If ANALYZE found no repeated non-null entries in its sample, it set the
column's stadistinct value to -1.0, intending to indicate that the entries
are all distinct. But what this value actually means is that the number
of distinct values is 100% of the table's rowcount, and thus it was
overestimating the number of distinct values by however many nulls there
are. This could lead to very poor selectivity estimates, as for example
in a recent report from Andreas Joseph Krogh. We should discount the
stadistinct value by whatever we've estimated the nulls fraction to be.
(That is what will happen if we choose to use a negative stadistinct for
a column that does have repeated entries, so this code path was just
inconsistent.)
In addition to fixing the stadistinct entries stored by several different
ANALYZE code paths, adjust the logic where get_variable_numdistinct()
forces an "all distinct" estimate on the basis of finding a relevant unique
index. Unique indexes don't reject nulls, so there's no reason to assume
that the null fraction doesn't apply.
Back-patch to all supported branches. Back-patching is a bit of a judgment
call, but this problem seems to affect only a few users (else we'd have
identified it long ago), and it's bad enough when it does happen that
destabilizing plan choices in a worse direction seems unlikely.
Patch by me, with documentation wording suggested by Dean Rasheed
Report: <VisenaEmail.26.df42f82acae38a58.156463942b8@tc7-visena>
Discussion: <16143.1470350371@sss.pgh.pa.us>
If we ANALYZE only selected columns of a table, we should not postpone
auto-analyze because of that; other columns may well still need stats
updates. As committed, the counter is left alone if a column list is
given, whether or not it includes all analyzable columns of the table.
Per complaint from Tomasz Ostrowski.
It's been like this a long time, so back-patch to all supported branches.
Report: <ef99c1bd-ff60-5f32-2733-c7b504eb960c@ato.waw.pl>
The reverted changes were intended to force a choice of whether any
newly-added BufferGetPage() calls needed to be accompanied by a
test of the snapshot age, to support the "snapshot too old"
feature. Such an accompanying test is needed in about 7% of the
cases, where the page is being used as part of a scan rather than
positioning for other purposes (such as DML or vacuuming). The
additional effort required for back-patching, and the doubt whether
the intended benefit would really be there, have indicated it is
best just to rely on developers to do the right thing based on
comments and existing usage, as we do with many other conventions.
This change should have little or no effect on generated executable
code.
Motivated by the back-patching pain of Tom Lane and Robert Haas
This patch is a no-op patch which is intended to reduce the chances
of failures of omission once the functional part of the "snapshot
too old" patch goes in. It adds parameters for snapshot, relation,
and an enum to specify whether the snapshot age check needs to be
done for the page at this point. This initial patch passes NULL
for the first two new parameters and BGP_NO_SNAPSHOT_TEST for the
third. The follow-on patch will change the places where the test
needs to be made.
Alex Shulgin complained that the underlying strategy wasn't all that
apparent, particularly not the fact that we intentionally have two
code paths depending on whether we think the column has a limited set
of possible values or not. Try to make it clearer.
On reflection, the pre-existing logic in ANALYZE is specifically meant to
compare the frequency of a candidate MCV against the estimated frequency of
a random distinct value across the whole table. The change to compare it
against the average frequency of values actually seen in the sample doesn't
seem very principled, and if anything it would make us less likely not more
likely to consider a value an MCV. So revert that, but keep the aspect of
considering only nonnull values, which definitely is correct.
In passing, rename the local variables in these stanzas to
"ndistinct_table", to avoid confusion with the "ndistinct" that appears at
an outer scope in compute_scalar_stats.
As with the previous patch, large numbers of null rows could skew this
calculation unfavorably, causing us to discard values that have a
legitimate claim to be MCVs, since our definition of MCV is that it's
most common among the non-null population of the column. Hence, make
the numerator of avgcount be the number of non-null sample values not
the number of sample rows; likewise for maxmincount in the
compute_scalar_stats variant.
Also, make the denominator be the number of distinct values actually
observed in the sample, rather than reversing it back out of the computed
stadistinct. This avoids depending on the accuracy of the Haas-Stokes
approximation, and really it's what we want anyway; the threshold should
depend only on what we see in the sample, not on what we extrapolate
about the contents of the whole column.
Alex Shulgin, reviewed by Tomas Vondra and myself
Previously, we included null rows in the values of n and N that went
into the formula, which amounts to considering null as a value in its
own right; but the d and f1 values do not include nulls. This is
inconsistent, and it contributes to significant underestimation of
ndistinct when the column is mostly nulls. In any case stadistinct
is defined as the number of distinct non-null values, so we should
exclude nulls when doing this computation.
This is an aboriginal bug in our application of the Haas-Stokes formula,
but we'll refrain from back-patching for fear of destabilizing plan
choices in released branches.
While at it, make the code a bit more readable by omitting unnecessary
casts and intermediate variables.
Observation and original patch by Tomas Vondra, adjusted to fix both
uses of the formula by Alex Shulgin, cosmetic improvements by me
The new bit indicates whether every tuple on the page is already frozen.
It is cleared only when the all-visible bit is cleared, and it can be
set only when we vacuum a page and find that every tuple on that page is
both visible to every transaction and in no need of any future
vacuuming.
A future commit will use this new bit to optimize away full-table scans
that would otherwise be triggered by XID wraparound considerations. A
page which is merely all-visible must still be scanned in that case, but
a page which is all-frozen need not be. This commit does not attempt
that optimization, although that optimization is the goal here. It
seems better to get the basic infrastructure in place first.
Per discussion, it's very desirable for pg_upgrade to automatically
migrate existing VM forks from the old format to the new format. That,
too, will be handled in a follow-on patch.
Masahiko Sawada, reviewed by Kyotaro Horiguchi, Fujii Masao, Amit
Kapila, Simon Riggs, Andres Freund, and others, and substantially
revised by me.
Previously, ANALYZE simply ignored columns of datatypes that have neither
a btree nor hash opclass (which means they have no recognized equality
operator). Without a notion of equality, we can't identify most-common
values nor estimate the number of distinct values. But we can still
count nulls and compute the average physical column width, and those
stats might be of value. Moreover there are some tools out there that
don't work so well if rows are missing from pg_statistic. So let's
add suitable logic for this case.
While this is arguably a bug fix, it also has the potential to change
query plans, and the gain seems not worth taking a risk of that in
stable branches. So back-patch into 9.5 but not further.
Oleksandr Shulgin, rewritten a bit by me.
Add a TABLESAMPLE clause to SELECT statements that allows
user to specify random BERNOULLI sampling or block level
SYSTEM sampling. Implementation allows for extensible
sampling functions to be written, using a standard API.
Basic version follows SQLStandard exactly. Usable
concrete use cases for the sampling API follow in later
commits.
Petr Jelinek
Reviewed by Michael Paquier and Simon Riggs
This is useful to control autovacuum log volume, for situations where
monitoring only a set of tables is necessary.
Author: Michael Paquier
Reviewed by: A team led by Naoya Anzai (also including Akira Kurosawa,
Taiki Kondo, Huong Dangminh), Fujii Masao.
Slow functions in index expressions might cause this loop to take long
enough to make it worth being cancellable. Probably it would be enough
to call CHECK_FOR_INTERRUPTS here, but for consistency with other
per-sample-row loops in this file, let's use vacuum_delay_point.
Report and patch by Jeff Janes. Back-patch to all supported branches.
Foreign tables can now be inheritance children, or parents. Much of the
system was already ready for this, but we had to fix a few things of
course, mostly in the area of planner and executor handling of row locks.
As side effects of this, allow foreign tables to have NOT VALID CHECK
constraints (and hence to accept ALTER ... VALIDATE CONSTRAINT), and to
accept ALTER SET STORAGE and ALTER SET WITH/WITHOUT OIDS. Continuing to
disallow these things would've required bizarre and inconsistent special
cases in inheritance behavior. Since foreign tables don't enforce CHECK
constraints anyway, a NOT VALID one is a complete no-op, but that doesn't
mean we shouldn't allow it. And it's possible that some FDWs might have
use for SET STORAGE or SET WITH OIDS, though doubtless they will be no-ops
for most.
An additional change in support of this is that when a ModifyTable node
has multiple target tables, they will all now be explicitly identified
in EXPLAIN output, for example:
Update on pt1 (cost=0.00..321.05 rows=3541 width=46)
Update on pt1
Foreign Update on ft1
Foreign Update on ft2
Update on child3
-> Seq Scan on pt1 (cost=0.00..0.00 rows=1 width=46)
-> Foreign Scan on ft1 (cost=100.00..148.03 rows=1170 width=46)
-> Foreign Scan on ft2 (cost=100.00..148.03 rows=1170 width=46)
-> Seq Scan on child3 (cost=0.00..25.00 rows=1200 width=46)
This was done mainly to provide an unambiguous place to attach "Remote SQL"
fields, but it is useful for inherited updates even when no foreign tables
are involved.
Shigeru Hanada and Etsuro Fujita, reviewed by Ashutosh Bapat and Kyotaro
Horiguchi, some additional hacking by me
We were involving the parser too much in setting up initial vacuuming
parameters. This patch moves that responsibility elsewhere to simplify
code, and also to make future additions easier. To do this, create a
new struct VacuumParams which is filled just prior to vacuum execution,
instead of at parse time; for user-invoked vacuuming this is set up in a
new function ExecVacuum, while autovacuum sets it up by itself.
While at it, add a new member VACOPT_SKIPTOAST to enum VacuumOption,
only set by autovacuum, which is used to disable vacuuming of the toast
table instead of the old do_toast parameter; this relieves the argument
list of vacuum() and some callees a bit. This partially makes up for
having added more arguments in an effort to avoid having autovacuum from
constructing a VacuumStmt parse node.
Author: Michael Paquier. Some tweaks by Álvaro
Reviewed by: Robert Haas, Stephen Frost, Álvaro Herrera
This commit extends the SortSupport infrastructure to allow operator
classes the option to provide abbreviated representations of Datums;
in the case of text, we abbreviate by taking the first few characters
of the strxfrm() blob. If the abbreviated comparison is insufficent
to resolve the comparison, we fall back on the normal comparator.
This can be much faster than the old way of doing sorting if the
first few bytes of the string are usually sufficient to resolve the
comparison.
There is the potential for a performance regression if all of the
strings to be sorted are identical for the first 8+ characters and
differ only in later positions; therefore, the SortSupport machinery
now provides an infrastructure to abort the use of abbreviation if
it appears that abbreviation is producing comparatively few distinct
keys. HyperLogLog, a streaming cardinality estimator, is included in
this commit and used to make that determination for text.
Peter Geoghegan, reviewed by me.
When checking a table that has an inheritance tree marked,
if no child tables remain, we skip ANALYZE. This patch emits
a message to show that the action has been skipped.
Author: Etsuro Fujita
Reviewer: Furuya Osamu
As noted by Noah Misch, my initial cut at fixing bug #11638 didn't cover
all cases where ANALYZE might be invoked in an unsafe context. We need to
test the result of IsInTransactionChain not IsTransactionBlock; which is
notationally a pain because IsInTransactionChain requires an isTopLevel
flag, which would have to be passed down through several levels of callers.
I chose to pass in_outer_xact (ie, the result of IsInTransactionChain)
rather than isTopLevel per se, as that seemed marginally more apropos
for the intermediate functions to know about.
This feature, building on previous commits, allows the write-ahead log
stream to be decoded into a series of logical changes; that is,
inserts, updates, and deletes and the transactions which contain them.
It is capable of handling decoding even across changes to the schema
of the effected tables. The output format is controlled by a
so-called "output plugin"; an example is included. To make use of
this in a real replication system, the output plugin will need to be
modified to produce output in the format appropriate to that system,
and to perform filtering.
Currently, information can be extracted from the logical decoding
system only via SQL; future commits will add the ability to stream
changes via walsender.
Andres Freund, with review and other contributions from many other
people, including Álvaro Herrera, Abhijit Menon-Sen, Peter Gheogegan,
Kevin Grittner, Robert Haas, Heikki Linnakangas, Fujii Masao, Abhijit
Menon-Sen, Michael Paquier, Simon Riggs, Craig Ringer, and Steve
Singer.
The standard typanalyze functions skip over values whose detoasted size
exceeds WIDTH_THRESHOLD (1024 bytes), so as to limit memory bloat during
ANALYZE. However, we (I think I, actually :-() failed to consider the
possibility that *every* non-null value in a column is too wide. While
compute_minimal_stats() seems to behave reasonably anyway in such a case,
compute_scalar_stats() just fell through and generated no pg_statistic
entry at all. That's unnecessarily pessimistic: we can still produce
valid stanullfrac and stawidth values in such cases, since we do include
too-wide values in the average-width calculation. Furthermore, since the
general assumption in this code is that too-wide values are probably all
distinct from each other, it seems reasonable to set stadistinct to -1
("all distinct").
Per complaint from Kadri Raudsepp. This has been like this since roughly
neolithic times, so back-patch to all supported branches.
Previously, these functions took a HeapTupleHeader, but upcoming
patches for logical replication will introduce new a new snapshot
type under which the tuple's TID will be used to lookup (CMIN, CMAX)
for visibility determination purposes. This makes that information
available. Code churn is minimal since HeapTupleSatisfiesVisibility
took the HeapTuple anyway, and deferenced it before calling the
satisfies function.
Independently of logical replication, this allows t_tableOid and
t_self to be cross-checked via assertions in tqual.c. This seems
like a useful way to make sure that all callers are setting these
values properly, which has been previously put forward as
desirable.
Andres Freund, reviewed by Álvaro Herrera
This saves several catalog lookups per reference. It's not all that
exciting right now, because we'd managed to minimize the number of places
that need to fetch the data; but the upcoming writable-foreign-tables patch
needs this info in a lot more places.
A materialized view has a rule just like a view and a heap and
other physical properties like a table. The rule is only used to
populate the table, references in queries refer to the
materialized data.
This is a minimal implementation, but should still be useful in
many cases. Currently data is only populated "on demand" by the
CREATE MATERIALIZED VIEW and REFRESH MATERIALIZED VIEW statements.
It is expected that future releases will add incremental updates
with various timings, and that a more refined concept of defining
what is "fresh" data will be developed. At some point it may even
be possible to have queries use a materialized in place of
references to underlying tables, but that requires the other
above-mentioned features to be working first.
Much of the documentation work by Robert Haas.
Review by Noah Misch, Thom Brown, Robert Haas, Marko Tiikkaja
Security review by KaiGai Kohei, with a decision on how best to
implement sepgsql still pending.
This patch introduces two additional lock modes for tuples: "SELECT FOR
KEY SHARE" and "SELECT FOR NO KEY UPDATE". These don't block each
other, in contrast with already existing "SELECT FOR SHARE" and "SELECT
FOR UPDATE". UPDATE commands that do not modify the values stored in
the columns that are part of the key of the tuple now grab a SELECT FOR
NO KEY UPDATE lock on the tuple, allowing them to proceed concurrently
with tuple locks of the FOR KEY SHARE variety.
Foreign key triggers now use FOR KEY SHARE instead of FOR SHARE; this
means the concurrency improvement applies to them, which is the whole
point of this patch.
The added tuple lock semantics require some rejiggering of the multixact
module, so that the locking level that each transaction is holding can
be stored alongside its Xid. Also, multixacts now need to persist
across server restarts and crashes, because they can now represent not
only tuple locks, but also tuple updates. This means we need more
careful tracking of lifetime of pg_multixact SLRU files; since they now
persist longer, we require more infrastructure to figure out when they
can be removed. pg_upgrade also needs to be careful to copy
pg_multixact files over from the old server to the new, or at least part
of multixact.c state, depending on the versions of the old and new
servers.
Tuple time qualification rules (HeapTupleSatisfies routines) need to be
careful not to consider tuples with the "is multi" infomask bit set as
being only locked; they might need to look up MultiXact values (i.e.
possibly do pg_multixact I/O) to find out the Xid that updated a tuple,
whereas they previously were assured to only use information readily
available from the tuple header. This is considered acceptable, because
the extra I/O would involve cases that would previously cause some
commands to block waiting for concurrent transactions to finish.
Another important change is the fact that locking tuples that have
previously been updated causes the future versions to be marked as
locked, too; this is essential for correctness of foreign key checks.
This causes additional WAL-logging, also (there was previously a single
WAL record for a locked tuple; now there are as many as updated copies
of the tuple there exist.)
With all this in place, contention related to tuples being checked by
foreign key rules should be much reduced.
As a bonus, the old behavior that a subtransaction grabbing a stronger
tuple lock than the parent (sub)transaction held on a given tuple and
later aborting caused the weaker lock to be lost, has been fixed.
Many new spec files were added for isolation tester framework, to ensure
overall behavior is sane. There's probably room for several more tests.
There were several reviewers of this patch; in particular, Noah Misch
and Andres Freund spent considerable time in it. Original idea for the
patch came from Simon Riggs, after a problem report by Joel Jacobson.
Most code is from me, with contributions from Marti Raudsepp, Alexander
Shulgin, Noah Misch and Andres Freund.
This patch was discussed in several pgsql-hackers threads; the most
important start at the following message-ids:
AANLkTimo9XVcEzfiBR-ut3KVNDkjm2Vxh+t8kAmWjPuv@mail.gmail.com1290721684-sup-3951@alvh.no-ip.org1294953201-sup-2099@alvh.no-ip.org1320343602-sup-2290@alvh.no-ip.org1339690386-sup-8927@alvh.no-ip.org4FE5FF020200002500048A3D@gw.wicourts.gov4FEAB90A0200002500048B7D@gw.wicourts.gov
When the "hot" members of PGPROC were split off to separate PGXACT structs,
many PGPROC fields referred to in comments were moved to PGXACT, but the
comments were neglected in the commit. Mostly this is just a search/replace
of PGPROC with PGXACT, but the way the dummy PGPROC entries are created for
prepared transactions changed more, making some of the comments totally
bogus.
Noah Misch
If we make the initially-called function return the table physical-size
estimate, acquire_inherited_sample_rows will be able to use that to
allocate numbers of samples among child tables, when the day comes that
we want to support foreign tables in inheritance trees.
ANALYZE now accepts foreign tables and allows the table's FDW to control
how the sample rows are collected. (But only manual ANALYZEs will touch
foreign tables, for the moment, since among other things it's not very
clear how to handle remote permissions checks in an auto-analyze.)
contrib/file_fdw is extended to support this.
Etsuro Fujita, reviewed by Shigeru Hanada, some further tweaking by me.
This patch improves selectivity estimation for the array <@, &&, and @>
(containment and overlaps) operators. It enables collection of statistics
about individual array element values by ANALYZE, and introduces
operator-specific estimators that use these stats. In addition,
ScalarArrayOpExpr constructs of the forms "const = ANY/ALL (array_column)"
and "const <> ANY/ALL (array_column)" are estimated by treating them as
variants of the containment operators.
Since we still collect scalar-style stats about the array values as a
whole, the pg_stats view is expanded to show both these stats and the
array-style stats in separate columns. This creates an incompatible change
in how stats for tsvector columns are displayed in pg_stats: the stats
about lexemes are now displayed in the array-related columns instead of the
original scalar-related columns.
There are a few loose ends here, notably that it'd be nice to be able to
suppress either the scalar-style stats or the array-element stats for
columns for which they're not useful. But the patch is in good enough
shape to commit for wider testing.
Alexander Korotkov, reviewed by Noah Misch and Nathan Boley
This patch creates an API whereby a btree index opclass can optionally
provide non-SQL-callable support functions for sorting. In the initial
patch, we only use this to provide a directly-callable comparator function,
which can be invoked with a bit less overhead than the traditional
SQL-callable comparator. While that should be of value in itself, the real
reason for doing this is to provide a datatype-extensible framework for
more aggressive optimizations, as in Peter Geoghegan's recent work.
Robert Haas and Tom Lane
This speeds up snapshot-taking and reduces ProcArrayLock contention.
Also, the PGPROC (and PGXACT) structures used by two-phase commit are
now allocated as part of the main array, rather than in a separate
array, and we keep ProcArray sorted in pointer order. These changes
are intended to minimize the number of cache lines that must be pulled
in to take a snapshot, and testing shows a substantial increase in
performance on both read and write workloads at high concurrencies.
Pavan Deolasee, Heikki Linnakangas, Robert Haas
Add a column pg_class.relallvisible to remember the number of pages that
were all-visible according to the visibility map as of the last VACUUM
(or ANALYZE, or some other operations that update pg_class.relpages).
Use relallvisible/relpages, instead of an arbitrary constant, to estimate
how many heap page fetches can be avoided during an index-only scan.
This is pretty primitive and will no doubt see refinements once we've
acquired more field experience with the index-only scan mechanism, but
it's way better than using a constant.
Note: I had to adjust an underspecified query in the window.sql regression
test, because it was changing answers when the plan changed to use an
index-only scan. Some of the adjacent tests perhaps should be adjusted
as well, but I didn't do that here.
This addresses only those cases that are easy to fix by adding or
moving a const qualifier or removing an unnecessary cast. There are
many more complicated cases remaining.
As per my recent proposal, this refactors things so that these typedefs and
macros are available in a header that can be included in frontend-ish code.
I also changed various headers that were undesirably including
utils/timestamp.h to include datatype/timestamp.h instead. Unsurprisingly,
this showed that half the system was getting utils/timestamp.h by way of
xlog.h.
No actual code changes here, just header refactoring.
Since the last couple of columns of pg_type are often NULL,
sizeof(FormData_pg_type) can be an overestimate of the actual size of the
tuple data part. Therefore memcpy'ing that much out of the catalog cache,
as analyze.c was doing, poses a small risk of copying past the end of
memory and incurring SIGSEGV. No such crash has been identified in the
field, but we've certainly seen the equivalent happen in other code paths,
so patch this one all the way back.
Per valgrind testing by Noah Misch, though this is not his proposed patch.
I chose to use SearchSysCacheCopy1 rather than inventing special-purpose
infrastructure for copying only the minimal part of a pg_type tuple.
walsender.h should depend on xlog.h, not vice versa. (Actually, the
inclusion was circular until a couple hours ago, which was even sillier;
but Bruce broke it in the expedient rather than logically correct
direction.) Because of that poor decision, plus blind application of
pgrminclude, we had a situation where half the system was depending on
xlog.h to include such unrelated stuff as array.h and guc.h. Clean up
the header inclusion, and manually revert a lot of what pgrminclude had
done so things build again.
This episode reinforces my feeling that pgrminclude should not be run
without adult supervision. Inclusion changes in header files in particular
need to be reviewed with great care. More generally, it'd be good if we
had a clearer notion of module layering to dictate which headers can sanely
include which others ... but that's a big task for another day.
In the past, relhassubclass always remained true if a relation had ever had
child relations, even if the last subclass was long gone. While this had
only marginal performance implications in most cases, it was annoying, and
I'm now considering some planner changes that would raise the cost of a
false positive. It was previously impractical to fix this because of race
condition concerns. However, given the recent change that made tablecmds.c
take ShareExclusiveLock on relations that are gaining a child (commit
fbcf4b92aa), we can now allow ANALYZE to
clear the flag when it's no longer relevant. There is no additional
locking cost to do so, since ANALYZE takes ShareExclusiveLock anyway.
I mis-simplified the test where ANALYZE decided if it could get away
without doing anything: under the new regime, that's never allowed. Per
bug #6068 from Jeff Janes. Back-patch to 8.4, just like previous patch.
We had already converted most places to this style, but this patch gets the
last few that were still doing it the old way. The main advantage is that
this exposes a greppable name for each target column, rather than having
to rely on comments (which a couple of places failed to provide anyhow).
Richard Hopkins, additional work by me to clean up update_attstats() too
When we added the ability for vacuum to skip heap pages by consulting the
visibility map, we made it just not update the reltuples/relpages
statistics if it skipped any pages. But this could leave us with extremely
out-of-date stats for a table that contains any unchanging areas,
especially for TOAST tables which never get processed by ANALYZE. In
particular this could result in autovacuum making poor decisions about when
to process the table, as in recent report from Florian Helmberger. And in
general it's a bad idea to not update the stats at all. Instead, use the
previous values of reltuples/relpages as an estimate of the tuple density
in unvisited pages. This approach results in a "moving average" estimate
of reltuples, which should converge to the correct value over multiple
VACUUM and ANALYZE cycles even when individual measurements aren't very
good.
This new method for updating reltuples is used by both VACUUM and ANALYZE,
with the result that we no longer need the grotty interconnections that
caused ANALYZE to not update the stats depending on what had happened
in the parent VACUUM command.
Also, fix the logic for skipping all-visible pages during VACUUM so that it
looks ahead rather than behind to decide what to do, as per a suggestion
from Greg Stark. This eliminates useless scanning of all-visible pages at
the start of the relation or just after a not-all-visible page. In
particular, the first few pages of the relation will not be invariably
included in the scanned pages, which seems to help in not overweighting
them in the reltuples estimate.
Back-patch to 8.4, where the visibility map was introduced.
Since collation is effectively an argument, not a property of the function,
FmgrInfo is really the wrong place for it; and this becomes critical in
cases where a cached FmgrInfo is used for varying purposes that might need
different collation settings. Fix by passing it in FunctionCallInfoData
instead. In particular this allows a clean fix for bug #5970 (record_cmp
not working). This requires touching a bit more code than the original
method, but nobody ever thought that collations would not be an invasive
patch...
All expression nodes now have an explicit output-collation field, unless
they are known to only return a noncollatable data type (such as boolean
or record). Also, nodes that can invoke collation-aware functions store
a separate field that is the collation value to pass to the function.
This avoids confusion that arises when a function has collatable inputs
and noncollatable output type, or vice versa.
Also, replace the parser's on-the-fly collation assignment method with
a post-pass over the completed expression tree. This allows us to use
a more complex (and hopefully more nearly spec-compliant) assignment
rule without paying for it in extra storage in every expression node.
Fix assorted bugs in the planner's handling of collations by making
collation one of the defining properties of an EquivalenceClass and
by converting CollateExprs into discardable RelabelType nodes during
expression preprocessing.
While this will give wrong answers when estimating selectivity for a
comparison operator that's using a non-default collation, the estimation
error probably won't be large; and anyway the former approach created
estimation errors of its own by trying to use a histogram that might have
been computed with some other collation. So we'll adopt this simplified
approach for now and perhaps improve it sometime in the future.
This patch incorporates changes from Andres Freund to make sure that
selfuncs.c passes a valid collation OID to any datatype-specific function
it calls, in case that function wants collation information. Said OID will
now always be DEFAULT_COLLATION_OID, but at least we won't get errors.
This adds collation support for columns and domains, a COLLATE clause
to override it per expression, and B-tree index support.
Peter Eisentraut
reviewed by Pavel Stehule, Itagaki Takahiro, Robert Haas, Noah Misch
Waiting for relation locks can lead to starvation - it pins down an
autovacuum worker for as long as the lock is held. But if we're doing
an anti-wraparound vacuum, then we still wait; maintenance can no longer
be put off.
To assist with troubleshooting, if log_autovacuum_min_duration >= 0,
we log whenever an autovacuum or autoanalyze is skipped for this reason.
Per a gripe by Josh Berkus, and ensuing discussion.
Foreign tables are a core component of SQL/MED. This commit does
not provide a working SQL/MED infrastructure, because foreign tables
cannot yet be queried. Support for foreign table scans will need to
be added in a future patch. However, this patch creates the necessary
system catalog structure, syntax support, and support for ancillary
operations such as COMMENT and SECURITY LABEL.
Shigeru Hanada, heavily revised by Robert Haas
The general design of memory management in Postgres is that intermediate
results computed by an expression are not freed until the end of the tuple
cycle. For expression indexes, ANALYZE has to re-evaluate each expression
for each of its sample rows, and it wasn't bothering to free intermediate
results until the end of processing of that index. This could lead to very
substantial leakage if the intermediate results were large, as in a recent
example from Jakub Ouhrabka. Fix by doing ResetExprContext for each sample
row. This necessitates adding a datumCopy step to ensure that the final
expression value isn't recycled too. Some quick testing suggests that this
change adds at worst about 10% to the time needed to analyze a table with
an expression index; which is annoying, but seems a tolerable price to pay
to avoid unexpected out-of-memory problems.
Back-patch to all supported branches.
The core of this patch is hash_array() and associated typcache
infrastructure, which works just about exactly like the existing support
for array comparison.
In addition I did some work to ensure that the planner won't think that an
array type is hashable unless its element type is hashable, and similarly
for sorting. This includes adding a datatype parameter to op_hashjoinable
and op_mergejoinable, and adding an explicit "hashable" flag to
SortGroupClause. The lack of a cross-check on the element type was a
pre-existing bug in mergejoin support --- but it didn't matter so much
before, because if you couldn't sort the element type there wasn't any good
alternative to failing anyhow. Now that we have the alternative of hashing
the array type, there are cases where we can avoid a failure by being picky
at the planner stage, so it's time to be picky.
The issue of exactly how to combine the per-element hash values to produce
an array hash is still open for discussion, but the rest of this is pretty
solid, so I'll commit it as-is.
indexes when the index column type (the opclass opckeytype) is different from
the expression's datatype. When coded, this limitation wasn't worth worrying
about because we had no intelligence to speak of in stats collection for the
datatypes used by such opclasses. However, now that there's non-toy
estimation capability for tsvector queries, it amounts to a bug that ANALYZE
fails to do this.
The fix changes struct VacAttrStats, and therefore constitutes an API break
for custom typanalyze functions. Therefore we can't back-patch it into
released branches, but it was agreed that 9.0 isn't yet frozen hard enough
to make such a change unacceptable. Ergo, back-patch to 9.0 but no further.
The API break had better be mentioned in 9.0 release notes.
The purpose of this change is to eliminate the need for every caller
of SearchSysCache, SearchSysCacheCopy, SearchSysCacheExists,
GetSysCacheOid, and SearchSysCacheList to know the maximum number
of allowable keys for a syscache entry (currently 4). This will
make it far easier to increase the maximum number of keys in a
future release should we choose to do so, and it makes the code
shorter, too.
Design and review by Tom Lane.
VACUUM FULL INPLACE), along with a boatload of subsidiary code and complexity.
Per discussion, the use case for this method of vacuuming is no longer large
enough to justify maintaining it; not to mention that we don't wish to invest
the work that would be needed to make it play nicely with Hot Standby.
Aside from the code directly related to old-style VACUUM FULL, this commit
removes support for certain WAL record types that could only be generated
within VACUUM FULL, redirect-pointer removal in heap_page_prune, and
nontransactional generation of cache invalidation sinval messages (the last
being the sticking point for Hot Standby).
We still have to retain all code that copes with finding HEAP_MOVED_OFF and
HEAP_MOVED_IN flag bits on existing tuples. This can't be removed as long
as we want to support in-place update from pre-9.0 databases.
When a column is renamed, we recursively rename the same column in
all descendent tables. But if one of those tables also inherits that
column from a table outside the inheritance hierarchy rooted at the
named table, we must throw an error. The previous coding correctly
prohibited the rename when the parent had inherited the column from
elsewhere, but overlooked the case where the parent was OK but a child
table also inherited the same column from a second, unrelated parent.
For now, not backpatched due to lack of complaints from the field.
KaiGai Kohei, with further changes by me.
Reviewed by Bernd Helme and Tom Lane.
Attributes can now have options, just as relations and tablespaces do, and
the reloptions code is used to parse, validate, and store them. For
simplicity and because these options are not performance critical, we store
them in a separate cache rather than the main relcache.
Thanks to Alex Hunsaker for the review.
decisions about when to auto-analyze.
The previous code depended on n_live_tuples + n_dead_tuples - last_anl_tuples,
where all three of these numbers could be bad estimates from ANALYZE itself.
Even worse, in the presence of a steady flow of HOT updates and matching
HOT-tuple reclamations, auto-analyze might never trigger at all, even if all
three numbers are exactly right, because n_dead_tuples could hold steady.
To fix, replace last_anl_tuples with an accurately tracked count of the total
number of committed tuple inserts + updates + deletes since the last ANALYZE
on the table. This can still be compared to the same threshold as before, but
it's much more trustworthy than the old computation. Tracking this requires
one more intra-transaction counter per modified table within backends, but no
additional memory space in the stats collector. There probably isn't any
measurable speed difference; if anything it might be a bit faster than before,
since I was able to eliminate some per-tuple arithmetic operations in favor of
adding sums once per (sub)transaction.
Also, simplify the logic around pgstat vacuum and analyze reporting messages
by not trying to fold VACUUM ANALYZE into a single pgstat message.
The original thought behind this patch was to allow scheduling of analyzes
on parent tables by artificially inflating their changes_since_analyze count.
I've left that for a separate patch since this change seems to stand on its
own merit.
and teach ANALYZE to compute such stats for tables that have subclasses.
Per my proposal of yesterday.
autovacuum still needs to be taught about running ANALYZE on parent tables
when their subclasses change, but the feature is useful even without that.
an allegedly immutable index function. It was previously recognized that
we had to prevent such a function from executing SET/RESET ROLE/SESSION
AUTHORIZATION, or it could trivially obtain the privileges of the session
user. However, since there is in general no privilege checking for changes
of session-local state, it is also possible for such a function to change
settings in a way that might subvert later operations in the same session.
Examples include changing search_path to cause an unexpected function to
be called, or replacing an existing prepared statement with another one
that will execute a function of the attacker's choosing.
The present patch secures VACUUM, ANALYZE, and CREATE INDEX/REINDEX against
these threats, which are the same places previously deemed to need protection
against the SET ROLE issue. GUC changes are still allowed, since there are
many useful cases for that, but we prevent security problems by forcing a
rollback of any GUC change after completing the operation. Other cases are
handled by throwing an error if any change is attempted; these include temp
table creation, closing a cursor, and creating or deleting a prepared
statement. (In 7.4, the infrastructure to roll back GUC changes doesn't
exist, so we settle for rejecting changes of "search_path" in these contexts.)
Original report and patch by Gurjeet Singh, additional analysis by
Tom Lane.
Security: CVE-2009-4136
adopted for EXPLAIN. This will allow additional options to be implemented
in future without having to make them fully-reserved keywords. The old syntax
remains available for existing options, however.
Itagaki Takahiro
to access a Relation entry it had just closed. I happened to be testing with
CLOBBER_CACHE_ALWAYS, which made this a guaranteed core dump (at least on
machines where sprintf %s isn't forgiving of a NULL pointer). It's probably
quite unlikely that it would fail in the field, but a bug is a bug. Fix by
moving the relation_close call down past the logging action.
behavior in cases where we don't know the heap tuple count accurately; in
particular partial vacuum, but this also makes the API a bit more useful
for ANALYZE. This patch adds "estimated_count" flags to both structs so
that an approximate count can be flagged as such, and adjusts the logic
so that approximate counts are not used for updating pg_class.reltuples.
This fixes my previous complaint that VACUUM was putting ridiculous values
into pg_class.reltuples for indexes. The actual impact of that bug is
limited, because the planner only pays attention to reltuples for an index
if the index is partial; which probably explains why beta testers hadn't
noticed a degradation in plan quality from it. But it needs to be fixed.
The whole thing is a bit messy and should be redesigned in future, because
reltuples now has the potential to drift quite far away from reality when
a long period elapses with no non-partial vacuums. But this is as good as
it's going to get for 8.4.
there's no analyzable attributes or indexes. We also used to report 0 live
and dead tuples for such tables, which messed with autovacuum threshold
calculations.
This fixes bug #4812 reported by George Su. Backpatch back to 8.1.
ANALYZE's total sample. The original coding is at risk of overflow for
statistics targets exceeding about 2675; this was not a problem before
8.4 but it is now. Per bug #4793 from Dennis Noordsij.
temp relations; this is no more expensive than before, now that we have
pg_class.relistemp. Insert tests into bufmgr.c to prevent attempting
to fetch pages from nonlocal temp relations. This provides a low-level
defense against bugs-of-omission allowing temp pages to be loaded into shared
buffers, as in the contrib/pgstattuple problem reported by Stuart Bishop.
While at it, tweak a bunch of places to use new relcache tests (instead of
expensive probes into pg_namespace) to detect local or nonlocal temp tables.
multiple index entries in a holding area before adding them to the main index
structure. This helps because bulk insert is (usually) significantly faster
than retail insert for GIN.
This patch also removes GIN support for amgettuple-style index scans. The
API defined for amgettuple is difficult to support with fastupdate, and
the previously committed partial-match feature didn't really work with
it either. We might eventually figure a way to put back amgettuple
support, but it won't happen for 8.4.
catversion bumped because of change in GIN's pg_am entry, and because
the format of GIN indexes changed on-disk (there's a metapage now,
and possibly a pending list).
Teodor Sigaev
skipped. We could update relpages anyway, but it seems better to only
update it together with reltuples, because we use the reltuples/relpages
ratio in the planner. Also don't update n_live_tuples in pgstat.
ANALYZE in VACUUM ANALYZE now needs to update pg_class, if the
VACUUM-phase didn't do so. Added some boolean-passing to let analyze_rel
know if it should update pg_class or not.
I also moved the relcache invalidation (to update rd_targblock) from
vac_update_relstats to where RelationTruncate is called, because
vac_update_relstats is not called for partial vacuums anymore. It's more
obvious to send the invalidation close to the truncation that requires it.
Per report by Ned T. Crigler.
and heap_deformtuple in favor of the newer functions heap_form_tuple et al
(which do the same things but use bool control flags instead of arbitrary
char values). Eliminate the former duplicate coding of these functions,
reducing the deprecated functions to mere wrappers around the newer ones.
We can't get rid of them entirely because add-on modules probably still
contain many instances of the old coding style.
Kris Jurka
functions into one ReadBufferExtended function, that takes the strategy
and mode as argument. There's three modes, RBM_NORMAL which is the default
used by plain ReadBuffer(), RBM_ZERO, which replaces ZeroOrReadBuffer, and
a new mode RBM_ZERO_ON_ERROR, which allows callers to read corrupt pages
without throwing an error. The FSM needs the new mode to recover from
corrupt pages, which could happend if we crash after extending an FSM file,
and the new page is "torn".
Add fork number to some error messages in bufmgr.c, that still lacked it.
into nodes/nodeFuncs, so as to reduce wanton cross-subsystem #includes inside
the backend. There's probably more that should be done along this line,
but this is a start anyway.
as per my recent proposal:
1. Fold SortClause and GroupClause into a single node type SortGroupClause.
We were already relying on them to be struct-equivalent, so using two node
tags wasn't accomplishing much except to get in the way of comparing items
with equal().
2. Add an "eqop" field to SortGroupClause to carry the associated equality
operator. This is cheap for the parser to get at the same time it's looking
up the sort operator, and storing it eliminates the need for repeated
not-so-cheap lookups during planning. In future this will also let us
represent GROUP/DISTINCT operations on datatypes that have hash opclasses
but no btree opclasses (ie, they have equality but no natural sort order).
The previous representation simply didn't work for that, since its only
indicator of comparison semantics was a sort operator.
3. Add a hasDistinctOn boolean to struct Query to explicitly record whether
the distinctClause came from DISTINCT or DISTINCT ON. This allows removing
some complicated and not 100% bulletproof code that attempted to figure
that out from the distinctClause alone.
This patch doesn't in itself create any new capability, but it's necessary
infrastructure for future attempts to use hash-based grouping for DISTINCT
and UNION/INTERSECT/EXCEPT.
of different types than the underlying column. The capability isn't yet
used for anything, but will be required by upcoming patch to analyze
tsvector columns.
Jan Urbanski
more logical that way, and also it reduces the amount of unnecessary includes
in bufpage.h, which is widely used.
Zdenek Kotala.
My previous patch to bufpage.h should also have credited him as author, but I
forgot (sorry about that).
unnecessary #include lines in it. Also, move some tuple routine prototypes and
macros to htup.h, which allows removal of heapam.h inclusion from some .c
files.
For this to work, a new header file access/sysattr.h needed to be created,
initially containing attribute numbers of system columns, for pg_dump usage.
While at it, make contrib ltree, intarray and hstore header files more
consistent with our header style.
where Datum is 8 bytes wide. Since this will break old-style C functions
(those still using version 0 calling convention) that have arguments or
results of these types, provide a configure option to disable it and retain
the old pass-by-reference behavior. Likewise, provide a configure option
to disable the recently-committed float4 pass-by-value change.
Zoltan Boszormenyi, plus configurability stuff by me.
uses of the long-deprecated float32 in contrib/seg; the definitions themselves
are still there, but no longer used. fmgr/README updated to match.
I added a CREATE FUNCTION to account for existing seg_center() code in seg.c
too, and some tests for it and the neighbor functions. At the same time,
remove checks for NULL which are not needed (because the functions are declared
STRICT).
I had to do some adjustments to contrib's btree_gist too. The choices for
representation there are not ideal for changing the underlying types :-(
Original patch by Zoltan Boszormenyi, with some adjustments by me.
classed all as "dead"; also get it to count DEAD item pointers as dead rows,
instead of ignoring them as before. Also improve matters so that tuples
previously inserted or deleted by our own transaction are handled nicely:
the stats collector's live-tuple and dead-tuple counts will end up correct
after our transaction ends, regardless of whether we end in commit or abort.
While there's more work that could be done to improve the counting of in-doubt
tuples in both VACUUM and ANALYZE, this commit is enough to alleviate some
known bad behaviors in 8.3; and the other stuff that's been discussed seems
like research projects anyway.
Pavan Deolasee and Tom Lane
Tom Lane
Robert Haas
Kevin Grittner
Bruce Momjian
Simon Riggs
Alvaro Herrera
Heikki Linnakangas
Peter Eisentraut
Magnus Hagander