The correct test for whether a redirection tuple is removable is whether
tuple's xid < RecentGlobalXmin, not OldestXmin; the previous coding
failed to protect index searches being done in concurrent transactions that
have no XID. This mirrors the recent fix in btree's page recycling logic
made in commit d3abbbebe5.
Also, WAL-log the newest XID of any removed redirection tuple on an index
page, and apply ResolveRecoveryConflictWithSnapshot during InHotStandby WAL
replay. This protects against concurrent Hot Standby transactions possibly
needing to see the redirection tuple(s).
Per my query of 2012-03-12 and subsequent discussion.
After taking awhile to digest the row-processor feature that was added to
libpq in commit 92785dac2e, we've concluded
it is over-complicated and too hard to use. Leave the core infrastructure
changes in place (that is, there's still a row processor function inside
libpq), but remove the exposed API pieces, and instead provide a "single
row" mode switch that causes PQgetResult to return one row at a time in
separate PGresult objects.
This approach incurs more overhead than proper use of a row processor
callback would, since construction of a PGresult per row adds extra cycles.
However, it is far easier to use and harder to break. The single-row mode
still affords applications the primary benefit that the row processor API
was meant to provide, namely not having to accumulate large result sets in
memory before processing them. Preliminary testing suggests that we can
probably buy back most of the extra cycles by micro-optimizing construction
of the extra results, but that task will be left for another day.
Marko Kreen
Parse analysis neglected to cover the case of a WITH clause attached to an
intermediate-level set operation; it only handled WITH at the top level
or WITH attached to a leaf-level SELECT. Per report from Adam Mackler.
In HEAD, I rearranged the order of SelectStmt's fields to put withClause
with the other fields that can appear on non-leaf SelectStmts. In back
branches, leave it alone to avoid a possible ABI break for third-party
code.
Back-patch to 8.4 where WITH support was added.
In the original coding of the log rotation stuff, we did not bother to make
the truncation logic work for the very first rotation after postmaster
start (or after a syslogger crash and restart). It just always appended
in that case. It did not seem terribly important at the time, but we've
recently had two separate complaints from people who expected it to work
unsurprisingly. (Both users tend to restart the postmaster about as often
as a log rotation is configured to happen, which is maybe not typical use,
but still...) Since the initial log file is opened in the postmaster,
fixing this requires passing down some more state to the syslogger child
process.
It's always been like this, so back-patch to all supported branches.
The most user-visible part of this is to change the long options
--statusint and --noloop to --status-interval and --no-loop,
respectively, per discussion.
Also, consistently enclose file names in double quotes, per our
conventions; and consistently use the term "transaction log file" to
talk about WAL segments. (Someday we may need to go over this
terminology and make it consistent across the whole source code.)
Finally, reflow the code to better fit in 80 columns, and have pgindent
fix it up some more.
This function suppressed any stderr output from the called program, which
is unnecessary in the normal case and unhelpful in error cases. It also
gave a rather opaque message along the lines of "fgets failure: Success"
in case the called program failed to return anything on stdout. Since
we've seen multiple reports of people not understanding what's wrong when
pg_ctl reports this, improve the message.
Back-patch to all active branches.
In the original coding of the autovacuum cancel feature, commit
acac68b2bc, an autovacuum process was
considered a target for cancellation if it was found to hard-block any
process examined in the deadlock search. This patch tightens the test so
that the autovacuum must directly hard-block the current process. This
should make the behavior more predictable in general, and in particular
it ensures that an autovacuum will not be canceled with less than
deadlock_timeout grace period. In the old coding, it was possible for an
autovacuum to be canceled almost instantly, given unfortunate timing of two
or more other processes' lock attempts.
This also justifies the logging methodology in the recent commit
d7318d43d891bd63e82dcfc27948113ed7b1db80; without this restriction, that
patch isn't providing enough information to see the connection of the
canceling process to the autovacuum. Like that one, patch all the way
back.
The old message was at DEBUG2, so typically it didn't show up in the
log at all. As a result, in most cases where autovacuum was canceled,
the only information that was logged was the table being vacuumed,
with no indication as to what problem caused the cancel. Crank up
the level to LOG and add some more details to assist with debugging.
Back-patch all the way, per discussion on pgsql-hackers.
If a crash occurred immediately after the first nextval() call for a serial
column, WAL replay would restore the sequence to a state in which it
appeared that no nextval() had been done, thus allowing the first sequence
value to be returned again by the next nextval() call; as reported in
bug #6748 from Xiangming Mei.
More generally, the problem would occur if an ALTER SEQUENCE was executed
on a freshly created or reset sequence. (The manifestation with serial
columns was introduced in 8.2 when we added an ALTER SEQUENCE OWNED BY step
to serial column creation.) The cause is that sequence creation attempted
to save one WAL entry by writing out a WAL record that made it appear that
the first nextval() had already happened (viz, with is_called = true),
while marking the sequence's in-database state with log_cnt = 1 to show
that the first nextval() need not emit a WAL record. However, ALTER
SEQUENCE would emit a new WAL entry reflecting the actual in-database state
(with is_called = false). Then, nextval would allocate the first sequence
value and set is_called = true, but it would trust the log_cnt value and
not emit any WAL record. A crash at this point would thus restore the
sequence to its post-ALTER state, causing the next nextval() call to return
the first sequence value again.
To fix, get rid of the idea of logging an is_called status different from
reality. This means that the first nextval-driven WAL record will happen
at the first nextval call not the second, but the marginal cost of that is
pretty negligible. In addition, make sure that ALTER SEQUENCE resets
log_cnt to zero in any case where it touches sequence parameters that
affect future nextval results. This will result in some user-visible
changes in the contents of a sequence's log_cnt column, as reflected in the
patch's regression test changes; but no application should be depending on
that anyway, since it was already true that log_cnt changes rather
unpredictably depending on checkpoint timing.
In addition, make some basically-cosmetic improvements to get rid of
sequence.c's undesirable intimacy with page layout details. It was always
really trying to WAL-log the contents of the sequence tuple, so we should
have it do that directly using a HeapTuple's t_data and t_len, rather than
backing into it with some magic assumptions about where the tuple would be
on the sequence's page.
Back-patch to all supported branches.
The initially implemented syntax, "CHECK NO INHERIT (expr)" was not
deemed very good, so switch to "CHECK (expr) NO INHERIT" instead. This
way it looks similar to SQL-standards compliant constraint attribute.
Backport to 9.2 where the new syntax and feature was introduced.
Per discussion.
This is apparently faster than doing things the other way around when
the scale factor is large.
Along the way, adjust -n to suppress vacuuming during initialization
as well as during test runs.
Jeff Janes, with some small changes by me.
Commit f5bcd398ad introduced a test using
a table named "circles" in inherit.sql. Unfortunately, the concurrently
executed constraints test was already using that table name, so the
parallel regression tests would sometimes fail. Rename table to dodge
the problem. Per buildfarm.
We should avoid calling sync_file_range or posix_fadvise in this case,
since (a) we don't really care if the data gets synced, and might as
well save the kernel calls; (b) at least on Linux we know that the
kernel might block us until it's scheduled the write.
Also, avoid making a useless second traversal of the directory tree
if we're not actually going to call fsync(2) after all.
We left this out of commit b966dd6c42
so as to get some more buildfarm testing of the new fsync code in initdb.
But since no problems have turned up, it's probably time to save the
cycles.
Antique versions of gcc complain about vars that are initialized outside
PG_TRY and then modified within it. Rather than marking the var volatile,
expend one more line of code.
We made use of the ROWS estimate for set-returning functions used in FROM,
but not for those used in SELECT targetlists; which is a bit of an
oversight considering there are common usages that require the latter
approach. Improve that. (I had initially thought it might be worth
folding this into cost_qual_eval, but after investigation concluded that
that wouldn't be very helpful, so just do it separately.) Per complaint
from David Johnston.
Back-patch to 9.2, but not further, for fear of destabilizing plan choices
in existing releases.
Commit 3a0e4d36eb arranged to
reference stack-allocated variables after they were out of scope.
That's no good, so let's arrange to not do that after all.
There is no point in running this test when prepared transactions are disabled,
which is the default. New make targets that include the test are provided. This
will save some useless waste of cycles on buildfarm machines.
Backpatch to 9.1 where these tests were introduced.
The code was setting it true for other constraints, which is
bogus. Doing so caused bogus catalog entries for such constraints, and
in particular caused an error to be raised when trying to drop a
constraint of types other than CHECK from a table that has children,
such as reported in bug #6712.
In 9.2, additionally ignore connoinherit=true for other constraint
types, to avoid having to force initdb; existing databases might already
contain bogus catalog entries.
Includes a catversion bump (in HEAD only).
Bug report from Miroslav Šulc
Analysis from Amit Kapila and Noah Misch; Amit also contributed the patch.
When a whole-row Var is reading the result of a subquery, we need it to
ignore any "resjunk" columns that the subquery might have evaluated for
GROUP BY or ORDER BY purposes. We've hacked this area before, in commit
68e40998d0, but that fix only covered
whole-row Vars of named composite types, not those of RECORD type; and it
was mighty klugy anyway, since it just assumed without checking that any
extra columns in the result must be resjunk. A proper fix requires getting
hold of the subquery's targetlist so we can actually see which columns are
resjunk (whereupon we can use a JunkFilter to get rid of them). So bite
the bullet and add some infrastructure to make that possible.
Per report from Andrew Dunstan and additional testing by Merlin Moncure.
Back-patch to all supported branches. In 8.3, also back-patch commit
292176a118, which for some reason I had
not done at the time, but it's a prerequisite for this change.
Commit 3855968f32 added syntax, pg_dump,
psql support, and documentation, but the triggers didn't actually fire.
With this commit, they now do. This is still a pretty basic facility
overall because event triggers do not get a whole lot of information
about what the user is trying to do unless you write them in C; and
there's still no option to fire them anywhere except at the very
beginning of the execution sequence, but it's better than nothing,
and a good building block for future work.
Along the way, add a regression test for ALTER LARGE OBJECT, since
testing of event triggers reveals that we haven't got one.
Dimitri Fontaine and Robert Haas
Instead of having one hash table entry per relation/fork/segment, just have
one per relation, and use bitmapsets to represent which specific segments
need to be fsync'd. This eliminates the need to scan the whole hash table
to implement FORGET_RELATION_FSYNC, which fixes the O(N^2) behavior
recently demonstrated by Jeff Janes for cases involving lots of TRUNCATE or
DROP TABLE operations during a single checkpoint cycle. Per an idea from
Robert Haas.
(FORGET_DATABASE_FSYNC still sucks, but since dropping a database is a
pretty expensive operation anyway, we'll live with that.)
In passing, improve the delayed-unlink code: remove the pass over the list
in mdpreckpt, since it wasn't doing anything for us except supporting a
useless Assert in mdpostckpt, and fix mdpostckpt so that it will absorb
fsync requests every so often when clearing a large backlog of deletion
requests.
We were sending one per fork, but a little bit of refactoring allows us
to send just one request with forknum == InvalidForkNumber. This not only
reduces pressure on the shared-memory request queue, but saves repeated
traversals of the checkpointer's hash table.
Functions like range_eq, range_before etc. are exposed at the SQL-level, but
they're also used internally by the GiST consistent support function. The
code sharing was done by a hack, TrickFunctionCall2, which relied on the
knowledge that all the functions used fn_extra the same way. This commit
splits the functions into internal versions that take a TypeCacheEntry as
argument, and thin wrappers to expose the functions at the SQL-level. The
internal versions can then be called directly and in a less hacky way from
the GiST consistent function.
This is just cosmetic, but backpatch to 9.2 anyway, to avoid having a
different version of this code in the 9.2 branch. That would make
backpatching fixes in this area more difficult.
Alexander Korotkov
ForwardFsyncRequest() supposed that it could only be called in regular
backends, which used to be true; but since the splitup of bgwriter and
checkpointer, it is also called in the bgwriter. We do not want to count
such calls in pg_stat_bgwriter.buffers_backend statistics, so fix things
so that they aren't.
(It's worth noting here that this implies an alarmingly large increase in
the expected amount of cross-process fsync request traffic, which may well
mean that the process splitup was not such a hot idea.)
mdinit() was misusing IsBootstrapProcessingMode() to decide whether to
create an fsync pending-operations table in the current process. This led
to creating a table not only in the startup and checkpointer processes as
intended, but also in the bgwriter process, not to mention other auxiliary
processes such as walwriter and walreceiver. Creation of the table in the
bgwriter is fatal, because it absorbs fsync requests that should have gone
to the checkpointer; instead they just sit in bgwriter local memory and are
never acted on. So writes performed by the bgwriter were not being fsync'd
which could result in data loss after an OS crash. I think there is no
live bug with respect to walwriter and walreceiver because those never
perform any writes of shared buffers; but the potential is there for
future breakage in those processes too.
To fix, make AuxiliaryProcessMain() export the current process's
AuxProcType as a global variable, and then make mdinit() test directly for
the types of aux process that should have a pendingOpsTable. Having done
that, we might as well also get rid of the random bool flags such as
am_walreceiver that some of the aux processes had grown. (Note that we
could not have fixed the bug by examining those variables in mdinit(),
because it's called from BaseInit() which is run by AuxiliaryProcessMain()
before entering any of the process-type-specific code.)
Back-patch to 9.2, where the problem was introduced by the split-up of
bgwriter and checkpointer processes. The bogus pendingOpsTable exists
in walwriter and walreceiver processes in earlier branches, but absent
any evidence that it causes actual problems there, I'll leave the older
branches alone.
They don't actually do anything yet; that will get fixed in a
follow-on commit. But this gets the basic infrastructure in place,
including CREATE/ALTER/DROP EVENT TRIGGER; support for COMMENT,
SECURITY LABEL, and ALTER EXTENSION .. ADD/DROP EVENT TRIGGER;
pg_dump and psql support; and documentation for the anticipated
initial feature set.
Dimitri Fontaine, with review and a bunch of additional hacking by me.
Thom Brown extensively reviewed earlier versions of this patch set,
but there's not a whole lot of that code left in this commit, as it
turns out.
Since the scandir() emulation was taken out of pg_upgrade, there's
no longer any need for scandir_file_pattern to exist as a global
variable. Replace it with a local in the one remaining function
that was making use of it.
Error out on out-of-memory, rather than returning -1, which the sole
existing caller wasn't checking for anyway. There doesn't seem to be
any use-case for making the caller check for failure here.
Detect failure return from readdir().
Use a less platform-dependent method of calculating the entrysize.
It's possible, but not yet confirmed, that this explains bug #6733,
in which Mike Wilson reports a pg_upgrade crash that did not occur
in 9.1. (Note that load_directory is effectively new code in 9.2,
at least on platforms that have scandir().)
Fix up comments, avoid uselessly using two counters, reduce the number
of realloc calls to something sane.
In all branches back to 8.3, this patch fixes a questionable assumption in
CompactCheckpointerRequestQueue/CompactBgwriterRequestQueue that there are
no uninitialized pad bytes in the request queue structs. This would only
cause trouble if (a) there were such pad bytes, which could happen in 8.4
and up if the compiler makes enum ForkNumber narrower than 32 bits, but
otherwise would require not-currently-planned changes in the widths of
other typedefs; and (b) the kernel has not uniformly initialized the
contents of shared memory to zeroes. Still, it seems a tad risky, and we
can easily remove any risk by pre-zeroing the request array for ourselves.
In addition to that, we need to establish a coding rule that struct
RelFileNode can't contain any padding bytes, since such structs are copied
into the request array verbatim. (There are other places that are assuming
this anyway, it turns out.)
In 9.1 and up, the risk was a bit larger because we were also effectively
assuming that struct RelFileNodeBackend contained no pad bytes, and with
fields of different types in there, that would be much easier to break.
However, there is no good reason to ever transmit fsync or delete requests
for temp files to the bgwriter/checkpointer, so we can revert the request
structs to plain RelFileNode, getting rid of the padding risk and saving
some marginal number of bytes and cycles in fsync queue manipulation while
we are at it. The savings might be more than marginal during deletion of
a temp relation, because the old code transmitted an entirely useless but
nonetheless expensive-to-process ForgetRelationFsync request to the
background process, and also had the background process perform the file
deletion even though that can safely be done immediately.
In addition, make some cleanup of nearby comments and small improvements to
the code in CompactCheckpointerRequestQueue/CompactBgwriterRequestQueue.
These only pass cleanly on UTF8 and SQL_ASCII encodings, besides the
Japanese encoding in which they were originally written, which is clearly
not good enough. Since the functionality they test has not ever been
tested from PL/Perl, the best answer seems to be to remove the new tests
completely.
Per buildfarm results and ensuing discussion.
Bruce Momjian