Each WAL record now carries information about the modified relation and
block(s) in a standardized format. That makes it easier to write tools that
need that information, like pg_rewind, prefetching the blocks to speed up
recovery, etc.
There's a whole new API for building WAL records, replacing the XLogRecData
chains used previously. The new API consists of XLogRegister* functions,
which are called for each buffer and chunk of data that is added to the
record. The new API also gives more control over when a full-page image is
written, by passing flags to the XLogRegisterBuffer function.
This also simplifies the XLogReadBufferForRedo() calls. The function can dig
the relation and block number from the WAL record, so they no longer need to
be passed as arguments.
For the convenience of redo routines, XLogReader now disects each WAL record
after reading it, copying the main data part and the per-block data into
MAXALIGNed buffers. The data chunks are not aligned within the WAL record,
but the redo routines can assume that the pointers returned by XLogRecGet*
functions are. Redo routines are now passed the XLogReaderState, which
contains the record in the already-disected format, instead of the plain
XLogRecord.
The new record format also makes the fixed size XLogRecord header smaller,
by removing the xl_len field. The length of the "main data" portion is now
stored at the end of the WAL record, and there's a separate header after
XLogRecord for it. The alignment padding at the end of XLogRecord is also
removed. This compansates for the fact that the new format would otherwise
be more bulky than the old format.
Reviewed by Andres Freund, Amit Kapila, Michael Paquier, Alvaro Herrera,
Fujii Masao.
There was a window in RestoreBackupBlock where a page would be zeroed out,
but not yet locked. If a backend pinned and locked the page in that window,
it saw the zeroed page instead of the old page or new page contents, which
could lead to missing rows in a result set, or errors.
To fix, replace RBM_ZERO with RBM_ZERO_AND_LOCK, which atomically pins,
zeroes, and locks the page, if it's not in the buffer cache already.
In stable branches, the old RBM_ZERO constant is renamed to RBM_DO_NOT_USE,
to avoid breaking any 3rd party extensions that might use RBM_ZERO. More
importantly, this avoids renumbering the other enum values, which would
cause even bigger confusion in extensions that use ReadBufferExtended, but
haven't been recompiled.
Backpatch to all supported versions; this has been racy since hot standby
was introduced.
The previous code, perhaps out of concern for avoid memory leaks, formed
the tuple in one memory context and then copied it to another memory
context. However, this doesn't appear to be necessary, since
index_form_tuple and the functions it calls take precautions against
leaking memory. In my testing, building the tuple directly inside the
sort context shaves several percent off the index build time.
Rearrange things so we do that.
Patch by me. Review by Amit Kapila, Tom Lane, Andres Freund.
Since C99, it's been standard for printf and friends to accept a "z" size
modifier, meaning "whatever size size_t has". Up to now we've generally
dealt with printing size_t values by explicitly casting them to unsigned
long and using the "l" modifier; but this is really the wrong thing on
platforms where pointers are wider than longs (such as Win64). So let's
start using "z" instead. To ensure we can do that on all platforms, teach
src/port/snprintf.c to understand "z", and add a configure test to force
use of that implementation when the platform's version doesn't handle "z".
Having done that, modify a bunch of places that were using the
unsigned-long hack to use "z" instead. This patch doesn't pretend to have
gotten everyplace that could benefit, but it catches many of them. I made
an effort in particular to ensure that all uses of the same error message
text were updated together, so as not to increase the number of
translatable strings.
It's possible that this change will result in format-string warnings from
pre-C99 compilers. We might have to reconsider if there are any popular
compilers that will warn about this; but let's start by seeing what the
buildfarm thinks.
Andres Freund, with a little additional work by me
This avoids an assumption about the signed number representation. It is
anticipated to have no functional changes on supported configurations;
many two's complement assumptions remain elsewhere.
Per a suggestion from Andres Freund.
MarkBufferDirtyHint() writes WAL, and should know if it's got a
standard buffer or not. Currently, the only callers where buffer_std
is false are related to the FSM.
In passing, rename XLOG_HINT to XLOG_FPI, which is more descriptive.
Back-patch to 9.3.
Checksums are set immediately prior to flush out of shared buffers
and checked when pages are read in again. Hint bit setting will
require full page write when block is dirtied, which causes various
infrastructure changes. Extensive comments, docs and README.
WARNING message thrown if checksum fails on non-all zeroes page;
ERROR thrown but can be disabled with ignore_checksum_failure = on.
Feature enabled by an initdb option, since transition from option off
to option on is long and complex and has not yet been implemented.
Default is not to use checksums.
Checksum used is WAL CRC-32 truncated to 16-bits.
Simon Riggs, Jeff Davis, Greg Smith
Wide input and assistance from many community members. Thank you.
This patch addresses the problem that applications currently have to
extract object names from possibly-localized textual error messages,
if they want to know for example which index caused a UNIQUE_VIOLATION
failure. It adds new error message fields to the wire protocol, which
can carry the name of a table, table column, data type, or constraint
associated with the error. (Since the protocol spec has always instructed
clients to ignore unrecognized field types, this should not create any
compatibility problem.)
Support for providing these new fields has been added to just a limited set
of error reports (mainly, those in the "integrity constraint violation"
SQLSTATE class), but we will doubtless add them to more calls in future.
Pavel Stehule, reviewed and extensively revised by Peter Geoghegan, with
additional hacking by Tom Lane.
Avoid using LockPage(rel, 0, lockmode) to protect against changes to
the bucket mapping. Instead, an exclusive buffer content lock is now
viewed as sufficient permission to modify the metapage, and a shared
buffer content lock is used when such modifications need to be
prevented. This more relaxed locking regimen makes it possible that,
when we're busy getting a heavyweight bucket on the bucket we intend
to search or insert into, a bucket split might occur underneath us.
To compenate for that possibility, we use a loop-and-retry system:
release the metapage content lock, acquire the heavyweight lock on the
target bucket, and then reacquire the metapage content lock and check
that the bucket mapping has not changed. Normally it hasn't, and
we're done. But if by chance it has, we simply unlock the metapage,
release the heavyweight lock we acquired previously, lock the new
bucket, and loop around again. Even in the worst case we cannot loop
very many times here, since we don't split the same bucket again until
we've split all the other buckets, and 2^N gets big pretty fast.
This results in greatly improved concurrency, because we're
effectively replacing two lwlock acquire-and-release cycles in
exclusive mode (on one of the lock manager locks) with a single
acquire-and-release cycle in shared mode (on the metapage buffer
content lock). Testing shows that it's still not quite as good as
btree; for that, we'd probably have to find some way of getting rid
of the heavyweight bucket locks as well, which does not appear
straightforward.
Patch by me, review by Jeff Janes.
The latter was already the dominant use, and it's preferable because
in C the convention is that intXX means XX bits. Therefore, allowing
mixed use of int2, int4, int8, int16, int32 is obviously confusing.
Remove the typedefs for int2 and int4 for now. They don't seem to be
widely used outside of the PostgreSQL source tree, and the few uses
can probably be cleaned up by the time this ships.
For those variables only used when asserts are enabled, use a new
macro PG_USED_FOR_ASSERTS_ONLY, which expands to
__attribute__((unused)) when asserts are not enabled.
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.
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...
The contents of an unlogged table are WAL-logged; thus, they are not
available on standby servers and are truncated whenever the database
system enters recovery. Indexes on unlogged tables are also unlogged.
Unlogged GiST indexes are not currently supported.
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.
Teodor Sigaev and Tom Lane
In the new API introduced by my patch to include the backend ID in
temprel filenames, the last argument to smrgextend() became skipFsync
rather than isTemp, but these calls didn't get the memo. It's not
really a problem to pass rel->rd_istemp rather than just plain false,
because smgrextend() now automatically skips the fsync for temprels
anyway, but this seems cleaner and saves some minute number of cycles.
we're not going to support that anymore.
I did keep the 64-bit-CRC-with-32-bit-arithmetic code, since it has a
performance excuse to live. It's a bit moot since that's all ifdef'd
out, of course.
This is more in keeping with modern practice, and is a first step towards
porting to Win64 (which has sizeof(pointer) > sizeof(long)).
Tsutomu Yamada, Magnus Hagander, Tom Lane
that it can scribble on scan->xs_ctup.t_self while following HOT chains,
so we can't rely on that to stay valid between hashgettuple() calls.
Introduce a private variable in HashScanOpaque, instead.
hash indexes keep entries sorted by hash value. First, the original plans for
concurrency assumed that insertions would happen only at the end of a page,
which is no longer true; this could cause scans to transiently fail to find
index entries in the presence of concurrent insertions. We can compensate
by teaching scans to re-find their position after re-acquiring read locks.
Second, neither the bucket split nor the bucket compaction logic had been
fixed to preserve hashvalue ordering, so application of either of those
processes could lead to permanent corruption of an index, in the sense
that searches might fail to find entries that are present.
This patch fixes the split and compaction logic to preserve hashvalue
ordering, but it cannot do anything about pre-existing corruption. We will
need to recommend reindexing all hash indexes in the 8.4.2 release notes.
To buy back the performance loss hereby induced in split and compaction,
fix them to use PageIndexMultiDelete instead of retail PageIndexDelete
operations. We might later want to do something with qsort'ing the
page contents rather than doing a binary search for each insertion,
but that seemed more invasive than I cared to risk in a back-patch.
Per bug #5157 from Jeff Janes and subsequent investigation.
friends). This code has all been ifdef'd out for many years, and doesn't
seem to have any prospect of becoming any more useful in the future.
EXPLAIN ANALYZE is what people use in practice, and I think if we did want
process-wide counters we'd be more likely to put in dtrace events for that
than try to resurrect this code. Get rid of it so as to have one less detail
to worry about while refactoring execMain.c.
The current implementation fires an AFTER ROW trigger for each tuple that
looks like it might be non-unique according to the index contents at the
time of insertion. This works well as long as there aren't many conflicts,
but won't scale to massive unique-key reassignments. Improving that case
is a TODO item.
Dean Rasheed
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.
points where we step right or left to the next page. This should ensure
reasonable response time to a query cancel request during an unsuccessful
index scan, as seen in recent gripe from Marc Cousin. It's a bit trickier
than it might seem at first glance, because CHECK_FOR_INTERRUPTS() is a no-op
if executed while holding a buffer lock. So we have to do it just at the
point where we've dropped one page lock and not yet acquired the next.
Remove CHECK_FOR_INTERRUPTS calls at the top level of btgetbitmap and
hashgetbitmap, since they're pointless given the added checks.
I think that GIST is okay already --- at least, there's a CHECK_FOR_INTERRUPTS
at a plausible-looking place in gistnext(). I don't claim to know GIN well
enough to try to poke it for this, if indeed it has a problem at all.
This is a pre-existing issue, but in view of the lack of prior complaints
I'm not going to risk back-patching.
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
a more complete framework for writing custom option processing routines
by user-defined access methods.
Catalog version bumped due to the general API changes, which are going to
affect user-defined "amoptions" routines.
for inserting tuples in increasing TID order. It's not clear whether this
fully explains Ivan Sergio Borgonovo's complaint, but simple testing
confirms that a scan that doesn't start at block 0 can slow GIN build by
a factor of three or four.
Backpatch to 8.3. Sync scan didn't exist before that.
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.
value. This means that hash index lookups are always lossy and have to be
rechecked when the heap is visited; however, the gain in index compactness
outweighs this when the indexed values are wide. Also, we only need to
perform datatype comparisons when the hash codes match exactly, rather than
for every entry in the hash bucket; so it could also win for datatypes that
have expensive comparison functions. A small additional win is gained by
keeping hash index pages sorted by hash code and using binary search to reduce
the number of index tuples we have to look at.
Xiao Meng
This commit also incorporates Zdenek Kotala's patch to isolate hash metapages
and hash bitmaps a bit better from the page header datastructures.
of multiple forks, and each fork can be created and grown separately.
The bulk of this patch is about changing the smgr API to include an extra
ForkNumber argument in every smgr function. Also, smgrscheduleunlink and
smgrdounlink no longer implicitly call smgrclose, because other forks might
still exist after unlinking one. The callers of those functions have been
modified to call smgrclose instead.
This patch in itself doesn't have any user-visible effect, but provides the
infrastructure needed for upcoming patches. The additional forks envisioned
are a rewritten FSM implementation that doesn't rely on a fixed-size shared
memory block, and a visibility map to allow skipping portions of a table in
VACUUM that have no dead tuples.
