Tom Lane [Fri, 10 Dec 2010 16:33:38 +0000 (11:33 -0500)]
Fix efficiency problems in tuplestore_trim().
The original coding in tuplestore_trim() was only meant to work efficiently
in cases where each trim call deleted most of the tuples in the store.
Which, in fact, was the pattern of the original usage with a Material node
supporting mark/restore operations underneath a MergeJoin. However,
WindowAgg now uses tuplestores and it has considerably less friendly
trimming behavior. In particular it can attempt to trim one tuple at a
time off a large tuplestore. tuplestore_trim() had O(N^2) runtime in this
situation because of repeatedly shifting its tuple pointer array. Fix by
avoiding shifting the array until a reasonably large number of tuples have
been deleted. This can waste some pointer space, but we do still reclaim
the tuples themselves, so the percentage wastage should be pretty small.
Per Jie Li's report of slow percent_rank() evaluation. cume_dist() and
ntile() would certainly be affected as well, along with any other window
function that has a moving frame start and requires reading substantially
ahead of the current row.
Back-patch to 8.4, where window functions were introduced. There's no
need to tweak it before that.
Tom Lane [Thu, 9 Dec 2010 18:03:11 +0000 (13:03 -0500)]
Eliminate O(N^2) behavior in parallel restore with many blobs.
With hundreds of thousands of TOC entries, the repeated searches in
reduce_dependencies() become the dominant cost. Get rid of that searching
by constructing reverse-dependency lists, which we can do in O(N) time
during the fix_dependencies() preprocessing. I chose to store the reverse
dependencies as DumpId arrays for consistency with the forward-dependency
representation, and keep the previously-transient tocsByDumpId[] array
around to locate actual TOC entry structs quickly from dump IDs.
While this fixes the slow case reported by Vlad Arkhipov, there is still
a potential for O(N^2) behavior with sufficiently many tables:
fix_dependencies itself, as well as mark_create_done and
inhibit_data_for_failed_table, are doing repeated searches to deal with
table-to-table-data dependencies. Possibly this work could be extended
to deal with that, although the latter two functions are also used in
non-parallel restore where we currently don't run fix_dependencies.
Another TODO is that we fail to parallelize restore of multiple blobs
at all. This appears to require changes in the archive format to fix.
Back-patch to 9.0 where the problem was reported. 8.4 has potential issues
as well; but since it doesn't create a separate TOC entry for each blob,
it's at much less risk of having enough TOC entries to cause real problems.
Simon Riggs [Thu, 9 Dec 2010 09:41:47 +0000 (09:41 +0000)]
Reduce spurious Hot Standby conflicts from never-visible records.
Hot Standby conflicts only with tuples that were visible at
some point. So ignore tuples from aborted transactions or for
tuples updated/deleted during the inserting transaction when
generating the conflict transaction ids.
Following detailed analysis and test case by Noah Misch.
Original report covered btree delete records, correctly observed
by Heikki Linnakangas that this applies to other cases also.
Fix covers all sources of cleanup records via common code.
Tom Lane [Thu, 9 Dec 2010 01:01:09 +0000 (20:01 -0500)]
Force default wal_sync_method to be fdatasync on Linux.
Recent versions of the Linux system header files cause xlogdefs.h to
believe that open_datasync should be the default sync method, whereas
formerly fdatasync was the default on Linux. open_datasync is a bad
choice, first because it doesn't actually outperform fdatasync (in fact
the reverse), and second because we try to use O_DIRECT with it, causing
failures on certain filesystems (e.g., ext4 with data=journal option).
This part of the patch is largely per a proposal from Marti Raudsepp.
More extensive changes are likely to follow in HEAD, but this is as much
change as we want to back-patch.
Also clean up confusing code and incorrect documentation surrounding the
fsync_writethrough option. Those changes shouldn't result in any actual
behavioral change, but I chose to back-patch them anyway to keep the
branches looking similar in this area.
In 9.0 and HEAD, also do some copy-editing on the WAL Reliability
documentation section.
Back-patch to all supported branches, since any of them might get used
on modern Linux versions.
Simon Riggs [Wed, 8 Dec 2010 18:48:03 +0000 (18:48 +0000)]
Optimize commit_siblings in two ways to improve group commit.
First, avoid scanning the whole ProcArray once we know there
are at least commit_siblings active; second, skip the check
altogether if commit_siblings = 0.
Fix bugs in the hot standby known-assigned-xids tracking logic. If there's
an old transaction running in the master, and a lot of transactions have
started and finished since, and a WAL-record is written in the gap between
the creating the running-xacts snapshot and WAL-logging it, recovery will fail
with "too many KnownAssignedXids" error. This bug was reported by
Joachim Wieland on Nov 19th.
In the same scenario, when fewer transactions have started so that all the
xids fit in KnownAssignedXids despite the first bug, a more serious bug
arises. We incorrectly initialize the clog code with the oldest still running
transaction, and when we see the WAL record belonging to a transaction with
an XID larger than one that committed already before the checkpoint we're
recovering from, we zero the clog page containing the already committed
transaction, leading to data loss.
In hindsight, trying to track xids in the known-assigned-xids array before
seeing the running-xacts record was too complicated. To fix that, hold
XidGenLock while the running-xacts snapshot is taken and WAL-logged. That
ensures that no transaction can begin or end in that gap, so that in recvoery
we know that the snapshot contains all transactions running at that point in
WAL.
Tom Lane [Tue, 7 Dec 2010 03:55:43 +0000 (22:55 -0500)]
Add a stack overflow check to copyObject().
There are some code paths, such as SPI_execute(), where we invoke
copyObject() on raw parse trees before doing parse analysis on them. Since
the bison grammar is capable of building heavily nested parsetrees while
itself using only minimal stack depth, this means that copyObject() can be
the front-line function that hits stack overflow before anything else does.
Accordingly, it had better have a check_stack_depth() call. I did a bit of
performance testing and found that this slows down copyObject() by only a
few percent, so the hit ought to be negligible in the context of complete
processing of a query.
Per off-list report from Toshihide Katayama. Back-patch to all supported
branches.
Andrew Dunstan [Mon, 6 Dec 2010 20:31:55 +0000 (15:31 -0500)]
Allow the low level COPY routines to read arbitrary numbers of fields.
This doesn't involve any user-visible change in behavior, but will be
useful when the COPY routines are exposed to allow their use by Foreign
Data Wrapper routines, which will be able to use these routines to read
irregular CSV files, for example.
Avoid eating quite so much memory for large inheritance trees, by
reclaiming the space used by temporary copies of the original parsetree and
range table, as well as the workspace needed during planning. The cost is
needing to copy the finished plan trees out of the child memory context.
Although this looks like it ought to slow things down, my testing shows
it actually is faster, apparently because fewer interactions with malloc()
are needed and/or we can do the work within a more readily cacheable amount
of memory. That result might be platform-dependent, but I'll take it.
Per a gripe from John Papandriopoulos, in which it was pointed out that the
memory consumption actually grew as O(N^2) for sufficiently many child
tables, since we were creating N copies of the N-element range table.
Tom Lane [Sat, 4 Dec 2010 18:47:08 +0000 (13:47 -0500)]
Fix two small bugs in new gistget.c logic.
1. Complain, rather than silently doing nothing, if an "invalid" tuple
is found on a leaf page. Per off-list discussion with Heikki.
2. Fix oversight in code that removes a GISTSearchItem from the search
queue: we have to reset lastHeap if this was the last heap item in the
parent GISTSearchTreeItem. Otherwise subsequent additions will do the
wrong thing. This was probably masked in early testing because in typical
cases the parent item would now be completely empty and would be deleted on
next call. You'd need a queued non-leaf page at exactly the same distance
as a heap tuple to expose the bug.
Tom Lane [Sat, 4 Dec 2010 01:52:18 +0000 (20:52 -0500)]
KNNGIST, otherwise known as order-by-operator support for GIST.
This commit represents a rather heavily editorialized version of
Teodor's builtin_knngist_itself-0.8.2 and builtin_knngist_proc-0.8.1
patches. I redid the opclass API to add a separate Distance method
instead of turning the Consistent method into an illogical mess,
fixed some bit-rot in the rbtree interfaces, and generally worked over
the code style and comments.
There's still no non-code documentation to speak of, but I'll work on
that separately. Some contrib-module changes are also yet to come
(right now, point <-> point is the only KNN-ified operator).
Tom Lane [Fri, 3 Dec 2010 01:50:48 +0000 (20:50 -0500)]
Create core infrastructure for KNNGIST.
This is a heavily revised version of builtin_knngist_core-0.9. The
ordering operators are no longer mixed in with actual quals, which would
have confused not only humans but significant parts of the planner.
Instead, ordering operators are carried separately throughout planning and
execution.
Since the API for ambeginscan and amrescan functions had to be changed
anyway, this commit takes the opportunity to rationalize that a bit.
RelationGetIndexScan no longer forces a premature index_rescan call;
instead, callers of index_beginscan must call index_rescan too. Aside from
making the AM-side initialization logic a bit less peculiar, this has the
advantage that we do not make a useless extra am_rescan call when there are
runtime key values. AMs formerly could not assume that the key values
passed to amrescan were actually valid; now they can.
Refactor the pg_dump zlib code from pg_backup_custom.c to a separate file,
to make it easier to reuse that code. There is no user-visible changes.
This is in preparation for the patch to add a new archive format, a directory,
to perform a custom-like dump but with each table being dumped to a separate
file (that in turn is a prerequisite for parallel pg_dump). This also makes it
easier to add new compression methods in the future, and makes the
pg_backup_custom.c code easier to read, when the compression-related code is
factored out.
Joachim Wieland, with heavy editorialization by me.
Tom Lane [Wed, 1 Dec 2010 05:53:18 +0000 (00:53 -0500)]
Prevent inlining a SQL function with multiple OUT parameters.
There were corner cases in which the planner would attempt to inline such
a function, which would result in a failure at runtime due to loss of
information about exactly what the result record type is. Fix by disabling
inlining when the function's recorded result type is RECORD. There might
be some sub-cases where inlining could still be allowed, but this is a
simple and backpatchable fix, so leave refinements for another day.
Per bug #5777 from Nate Carson.
Back-patch to all supported branches. 8.1 happens to avoid a core-dump
here, but it still does the wrong thing.
Tom Lane [Mon, 29 Nov 2010 17:29:42 +0000 (12:29 -0500)]
Simplify and speed up mapping of index opfamilies to pathkeys.
Formerly we looked up the operators associated with each index (caching
them in relcache) and then the planner looked up the btree opfamily
containing such operators in order to build the btree-centric pathkey
representation that describes the index's sort order. This is quite
pointless for btree indexes: we might as well just use the index's opfamily
information directly. That saves syscache lookup cycles during planning,
and furthermore allows us to eliminate the relcache's caching of operators
altogether, which may help in reducing backend startup time.
I added code to plancat.c to perform the same type of double lookup
on-the-fly if it's ever faced with a non-btree amcanorder index AM.
If such a thing actually becomes interesting for production, we should
replace that logic with some more-direct method for identifying the
corresponding btree opfamily; but it's not worth spending effort on now.
There is considerably more to do pursuant to my recent proposal to get rid
of sort-operator-based representations of sort orderings, but this patch
grabs some of the low-hanging fruit. I'll look at the remainder of that
work after the current commitfest.
Simon Riggs [Mon, 29 Nov 2010 01:08:02 +0000 (01:08 +0000)]
Move call to GetTopTransactionId() earlier in LockAcquire(),
removing an infrequently occurring race condition in Hot Standby.
An xid must be assigned before a lock appears in shared memory,
rather than immediately after, else GetRunningTransactionLocks()
may see InvalidTransactionId, causing assertion failures during
lock processing on standby.
Bug report and diagnosis by Fujii Masao, fix by me.
Tom Lane [Sat, 27 Nov 2010 06:30:34 +0000 (01:30 -0500)]
Rewrite PQping to be more like what we agreed to last week.
Basically, we want to distinguish all cases where the connection was
not made from those where it was. A convenient proxy for this is to
see if we got a message with a SQLSTATE code back from the postmaster.
This presumes that the postmaster will always send us a SQLSTATE in
a failure message, which is true for 7.4 and later postmasters in
every case except fork failure. (We could possibly complicate the
postmaster code to do something about that, but it seems not worth
the trouble, especially since pg_ctl's response for that case should
be to keep waiting anyway.)
If we did get a SQLSTATE from the postmaster, there are basically only
two cases, as per last week's discussion: ERRCODE_CANNOT_CONNECT_NOW
and everything else. Any other error code implies that the postmaster
is in principle willing to accept connections, it just didn't like or
couldn't handle this particular request. We want to make a special
case for ERRCODE_CANNOT_CONNECT_NOW so that "pg_ctl start -w" knows
it should keep waiting.
In passing, pick names for the enum constants that are a tad less
likely to present collision hazards in future.
Tom Lane [Fri, 26 Nov 2010 22:59:10 +0000 (17:59 -0500)]
Fix portability issues in new src/port/inet_net_ntop.c file.
1. Don't #include postgres.h in a frontend build.
2. Don't assume that the backend's symbol PGSQL_AF_INET6 has anything to do
with the constant that will be used by system library functions (because,
in point of fact, it usually doesn't). Fortunately, PGSQL_AF_INET is equal
to AF_INET, so we can just cater for both sets of values in one case
construct without fear of conflict.
Robert Haas [Fri, 26 Nov 2010 22:27:23 +0000 (17:27 -0500)]
Add more ALTER <object> .. SET SCHEMA commands.
This adds support for changing the schema of a conversion, operator,
operator class, operator family, text search configuration, text search
dictionary, text search parser, or text search template.
Dimitri Fontaine, with assorted corrections and other kibitzing.
Tom Lane [Fri, 26 Nov 2010 20:20:51 +0000 (15:20 -0500)]
Fix significant memory leak in contrib/xml2 functions.
Most of the functions that execute XPath queries leaked the data structures
created by libxml2. This memory would not be recovered until end of
session, so it mounts up pretty quickly in any serious use of the feature.
Per report from Pavel Stehule, though this isn't his patch.
Bruce Momjian [Thu, 25 Nov 2010 18:09:38 +0000 (13:09 -0500)]
Add PQping and PQpingParams to libpq to allow detection of the server's
status, including a status where the server is running but refuses a
postgres connection.
Have pg_ctl use this new function. This fixes the case where pg_ctl
reports that the server is not running (cannot connect) but in fact it
is running.
Robert Haas [Thu, 25 Nov 2010 16:48:49 +0000 (11:48 -0500)]
Object access hook framework, with post-creation hook.
After a SQL object is created, we provide an opportunity for security
or logging plugins to get control; for example, a security label provider
could use this to assign an initial security label to newly created
objects. The basic infrastructure is (hopefully) reusable for other types
of events that might require similar treatment.
Robert Haas [Thu, 25 Nov 2010 05:06:46 +0000 (00:06 -0500)]
Remove belt-and-suspenders guards against buffer pin leaks.
Forcibly releasing all leftover buffer pins should be unnecessary now
that we have a robust ResourceOwner mechanism, and it significantly
increases the cost of process shutdown. Instead, in an assert-enabled
build, assert that no pins are held; in a non-assert-enabled build, do
nothing.
Bruce Momjian [Wed, 24 Nov 2010 22:04:19 +0000 (17:04 -0500)]
When reporting the server as not responding, if the hostname was
supplied, also print the IP address. This allows IPv4 and IPv6 failures
to be distinguished. Also useful when a hostname resolves to multiple
IP addresses.
Also, remove use of inet_ntoa() and use our own inet_net_ntop() in all
places, including in libpq, because it is thread-safe.
Tom Lane [Wed, 24 Nov 2010 19:20:39 +0000 (14:20 -0500)]
Create the system catalog infrastructure needed for KNNGIST.
This commit adds columns amoppurpose and amopsortfamily to pg_amop, and
column amcanorderbyop to pg_am. For the moment all the entries in
amcanorderbyop are "false", since the underlying support isn't there yet.
Also, extend the CREATE OPERATOR CLASS/ALTER OPERATOR FAMILY commands with
[ FOR SEARCH | FOR ORDER BY sort_operator_family ] clauses to allow the new
columns of pg_amop to be populated, and create pg_dump support for dumping
that information.
I also added some documentation, although it's perhaps a bit premature
given that the feature doesn't do anything useful yet.
Peter Eisentraut [Tue, 23 Nov 2010 22:00:34 +0000 (00:00 +0200)]
Add index entries for more functions
Also, move index entries into the tables, closer to the function description,
for easier editing in the future. Resort some tables to be more alphabetical.
Remove the entries for count, max, min, and sum in the tutorial area, because
that was felt to be confusing.
Robert Haas [Tue, 23 Nov 2010 00:46:15 +0000 (19:46 -0500)]
Centralize some ALTER <whatever> .. SET SCHEMA checks.
Any flavor of ALTER <whatever> .. SET SCHEMA fails if (1) the object
is already in the new schema, (2) either the old or new schema is
a temp schema, or (3) either the old or new schema is the TOAST schema.
Extraced from a patch by Dimitri Fontaine, with additional hacking by me.
Robert Haas [Sat, 20 Nov 2010 05:21:17 +0000 (00:21 -0500)]
Add new SQL function, format(text).
Currently, three conversion format specifiers are supported: %s for a
string, %L for an SQL literal, and %I for an SQL identifier. The latter
two are deliberately designed not to overlap with what sprintf() already
supports, in case we want to add more of sprintf()'s functionality here
later.
Patch by Pavel Stehule, heavily revised by me. Reviewed by Jeff Janes
and, in earlier versions, by Itagaki Takahiro and Tom Lane.
Tom Lane [Sat, 20 Nov 2010 20:07:16 +0000 (15:07 -0500)]
Further cleanup of indxpath logic related to IndexOptInfo.opfamily array.
We no longer need the terminating zero entry in opfamily[], so get rid of
it. Also replace assorted ad-hoc looping logic with simple for and foreach
constructs. This code is now noticeably more readable than it was an hour
ago; credit to Robert for seeing that it could be simplified.
Tom Lane [Sat, 20 Nov 2010 17:09:36 +0000 (12:09 -0500)]
Assorted further cleanup for integer-conversion patch.
Avoid depending on LL notation, which is likely to not work in pre-C99
compilers; don't pointlessly use INT32_MIN/INT64_MIN in code that has
the numerical value hard-wired into it anyway; remove some gratuitous
style inconsistencies between pg_ltoa and pg_lltoa; fix int2 test case
so it actually tests int2.
Robert Haas [Sat, 20 Nov 2010 15:04:48 +0000 (10:04 -0500)]
Expose quote_literal_cstr() from core.
This eliminates the need for inefficient implementions of this
functionality in both contrib/dblink and contrib/tablefunc, so remove
them. The upcoming patch implementing an in-core format() function
will also require this functionality.
Robert Haas [Sat, 20 Nov 2010 06:07:04 +0000 (01:07 -0500)]
Attempt to fix breakage caused by signed integer conversion patch.
Use INT_MIN rather than INT32_MIN as we do elsewhere in the code, and
try to work around nonexistence of INT64_MIN if necessary. Adjust the
new regression tests to something hopefully saner, per observation by
Tom Lane.
Tom Lane [Sat, 20 Nov 2010 03:28:20 +0000 (22:28 -0500)]
Fix leakage of cost_limit when multiple autovacuum workers are active.
When using default autovacuum_vac_cost_limit, autovac_balance_cost relied
on VacuumCostLimit to contain the correct global value ... but after the
first time through in a particular worker process, it didn't, because we'd
trashed it in previous iterations. Depending on the state of other autovac
workers, this could result in a steady reduction of the effective
cost_limit setting as a particular worker processed more and more tables,
causing it to go slower and slower. Spotted by Simon Poole (bug #5759).
Fix by saving and restoring the GUC variables in the loop in do_autovacuum.
In passing, improve a few comments.
Back-patch to 8.3 ... the cost rebalancing code has been buggy since it was
put in.
Tom Lane [Fri, 19 Nov 2010 22:31:50 +0000 (17:31 -0500)]
Improve relation width estimation for subqueries.
As per the ancient comment for set_rel_width, it really wasn't much good
for relations that aren't plain tables: it would never find any stats and
would always fall back on datatype-based estimates, which are often pretty
silly. Fix that by copying up width estimates from the subquery planning
process.
At some point we might want to do this for CTEs too, but that would be a
significantly more invasive patch because the sub-PlannerInfo is no longer
accessible by the time it's needed. I refrained from doing anything about
that, partly for fear of breaking the unmerged CTE-related patches.
In passing, also generate less bogus width estimates for whole-row Vars.
Tom Lane [Thu, 18 Nov 2010 22:06:57 +0000 (17:06 -0500)]
Improve plpgsql's error reporting for no-such-column cases.
Given a column reference foo.bar, where there is a composite plpgsql
variable foo but it doesn't contain a column bar, the pre-9.0 coding would
immediately throw a "record foo has no field bar" error. In 9.0 the parser
hook instead falls through to let the core parser see if it can resolve the
reference. If not, you get a complaint about "missing FROM-clause entry
for table foo", which while in some sense correct isn't terribly helpful.
Complicate things a bit so that we can throw the old error message if
neither the core parser nor the hook are able to resolve the column
reference, while not changing the behavior in any other case.
Per bug #5757 from Andrey Galkin.
Tom Lane [Thu, 18 Nov 2010 16:53:49 +0000 (11:53 -0500)]
Dept of second thoughts: don't try to push LIMIT below a SRF.
If we have Limit->Result->Sort, the Result might be projecting a tlist
that contains a set-returning function. If so, it's possible for the
SRF to sometimes return zero rows, which means we could need to fetch
more than N rows from the Sort in order to satisfy LIMIT N.
So top-N sorting cannot be used in this scenario.
Tom Lane [Thu, 18 Nov 2010 05:30:10 +0000 (00:30 -0500)]
Further fallout from the MergeAppend patch.
Fix things so that top-N sorting can be used in child Sort nodes of a
MergeAppend node, when there is a LIMIT and no intervening joins or
grouping. Actually doing this on the executor side isn't too bad,
but it's a bit messier to get the planner to cost it properly.
Per gripe from Robert Haas.
In passing, fix an oversight in the original top-N-sorting patch:
query_planner should not assume that a LIMIT can be used to make an
explicit sort cheaper when there will be grouping or aggregation in
between. Possibly this should be back-patched, but I'm not sure the
mistake is serious enough to be a real problem in practice.
Tom Lane [Wed, 17 Nov 2010 21:42:18 +0000 (16:42 -0500)]
Make TRUNCATE ... RESTART IDENTITY restart sequences transactionally.
In the previous coding, we simply issued ALTER SEQUENCE RESTART commands,
which do not roll back on error. This meant that an error between
truncating and committing left the sequences out of sync with the table
contents, with potentially bad consequences as were noted in a Warning on
the TRUNCATE man page.
To fix, create a new storage file (relfilenode) for a sequence that is to
be reset due to RESTART IDENTITY. If the transaction aborts, we'll
automatically revert to the old storage file. This acts just like a
rewriting ALTER TABLE operation. A penalty is that we have to take
exclusive lock on the sequence, but since we've already got exclusive lock
on its owning table, that seems unlikely to be much of a problem.
The interaction of this with usual nontransactional behaviors of sequence
operations is a bit weird, but it's hard to see what would be completely
consistent. Our choice is to discard cached-but-unissued sequence values
both when the RESTART is executed, and at rollback if any; but to not touch
the currval() state either time.
In passing, move the sequence reset operations to happen before not after
any AFTER TRUNCATE triggers are fired. The previous ordering was not
logically sensible, but was forced by the need to minimize inconsistency
if the triggers caused an error. Transactional rollback is a much better
solution to that.
Patch by Steve Singer, rather heavily adjusted by me.
Peter Eisentraut [Wed, 17 Nov 2010 06:08:41 +0000 (08:08 +0200)]
Additional fixes for parallel make
Add some additional dependencies to constrain the build order to prevent
parallel make from failing. In the case of src/Makefile, this is likely to be
too complicated to be worth maintaining, so just add .NOTPARALLEL to get the
old for-loop-like behavior.
More fine-tuning might be necessary for some platforms or configurations.
Magnus Hagander [Tue, 16 Nov 2010 11:40:56 +0000 (12:40 +0100)]
Send paramHandle to subprocesses as 64-bit on Win64
The handle to the shared memory segment containing startup
parameters was sent as 32-bit even on 64-bit systems. Since
HANDLEs appear to be allocated sequentially this shouldn't
be a problem until we reach 2^32 open handles in the postmaster,
but a 64-bit value should be sent across as 64-bit, and not
zero out the top 32 bits.
The GiST scan algorithm uses LSNs to detect concurrent pages splits, but
temporary indexes are not WAL-logged. We used a constant LSN for temporary
indexes, on the assumption that we don't need to worry about concurrent page
splits in temporary indexes because they're only visible to the current
session. But that assumption is wrong, it's possible to insert rows and
split pages in the same session, while a scan is in progress. For example,
by opening a cursor and fetching some rows, and INSERTing new rows before
fetching some more.
Fix by generating fake increasing LSNs, used in place of real LSNs in
temporary GiST indexes.
Tom Lane [Mon, 15 Nov 2010 19:26:55 +0000 (14:26 -0500)]
Fix aboriginal mistake in plpython's set-returning-function support.
We must stay in the function's SPI context until done calling the iterator
that returns the set result. Otherwise, any attempt to invoke SPI features
in the python code called by the iterator will malfunction. Diagnosis and
patch by Jan Urbanski, per bug report from Jean-Baptiste Quenot.
Back-patch to 8.2; there was no support for SRFs in previous versions of
plpython.
Robert Haas [Mon, 15 Nov 2010 17:42:59 +0000 (12:42 -0500)]
Add new buffers_backend_fsync field to pg_stat_bgwriter.
This new field counts the number of times that a backend which writes a
buffer out to the OS must also fsync() it. This happens when the
bgwriter fsync request queue is full, and is generally detrimental to
performance, so it's good to know when it's happening. Along the way,
log a new message at level DEBUG1 whenever we fail to hand off an fsync,
so that the problem can also be seen in examination of log files
(if the logging level is cranked up high enough).