did not expect that a DEAD tuple could follow a RECENTLY_DEAD tuple in an
update chain, but because the OldestXmin rule for determining deadness is a
simplification of reality, it is possible for this situation to occur
(implying that the RECENTLY_DEAD tuple is in fact dead to all observers,
but this patch does not attempt to exploit that). The code would follow a
chain forward all the way, but then stop before a DEAD tuple when backing
up, meaning that not all of the chain got moved. This could lead to copying
the chain multiple times (resulting in duplicate copies of the live tuple at
its end), or leaving dangling index entries behind (which, aside from
generating warnings from later vacuums, creates a risk of wrong query
results or bogus duplicate-key errors once the heap slot the index entry
points to is repopulated).
The fix is to recheck HeapTupleSatisfiesVacuum while following a chain
forward, and to stop if a DEAD tuple is reached. Each contiguous group
of RECENTLY_DEAD tuples will therefore be copied as a separate chain.
The patch also adds a couple of extra sanity checks to verify correct
behavior.
Per report and test case from Pavan Deolasee.
even if none of the fields in the pg_class row change. This behavior is
necessary to ensure other backends flush rd_targblock values that might
point to truncated-away pages. We got this right pre-8.2 but it was broken
by overoptimistic change to not write out the pg_class row if unchanged.
Per report from Pavan Deolasee.
thought that it didn't have to reposition the underlying tuplestore if the
portal is atEnd. But this is not so, because tuplestores have separate read
and write cursors ... and the read cursor hasn't moved from the start.
This mistake explains bug #2970 from William Zhang.
Note: the coding here is pretty inefficient, but given that no one has noticed
this bug until now, I'd say hardly anyone uses the case where the cursor has
been advanced before being persisted. So maybe it's not worth worrying about.
made query plan. Use of ALTER COLUMN TYPE creates a hazard for cached
query plans: they could contain Vars that claim a column has a different
type than it now has. Fix this by checking during plan startup that Vars
at relation scan level match the current relation tuple descriptor. Since
at that point we already have at least AccessShareLock, we can be sure the
column type will not change underneath us later in the query. However,
since a backend's locks do not conflict against itself, there is still a
hole for an attacker to exploit: he could try to execute ALTER COLUMN TYPE
while a query is in progress in the current backend. Seal that hole by
rejecting ALTER TABLE whenever the target relation is already open in
the current backend.
This is a significant security hole: not only can one trivially crash the
backend, but with appropriate misuse of pass-by-reference datatypes it is
possible to read out arbitrary locations in the server process's memory,
which could allow retrieving database content the user should not be able
to see. Our thanks to Jeff Trout for the initial report.
Security: CVE-2007-0556
DROP TABLE and DROP DATABASE. Should prevent unexpected "permission denied"
failures on Windows, and is cleaner on other platforms too since we no longer
have to take it on faith that ENOENT is okay during an fsync attempt.
Patched as far back as 8.1; per recent discussion I think we are not going
to worry about Windows-specific issues in 8.0 anymore.
AbortTransaction, which would lead to recursion and eventual PANIC exit
as illustrated in recent report from Jeff Davis. First, in xact.c create
a special dedicated memory context for AbortTransaction to run in. This
solves the problem as long as AbortTransaction doesn't need more than 32K
(or whatever other size we create the context with). But in corner cases
it might. Second, in trigger.c arrange to keep pending after-trigger event
records in separate contexts that can be freed near the beginning of
AbortTransaction, rather than having them persist until CleanupTransaction
as before. Third, in portalmem.c arrange to free executor state data
earlier as well. These two changes should result in backing off the
out-of-memory condition before AbortTransaction needs any significant
amount of memory, at least in typical cases such as memory overrun due
to too many trigger events or too big an executor hash table. And all
the same for subtransaction abort too, of course.
in PITR scenarios. We now WAL-log the replacement of old XIDs with
FrozenTransactionId, so that such replacement is guaranteed to propagate to
PITR slave databases. Also, rather than relying on hint-bit updates to be
preserved, pg_clog is not truncated until all instances of an XID are known to
have been replaced by FrozenTransactionId. Add new GUC variables and
pg_autovacuum columns to allow management of the freezing policy, so that
users can trade off the size of pg_clog against the amount of freezing work
done. Revise the already-existing code that forces autovacuum of tables
approaching the wraparound point to make it more bulletproof; also, revise the
autovacuum logic so that anti-wraparound vacuuming is done per-table rather
than per-database. initdb forced because of changes in pg_class, pg_database,
and pg_autovacuum catalogs. Heikki Linnakangas, Simon Riggs, and Tom Lane.
that conflict with the OID that we want to use for the new database.
This avoids the risk of trying to remove files that maybe we shouldn't
remove. Per gripe from Jon Lapham and subsequent discussion of 27-Sep.
static variables. This avoids any risk of potential non-reentrancy,
and in particular offers a much cleaner workaround for the Intel compiler
bug that was affecting ginutil.c.
to performance. (A wholesale effort to get rid of strncpy should be
undertaken sometime, but not during beta.) This commit also fixes dynahash.c
to correctly truncate overlength string keys for hashtables, so that its
callers don't have to anymore.
even when a single relation requires more than max_fsm_pages pages. Also,
make VACUUM emit a warning in this case, since it likely means that VACUUM
FULL or other drastic corrective measure is needed. Per reports from Jeff
Frost and others of unexpected changes in the claimed max_fsm_pages need.
the table being analyzed. This prevents two ANALYZEs from running
concurrently on the same table and possibly suffering concurrent-update
failures while trying to store their results into pg_statistic. The
downside is that a database-wide ANALYZE executed within a transaction
block will hold ShareUpdateExclusiveLock on many tables simultaneously,
which could lead to concurrency issues or even deadlock against another
such ANALYZE. However, this seems a corner case of less importance
than getting unexpected errors from a foreground ANALYZE when autovacuum
elects to analyze the same table concurrently. Per discussion.
after an error during VACUUM. We have a PG_TRY block anyway around the only
call sites, so just reset it in the CATCH clause instead of having
AtEOXact_Buffers blindly do it during xact end. I think the old code was
actively wrong for the case of a failure during ANALYZE inside a
subtransaction --- the flag wouldn't get cleared until main transaction end.
Probably not worth back-patching though.
proposal. Parameter logging works even for binary-format parameters, and
logging overhead is avoided when disabled.
log_statement = all output for the src/test/examples/testlibpq3.c example
now looks like
LOG: statement: execute <unnamed>: SELECT * FROM test1 WHERE t = $1
DETAIL: parameters: $1 = 'joe''s place'
LOG: statement: execute <unnamed>: SELECT * FROM test1 WHERE i = $1::int4
DETAIL: parameters: $1 = '2'
and log_min_duration_statement = 0 results in
LOG: duration: 2.431 ms parse <unnamed>: SELECT * FROM test1 WHERE t = $1
LOG: duration: 2.335 ms bind <unnamed> to <unnamed>: SELECT * FROM test1 WHERE t = $1
DETAIL: parameters: $1 = 'joe''s place'
LOG: duration: 0.394 ms execute <unnamed>: SELECT * FROM test1 WHERE t = $1
DETAIL: parameters: $1 = 'joe''s place'
LOG: duration: 1.251 ms parse <unnamed>: SELECT * FROM test1 WHERE i = $1::int4
LOG: duration: 0.566 ms bind <unnamed> to <unnamed>: SELECT * FROM test1 WHERE i = $1::int4
DETAIL: parameters: $1 = '2'
LOG: duration: 0.173 ms execute <unnamed>: SELECT * FROM test1 WHERE i = $1::int4
DETAIL: parameters: $1 = '2'
(This example demonstrates the folly of ignoring parse/bind steps for duration
logging purposes, BTW.)
Along the way, create a less ad-hoc mechanism for determining which commands
are logged by log_statement = mod and log_statement = ddl. The former coding
was actually missing quite a few things that look like ddl to me, and it
did not handle EXECUTE or extended query protocol correctly at all.
This commit does not do anything about the question of whether log_duration
should be removed or made less redundant with log_min_duration_statement.
that has parameters is always planned afresh for each Bind command,
treating the parameter values as constants in the planner. This removes
the performance penalty formerly often paid for using out-of-line
parameters --- with this definition, the planner can do constant folding,
LIKE optimization, etc. After a suggestion by Andrew@supernews.
can create or modify rules for the table. Do setRuleCheckAsUser() while
loading rules into the relcache, rather than when defining a rule. This
ensures that permission checks for tables referenced in a rule are done with
respect to the current owner of the rule's table, whereas formerly ALTER TABLE
OWNER would fail to update the permission checking for associated rules.
Removal of separate RULE privilege is needed to prevent various scenarios
in which a grantee of RULE privilege could effectively have any privilege
of the table owner. For backwards compatibility, GRANT/REVOKE RULE is still
accepted, but it doesn't do anything. Per discussion here:
http://archives.postgresql.org/pgsql-hackers/2006-04/msg01138.php
the target relation(s). There might be some cases where we could discard
the pending event instead, but for the moment a conservative approach
seems sufficient. Per report from Markus Schiltknecht and subsequent
discussion.
optionally bind. I re-added the "statement:" label so people will
understand why the line is being printed (it is log_*statement
behavior).
Use single quotes for bind values, instead of double quotes, and double
literal single quotes in bind values (and document that). I also made
use of the DETAIL line to have much cleaner output.
locks that would conflict with a specified lock request, without
actually trying to get that lock. Use this instead of the former ad hoc
method of doing the first wait step in CREATE INDEX CONCURRENTLY.
Fixes problem with undetected deadlock and in many cases will allow the
index creation to proceed sooner than it otherwise could've. Per
discussion with Greg Stark.
by abandoning the idea that it should say SERIAL in the dump. Instead,
dump serial sequences and column defaults just like regular ones.
Add a new backend command ALTER SEQUENCE OWNED BY to let pg_dump recreate
the sequence-to-column dependency that was formerly created "behind the
scenes" by SERIAL. This restores SERIAL to being truly "just a macro"
consisting of component operations that can be stated explicitly in SQL.
Furthermore, the new command allows sequence ownership to be reassigned,
so that old mistakes can be cleaned up.
Also, downgrade the OWNED-BY dependency from INTERNAL to AUTO, since there
is no longer any very compelling argument why the sequence couldn't be
dropped while keeping the column. (This forces initdb, to be sure the
right kinds of dependencies are in there.)
Along the way, add checks to prevent ALTER OWNER or SET SCHEMA on an
owned sequence; you can now only do this indirectly by changing the
owning table's owner or schema. This is an oversight in previous
releases, but probably not worth back-patching.
the rel, it's easy to get rid of the narrow race-condition window that
used to exist in VACUUM and CLUSTER. Did some minor code-beautification
work in the same area, too.
cannot assume that there's exactly one Query in the Portal, as we can for
ONE_SELECT mode, because non-SELECT queries might have extra queries added
during rule rewrites. Fix things up so that we'll use ONE_RETURNING mode
when a Portal contains one primary (canSetTag) query and that query has
a RETURNING list. This appears to be a second showstopper reason for running
the Portal to completion before we start to hand anything back --- we want
to be sure that the rule-added queries get run too.
merely a matter of fixing the error check, since the underlying Portal
infrastructure already handles it. This in turn allows these statements
to be used in some existing plpgsql and plperl contexts, such as a
plpgsql FOR loop. Also, do some marginal code cleanup in places that
were being sloppy about distinguishing SELECT from SELECT INTO.
plpgsql support to come later. Along the way, convert execMain's
SELECT INTO support into a DestReceiver, in order to eliminate some ugly
special cases.
Jonah Harris and Tom Lane
o print user name for all
o print portal name if defined for all
o print query for all
o reduce log_statement header to single keyword
o print bind parameters as DETAIL if text mode
the DROP pass rather than the ADD_CONSTR pass. On examining the code I
think this was just an oversight rather than intentional, and it seems
to satisfy the principle of least surprise better than the alternative
solution that was discussed. Add an example to the ref page showing how
to do ALTER TYPE and update the default in one command. Per gripe from
Markus Bertheau that that wasn't possible.
(e.g. "INSERT ... VALUES (...), (...), ...") and elsewhere as allowed
by the spec. (e.g. similar to a FROM clause subselect). initdb required.
Joe Conway and Tom Lane.
(table or index) before trying to open its relcache entry. This fixes
race conditions in which someone else commits a change to the relation's
catalog entries while we are in process of doing relcache load. Problems
of that ilk have been reported sporadically for years, but it was not
really practical to fix until recently --- for instance, the recent
addition of WAL-log support for in-place updates helped.
Along the way, remove pg_am.amconcurrent: all AMs are now expected to support
concurrent update.
created in the bootstrap phase proper, rather than added after-the-fact
by initdb. This is cleaner than before because it allows us to retire the
undocumented ALTER TABLE ... CREATE TOAST TABLE command, but the real reason
I'm doing it is so that toast tables of shared catalogs will now have
predetermined OIDs. This will allow a reasonably clean solution to the
problem of locking tables before we load their relcache entries, to appear
in a forthcoming patch.
vacuums. This allows a OLTP-like system with big tables to continue
regular vacuuming on small-but-frequently-updated tables while the
big tables are being vacuumed.
Original patch from Hannu Krossing, rewritten by Tom Lane and updated
by me.
the opportunity to treat COUNT(*) as a zero-argument aggregate instead
of the old hack that equated it to COUNT(1); this is materially cleaner
(no more weird ANYOID cases) and ought to be at least a tiny bit faster.
Original patch by Sergey Koposov; review, documentation, simple regression
tests, pg_dump and psql support by moi.
