Further fallout from commit c29aff959: there are some files that need
<float.h>, and were getting it from datatype/timestamp.h, but it was not
apparent in my (tgl's) testing because the requirement for <float.h>
exists only on certain Windows toolchains.
Report and patch by David Rowley.
Discussion: https://postgr.es/m/CAKJS1f-BHceaFzZScFapDV48gUVM2CAOBfhkgffdqXzFb+kwew@mail.gmail.com
Previously, only IndexTuple format was supported for the output data of
an index-only scan. This is fine for btree, which is just returning a
verbatim index tuple anyway. It's not so fine for SP-GiST, which can
return reconstructed data that's much larger than a page.
To fix, extend the index AM API so that index-only scan data can be
returned in either HeapTuple or IndexTuple format. There's other ways
we could have done it, but this way avoids an API break for index AMs
that aren't concerned with the issue, and it costs little except a couple
more fields in IndexScanDescs.
I changed both GiST and SP-GiST to use the HeapTuple method. I'm not
very clear on whether GiST can reconstruct data that's too large for an
IndexTuple, but that seems possible, and it's not much of a code change to
fix.
Per a complaint from Vik Fearing. Reviewed by Jason Li.
Discussion: https://postgr.es/m/49527f79-530d-0bfe-3dad-d183596afa92@2ndquadrant.fr
With Asserts off, these variables are set but never used, resulting
in warnings from pickier compilers. Fix that with our standard solution.
Per report from Jeff Janes.
Per discussion, we should provide such functions to replace the lost
ability to discover AM properties by inspecting pg_am (cf commit
65c5fcd35). The added functionality is also meant to displace any code
that was looking directly at pg_index.indoption, since we'd rather not
believe that the bit meanings in that field are part of any client API
contract.
As future-proofing, define the SQL API to not assume that properties that
are currently AM-wide or index-wide will remain so unless they logically
must be; instead, expose them only when inquiring about a specific index
or even specific index column. Also provide the ability for an index
AM to override the behavior.
In passing, document pg_am.amtype, overlooked in commit 473b93287.
Andrew Gierth, with kibitzing by me and others
Discussion: <87mvl5on7n.fsf@news-spur.riddles.org.uk>
The reverted changes were intended to force a choice of whether any
newly-added BufferGetPage() calls needed to be accompanied by a
test of the snapshot age, to support the "snapshot too old"
feature. Such an accompanying test is needed in about 7% of the
cases, where the page is being used as part of a scan rather than
positioning for other purposes (such as DML or vacuuming). The
additional effort required for back-patching, and the doubt whether
the intended benefit would really be there, have indicated it is
best just to rely on developers to do the right thing based on
comments and existing usage, as we do with many other conventions.
This change should have little or no effect on generated executable
code.
Motivated by the back-patching pain of Tom Lane and Robert Haas
This patch is a no-op patch which is intended to reduce the chances
of failures of omission once the functional part of the "snapshot
too old" patch goes in. It adds parameters for snapshot, relation,
and an enum to specify whether the snapshot age check needs to be
done for the page at this point. This initial patch passes NULL
for the first two new parameters and BGP_NO_SNAPSHOT_TEST for the
third. The follow-on patch will change the places where the test
needs to be made.
This patch reduces pg_am to just two columns, a name and a handler
function. All the data formerly obtained from pg_am is now provided
in a C struct returned by the handler function. This is similar to
the designs we've adopted for FDWs and tablesample methods. There
are multiple advantages. For one, the index AM's support functions
are now simple C functions, making them faster to call and much less
error-prone, since the C compiler can now check function signatures.
For another, this will make it far more practical to define index access
methods in installable extensions.
A disadvantage is that SQL-level code can no longer see attributes
of index AMs; in particular, some of the crosschecks in the opr_sanity
regression test are no longer possible from SQL. We've addressed that
by adding a facility for the index AM to perform such checks instead.
(Much more could be done in that line, but for now we're content if the
amvalidate functions more or less replace what opr_sanity used to do.)
We might also want to expose some sort of reporting functionality, but
this patch doesn't do that.
Alexander Korotkov, reviewed by Petr Jelínek, and rather heavily
editorialized on by me.
We cannot use the index's tuple descriptor directly to describe the index
tuples returned in an index-only scan. That's because the index might use
a different datatype for the values stored on disk than the type originally
indexed. As long as they were both pass-by-ref, it worked, but will not work
for pass-by-value types of different sizes. I noticed this as a crash when I
started hacking a patch to add fetch methods to btree_gist.
This adds a new GiST opclass method, 'fetch', which is used to reconstruct
the original Datum from the value stored in the index. Also, the 'canreturn'
index AM interface function gains a new 'attno' argument. That makes it
possible to use index-only scans on a multi-column index where some of the
opclasses support index-only scans but some do not.
This patch adds support in the box and point opclasses. Other opclasses
can added later as follow-on patches (btree_gist would be particularly
interesting).
Anastasia Lubennikova, with additional fixes and modifications by me.
The reason this wasn't supported before was that GiST indexes need an
increasing sequence to detect concurrent page-splits. In a regular WAL-
logged GiST index, the LSN of the page-split record is used for that
purpose, and in a temporary index, we can get away with a backend-local
counter. Neither of those methods works for an unlogged relation.
To provide such an increasing sequence of numbers, create a "fake LSN"
counter that is saved and restored across shutdowns. On recovery, unlogged
relations are blown away, so the counter doesn't need to survive that
either.
Jeevan Chalke, based on discussions with Robert Haas, Tom Lane and me.
When considering a non-last column in a multi-column GiST index,
gistsplit.c tries to improve on the split chosen by the opclass-specific
pickSplit function by considering penalties for the next column. However,
there were two bugs in this code: it failed to recompute the union keys for
the leftmost index columns, even though these might well change after
reassigning tuples; and it included the old union keys in the recomputation
for the columns it did recompute, so that those keys couldn't get smaller
even if they should. The first problem could result in an invalid index
in which searches wouldn't find index entries that are in fact present;
the second would make the index less efficient to search.
Both of these errors were caused by misuse of gistMakeUnionItVec, whose
API was designed in a way that just begged such errors to be made. There
is no situation in which it's safe or useful to compute the union keys for
a subset of the index columns, and there is no caller that wants any
previous union keys to be included in the computation; so the undocumented
choice to treat the union keys as in/out rather than pure output parameters
is a waste of code as well as being dangerous.
Hence, rather than just making a minimal patch, I've changed the API of
gistMakeUnionItVec to remove the "startkey" parameter (it now always
processes all index columns) and treat the attr/isnull arrays as purely
output parameters.
In passing, also get rid of a couple of unnecessary and dangerous uses
of static variables in gistutil.c. It's remarkable that the one in
gistMakeUnionKey hasn't given us portability troubles before now, because
in addition to posing a re-entrancy hazard, it was unsafely assuming that
a static char[] array would have at least Datum alignment.
Per investigation of a trouble report from Tomas Vondra. (There are also
some bugs in contrib/btree_gist to be fixed, but that seems like material
for a separate patch.) Back-patch to all supported branches.
When descending the tree for an insert, and there are multiple equally good
pages we could insert to, make the choice in random. Previously, we would
always choose the tuple with lowest offset number. That meant that when two
non-leaf pages overlap - in the extreme case they might have exactly the same
key - all but the first such page went unused. That wasn't optimal for space
usage; if you deleted some tuples from the non-first pages, the space would
never be reused.
With this patch, the other pages are sometimes chosen too, although there's
still a heavy bias towards low-offset tuples, so that we don't lose cache
locality when doing a lot of inserts with similar keys.
Original idea by Alexander Korotkov, although this patch version was written
by me and copy-edited by Tom Lane.
This is mostly cosmetic, but it does eliminate a speculative portability
issue. The previous coding ignored the fact that sum_grow could easily
overflow (in fact, it could be summing multiple IEEE float infinities).
On a platform where that didn't guarantee to produce a positive result,
the code would misbehave. In any case, it was less than readable.
Every time the best-tuple-found-so-far changes, we need to reset all
the penalty values in which_grow[] to the penalties for the new best
tuple. The old code failed to do this, resulting in inferior index
quality.
The original patch from Alexander Korotkov was just two lines; I took
the liberty of fleshing that out by adding a bunch of comments that I
hope will make this logic easier for others to understand than it was
for me.
This simplifies code that needs to do arithmetic on XLogRecPtrs.
To avoid changing on-disk format of data pages, the LSN on data pages is
still stored in the old format. That should keep pg_upgrade happy. However,
we have XLogRecPtrs embedded in the control file, and in the structs that
are sent over the replication protocol, so this changes breaks compatibility
of pg_basebackup and server. I didn't do anything about this in this patch,
per discussion on -hackers, the right thing to do would to be to change the
replication protocol to be architecture-independent, so that you could use
a newer version of pg_receivexlog, for example, against an older server
version.
Use of a randomly chosen large value was never exactly graceful, and
now that there are penalty functions that are intentionally using infinity,
it doesn't seem like a good idea for null-vs-not-null to be using something
less.
When building a GiST index that doesn't fit in cache, buffers are attached
to some internal nodes in the index. This speeds up the build by avoiding
random I/O that would otherwise be needed to traverse all the way down the
tree to the find right leaf page for tuple.
Alexander Korotkov
Apparently sane-looking penalty code might return small negative values,
for example because of roundoff error. This will confuse places like
gistchoose(). Prevent problems by clamping negative penalty values to
zero. (Just to be really sure, I also made it force NaNs to zero.)
Back-patch to all supported branches.
Alexander Korotkov
Experimentation with contrib/btree_gist shows that the majority of the GIST
support functions potentially need collation information. Safest policy
seems to be to pass it to all of them, instead of making assumptions about
which ones could possibly need it.
cleanup stage to finish incomplete inserts or splits anymore. There was two
reasons for the cleanup step:
1. When a new tuple was inserted to a leaf page, the downlink in the parent
needed to be updated to contain (ie. to be consistent with) the new key.
Updating the parent in turn might require recursively updating the parent of
the parent. We now handle that by updating the parent while traversing down
the tree, so that when we insert the leaf tuple, all the parents are already
consistent with the new key, and the tree is consistent at every step.
2. When a page is split, we need to insert the downlink for the new right
page(s), and update the downlink for the original page to not include keys
that moved to the right page(s). We now handle that by setting a new flag,
F_FOLLOW_RIGHT, on the non-rightmost pages in the split. When that flag is
set, scans always follow the rightlink, regardless of the NSN mechanism used
to detect concurrent page splits. That way the tree is consistent right after
split, even though the downlink is still missing. This is very similar to the
way B-tree splits are handled. When the downlink is inserted in the parent,
the flag is cleared. To keep the insertion algorithm simple, when an
insertion sees an incomplete split, indicated by the F_FOLLOW_RIGHT flag, it
finishes the split before doing anything else.
These changes allow removing the whole "invalid tuple" mechanism, but I
retained the scan code to still follow invalid tuples correctly. While we
don't create any such tuples anymore, we want to handle them gracefully in
case you pg_upgrade a GiST index that has them. If we encounter any on an
insert, though, we just throw an error saying that you need to REINDEX.
The issue that got me into doing this is that if you did a checkpoint while
an insert or split was in progress, and the checkpoint finishes quickly so
that there is no WAL record related to the insert between RedoRecPtr and the
checkpoint record, recovery from that checkpoint would not know to finish
the incomplete insert. IOW, we have the same issue we solved with the
rm_safe_restartpoint mechanism during normal operation too. It's highly
unlikely to happen in practice, and this fix is far too large to backpatch,
so we're just going to live with in previous versions, but this refactoring
fixes it going forward.
With this patch, you don't get the annoying
'index "FOO" needs VACUUM or REINDEX to finish crash recovery' notices
anymore if you crash at an unfortunate moment.
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.
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.
free space information is stored in a dedicated FSM relation fork, with each
relation (except for hash indexes; they don't use FSM).
This eliminates the max_fsm_relations and max_fsm_pages GUC options; remove any
trace of them from the backend, initdb, and documentation.
Rewrite contrib/pg_freespacemap to match the new FSM implementation. Also
introduce a new variant of the get_raw_page(regclass, int4, int4) function in
contrib/pageinspect that let's you to return pages from any relation fork, and
a new fsm_page_contents() function to inspect the new FSM pages.
SizeOfPageHeaderData instead of sizeof(PageHeaderData) in places where that
makes the code clearer, and avoid casting between Page and PageHeader where
possible. Zdenek Kotala, with some additional cleanup by Heikki Linnakangas.
I did not apply the parts of the proposed patch that would have resulted in
slightly changing the on-disk format of hash indexes; it seems to me that's
not a win as long as there's any chance of having in-place upgrade for 8.4.
corresponding struct definitions. This allows other headers to avoid including
certain highly-loaded headers such as rel.h and relscan.h, instead using just
relcache.h, heapam.h or genam.h, which are more lightweight and thus cause less
unnecessary dependencies.
forks. XLogOpenRelation() and the associated light-weight relation cache in
xlogutils.c is gone, and XLogReadBuffer() now takes a RelFileNode as argument,
instead of Relation.
For functions that still need a Relation struct during WAL replay, there's a
new function called CreateFakeRelcacheEntry() that returns a fake entry like
XLogOpenRelation() used to.
unnecessary #include lines in it. Also, move some tuple routine prototypes and
macros to htup.h, which allows removal of heapam.h inclusion from some .c
files.
For this to work, a new header file access/sysattr.h needed to be created,
initially containing attribute numbers of system columns, for pg_dump usage.
While at it, make contrib ltree, intarray and hstore header files more
consistent with our header style.
columns, and the new version can be stored on the same heap page, we no longer
generate extra index entries for the new version. Instead, index searches
follow the HOT-chain links to ensure they find the correct tuple version.
In addition, this patch introduces the ability to "prune" dead tuples on a
per-page basis, without having to do a complete VACUUM pass to recover space.
VACUUM is still needed to clean up dead index entries, however.
Pavan Deolasee, with help from a bunch of other people.
than two independent bits (one of which was never used in heap pages anyway,
or at least hadn't been in a very long time). This gives us flexibility to
add the HOT notions of redirected and dead item pointers without requiring
anything so klugy as magic values of lp_off and lp_len. The state values
are chosen so that for the states currently in use (pre-HOT) there is no
change in the physical representation.
