The walproposer pretends to be a walsender in many ways. It has a
WalSnd slot, it claims to be a walsender by calling
MarkPostmasterChildWalSender() etc. But one different to real
walsenders was that the postmaster still treated it as a bgworker
rather than a walsender. The difference is that at shutdown,
walsenders are not killed until the very end, after the checkpointer
process has written the shutdown checkpoint and exited.
As a result, the walproposer always got killed before the shutdown
checkpoint was written, so the shutdown checkpoint never made it to
safekeepers. That's fine in principle, we don't require a clean
shutdown after all. But it also feels a bit silly not to stream the
shutdown checkpoint. It could be useful for initializing hot standby
mode in a read replica, for example.
Change postmaster to treat background workers that have called
MarkPostmasterChildWalSender() as walsenders. That unfortunately
requires another small change in postgres core.
After doing that, walproposers stay alive longer. However, it also
means that the checkpointer will wait for the walproposer to switch to
WALSNDSTATE_STOPPING state, when the checkpointer sends the
PROCSIG_WALSND_INIT_STOPPING signal. We don't have the machinery in
walproposer to receive and handle that signal reliably. Instead, we
mark walproposer as being in WALSNDSTATE_STOPPING always.
In commit 568f91420a, I assumed that shutdown will wait for all the
remaining WAL to be streamed to safekeepers, but before this commit
that was not true, and the test became flaky. This should make it
stable again.
Some tests wrongly assumed that no WAL could have been written between
pg_current_wal_flush_lsn and quick pg stop after it. Fix them by introducing
flush_ep_to_pageserver which first stops the endpoint and then waits till all
committed WAL reaches the pageserver.
In passing extract safekeeper http client to its own module.
