5983a4cff added CompactAttribute as an abbreviated alternative to
FormData_pg_attribute to allow more cache-friendly processing in tasks
related to TupleDescs. That commit contained some assert-only code to
check that the CompactAttribute had been populated correctly, however,
the method used to do that checking caused the TupleDesc's
CompactAttribute to be zeroed before it was repopulated and compared to
the snapshot taken before the memset call. This caused issues as the type
cache caches TupleDescs in shared memory which can be used by multiple
backend processes at the same time. There was a window of time between
the zero and repopulation of the CompactAttribute where another process
would mistakenly think that the CompactAttribute is invalid due to the
memset.
To fix this, instead of taking a snapshot of the CompactAttribute and
calling populate_compact_attribute() and comparing the snapshot to the
freshly populated TupleDesc's CompactAttribute, refactor things so we
can just populate a temporary CompactAttribute on the stack. This way
we don't touch the TupleDesc's memory.
Reported-by: Alexander Lakhin, SQLsmith
Discussion: https://postgr.es/m/ca3a256a-5d12-42db-aabe-a75a030d9fb9@gmail.com
Here we convert CompactAttribute.attalign from a char, which is directly
derived from pg_attribute.attalign into a uint8, which stores the number
of bytes to align the column's value by in the tuple.
This allows tuple deformation and tuple size calculations to move away
from using the inefficient att_align_nominal() macro, which manually
checks each TYPALIGN_* char to translate that into the alignment bytes
for the given type. Effectively, this commit changes those to TYPEALIGN
calls, which are branchless and only perform some simple arithmetic with
some bit-twiddling.
The removed branches were often mispredicted by CPUs, especially so in
real-world tables which often contain a mishmash of different types
with different alignment requirements.
Author: David Rowley
Reviewed-by: Andres Freund, Victor Yegorov
Discussion: https://postgr.es/m/CAApHDvrBztXP3yx=NKNmo3xwFAFhEdyPnvrDg3=M0RhDs+4vYw@mail.gmail.com
The new compact_attrs array stores a few select fields from
FormData_pg_attribute in a more compact way, using only 16 bytes per
column instead of the 104 bytes that FormData_pg_attribute uses. Using
CompactAttribute allows performance-critical operations such as tuple
deformation to be performed without looking at the FormData_pg_attribute
element in TupleDesc which means fewer cacheline accesses.
For some workloads, tuple deformation can be the most CPU intensive part
of processing the query. Some testing with 16 columns on a table
where the first column is variable length showed around a 10% increase in
transactions per second for an OLAP type query performing aggregation on
the 16th column. However, in certain cases, the increases were much
higher, up to ~25% on one AMD Zen4 machine.
This also makes pg_attribute.attcacheoff redundant. A follow-on commit
will remove it, thus shrinking the FormData_pg_attribute struct by 4
bytes.
Author: David Rowley
Reviewed-by: Andres Freund, Victor Yegorov
Discussion: https://postgr.es/m/CAApHDvrBztXP3yx=NKNmo3xwFAFhEdyPnvrDg3=M0RhDs+4vYw@mail.gmail.com
Remove the 'whenTaken' and 'lsn' fields from SnapshotData. After the
removal of the "snapshot too old" feature, they were never set to a
non-zero value.
This largely reverts commit 3e2f3c2e42, which added the
OldestActiveSnapshot tracking, and the init_toast_snapshot()
function. That was only required for setting the 'whenTaken' and 'lsn'
fields. SnapshotToast is now a constant again, like SnapshotSelf and
SnapshotAny. I kept a thin get_toast_snapshot() wrapper around
SnapshotToast though, to check that you have a registered or active
snapshot. That's still a useful sanity check.
Reviewed-by: Nathan Bossart, Andres Freund, Tom Lane
Discussion: https://www.postgresql.org/message-id/cd4b4f8c-e63a-41c0-95f6-6e6cd9b83f6d@iki.fi
The new compact_attrs array stores a few select fields from
FormData_pg_attribute in a more compact way, using only 16 bytes per
column instead of the 104 bytes that FormData_pg_attribute uses. Using
CompactAttribute allows performance-critical operations such as tuple
deformation to be performed without looking at the FormData_pg_attribute
element in TupleDesc which means fewer cacheline accesses. With this
change, NAMEDATALEN could be increased with a much smaller negative impact
on performance.
For some workloads, tuple deformation can be the most CPU intensive part
of processing the query. Some testing with 16 columns on a table
where the first column is variable length showed around a 10% increase in
transactions per second for an OLAP type query performing aggregation on
the 16th column. However, in certain cases, the increases were much
higher, up to ~25% on one AMD Zen4 machine.
This also makes pg_attribute.attcacheoff redundant. A follow-on commit
will remove it, thus shrinking the FormData_pg_attribute struct by 4
bytes.
Author: David Rowley
Discussion: https://postgr.es/m/CAApHDvrBztXP3yx=NKNmo3xwFAFhEdyPnvrDg3=M0RhDs+4vYw@mail.gmail.com
Reviewed-by: Andres Freund, Victor Yegorov
There was no need for these to be static buffers, local variables work
just as well. I think they were marked as 'static' to imply that they
are read-only, but 'const' is more appropriate for that, so change
them to const.
To make it possible to mark the variables as 'const', also add 'const'
decorations to the transformRelOptions() signature.
Reviewed-by: Andres Freund
Discussion: https://www.postgresql.org/message-id/54c29fb0-edf2-48ea-9814-44e918bbd6e8@iki.fi
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
Commit f4b54e1ed9, which introduced macros for protocol characters,
missed updating a few places. It also did not introduce macros for
messages sent from parallel workers to their leader processes.
This commit adds a new section in protocol.h for those.
Author: Aleksander Alekseev
Discussion: https://postgr.es/m/CAJ7c6TNTd09AZq8tGaHS3LDyH_CCnpv0oOz2wN1dGe8zekxrdQ%40mail.gmail.com
Backpatch-through: 17
This is a C11 feature, and we require C99. While at it, go the further
step and get rid of the surrounding union (with uintptr_t) entirely,
as there is currently no use case for this file to access the header of
BlocktableEntry as a uintptr_t, and there are no additional alignment
requirements. The least invasive way seems to be to transfer the old
union name to this struct.
Reported by Pavel Borisov and Andres Freund, per buildfarm member mylodon
Reviewed by Pavel Borisov
Discussion: https://postgr.es/m/CALT9ZEH11NYV8AOzKb1bWhCf6J0H=H31f0MgT9xX+HdqvcA1rw@mail.gmail.com
Previously, the decision to store values in leaves or within the child
pointer was made at compile time, with variable length values using
leaves by necessity. This commit allows introspecting the length of
variable length values at runtime for that decision. This requires
the ability to tell whether the last-level child pointer is actually
a value, so we use a pointer tag in the lowest level bit.
Use this in TID store. This entails adding a byte to the header to
reserve space for the tag. Commit f35bd9bf3 stores up to three offsets
within the header with no bitmap, and now the header can be embedded
as above. This reduces worst-case memory usage when TIDs are sparse.
Reviewed (in an earlier version) by Masahiko Sawada
Discussion: https://postgr.es/m/CANWCAZYw+_KAaUNruhJfE=h6WgtBKeDG32St8vBJBEY82bGVRQ@mail.gmail.com
Discussion: https://postgr.es/m/CAD21AoBci3Hujzijubomo1tdwH3XtQ9F89cTNQ4bsQijOmqnEw@mail.gmail.com
Let table AM define custom reloptions for its tables. This allows specifying
AM-specific parameters by the WITH clause when creating a table.
The reloptions, which could be used outside of table AM, are now extracted
into the CommonRdOptions data structure. These options could be by decision
of table AM directly specified by a user or calculated in some way.
The new test module test_tam_options evaluates the ability to set up custom
reloptions and calculate fields of CommonRdOptions on their base.
The code may use some parts from prior work by Hao Wu.
Discussion: https://postgr.es/m/CAPpHfdurb9ycV8udYqM%3Do0sPS66PJ4RCBM1g-bBpvzUfogY0EA%40mail.gmail.com
Discussion: https://postgr.es/m/AMUA1wBBBxfc3tKRLLdU64rb.1.1683276279979.Hmail.wuhao%40hashdata.cn
Reviewed-by: Reviewed-by: Pavel Borisov, Matthias van de Meent, Jess Davis
EXPLAIN (ANALYZE, SERIALIZE) allows collection of statistics about
the volume of data emitted by a query, as well as the time taken
to convert the data to the on-the-wire format. Previously there
was no way to investigate this without actually sending the data
to the client, in which case network transmission costs might
swamp what you wanted to see. In particular this feature allows
investigating the costs of de-TOASTing compressed or out-of-line
data during formatting.
Stepan Rutz and Matthias van de Meent,
reviewed by Tomas Vondra and myself
Discussion: https://postgr.es/m/ca0adb0e-fa4e-c37e-1cd7-91170b18cae1@gmx.de
Previously, the behavior of TidStoreCreate() was inconsistent between
local and shared TidStore instances in terms of memory limitation. For
local TidStore, a memory context was created with initial and maximum
memory block sizes, as well as a minimum memory context size, based on
the specified max_bytes values. However, for shared TidStore, the
provided DSA area was used for TID storage. Although commit bb952c8c8b
allowed specifying the initial and maximum DSA segment sizes, callers
would have needed to clamp their own limits, which was not consistent
and user-friendly.
With this commit, when creating a shared TidStore, a dedicated DSA
area is created for TID storage instead of using a provided DSA
area. The initial and maximum DSA segment sizes are chosen based on
the specified max_bytes. Other processes can attach to the shared
TidStore using the handle of the created DSA returned by the new
TidStoreGetDSA() function and the DSA pointer returned by
TidStoreGetHandle(). The created DSA has the same lifetime as the
shared TidStore and is deleted when all processes detach from it.
To improve clarity, the TidStoreCreate() function has been divided
into two separate functions: TidStoreCreateLocal() and
TidStoreCreateShared().
Reviewed-by: John Naylor
Discussion: https://postgr.es/m/CAD21AoAyc1j%3DBCdUqZfk6qbdjZ68UgRx1Gkpk0oah4K7S0Ri9g%40mail.gmail.com
TIDStore is a data structure designed to efficiently store large sets
of TIDs. For TID storage, it employs a radix tree, where the key is
a block number, and the value is a bitmap representing offset
numbers. The TIDStore can be created on a DSA area and used by
multiple backend processes simultaneously.
There are potential future users such as tidbitmap.c, though it's very
likely the interface will need to evolve as we come to understand the
needs of different kinds of users. For example, we can support
updating the offset bitmap of existing values.
Currently, the TIDStore is not used for anything yet, aside from the
test code. But an upcoming patch will use it.
This includes a unit test module, in src/test/modules/test_tidstore.
Co-authored-by: John Naylor
Discussion: https://postgr.es/m/CAD21AoAfOZvmfR0j8VmZorZjL7RhTiQdVttNuC4W-Shdc2a-AA%40mail.gmail.com
This introduces a new function equalRowTypes() that is effectively a
subset of equalTupleDescs() but only compares the number of attributes
and attribute name, type, typmod, and collation. This is enough for
most existing uses of equalTupleDescs(), which are changed to use the
new function. The only remaining callers of equalTupleDescs() are
those that really want to check the full tuple descriptor as such,
without concern about record or row or record type semantics.
The existing function hashTupleDesc() is renamed to hashRowType(),
because it now corresponds more to equalRowTypes().
The purpose of this change is to be clearer about the semantics of the
equality asked for by each caller. (At least one caller had a comment
that questioned whether equalTupleDescs() was too restrictive.) For
example, 4f622503d6 removed attstattarget from the tuple descriptor
structure. It was not fully clear at the time how this should affect
equalTupleDescs(). Now the answer is clear: By their own definitions,
equalRowTypes() does not care, and equalTupleDescs() just compares
whatever is in the tuple descriptor but does not care why it is in
there.
Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
Discussion: https://www.postgresql.org/message-id/flat/f656d6d9-6660-4518-a006-2f65cafbebd1%40eisentraut.org
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
This changes the pg_attribute field attstattarget into a nullable
field in the variable-length part of the row. If no value is set by
the user for attstattarget, it is now null instead of previously -1.
This saves space in pg_attribute and tuple descriptors for most
practical scenarios. (ATTRIBUTE_FIXED_PART_SIZE is reduced from 108
to 104.) Also, null is the semantically more correct value.
The ANALYZE code internally continues to represent the default
statistics target by -1, so that that code can avoid having to deal
with null values. But that is now contained to the ANALYZE code.
Only the DDL code deals with attstattarget possibly null.
For system columns, the field is now always null. The ANALYZE code
skips system columns anyway.
To set a column's statistics target to the default value, the new
command form ALTER TABLE ... SET STATISTICS DEFAULT can be used. (SET
STATISTICS -1 still works.)
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://www.postgresql.org/message-id/flat/4da8d211-d54d-44b9-9847-f2a9f1184c76@eisentraut.org
Instead of having a separate array/hash for each resource kind, use a
single array and hash to hold all kinds of resources. This makes it
possible to introduce new resource "kinds" without having to modify
the ResourceOwnerData struct. In particular, this makes it possible
for extensions to register custom resource kinds.
The old approach was to have a small array of resources of each kind,
and if it fills up, switch to a hash table. The new approach also uses
an array and a hash, but now the array and the hash are used at the
same time. The array is used to hold the recently added resources, and
when it fills up, they are moved to the hash. This keeps the access to
recent entries fast, even when there are a lot of long-held resources.
All the resource-specific ResourceOwnerEnlarge*(),
ResourceOwnerRemember*(), and ResourceOwnerForget*() functions have
been replaced with three generic functions that take resource kind as
argument. For convenience, we still define resource-specific wrapper
macros around the generic functions with the old names, but they are
now defined in the source files that use those resource kinds.
The release callback no longer needs to call ResourceOwnerForget on
the resource being released. ResourceOwnerRelease unregisters the
resource from the owner before calling the callback. That needed some
changes in bufmgr.c and some other files, where releasing the
resources previously always called ResourceOwnerForget.
Each resource kind specifies a release priority, and
ResourceOwnerReleaseAll releases the resources in priority order. To
make that possible, we have to restrict what you can do between
phases. After calling ResourceOwnerRelease(), you are no longer
allowed to remember any more resources in it or to forget any
previously remembered resources by calling ResourceOwnerForget. There
was one case where that was done previously. At subtransaction commit,
AtEOSubXact_Inval() would handle the invalidation messages and call
RelationFlushRelation(), which temporarily increased the reference
count on the relation being flushed. We now switch to the parent
subtransaction's resource owner before calling AtEOSubXact_Inval(), so
that there is a valid ResourceOwner to temporarily hold that relcache
reference.
Other end-of-xact routines make similar calls to AtEOXact_Inval()
between release phases, but I didn't see any regression test failures
from those, so I'm not sure if they could reach a codepath that needs
remembering extra resources.
There were two exceptions to how the resource leak WARNINGs on commit
were printed previously: llvmjit silently released the context without
printing the warning, and a leaked buffer io triggered a PANIC. Now
everything prints a WARNING, including those cases.
Add tests in src/test/modules/test_resowner.
Reviewed-by: Aleksander Alekseev, Michael Paquier, Julien Rouhaud
Reviewed-by: Kyotaro Horiguchi, Hayato Kuroda, Álvaro Herrera, Zhihong Yu
Reviewed-by: Peter Eisentraut, Andres Freund
Discussion: https://www.postgresql.org/message-id/cbfabeb0-cd3c-e951-a572-19b365ed314d%40iki.fi
BuildDescForRelation() main job is to convert ColumnDef lists to
pg_attribute/tuple descriptor arrays, which is really mostly an
internal subroutine of DefineRelation() and some related functions,
which is more the remit of tablecmds.c and doesn't have much to do
with the basic tuple descriptor interfaces in tupdesc.c. This is also
supported by observing the header includes we can remove in tupdesc.c.
By moving it over, we can also (in the future) make
BuildDescForRelation() use more internals of tablecmds.c that are not
sensible to be exposed in tupdesc.c.
Discussion: https://www.postgresql.org/message-id/flat/52a125e4-ff9a-95f5-9f61-b87cf447e4da@eisentraut.org
This unifies some repetitive code.
Note: I didn't push the "not found" error message into the new
function, even though all existing callers would be able to make use
of it. Using the existing error handling as-is would probably require
exposing the Relation type via tupdesc.h, which doesn't seem
desirable. (Or even if we changed it to just report the OID, it would
inject the concept of a relation containing the tuple descriptor into
tupdesc.h, which might be a layering violation. Perhaps some further
improvements could be considered here separately.)
Discussion: https://www.postgresql.org/message-id/flat/52a125e4-ff9a-95f5-9f61-b87cf447e4da%40eisentraut.org
This commit introduces descriptively-named macros for the
identifiers used in wire protocol messages. These new macros are
placed in a new header file so that they can be easily used by
third-party code.
Author: Dave Cramer
Reviewed-by: Alvaro Herrera, Tatsuo Ishii, Peter Smith, Robert Haas, Tom Lane, Peter Eisentraut, Michael Paquier
Discussion: https://postgr.es/m/CADK3HHKbBmK-PKf1bPNFoMC%2BoBt%2BpD9PH8h5nvmBQskEHm-Ehw%40mail.gmail.com
Attribute missing values might be needed past the lifetime of the tuple
descriptors from which they are extracted. To avoid possibly using
pointers for by-reference values which might thus be left dangling, we
cache a datumCopy'd version of the datum in the TopMemoryContext. Since
we first search for the value this only needs to be done once per
session for any such value.
Original complaint from Tom Lane, idea for mitigation by Andrew Dunstan,
tweaked by Tom Lane.
Backpatch to version 11 where missing values were introduced.
Discussion: https://postgr.es/m/1306569.1687978174@sss.pgh.pa.us
Run pgindent, pgperltidy, and reformat-dat-files.
This set of diffs is a bit larger than typical. We've updated to
pg_bsd_indent 2.1.2, which properly indents variable declarations that
have multi-line initialization expressions (the continuation lines are
now indented one tab stop). We've also updated to perltidy version
20230309 and changed some of its settings, which reduces its desire to
add whitespace to lines to make assignments etc. line up. Going
forward, that should make for fewer random-seeming changes to existing
code.
Discussion: https://postgr.es/m/20230428092545.qfb3y5wcu4cm75ur@alvherre.pgsql
We need to call them only when validate == true.
Backpatch to 13, where opclass options were introduced.
Reported-by: Tom Lane
Discussion: https://postgr.es/m/2656633.1681831542%40sss.pgh.pa.us
Reviewed-by: Tom Lane, Pavel Borisov
Backpatch-through: 13
Change the columns attndims, attstattarget, and attinhcount from int32
to int16, and reorder a bit. This saves some space (currently 4
bytes) in pg_attribute and tuple descriptors, which translates into
small performance benefits and/or room for new columns in pg_attribute
needed by future features.
attndims and attinhcount are never realistically used with values
larger than int16. Just to be sure, add some overflow checks.
attstattarget is currently limited explicitly to 10000.
For consistency, pg_constraint.coninhcount is also changed like
attinhcount.
Discussion: https://www.postgresql.org/message-id/flat/d07ffc2b-e0e8-77f7-38fb-be921dff71af%40enterprisedb.com
Eager freezing strategy avoids large build-ups of all-visible pages. It
makes VACUUM trigger page-level freezing whenever doing so will enable
the page to become all-frozen in the visibility map. This is useful for
tables that experience continual growth, particularly strict append-only
tables such as pgbench's history table. Eager freezing significantly
improves performance stability by spreading out the cost of freezing
over time, rather than doing most freezing during aggressive VACUUMs.
It complements the insert autovacuum mechanism added by commit b07642db.
VACUUM determines its freezing strategy based on the value of the new
vacuum_freeze_strategy_threshold GUC (or reloption) with logged tables.
Tables that exceed the size threshold use the eager freezing strategy.
Unlogged tables and temp tables always use eager freezing strategy,
since the added cost is negligible there. Non-permanent relations won't
incur any extra overhead in WAL written (for the obvious reason), nor in
pages dirtied (since any extra freezing will only take place on pages
whose PD_ALL_VISIBLE bit needed to be set either way).
VACUUM uses lazy freezing strategy for logged tables that fall under the
GUC size threshold. Page-level freezing triggers based on the criteria
established in commit 1de58df4, which added basic page-level freezing.
Eager freezing is strictly more aggressive than lazy freezing. Settings
like vacuum_freeze_min_age still get applied in just the same way in
every VACUUM, independent of the strategy in use. The only mechanical
difference between eager and lazy freezing strategies is that only the
former applies its own additional criteria to trigger freezing pages.
Note that even lazy freezing strategy will trigger freezing whenever a
page happens to have required that an FPI be written during pruning,
provided that the page will thereby become all-frozen in the visibility
map afterwards (due to the FPI optimization from commit 1de58df4).
The vacuum_freeze_strategy_threshold default setting is 4GB. This is a
relatively low setting that prioritizes performance stability. It will
be reviewed at the end of the Postgres 16 beta period.
Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: Jeff Davis <pgsql@j-davis.com>
Reviewed-By: Andres Freund <andres@anarazel.de>
Reviewed-By: Matthias van de Meent <boekewurm+postgres@gmail.com>
Discussion: https://postgr.es/m/CAH2-WzkFok_6EAHuK39GaW4FjEFQsY=3J0AAd6FXk93u-Xq3Fg@mail.gmail.com
