In similar vein to commit ccc8194e42, a reset instance of a shared
memory TID store happened to occupy the same private memory as the old
one for the entry point, since the chunk freed after the last round
of index vacuuming was put on the context's freelist. The failure
to update the vacrel->dead_items pointer was evident by nudging the
system to allocate memory in a different area. This was not discovered
at the time of the earlier commit since our regression tests didn't
cover multiple index passes with parallel vacuum.
Backpatch to v17, when TidStore came in.
Author: Kevin Oommen Anish <kevin.o@zohocorp.com>
Reviewed-by: Richard Guo <guofenglinux@gmail.com>
Tested-by: Richard Guo <guofenglinux@gmail.com>
Discussion: https://postgr.es/m/199a07cbdfc.7a1c4aac25838.1675074408277594551%40zohocorp.com
Backpatch-through: 17
Commit c120550edb optimized the vacuuming of relations without
indexes (a.k.a. one-pass strategy) by directly marking dead item IDs
as LP_UNUSED. However, the periodic FSM vacuum was still checking if
dead item IDs had been marked as LP_DEAD when attempting to vacuum the
FSM every VACUUM_FSM_EVERY_PAGES blocks. This condition was never met
due to the optimization, resulting in missed FSM vacuum
opportunities.
This commit modifies the periodic FSM vacuum condition to use the
number of tuples deleted during HOT pruning. This count includes items
marked as either LP_UNUSED or LP_REDIRECT, both of which are expected
to result in new free space to report.
Back-patch to v17 where the vacuum optimization for tables with no
indexes was introduced.
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://postgr.es/m/CAD21AoBL8m6B9GSzQfYxVaEgvD7-Kr3AJaS-hJPHC+avm-29zw@mail.gmail.com
Backpatch-through: 17
We can simplify the VM counters added in dc6acfd910 to
lazy_vacuum_heap_page() and lazy_scan_new_or_empty().
We won't invoke lazy_vacuum_heap_page() unless there are dead line
pointers, so we know the page can't be all-visible.
In lazy_scan_new_or_empty(), we only update the VM if the page-level
hint PD_ALL_VISIBLE is clear, and the VM bit cannot be set if the page
level bit is clear because a subsequent page update would fail to clear
the visibility map bit.
Simplify the logic for determining which log counters to increment based
on this knowledge. Doing so is worthwhile because the old logic was
confusing and misguided.
Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Discussion: https://postgr.es/m/flat/CAAKRu_a9w_n2mwY%3DG4LjfWTvRTJtjbfvnYAKi4WjO8QXHHrA0g%40mail.gmail.com
052026c9b9 mistakenly reordered setup steps in heap_vacuum_rel(),
incorrectly moving RelationGetNumberOfBlocks() before
vacuum_get_cutoffs().
OldestXmin must be determined before RelationGetNumberOfBlocks()
calculates the number of blocks in the relation that will be vacuumed.
Otherwise tuples older than OldestXmin may be inserted into the end of
the relation into blocks that are not vacuumed. If additional tuples
newer than those inserted into unscanned blocks but older than
OldestXmin are inserted into free space earlier in the relation, the
result could be advancing pg_class.relfrozenxid to a newer value than an
unfrozen XID in one of the unscanned heap pages.
Assigning an incorrect relfrozenxid can lead to data loss, so it is
imperative that it correctly reflect the oldest unfrozen xid.
Reported-by: Peter Geoghegan <pg@bowt.ie>
Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Peter Geoghegan <pg@bowt.ie>
Discussion: https://postgr.es/m/CAH2-WzntqvVEdbbpqG5JqSZGuLWmy4PBfUO-OswfivKchr2gvw%40mail.gmail.com
Previously, we asserted that the eager scan's success and failure
counters were positive before decrementing them. However, this
assumption was incorrect, as it's possible that some blocks have
already been eagerly scanned by the time eager scanning is disabled.
This commit replaces the assertions with guards to handle this
scenario gracefully.
With this change, we continue to allow read-ahead operations by the
read stream that exceed the success and failure caps. While there is a
possibility that overruns will trigger eager scans of additional
pages, this does not pose a practical concern as the overruns will not
be substantial and remain within an acceptable range.
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://postgr.es/m/CAD21AoConf6tkVCv-=JhQJj56kYsDwo4jG5+WqgT+ukSkYomSQ@mail.gmail.com
Submitting IO in larger batches can be more efficient than doing so
one-by-one, particularly for many small reads. It does, however, require
the ReadStreamBlockNumberCB callback to abide by the restrictions of AIO
batching (c.f. pgaio_enter_batchmode()). Basically, the callback may not:
a) block without first calling pgaio_submit_staged(), unless a
to-be-waited-on lock cannot be part of a deadlock, e.g. because it is
never held while waiting for IO.
b) directly or indirectly start another batch pgaio_enter_batchmode()
As this requires care and is nontrivial in some cases, batching is only
used with explicit opt-in.
This patch adds an explicit flag (READ_STREAM_USE_BATCHING) to read_stream and
uses it where appropriate.
There are two cases where batching would likely be beneficial, but where we
aren't using it yet:
1) bitmap heap scans, because the callback reads the VM
This should soon be solved, because we are planning to remove the use of
the VM, due to that not being sound.
2) The first phase of heap vacuum
This could be made to support batchmode, but would require some care.
Reviewed-by: Noah Misch <noah@leadboat.com>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://postgr.es/m/uvrtrknj4kdytuboidbhwclo4gxhswwcpgadptsjvjqcluzmah%40brqs62irg4dt
bbf668d66f lowered the minimum value of maintenance_work_mem to
64kB. However, in parallel vacuum cases, since the initial underlying
DSA size is 256kB, it attempts to perform a cycle of index vacuuming
and table vacuuming with an empty TID store, resulting in an assertion
failure.
This commit ensures that at least one page is processed before index
vacuuming and table vacuuming begins.
Backpatch to 17, where the minimum maintenance_work_mem value was
lowered.
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/CAD21AoCEAmbkkXSKbj4dB+5pJDRL4ZHxrCiLBgES_g_g8mVi1Q@mail.gmail.com
Backpatch-through: 17
Add relallfrozen, an estimate of the number of pages marked all-frozen
in the visibility map.
pg_class already has relallvisible, an estimate of the number of pages
in the relation marked all-visible in the visibility map. This is used
primarily for planning.
relallfrozen, together with relallvisible, is useful for estimating the
outstanding number of all-visible but not all-frozen pages in the
relation for the purposes of scheduling manual VACUUMs and tuning vacuum
freeze parameters.
A future commit will use relallfrozen to trigger more frequent vacuums
on insert-focused workloads with significant volume of frozen data.
Bump catalog version
Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>
Reviewed-by: Robert Treat <rob@xzilla.net>
Reviewed-by: Corey Huinker <corey.huinker@gmail.com>
Reviewed-by: Greg Sabino Mullane <htamfids@gmail.com>
Discussion: https://postgr.es/m/flat/CAAKRu_aj-P7YyBz_cPNwztz6ohP%2BvWis%3Diz3YcomkB3NpYA--w%40mail.gmail.com
Move lazy_scan_heap()'s per_buffer_data variable into a tighter scope.
In lazy_scan_heap()'s phase I heap vacuuming, the read stream API
returns a pointer to the next block number to vacuum. As long as
read_stream_next_buffer() returns a valid buffer, per_buffer_data should
always be valid.
Move per_buffer_data into a tighter scope and make sure it is reset to
NULL on each iteration so that we get a core dump instead of bogus data
from a previous block if something goes wrong in the read stream API.
Suggested-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/626104.1739729538%40sss.pgh.pa.us
This commit adds the information about the number of times WAL buffers
have been full to the logs generated by VACUUM/ANALYZE (VERBOSE) and in
the logs generated by autovacuum, complementing the existing information
stored by WalUsage.
This is the last part of the backend code where the value of
wal_buffers_full can be reported, similarly to all the other fields of
WalUsage. 320545bfcf and ce5bcc4a9f have done the same for EXPLAIN
and pgss.
Author: Bertrand Drouvot
Reviewed-by: Ilia Evdokimov
Discussion: https://postgr.es/m/Z6SOha5YFFgvpwQY@ip-10-97-1-34.eu-west-3.compute.internal
The read stream API only allows one piece of extra per block state to be
passed back to the API user (per_buffer_data). lazy_scan_heap() needs
two pieces of per-buffer data: whether or not the block was all-visible
in the visibility map and whether or not it was eagerly scanned.
Convert these two pieces of information to flags so that they can be
populated by heap_vac_scan_next_block() and returned to
lazy_scan_heap(). A future commit will turn heap_vac_scan_next_block()
into the read stream callback for heap phase I vacuuming.
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://postgr.es/m/CAAKRu_bmx33jTqATP5GKNFYwAg02a9dDtk4U_ciEjgBHZSVkOQ%40mail.gmail.com
Aggressive vacuums must scan every unfrozen tuple in order to advance
the relfrozenxid/relminmxid. Because data is often vacuumed before it is
old enough to require freezing, relations may build up a large backlog
of pages that are set all-visible but not all-frozen in the visibility
map. When an aggressive vacuum is triggered, all of these pages must be
scanned. These pages have often been evicted from shared buffers and
even from the kernel buffer cache. Thus, aggressive vacuums often incur
large amounts of extra I/O at the expense of foreground workloads.
To amortize the cost of aggressive vacuums, eagerly scan some
all-visible but not all-frozen pages during normal vacuums.
All-visible pages that are eagerly scanned and set all-frozen in the
visibility map are counted as successful eager freezes and those not
frozen are counted as failed eager freezes.
If too many eager scans fail in a row, eager scanning is temporarily
suspended until a later portion of the relation. The number of failures
tolerated is configurable globally and per table.
To effectively amortize aggressive vacuums, we cap the number of
successes as well. Capping eager freeze successes also limits the amount
of potentially wasted work if these pages are modified again before the
next aggressive vacuum. Once we reach the maximum number of blocks
successfully eager frozen, eager scanning is disabled for the remainder
of the vacuum of the relation.
Original design idea from Robert Haas, with enhancements from
Andres Freund, Tomas Vondra, and me
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Robert Treat <rob@xzilla.net>
Reviewed-by: Bilal Yavuz <byavuz81@gmail.com>
Discussion: https://postgr.es/m/flat/CAAKRu_ZF_KCzZuOrPrOqjGVe8iRVWEAJSpzMgRQs%3D5-v84cXUg%40mail.gmail.com
Consistently use "Size" (or size_t, or in some places int64 or double)
as the type for variables holding memory allocation sizes. In most
places variables' data types were fine already, but we had an ancient
habit of computing bytes from kilobytes-units GUCs with code like
"work_mem * 1024L". That risks overflow on Win64 where they did not
make "long" as wide as "size_t". We worked around that by restricting
such GUCs' ranges, so you couldn't set work_mem et al higher than 2GB
on Win64. This patch removes that restriction, after replacing such
calculations with "work_mem * (Size) 1024" or variants of that.
It should be noted that this patch was constructed by searching
outwards from the GUCs that have MAX_KILOBYTES as upper limit.
So I can't positively guarantee there are no other places doing
memory-size arithmetic in int or long variables. I do however feel
pretty confident that increasing MAX_KILOBYTES on Win64 is safe now.
Also, nothing in our code should be dealing in multiple-gigabyte
allocations without authorization from a relevant GUC, so it seems
pretty likely that this search caught everything that could be at
risk of overflow.
Author: Vladlen Popolitov <v.popolitov@postgrespro.ru>
Co-authored-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/1a01f0-66ec2d80-3b-68487680@27595217
This commit adds four fields to the statistics of relations, aggregating
the amount of time spent for each operation on a relation:
- total_vacuum_time, for manual vacuum.
- total_autovacuum_time, for vacuum done by the autovacuum daemon.
- total_analyze_time, for manual analyze.
- total_autoanalyze_time, for analyze done by the autovacuum daemon.
This gives users the option to derive the average time spent for these
operations with the help of the related "count" fields.
Bump catalog version (for the catalog changes) and PGSTAT_FILE_FORMAT_ID
(for the additions in PgStat_StatTabEntry).
Author: Sami Imseih
Reviewed-by: Bertrand Drouvot, Michael Paquier
Discussion: https://postgr.es/m/CAA5RZ0uVOGBYmPEeGF2d1B_67tgNjKx_bKDuL+oUftuoz+=Y1g@mail.gmail.com
Add more comments at the top of vacuumlazy.c on heap relation vacuuming
implementation.
Previously vacuumlazy.c only had details related to dead TID storage.
This commit adds a more general summary to help future developers
understand the heap relation vacuum design and implementation at a high
level.
Reviewed-by: Alena Rybakina, Robert Haas, Andres Freund, Bilal Yavuz
Discussion: https://postgr.es/m/flat/CAAKRu_ZF_KCzZuOrPrOqjGVe8iRVWEAJSpzMgRQs%3D5-v84cXUg%40mail.gmail.com
Rename frozen_pages to new_frozen_tuple_pages in LVRelState, the struct
used for tracking state during vacuuming of a heap relation.
frozen_pages sounds like it tracks pages set all-frozen. That is a
misnomer. It only includes pages with at least one newly frozen tuple.
It also includes pages that are not all-frozen.
Author: Melanie Plageman
Reviewed-by: Andres Freund, Masahiko Sawada, Nitin Jadhav, Bilal Yavuz
Discussion: https://postgr.es/m/ctdjzroezaxmiyah3gwbwm67defsrwj2b5fpfs4ku6msfpxeia%40mwjyqlhwr2wu
parallel_vacuum_reset_dead_items used a local variable to hold a
pointer from the passed vacrel, purely as a shorthand. This pointer
was later freed and a new allocation was made and stored to the
struct. Then the local pointer was mistakenly referenced again.
This apparently happened not to break anything since the freed chunk
would have been put on the context's freelist, so it was accidentally
the same pointer anyway, in which case the DSA handle was correctly
updated. The minimal fix is to change two places so they access
dead_items through the vacrel. This coding style is a maintenance
hazard, so while at it get rid of most other similar usages, which
were inconsistently used anyway.
Analysis and patch by Vallimaharajan G, with further defensive coding
by me
Backpath to v17, when TidStore came in
Discussion: https://postgr.es/m/1936493cc38.68cb2ef27266.7456585136086197135@zohocorp.com
Previously, (auto)analyze used global variables VacuumPageHit,
VacuumPageMiss, and VacuumPageDirty to track buffer usage. However,
pgBufferUsage provides a more generic way to track buffer usage with
support functions.
This change replaces those global variables with pgBufferUsage in
analyze. Since analyze was the sole user of those variables, it
removes their declarations. Vacuum previously used those variables but
replaced them with pgBufferUsage as part of a bug fix, commit
5cd72cc0c.
Additionally, it adjusts the buffer usage message in both vacuum and
analyze for better consistency.
Author: Anthonin Bonnefoy
Reviewed-by: Masahiko Sawada, Michael Paquier
Discussion: https://postgr.es/m/CAO6_Xqr__kTTCLkftqS0qSCm-J7_xbRG3Ge2rWhucxQJMJhcRA%40mail.gmail.com
Previously, TidStoreIterateNext() would expand the set of offsets for
each block into an internal buffer that it overwrote each time. In
order to be able to collect the offsets for multiple blocks before
working with them, change the contract. Now, the offsets are obtained
by a separate call to TidStoreGetBlockOffsets(), which can be called at
a later time. TidStoreIteratorResult objects are safe to copy and store
in a queue.
Reviewed-by: Noah Misch <noah@leadboat.com>
Discussion: https://postgr.es/m/CAAKRu_bbkmwAzSBgnezancgJeXrQZXy4G4kBTd+5=cr86H5yew@mail.gmail.com
If vacuum fails to remove a tuple with xmax older than
VacuumCutoffs->OldestXmin and younger than GlobalVisState->maybe_needed,
it may attempt to freeze the tuple's xmax and then ERROR out in
pre-freeze checks with "cannot freeze committed xmax".
Fix this by having vacuum always remove tuples older than OldestXmin.
It is possible for GlobalVisState->maybe_needed to precede OldestXmin if
maybe_needed is forced to go backward while vacuum is running. This can
happen if a disconnected standby with a running transaction older than
VacuumCutoffs->OldestXmin reconnects to the primary after vacuum
initially calculates GlobalVisState and OldestXmin.
In back branches starting with 14, the first version using
GlobalVisState, failing to remove tuples older than OldestXmin during
pruning caused vacuum to infinitely loop in lazy_scan_prune(), as
investigated on this [1] thread. After 1ccc1e05ae removed the retry loop
in lazy_scan_prune() and stopped comparing tuples to OldestXmin, the
hang could no longer happen, but we could still attempt to freeze dead
tuples with xmax older than OldestXmin -- resulting in an ERROR.
Fix this by always removing dead tuples with xmax older than
VacuumCutoffs->OldestXmin. This is okay because the standby won't replay
the tuple removal until the tuple is removable. Thus, the worst that can
happen is a recovery conflict.
[1] https://postgr.es/m/20240415173913.4zyyrwaftujxthf2%40awork3.anarazel.de#1b216b7768b5bd577a3d3d51bd5aadee
Back-patch through 14
Author: Melanie Plageman
Reviewed-by: Peter Geoghegan, Robert Haas, Andres Freund, Heikki Linnakangas, and Noah Misch
Discussion: https://postgr.es/m/CAAKRu_bDD7oq9ZwB2OJqub5BovMG6UjEYsoK2LVttadjEqyRGg%40mail.gmail.com
Commit 667e65aac3 changed both num_dead_tuples and max_dead_tuples
columns to dead_tuple_bytes and max_dead_tuple_bytes columns,
respectively. But as per discussion, the number of dead tuples
collected still provides meaningful insights for users.
This commit reintroduces the column for the count of dead tuples,
renamed as num_dead_item_ids. It avoids confusion with the number of
dead tuples removed by VACUUM, which includes dead heap-only tuples
but excludes any pre-existing LP_DEAD items left behind by
opportunistic pruning.
Bump catalog version.
Reviewed-by: Peter Geoghegan, Álvaro Herrera, Andrey Borodin
Discussion: https://postgr.es/m/CAD21AoBL5sJE9TRWPyv%2Bw7k5Ee5QAJqDJEDJBUdAaCzGWAdvZw%40mail.gmail.com
Make sure that function declarations use names that exactly match the
corresponding names from function definitions in a few places. These
inconsistencies were all introduced during Postgres 17 development.
pg_bsd_indent still has a couple of similar inconsistencies, which I
(pgeoghegan) have left untouched for now.
This commit was written with help from clang-tidy, by mechanically
applying the same rules as similar clean-up commits (the earliest such
commit was commit 035ce1fe).
After further review, we want to move in the direction of always
quoting GUC names in error messages, rather than the previous (PG16)
wildly mixed practice or the intermittent (mid-PG17) idea of doing
this depending on how possibly confusing the GUC name is.
This commit applies appropriate quotes to (almost?) all mentions of
GUC names in error messages. It partially supersedes a243569bf6 and
8d9978a717, which had moved things a bit in the opposite direction
but which then were abandoned in a partial state.
Author: Peter Smith <smithpb2250@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAHut%2BPv-kSN8SkxSdoHano_wPubqcg5789ejhCDZAcLFceBR-w%40mail.gmail.com
A parallel worker's buffer usage is accumulated to its pgBufferUsage
and then is accumulated into the leader's one at the end of the
parallel vacuum. However, since the leader process used to use
dedicated VacuumPage{Hit, Miss, Dirty} globals for the buffer usage
reporting, the worker's buffer usage was not included, leading to an
incorrect buffer usage report.
To fix the problem, this commit makes vacuum use pgBufferUsage
instruments for buffer usage reporting instead of VacuumPage{Hit,
Miss, Dirty} globals. These global variables are still used by ANALYZE
command and autoanalyze.
This also fixes the buffer usage report of vacuuming on temporary
tables, since the buffers dirtied by MarkLocalBufferDirty() were not
tracked by the VacuumPageDirty variable.
Parallel vacuum was introduced in 13, but the buffer usage reporting
for VACUUM command with the VERBOSE option was implemented in
15. So backpatch to 15.
Reported-by: Anthonin Bonnefoy
Author: Anthonin Bonnefoy
Reviewed-by: Alena Rybakina, Masahiko Sawada
Discussion: https://postgr.es/m/CAO6_XqrQk+QZQcYs_C6nk0cMfHuUWk85vT9CrcA1NffFbAVE2A@mail.gmail.com
Backpatch-through: 15
Execute both freezing and pruning of tuples in the same
heap_page_prune() function, now called heap_page_prune_and_freeze(),
and emit a single WAL record containing all changes. That reduces the
overall amount of WAL generated.
This moves the freezing logic from vacuumlazy.c to the
heap_page_prune_and_freeze() function. The main difference in the
coding is that in vacuumlazy.c, we looked at the tuples after the
pruning had already happened, but in heap_page_prune_and_freeze() we
operate on the tuples before pruning. The heap_prepare_freeze_tuple()
function is now invoked after we have determined that a tuple is not
going to be pruned away.
VACUUM no longer needs to loop through the items on the page after
pruning. heap_page_prune_and_freeze() does all the work. It now
returns the list of dead offsets, including existing LP_DEAD items, to
the caller. Similarly it's now responsible for tracking 'all_visible',
'all_frozen', and 'hastup' on the caller's behalf.
Author: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://www.postgresql.org/message-id/20240330055710.kqg6ii2cdojsxgje@liskov
Previously, we used a simple array for storing dead tuple IDs during
lazy vacuum, which had a number of problems:
* The array used a single allocation and so was limited to 1GB.
* The allocation was pessimistically sized according to table size.
* Lookup with binary search was slow because of poor CPU cache and
branch prediction behavior.
This commit replaces that array with the TID store from commit
30e144287a.
Since the backing radix tree makes small allocations as needed, the
1GB limit is now gone. Further, the total memory used is now often
smaller by an order of magnitude or more, depending on the
distribution of blocks and offsets. These two features should make
multiple rounds of heap scanning and index cleanup an extremely rare
event. TID lookup during index cleanup is also several times faster,
even more so when index order is correlated with heap tuple order.
Since there is no longer a predictable relationship between the number
of dead tuples vacuumed and the space taken up by their TIDs, the
number of tuples no longer provides any meaningful insights for users,
nor is the maximum number predictable. For that reason this commit
also changes to byte-based progress reporting, with the relevant
columns of pg_stat_progress_vacuum renamed accordingly to
max_dead_tuple_bytes and dead_tuple_bytes.
For parallel vacuum, both the TID store and supplemental information
specific to vacuum are shared among the parallel vacuum workers. As
with the previous array, we don't take any locks on TidStore during
parallel vacuum since writes are still only done by the leader
process.
Bump catalog version.
Reviewed-by: John Naylor, (in an earlier version) Dilip Kumar
Discussion: https://postgr.es/m/CAD21AoAfOZvmfR0j8VmZorZjL7RhTiQdVttNuC4W-Shdc2a-AA%40mail.gmail.com
Currently there is only one option, HEAP_PAGE_PRUNE_MARK_UNUSED_NOW
which replaces the old boolean argument, but upcoming patches will
introduce at least one more. Having a lot of boolean arguments makes
it hard to see at the call sites what the arguments mean, so prefer a
bitmask of options with human-readable names.
Author: Melanie Plageman <melanieplageman@gmail.com>
Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Discussion: https://www.postgresql.org/message-id/20240401172219.fngjosaqdgqqvg4e@liskov
The new combined WAL record is now used for pruning, freezing and 2nd
pass of vacuum. This is in preparation for changing VACUUM to write a
combined prune+freeze record per page, instead of separate two
records. The new WAL record format now supports that, but the code
still always writes separate records for pruning and freezing.
This reserves separate XLOG_HEAP2_* info codes for when the pruning
record is emitted for on-access pruning or VACUUM, per Peter
Geoghegan's suggestion. The record format is identical, but having
separate info codes makes it easier analyze pruning and vacuuming with
pg_waldump.
The function to emit the new WAL record, log_heap_prune_and_freeze(),
is in pruneheap.c. The existing heap_log_freeze_plan() and its
subroutines are moved to pruneheap.c without changes, to keep them
together with log_heap_prune_and_freeze().
Author: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://www.postgresql.org/message-id/CAAKRu_azf-zH%3DDgVbquZ3tFWjMY1w5pO8m-TXJaMdri8z3933g@mail.gmail.com
Discussion: https://www.postgresql.org/message-id/CAAKRu_b2oE4GL%3Dq4g9mcByS9yT7wTQvEH9OLpabj28e%2BWKFi2A@mail.gmail.com
heap_vac_scan_get_next_block() does relatively little work, so there
is no need to call vacuum_delay_point(). A future commit will call
heap_vac_scan_get_next_block() from a callback, and we would like to
avoid calling vacuum_delay_point() in that callback.
Author: Melanie Plageman
Discussion: https://postgr.es/m/CAAKRu_Yf3gvXGcCnqqfoq0Q8LX8UM-e-qbm_B1LeZh60f8WhWA%40mail.gmail.com
Rename lazy_scan_skip() to heap_vac_scan_next_block() and move more
code into the function, so that the caller doesn't need to know about
ranges or skipping anymore. heap_vac_scan_next_block() returns the
next block to process, and the logic for determining that block is all
within the function. This makes the skipping logic easier to
understand, as it's all in the same function, and makes the calling
code easier to understand as it's less cluttered. The state variables
needed to manage the skipping logic are moved to LVRelState.
heap_vac_scan_next_block() now manages its own VM buffer separately
from the caller's vmbuffer variable. The caller's vmbuffer holds the
VM page for the current block its processing, while
heap_vac_scan_next_block() keeps a pin on the VM page for the next
unskippable block. Most of the time they are the same, so we hold two
pins on the same buffer, but it's more convenient to manage them
separately.
For readability inside heap_vac_scan_next_block(), move the logic of
finding the next unskippable block to separate function, and add some
comments.
This refactoring will also help future patches to switch to using a
streaming read interface, and eventually AIO
(https://postgr.es/m/CA%2BhUKGJkOiOCa%2Bmag4BF%2BzHo7qo%3Do9CFheB8%3Dg6uT5TUm2gkvA%40mail.gmail.com)
Author: Melanie Plageman, Heikki Linnakangas
Reviewed-by: Andres Freund (older version)
Discussion: https://postgr.es/m/CAAKRu_Yf3gvXGcCnqqfoq0Q8LX8UM-e-qbm_B1LeZh60f8WhWA%40mail.gmail.com
It's important for 'all_visible_according_to_vm' to correctly reflect
whether the VM bit is set or not, even when we are not trusting the VM
to skip pages, because contrary to what the comment said,
lazy_scan_prune() relies on it.
If it's incorrectly set to 'false', when the VM bit is in fact set,
lazy_scan_prune() will try to set the VM bit again and dirty the page
unnecessarily. As a result, if you used DISABLE_PAGE_SKIPPING, all
heap pages were dirtied, even if there were no changes. We would also
fail to clear any VM bits that were set incorrectly.
This was broken in commit 980ae17310, so backpatch to v16.
Backpatch-through: 16
Reviewed-by: Melanie Plageman, Peter Geoghegan
Discussion: https://www.postgresql.org/message-id/3df2b582-dc1c-46b6-99b6-38eddd1b2784@iki.fi
as determined by include-what-you-use (IWYU)
While IWYU also suggests to *add* a bunch of #include's (which is its
main purpose), this patch does not do that. In some cases, a more
specific #include replaces another less specific one.
Some manual adjustments of the automatic result:
- IWYU currently doesn't know about includes that provide global
variable declarations (like -Wmissing-variable-declarations), so
those includes are being kept manually.
- All includes for port(ability) headers are being kept for now, to
play it safe.
- No changes of catalog/pg_foo.h to catalog/pg_foo_d.h, to keep the
patch from exploding in size.
Note that this patch touches just *.c files, so nothing declared in
header files changes in hidden ways.
As a small example, in src/backend/access/transam/rmgr.c, some IWYU
pragma annotations are added to handle a special case there.
Discussion: https://www.postgresql.org/message-id/flat/af837490-6b2f-46df-ba05-37ea6a6653fc%40eisentraut.org
Remove IsBackgroundWorker, IsAutoVacuumLauncherProcess(),
IsAutoVacuumWorkerProcess(), and IsLogicalSlotSyncWorker() in favor of
new Am*Process() macros that use MyBackendType. For consistency with
the existing Am*Process() macros.
Reviewed-by: Andres Freund
Discussion: https://www.postgresql.org/message-id/f3ecd4cb-85ee-4e54-8278-5fabfb3a4ed0@iki.fi
lazy_scan_prune() and lazy_scan_noprune() update the freespace map
with identical conditions; combine them. This consolidation is easier
now that cb970240f1 moved visibility map
updates into lazy_scan_prune().
While combining the FSM updates, simplify the logic for calling
lazy_scan_new_or_empty() and lazy_scan_noprune().
Also update a few comemnts in this part of the code to make them,
hopefully, clearer.
Melanie Plageman and Robert Haas
Discussion: https://postgr.es/m/CA%2BTgmoaLTvipm%3Dxx4rJLr07m908PCu%3DQH3uCjD1UOn8YaEuO2g%40mail.gmail.com
Commit cb970240f1 moved some code from
lazy_scan_heap() to lazy_scan_prune(), and now some things that used to
need to be passed back and forth are completely local to lazy_scan_prune().
Hence, this struct is mostly obsolete. The only thing that still
needs to be passed back to the caller is has_lpdead_items, and that's
also passed back by lazy_scan_noprune(), so do it the same way in both
cases.
Melanie Plageman, reviewed and slightly revised by me.
Discussion: http://postgr.es/m/CAAKRu_aM=OL85AOr-80wBsCr=vLVzhnaavqkVPRkFBtD0zsuLQ@mail.gmail.com
Most of the output parameters of lazy_scan_prune() were being
used to update the VM in lazy_scan_heap(). Moving that code into
lazy_scan_prune() simplifies lazy_scan_heap() and requires less
communication between the two.
This change permits some further code simplification, but that
is left for a separate commit.
Melanie Plageman, reviewed by me.
Discussion: http://postgr.es/m/CAAKRu_aM=OL85AOr-80wBsCr=vLVzhnaavqkVPRkFBtD0zsuLQ@mail.gmail.com
If there are no indexes on a relation, items can be marked LP_UNUSED
instead of LP_DEAD when pruning. This significantly reduces WAL
volume, since we no longer need to emit one WAL record for pruning
and a second to change the LP_DEAD line pointers thus created to
LP_UNUSED.
Melanie Plageman, reviewed by Andres Freund, Peter Geoghegan, and me
Discussion: https://postgr.es/m/CAAKRu_bgvb_k0gKOXWzNKWHt560R0smrGe3E8zewKPs8fiMKkw%40mail.gmail.com
