Commit ea92368cd1 made max_wal_senders
a separate pool of backends from max_connections, but the documentation
and error message for superuser_reserved_connections weren't updated
at the time, and as a result are somewhat misleading. Update.
This is arguably a back-patchable bug fix, but because it seems quite
minor, no back-patch.
Patch by Nathan Bossart. Reviewed by Tushar Ahuja and by me.
Discussion: http://postgr.es/m/20230119194601.GA4105788@nathanxps13
This adjusts a few places which were appending a string constant
containing spaces onto a StringInfo. We have appendStringInfoSpaces for
that job, so let's use that instead.
For the change to jsonb.c's add_indent() function, appendStringInfoString
was being called inside a loop to append 4 spaces on each loop. This
meant that enlargeStringInfo would get called once per loop. Here it
should be much more efficient to get rid of the loop and just calculate
the number of spaces with "level * 4" and just append all the spaces in
one go.
Here we additionally adjust the appendStringInfoSpaces function so it
makes use of memset rather than a while loop to apply the required spaces
to the StringInfo. One of the problems with the while loop was that it
was incrementing one variable and decrementing another variable once per
loop. That's more work than what's required to get the job done. We may
as well use memset for this rather than trying to optimize the existing
loop. Some testing has shown memset is faster even for very small sizes.
Discussion: https://postgr.es/m/CAApHDvp_rKkvwudBKgBHniNRg67bzXVjyvVKfX0G2zS967K43A@mail.gmail.com
This patch largely reverts what I did in commits c9b0c678d and
78e73e875. The maximum cover length limit that I added in 78e73e875
(to band-aid over c9b0c678d's performance issues) creates too many
user-visible behavior discrepancies, as complained of for example in
bug #17691. The real problem with hlCover() is not what I thought
at the time, but more that it seems to have been designed with only
AND tsquery semantics in mind. It doesn't work quite right for OR,
and even less so for NOT or phrase queries. However, we can improve
that situation by building a variant of TS_execute() that returns a
list of match locations. We already get an ExecPhraseData struct
representing match locations for the primitive case of a simple match,
as well as one for a phrase match; we just need to add some logic to
combine these for AND and OR operators. The result is a list of
ExecPhraseDatas, which hlCover can regard as having simple AND
semantics, so that its old algorithm works correctly.
There's still a lot not to like about ts_headline's behavior, but
I think the remaining issues have to do with the heuristics used
in mark_hl_words and mark_hl_fragments (which, likewise, were not
revisited when phrase search was added). Improving those is a task
for another day.
Patch by me; thanks to Alvaro Herrera for review.
Discussion: https://postgr.es/m/840.1669405935@sss.pgh.pa.us
RelOptInfo.userid is the same for all relations in a given inheritance
tree, so the code in examine_variable() and example_simple_variable()
that repeats the ACL checks on the root parent rel instead of a given
leaf child relations need not recompute userid too.
Author: Amit Langote <amitlangote09@gmail.com>
Reported-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://postgr.es/m/20221210201753.GA27893@telsasoft.com
This is wrong since 88e9823, that has switched the WAL sizing
configuration from checkpoint_segments to min_wal_size and
max_wal_size. This missed the recalculation of the internal value of
the internal "CheckPointSegments", that works as a mapping of the old
GUC checkpoint_segments, on reload, for example, and it controls the
timing of checkpoints depending on the volume of WAL generated.
Most users tend to leave checkpoint_completion_target at 0.9 to smooth
the I/O workload, which is why I guess this has gone unnoticed for so
long, still it can be useful to tweak and reload the value dynamically
in some cases to control the timing of checkpoints.
Author: Bharath Rupireddy
Discussion: https://postgr.es/m/CALj2ACXgPPAm28mruojSBno+F_=9cTOOxHAywu_dfZPeBdybQw@mail.gmail.com
Backpatch-through: 11
The rule system needs "old" and/or "new" pseudo-RTEs in rule actions
that are ON INSERT/UPDATE/DELETE. Historically it's put such entries
into the ON SELECT rules of views as well, but those are really quite
vestigial. The only thing we've used them for is to carry the
view's relid forward to AcquireExecutorLocks (so that we can
re-lock the view to verify it hasn't changed before re-using a plan)
and to carry its relid and permissions data forward to execution-time
permissions checks. What we can do instead of that is to retain
these fields of the RTE_RELATION RTE for the view even after we
convert it to an RTE_SUBQUERY RTE. This requires a tiny amount of
extra complication in the planner and AcquireExecutorLocks, but on
the other hand we can get rid of the logic that moves that data from
one place to another.
The principal immediate benefit of doing this, aside from a small
saving in the pg_rewrite data for views, is that these pseudo-RTEs
no longer trigger ruleutils.c's heuristic about qualifying variable
names when the rangetable's length is more than 1. That results
in quite a number of small simplifications in regression test outputs,
which are all to the good IMO.
Bump catversion because we need to dump a few more fields of
RTE_SUBQUERY RTEs. While those will always be zeroes anyway in
stored rules (because we'd never populate them until query rewrite)
they are useful for debugging, and it seems like we'd better make
sure to transmit such RTEs accurately in plans sent to parallel
workers. I don't think the executor actually examines these fields
after startup, but someday it might.
This is a second attempt at committing 1b4d280ea. The difference
from the first time is that now we can add some filtering rules to
AdjustUpgrade.pm to allow cross-version upgrade testing to pass
despite all the cosmetic changes in CREATE VIEW outputs.
Amit Langote (filtering rules by me)
Discussion: https://postgr.es/m/CA+HiwqEf7gPN4Hn+LoZ4tP2q_Qt7n3vw7-6fJKOf92tSEnX6Gg@mail.gmail.com
Discussion: https://postgr.es/m/891521.1673657296@sss.pgh.pa.us
Add leader_pid to pg_stat_subscription. leader_pid is the process ID of
the leader apply worker if this process is a parallel apply worker. If
this field is NULL, it indicates that the process is a leader apply
worker or a synchronization worker. The new column makes it easier to
distinguish parallel apply workers from other kinds of workers and helps
to identify the leader for the parallel workers corresponding to a
particular subscription.
Additionally, update the leader_pid column in pg_stat_activity as well to
display the PID of the leader apply worker for parallel apply workers.
Author: Hou Zhijie
Reviewed-by: Peter Smith, Sawada Masahiko, Amit Kapila, Shveta Mallik
Discussion: https://postgr.es/m/CAA4eK1+wyN6zpaHUkCLorEWNx75MG0xhMwcFhvjqm2KURZEAGw@mail.gmail.com
Remove some code guarded by IS_MINUS() or IS_PLUS(), where the entire
stanza is inside an else-block where both of these are false. This
should slightly improve test coverage.
While at it, remove coding that apparently assumes that unsetting a
bit is so expensive that we have to first check if it's already set
in the first place.
Per Coverity report from Ranier Vilela
Analysis and review by Justin Pryzby
Discussion: https://www.postgresql.org/message-id/20221223010818.GP1153%40telsasoft.com
Most callers of BufFileRead() want to check whether they read the full
specified length. Checking this at every call site is very tedious.
This patch provides additional variants BufFileReadExact() and
BufFileReadMaybeEOF() that include the length checks.
I considered changing BufFileRead() itself, but this function is also
used in extensions, and so changing the behavior like this would
create a lot of problems there. The new names are analogous to the
existing LogicalTapeReadExact().
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/f3501945-c591-8cc3-5ef0-b72a2e0eaa9c@enterprisedb.com
While system_user was stored as an AuthToken in IdentLine, pg_user was
stored as a plain string. This commit changes the code as we start
storing pg_user as an AuthToken too.
This does not have any functional changes, as all the operations on
pg_user only use the string from the AuthToken. There is no regexp
compiled and no check based on its quoting, yet. This is in preparation
of more features that intend to extend its capabilities, like support
for regexps and group membership.
Author: Jelte Fennema
Discussion: https://postgr.es/m/CAGECzQRNow4MwkBjgPxywXdJU_K3a9+Pm78JB7De3yQwwkTDew@mail.gmail.com
int2vectorin limited the number of array elements it'd take to
FUNC_MAX_ARGS, which is probably fine for the traditional use-cases.
But now that pg_publication_rel.prattrs is an int2vector, it's not
fine at all: it's easy to construct cases where that can have up to
about MaxTupleAttributeNumber entries. Trying to replicate such
tables leads to logical-replication failures.
As long as we have to touch this code anyway, let's just remove
the a-priori limit altogether, and let it accept any size that'll
be allowed by repalloc. (Note that since int2vector isn't toastable,
we cannot store arrays longer than about BLCKSZ/2; but there is no
good excuse for letting int2vectorin depend on that. Perhaps we
will lift the no-toast restriction someday.)
While at it, also improve the equivalent logic in oidvectorin.
I don't know of any practical use-case for long oidvectors right
now, but doing it right actually makes the code shorter.
Per report from Erik Rijkers. Back-patch to v15 where
pg_publication_rel.prattrs was added.
Discussion: https://postgr.es/m/668ba539-33c5-8190-ca11-def2913cb94b@xs4all.nl
The current jsonpath code assumes that the referenced variable always exists.
It could only throw an error at the value valuation time. At the same time
existence checking assumes variable is present without valuation, and error
suppression doesn't work for missing variables.
This commit makes existense checking trigger an error for missing variables.
This makes the overall behavior consistent.
Backpatch to 12 where jsonpath was introduced.
Reported-by: David G. Johnston
Discussion: https://postgr.es/m/CAKFQuwbeytffJkVnEqDyLZ%3DrQsznoTh1OgDoOF3VmOMkxcTMjA%40mail.gmail.com
Author: Alexander Korotkov, David G. Johnston
Backpatch-through: 12
The code that handles authentication for user maps was pretty confusing
with its choice of variable names. It involves two types of users: a
system user and a Postgres user (well, role), and these were not named
consistently throughout the code that processes the user maps loaded
from pg_ident.conf at authentication.
This commit changes the following things to improve the situation:
- Rename "pg_role" to "pg_user" and "token" to "system_user" in
IndetLine. These choices are more consistent with the pg_ident.conf
example in the docs, as well. "token" has been introduced recently in
fc579e1, and it is way worse than the choice before that, "ident_user".
- Switch the order of the fields in IdentLine to map with the order of
the items in the ident files, as of map name, system user and PG user.
- In check_ident_usermap(), rename "regexp_pgrole" to "expanded_pg_user"
when processing a regexp for the system user entry in a user map. This
variable does not store a regular expression at all: it would be either
a string or a substitution to \1 if the Postgres role is specified as
such.
Author: Jelte Fennema
Discussion: https://postgr.es/m/CAGECzQTkwELHUOAKhvdA+m3tWbUQySHHkExJV8GAZ1pwgbEgXg@mail.gmail.com
This reverts commit 1b4d280ea1.
It's broken the buildfarm members that run cross-version-upgrade tests,
because they're not prepared to deal with cosmetic differences between
CREATE VIEW commands emitted by older servers and HEAD. Even if we had
a solution to that, which we don't, it'd take some time to roll it out
to the affected animals. This improvement isn't valuable enough to
justify addressing that problem on an emergency basis, so revert it
for now.
Switch to a design similar to regular backends, instead of the previous
arrangement where signal handlers did non-trivial state management and
called fork(). The main changes are:
* The postmaster now has its own local latch to wait on. (For now, we
don't want other backends setting its latch directly, but that could
probably be made to work with more research on robustness.)
* The existing signal handlers are cut in two: a handle_pm_XXX() part
that just sets pending_pm_XXX flags and the latch, and a
process_pm_XXX() part that runs later when the latch is seen.
* Signal handlers are now installed with the regular pqsignal()
function rather than the special pqsignal_pm() function; historical
portability concerns about the effect of SA_RESTART on select() are no
longer relevant, and we don't need to block signals anymore.
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA%2BhUKG%2BZ-HpOj1JsO9eWUP%2Bar7npSVinsC_npxSy%2BjdOMsx%3DGg%40mail.gmail.com
The rule system needs "old" and/or "new" pseudo-RTEs in rule actions
that are ON INSERT/UPDATE/DELETE. Historically it's put such entries
into the ON SELECT rules of views as well, but those are really quite
vestigial. The only thing we've used them for is to carry the
view's relid forward to AcquireExecutorLocks (so that we can
re-lock the view to verify it hasn't changed before re-using a plan)
and to carry its relid and permissions data forward to execution-time
permissions checks. What we can do instead of that is to retain
these fields of the RTE_RELATION RTE for the view even after we
convert it to an RTE_SUBQUERY RTE. This requires a tiny amount of
extra complication in the planner and AcquireExecutorLocks, but on
the other hand we can get rid of the logic that moves that data from
one place to another.
The principal immediate benefit of doing this, aside from a small
saving in the pg_rewrite data for views, is that these pseudo-RTEs
no longer trigger ruleutils.c's heuristic about qualifying variable
names when the rangetable's length is more than 1. That results
in quite a number of small simplifications in regression test outputs,
which are all to the good IMO.
Bump catversion because we need to dump a few more fields of
RTE_SUBQUERY RTEs. While those will always be zeroes anyway in
stored rules (because we'd never populate them until query rewrite)
they are useful for debugging, and it seems like we'd better make
sure to transmit such RTEs accurately in plans sent to parallel
workers. I don't think the executor actually examines these fields
after startup, but someday it might.
Amit Langote
Discussion: https://postgr.es/m/CA+HiwqEf7gPN4Hn+LoZ4tP2q_Qt7n3vw7-6fJKOf92tSEnX6Gg@mail.gmail.com
Can be set to the empty string, or to either or both of "set" or
"inherit". If set to a non-empty value, a non-superuser who creates
a role (necessarily by relying up the CREATEROLE privilege) will
grant that role back to themselves with the specified options.
This isn't a security feature, because the grant that this feature
triggers can also be performed explicitly. Instead, it's a user experience
feature. A superuser would necessarily inherit the privileges of any
created role and be able to access all such roles via SET ROLE;
with this patch, you can configure createrole_self_grant = 'set, inherit'
to provide a similar experience for a user who has CREATEROLE but not
SUPERUSER.
Discussion: https://postgr.es/m/CA+TgmobN59ct+Emmz6ig1Nua2Q-_o=r6DSD98KfU53kctq_kQw@mail.gmail.com
This allows left join removals and unique joins to work with partitioned
tables. The planner just lacked sufficient proofs that a given join
would not cause any row duplication. Unique indexes currently serve as
that proof, so have get_relation_info() populate the indexlist for
partitioned tables too.
Author: Arne Roland
Reviewed-by: Alvaro Herrera, Zhihong Yu, Amit Langote, David Rowley
Discussion: https://postgr.es/m/c3b2408b7a39433b8230bbcd02e9f302@index.de
Currently, for large transactions, the publisher sends the data in
multiple streams (changes divided into chunks depending upon
logical_decoding_work_mem), and then on the subscriber-side, the apply
worker writes the changes into temporary files and once it receives the
commit, it reads from those files and applies the entire transaction. To
improve the performance of such transactions, we can instead allow them to
be applied via parallel workers.
In this approach, we assign a new parallel apply worker (if available) as
soon as the xact's first stream is received and the leader apply worker
will send changes to this new worker via shared memory. The parallel apply
worker will directly apply the change instead of writing it to temporary
files. However, if the leader apply worker times out while attempting to
send a message to the parallel apply worker, it will switch to
"partial serialize" mode - in this mode, the leader serializes all
remaining changes to a file and notifies the parallel apply workers to
read and apply them at the end of the transaction. We use a non-blocking
way to send the messages from the leader apply worker to the parallel
apply to avoid deadlocks. We keep this parallel apply assigned till the
transaction commit is received and also wait for the worker to finish at
commit. This preserves commit ordering and avoid writing to and reading
from files in most cases. We still need to spill if there is no worker
available.
This patch also extends the SUBSCRIPTION 'streaming' parameter so that the
user can control whether to apply the streaming transaction in a parallel
apply worker or spill the change to disk. The user can set the streaming
parameter to 'on/off', or 'parallel'. The parameter value 'parallel' means
the streaming will be applied via a parallel apply worker, if available.
The parameter value 'on' means the streaming transaction will be spilled
to disk. The default value is 'off' (same as current behaviour).
In addition, the patch extends the logical replication STREAM_ABORT
message so that abort_lsn and abort_time can also be sent which can be
used to update the replication origin in parallel apply worker when the
streaming transaction is aborted. Because this message extension is needed
to support parallel streaming, parallel streaming is not supported for
publications on servers < PG16.
Author: Hou Zhijie, Wang wei, Amit Kapila with design inputs from Sawada Masahiko
Reviewed-by: Sawada Masahiko, Peter Smith, Dilip Kumar, Shi yu, Kuroda Hayato, Shveta Mallik
Discussion: https://postgr.es/m/CAA4eK1+wyN6zpaHUkCLorEWNx75MG0xhMwcFhvjqm2KURZEAGw@mail.gmail.com
GIN index scans were not taking any descent CPU-based cost into account. That
made them look cheaper than other types of indexes when they shouldn't be.
We use the same heuristic as for btree indexes, but multiply it by the number
of searched entries.
Additionally, the CPU cost for the tree was based largely on a
genericcostestimate. For a GIN index, we should not charge index quals per
tuple, but per entry. On top of this, charge cpu_index_tuple_cost per actual
tuple.
This should fix the cases where a GIN index is preferred over a btree and
the ones where a memoize node is not added on top of the GIN index scan
because it seemed too cheap.
We don't packpatch this to evade unexpected plan changes in stable versions.
Discussion: https://postgr.es/m/CABs3KGQnOkyQ42-zKQqiE7M0Ks9oWDSee%3D%2BJx3-TGq%3D68xqWYw%40mail.gmail.com
Discussion: https://postgr.es/m/3188617.44csPzL39Z%40aivenronan
Author: Ronan Dunklau
Reported-By: Hung Nguyen
Reviewed-by: Tom Lane, Alexander Korotkov
This fixes a couple of unused variable warnings that could be seen when
compiling with MEMORY_CONTEXT_CHECKING but not USE_ASSERT_CHECKING.
Defining MEMORY_CONTEXT_CHECKING without asserts is a little unusual,
however, we shouldn't be producing any warnings from such a build.
Author: Richard Guo
Discussion: https://postgr.es/m/CAMbWs4_D-vgLEh7eO47p=73u1jWO78NWf6Qfv1FndY1kG-Q-jA@mail.gmail.com
While on it, newlines are removed from the end of two elog() strings.
The others are simple grammar mistakes. One comment in pg_upgrade
referred incorrectly to sequences since a7e5457.
Author: Justin Pryzby
Discussion: https://postgr.es/m/20221230231257.GI1153@telsasoft.com
Backpatch-through: 11
f193883 has been incorrectly setting up the precision used in the
timestamp compilations returned by the following functions:
- LOCALTIME
- LOCALTIMESTAMP
- CURRENT_TIME
- CURRENT_TIMESTAMP
Specifying an out-of-range precision for CURRENT_TIMESTAMP and
LOCALTIMESTAMP was raising a WARNING without adjusting the precision,
leading to a subsequent error. LOCALTIME and CURRENT_TIME raised a
WARNING without an error, still the precision given to the internal
routines was not correct, so let's be clean.
Ian has reported the problems in timestamp.c, while I have noticed the
ones in date.c. Regression tests are added for all of them with
precisions high enough to provide coverage for the warnings, something
that went missing up to this commit.
Author: Ian Lawrence Barwick, Michael Paquier
Discussion: https://postgr.es/m/CAB8KJ=jQEnn9sYG+N752spt68wMrhmT-ocHCh4oeNmHF82QMWA@mail.gmail.com
The modified error message for regcollationin failure includes
the database encoding, which it should've occurred to me is a
portability hazard for the regression tests. Adjust the test
so the expected output doesn't include that.
In passing, fix a comment typo introduced in b8c0ffbd2.
Per buildfarm.
Given the soft-input-error feature, we can reduce these functions
to be just thin wrappers around a soft-error call of the
corresponding datatype input function. This means less code and
more certainty that the to_reg* functions match the normal input
behavior.
Notably, it also means that they will accept numeric OID input,
which they didn't before. It's not clear to me if that omission
had more than laziness behind it, but it doesn't seem like
something we need to work hard to preserve.
Discussion: https://postgr.es/m/3910031.1672095600@sss.pgh.pa.us
This is not really complete, but it catches most cases of practical
interest. The main omissions are:
* regtype, regprocedure, and regoperator parse type names by
calling the main grammar, so any grammar-detected syntax error
will still be a hard error. Also, if one includes a type
modifier in such a type specification, errors detected by the
typmodin function will be hard errors.
* Lookup errors are handled just by passing missing_ok = true
to the relevant catalog lookup function. Because we've used
quite a restrictive definition of "missing_ok", this means that
edge cases such as "the named schema exists, but you lack
USAGE permission on it" are still hard errors.
It would make sense to me to replace most/all missing_ok
parameters with an escontext parameter and then allow these
additional lookup failure cases to be trapped too. But that's
a job for some other day.
Discussion: https://postgr.es/m/3342239.1671988406@sss.pgh.pa.us
This is slightly tedious because the adjustments cascade through
a couple of levels of subroutines, but it's not very hard.
I chose to avoid changing function signatures more than absolutely
necessary, by passing the escontext pointer in existing structs
where possible.
tsquery's nuisance NOTICEs about empty queries are suppressed in
soft-error mode, since they're not errors and we surely don't want
them to be shown to the user anyway. Maybe that whole behavior
should be reconsidered.
Discussion: https://postgr.es/m/3824377.1672076822@sss.pgh.pa.us
Historically these input functions just called strtoul or strtoull
and returned the result, with no error detection whatever. Upgrade
them to reject garbage input and out-of-range values, similarly to
our other numeric input routines.
To share the code for this with type oid, adjust the existing
"oidin_subr" to be agnostic about the SQL name of the type it is
handling, and move it to numutils.c; then clone it for 64-bit types.
Because the xid types previously accepted hex and octal input by
reason of calling strtoul[l] with third argument zero, I made the
common subroutine do that too, with the consequence that type oid
now also accepts hex and octal input. In view of 6fcda9aba, that
seems like a good thing.
While at it, simplify the existing over-complicated handling of
syntax errors from strtoul: we only need one ereturn not three.
Discussion: https://postgr.es/m/3526121.1672000729@sss.pgh.pa.us
This enables streaming or serializing changes immediately in logical
decoding. This parameter is intended to be used to test logical decoding
and replication of large transactions for which otherwise we need to
generate the changes till logical_decoding_work_mem is reached.
This helps in reducing the timing of existing tests related to logical
replication of in-progress transactions and will help in writing tests for
for the upcoming feature for parallelly applying large in-progress
transactions.
Author: Shi yu
Reviewed-by: Sawada Masahiko, Shveta Mallik, Amit Kapila, Dilip Kumar, Kuroda Hayato, Kyotaro Horiguchi
Discussion: https://postgr.es/m/OSZPR01MB63104E7449DBE41932DB19F1FD1B9@OSZPR01MB6310.jpnprd01.prod.outlook.com
While at it, use a common subroutine already.
This doesn't move the needle very far in terms of making these
functions non-throwing; the only case we're now able to trap is
numeric-OID-is-out-of-range. Still, it seems like a pretty
non-controversial step in that direction.
WindowFuncs such as row_number() don't care if it's called with ROWS
UNBOUNDED PRECEDING AND CURRENT ROW or with RANGE UNBOUNDED PRECEDING AND
CURRENT ROW. The latter is less efficient as the RANGE option requires
that the executor check for peer rows, so using the ROW option instead
would cause less overhead. Because RANGE is part of the default frame
options for WindowClauses, it means WindowAgg is, by default, working much
harder than it needs to for window functions where the ROWS / RANGE option
has no effect on the window function's result.
On a test query from the discussion thread, a performance improvement of
344% was seen by using ROWS instead of RANGE.
Here we add a new support function node type to allow support functions to
be called for window functions so that the most optimal version of the
frame options can be set. The planner has been adjusted so that the frame
options are changed only if all window functions sharing the same window
clause agree on what the optimized frame options are.
Here we give the ability for row_number(), rank(), dense_rank(),
percent_rank(), cume_dist() and ntile() to alter their WindowClause's
frameOptions.
Reviewed-by: Vik Fearing, Erwin Brandstetter, Zhihong Yu
Discussion: https://postgr.es/m/CAGHENJ7LBBszxS+SkWWFVnBmOT2oVsBhDMB1DFrgerCeYa_DyA@mail.gmail.com
Discussion: https://postgr.es/m/CAApHDvohAKEtTXxq7Pc-ic2dKT8oZfbRKeEJP64M0B6+S88z+A@mail.gmail.com
This introduces palloc_aligned() and MemoryContextAllocAligned() which
allow callers to obtain memory which is allocated to the given size and
also aligned to the specified alignment boundary. The alignment
boundaries may be any power-of-2 value. Currently, the alignment is
capped at 2^26, however, we don't expect values anything like that large.
The primary expected use case is to align allocations to perhaps CPU
cache line size or to maybe I/O page size. Certain use cases can benefit
from having aligned memory by either having better performance or more
predictable performance.
The alignment is achieved by requesting 'alignto' additional bytes from
the underlying allocator function and then aligning the address that is
returned to the requested alignment. This obviously does waste some
memory, so alignments should be kept as small as what is required.
It's also important to note that these alignment bytes eat into the
maximum allocation size. So something like:
palloc_aligned(MaxAllocSize, 64, 0);
will not work as we cannot request MaxAllocSize + 64 bytes.
Additionally, because we're just requesting the requested size plus the
alignment requirements from the given MemoryContext, if that context is
the Slab allocator, then since slab can only provide chunks of the size
that's specified when the slab context is created, then this is not going
to work. Slab will generate an error to indicate that the requested size
is not supported.
The alignment that is requested in palloc_aligned() is stored along with
the allocated memory. This allows the alignment to remain intact through
repalloc() calls.
Author: Andres Freund, David Rowley
Reviewed-by: Maxim Orlov, Andres Freund, John Naylor
Discussion: https://postgr.es/m/CAApHDvpxLPUMV1mhxs6g7GNwCP6Cs6hfnYQL5ffJQTuFAuxt8A%40mail.gmail.com
This is the guts of float4in, callable as a routine to input floats,
which will be useful in an upcoming patch for allowing soft errors in
the seg module's input function.
A similar operation was performed some years ago for float8in in
commit 50861cd683.
Reviewed by Tom Lane
Discussion: https://postgr.es/m/cee4e426-d014-c0b7-aa22-a659f2cd9130@dunslane.net
d21ded75f changed the way slab.c works but introduced a bug that meant we
could end up with the slab's curBlocklistIndex pointing to the wrong list.
The condition which was checking for this was failing to account for two
things:
1. The curBlocklistIndex could be 0 as we've currently got no non-full
blocks to put chunks on. In this case, the dlist_is_empty() check cannot
be performed as there can be any number of completely full blocks at that
index.
2. The curBlocklistIndex may be greater than the index we just moved the
block onto. Since we need to ensure we fill up fuller blocks first, we
must reset curBlocklistIndex when changing any blocklist element that's
less than the curBlocklistIndex too.
Reported-by: Takamichi Osumi
Discussion: https://postgr.es/m/TYCPR01MB8373329C6329768D7E093D68EDEB9@TYCPR01MB8373.jpnprd01.prod.outlook.com
