The various places that transferred fast-path locks to the main lock table
neglected to release the PGPROC's backendLock if SetupLockInTable failed
due to being out of shared memory.  In most cases this is no big deal since
ensuing error cleanup would release all held LWLocks anyway.  But there are
some hot-standby functions that don't consider failure of
FastPathTransferRelationLocks to be a hard error, and in those cases this
oversight could lead to system lockup.  For consistency, make all of these
places look the same as FastPathTransferRelationLocks.

Noted while looking for the cause of Dan Wood's bugs --- this wasn't it,
but it's a bug anyway.

Prevent handle_sig_alarm from losing control partway through due to a query
cancel (either an asynchronous SIGINT, or a cancel triggered by one of the
timeout handler functions).  That would at least result in failure to
schedule any required future interrupt, and might result in actual
corruption of timeout.c's data structures, if the interrupt happened while
we were updating those.

We could still lose control if an asynchronous SIGINT arrives just as the
function is entered.  This wouldn't break any data structures, but it would
have the same effect as if the SIGALRM interrupt had been silently lost:
we'd not fire any currently-due handlers, nor schedule any new interrupt.
To forestall that scenario, forcibly reschedule any pending timer interrupt
during AbortTransaction and AbortSubTransaction.  We can avoid any extra
kernel call in most cases by not doing that until we've allowed
LockErrorCleanup to kill the DEADLOCK_TIMEOUT and LOCK_TIMEOUT events.

Another hazard is that some platforms (at least Linux and *BSD) block a
signal before calling its handler and then unblock it on return.  When we
longjmp out of the handler, the unblock doesn't happen, and the signal is
left blocked indefinitely.  Again, we can fix that by forcibly unblocking
signals during AbortTransaction and AbortSubTransaction.

These latter two problems do not manifest when the longjmp reaches
postgres.c, because the error recovery code there kills all pending timeout
events anyway, and it uses sigsetjmp(..., 1) so that the appropriate signal
mask is restored.  So errors thrown outside any transaction should be OK
already, and cleaning up in AbortTransaction and AbortSubTransaction should
be enough to fix these issues.  (We're assuming that any code that catches
a query cancel error and doesn't re-throw it will do at least a
subtransaction abort to clean up; but that was pretty much required already
by other subsystems.)

Lastly, ProcSleep should not clear the LOCK_TIMEOUT indicator flag when
disabling that event: if a lock timeout interrupt happened after the lock
was granted, the ensuing query cancel is still going to happen at the next
CHECK_FOR_INTERRUPTS, and we want to report it as a lock timeout not a user
cancel.

Per reports from Dan Wood.

Back-patch to 9.3 where the new timeout handling infrastructure was
introduced.  We may at some point decide to back-patch the signal
unblocking changes further, but I'll desist from that until we hear
actual field complaints about it.

Although user-defined relations can't be directly created in
pg_catalog, it's possible for them to end up there, because you can
create them in some other schema and then use ALTER TABLE .. SET SCHEMA
to move them there.  Previously, such relations couldn't afterwards
be manipulated, because IsSystemRelation()/IsSystemClass() rejected
all attempts to modify objects in the pg_catalog schema, regardless
of their origin.  With this patch, they now reject only those
objects in pg_catalog which were created at initdb-time, allowing
most operations on user-created tables in pg_catalog to proceed
normally.

This patch also adds new functions IsCatalogRelation() and
IsCatalogClass(), which is similar to IsSystemRelation() and
IsSystemClass() but with a slightly narrower definition: only TOAST
tables of system catalogs are included, rather than *all* TOAST tables.
This is currently used only for making decisions about when
invalidation messages need to be sent, but upcoming logical decoding
patches will find other uses for this information.

Andres Freund, with some modifications by me.

The number of items inserted was incorrectly printed as if it was a boolean.

In the GIN incomplete-splits patch, I used BlockIdDatas to store the block
number of left and right children, when inserting a downlink after a split
to an internal page posting list page. But gin_desc thought they were stored
as BlockNumbers.

We have for a long time checked the head pointer of each of the backend's
proclock lists and skipped acquiring the corresponding locktable partition
lock if the head pointer was NULL.  This was safe enough in the days when
proclock lists were changed only by the owning backend, but it is pretty
questionable now that the fast-path patch added cases where backends add
entries to other backends' proclock lists.  However, we don't really wish
to revert to locking each partition lock every time, because in simple
transactions that would add a lot of useless lock/unlock cycles on
already-heavily-contended LWLocks.  Fortunately, the only way that another
backend could be modifying our proclock list at this point would be if it
was promoting a formerly fast-path lock of ours; and any such lock must be
one that we'd decided not to delete in the previous loop over the locallock
table.  So it's okay if we miss seeing it in this loop; we'd just decide
not to delete it again.  However, once we've detected a non-empty list,
we'd better re-fetch the list head pointer after acquiring the partition
lock.  This guards against possibly fetching a corrupt-but-non-null pointer
if pointer fetch/store isn't atomic.  It's not clear if any practical
architectures are like that, but we've never assumed that before and don't
wish to start here.  In any case, the situation certainly deserves a code
comment.

While at it, refactor the partition traversal loop to use a for() construct
instead of a while() loop with goto's.

Back-patch, just in case the risk is real and not hypothetical.

I removed an intermediate commit before pushing and forgot to test the
resulting tree :-(

Instead of simply checking the KEYS_UPDATED bit, we need to check
whether each lock held on the future version of the tuple conflicts with
the lock we're trying to acquire.

Per bug report #8434 by Tomonari Katsumata

Not doing so causes us to traverse an update chain that has been broken
by concurrent page pruning.  All other code that traverses update chains
uses this check as one of the cases in which to stop iterating, so
replicate it here too.  Failure to do so leads to erroneous CLOG,
subtrans or multixact lookups.

Per discussion following the bug report by J Smith in
CADFUPgc5bmtv-yg9znxV-vcfkb+JPRqs7m2OesQXaM_4Z1JpdQ@mail.gmail.com
as diagnosed by Andres Freund.

If a transaction updates/deletes a tuple just before aborting, and a
concurrent transaction tries to prune the page concurrently, the pruner
may see HeapTupleSatisfiesVacuum return HEAPTUPLE_DELETE_IN_PROGRESS,
but a later call to HeapTupleGetUpdateXid() return InvalidXid.  This
would cause an assertion failure in development builds, but would be
otherwise Mostly Harmless.

Fix by checking whether the updater Xid is valid before trying to apply
it as page prune point.

Reported by Andres in 20131124000203.GA4403@alap2.anarazel.de

The reason for the fetch failure is that the tuple was removed because
it was dead; so the failure is innocuous and can be ignored.  Moreover,
there's no need for further work and we can return success to the caller
immediately.  EvalPlanQualFetch is doing something very similar to this
already.

Report and test case from Andres Freund in
20131124000203.GA4403@alap2.anarazel.de

Adjust order of fields to match view order.

Jaime Casanova

From: Andreas Karlsson <andreas@proxel.se>

When acquiring a lock in fast-path mode, we must reset the locallock
object's lock and proclock fields to NULL.  They are not necessarily that
way to start with, because the locallock could be left over from a failed
lock acquisition attempt earlier in the transaction.  Failure to do this
led to all sorts of interesting misbehaviors when LockRelease tried to
clean up no-longer-related lock and proclock objects in shared memory.
Per report from Dan Wood.

In passing, modify LockRelease to elog not just Assert if it doesn't find
lock and proclock objects for a formerly fast-path lock, matching the code
in FastPathGetRelationLockEntry and LockRefindAndRelease.  This isn't a
bug but it will help in diagnosing any future bugs in this area.

Also, modify FastPathTransferRelationLocks and FastPathGetRelationLockEntry
to break out of their loops over the fastpath array once they've found the
sole matching entry.  This was inconsistently done in some search loops
and not others.

Improve assorted related comments, too.

Back-patch to 9.2 where the fast-path mechanism was introduced.

Per report from AK

Correct an obsolete statement that no backend touches another backend's
PROCLOCK lists.  This was probably wrong even when written (the deadlock
checker looks at everybody's lists), and it's certainly quite wrong now
that fast-path locking can require creation of lock and proclock objects
on behalf of another backend.  Also improve some statements in the hot
standby explanation, and do one or two other trivial bits of wordsmithing/
reformatting.

Replace it with an approach similar to what GiST uses: when a page is split,
the left sibling is marked with a flag indicating that the parent hasn't been
updated yet. When the parent is updated, the flag is cleared. If an insertion
steps on a page with the flag set, it will finish split before proceeding
with the insertion.

The post-recovery cleanup mechanism was never totally reliable, as insertion
to the parent could fail e.g because of running out of memory or disk space,
leaving the tree in an inconsistent state.

This also divides the responsibility of WAL-logging more clearly between
the generic ginbtree.c code, and the parts specific to entry and posting
trees. There is now a common WAL record format for insertions and deletions,
which is written by ginbtree.c, followed by tree-specific payload, which is
returned by the placetopage- and split- callbacks.

Separate the insertion payload from the more static portions of GinBtree.
GinBtree now only contains information related to searching the tree, and
the information of what to insert is passed separately.

Add root block number to GinBtree, instead of passing it around all the
functions as argument.

Split off ginFinishSplit() from ginInsertValue(). ginFinishSplit is
responsible for finding the parent and inserting the downlink to it.

I neglected this in the previous commit that updated the plpython2 output,
which I forgot to "git add" earlier.

As pointed out by Rodolfo Campero and Marko Kreen.

Vacuum recognizes that it can update relfrozenxid by checking whether it has
processed all pages of a relation. Unfortunately it performed that check
after truncating the dead pages at the end of the relation, and used the new
number of pages to decide whether all pages have been scanned. If the new
number of pages happened to be smaller or equal to the number of pages
scanned, it incorrectly decided that all pages were scanned.

This can lead to relfrozenxid being updated, even though some pages were
skipped that still contain old XIDs. That can lead to data loss due to xid
wraparounds with some rows suddenly missing. This likely has escaped notice
so far because it takes a large number (~2^31) of xids being used to see the
effect, while a full-table vacuum before that would fix the issue.

The incorrect logic was introduced by commit
b4b6923e. Backpatch this fix down to 8.4,
like that commit.

Andres Freund, with some modifications by me.

The latest fixes removed a limitation that was still in the docs, so Zoltan updated the docs, too.

Patch by Böszörményi Zoltán <zb@cybertec.at>

Haribabu kommi, slightly modified by me.

Backpatch to 9.1.

Josh Kupershmidt

Reviewed-by: Ali Dar <ali.munir.dar@gmail.com>
Reviewed-by: Amit Khandekar <amit.khandekar@enterprisedb.com>
Reviewed-by: Rodolfo Campero <rodolfo.campero@anachronics.com>

That way, the HTML file name of the index will be the same as currently
for the DSSSL build.

Patch by Boszormenyi Zoltan <zb@cybertec.at>

Patch by Boszormenyi Zoltan <zb@cybertec.at>

Patch by Boszormenyi Zoltan <zb@cybertec.at>

Valgrind runs.

Patch by Boszormenyi Zoltan <zb@cybertec.at>

variables is varchar. This fixes this test case:

int main(void)
{
    exec sql begin declare section;
    varchar a[50], b[50];
    exec sql end declare section;

    return 0;
}

Since varchars are internally turned into custom structs and
the type name is emitted for these variable declarations,
the preprocessed code previously had:

struct varchar_1  { ... }  a _,_  struct varchar_2  { ... }  b ;

The comma in the generated C file was a syntax error.

There are no regression test changes since it's not exercised.

Patch by Boszormenyi Zoltan <zb@cybertec.at>

Domains over arrays are now converted to/from python lists when passed as
arguments or return values. Like regular arrays.

This has some potential to break applications that rely on the old behavior
that they are passed as strings, but in practice there probably aren't many
such applications out there.

Rodolfo Campero

The omission was apparently an oversight in the original patch.

Change SET LOCAL/CONSTRAINTS/TRANSACTION behavior outside of a
transaction block from error (post-9.3) to warning.  (Was nothing in <=
9.3.)  Also change ABORT outside of a transaction block from notice to
warning.

ECPG is not supposed to allow and output nested comments in C. These comments
are only allowed in the SQL parts and must not be written into the C file.
Also the different handling of different comments is documented.

The last fix used the wrong non-terminal to define valid types.