Standard English uses "may", "can", and "might" in different ways:
may - permission, "You may borrow my rake."
can - ability, "I can lift that log."
might - possibility, "It might rain today."
Unfortunately, in conversational English, their use is often mixed, as
in, "You may use this variable to do X", when in fact, "can" is a better
choice. Similarly, "It may crash" is better stated, "It might crash".
currentMarkData from IndexScanDesc to the opaque structs for the
AMs that need this information (currently gist and hash).
Patch from Heikki Linnakangas, fixes by Neil Conway.
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.
agreed these symbols are less easily confused. I made new pg_operator
entries (with new OIDs) for the old names, so as to provide backward
compatibility while making it pretty easy to remove the old names in
some future release cycle. This commit only touches the core datatypes,
contrib will be fixed separately.
operation every so often. This improves the usefulness of PITR log
shipping for hot standby: formerly, if the standby server crashed, it
was necessary to restart it from the last base backup and replay all
the WAL since then. Now it will only need to reread about the same
amount of WAL as the master server would. The behavior might also
come in handy during a long PITR replay sequence. Simon Riggs,
with some editorialization by 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.
discussion (including making def_arg allow reserved words), add missed
opt_definition for UNIQUE case. Put the reloptions support code in a less
random place (I chose to make a new file access/common/reloptions.c).
Eliminate header inclusion creep. Make the index options functions safely
user-callable (seems like client apps might like to be able to test validity
of options before trying to make an index). Reduce overhead for normal case
with no options by allowing rd_options to be NULL. Fix some unmaintainably
klugy code, including getting rid of Natts_pg_class_fixed at long last.
Some stylistic cleanup too, and pay attention to keeping comments in sync
with code.
Documentation still needs work, though I did fix the omissions in
catalogs.sgml and indexam.sgml.
* new split algorithm (as proposed in http://archives.postgresql.org/pgsql-hackers/2006-06/msg00254.php)
* possible call pickSplit() for second and below columns
* add spl_(l|r)datum_exists to GIST_SPLITVEC -
pickSplit should check its values to use already defined
spl_(l|r)datum for splitting. pickSplit should set
spl_(l|r)datum_exists to 'false' (if they was 'true') to
signal to caller about using spl_(l|r)datum.
* support for old pickSplit(): not very optimal
but correct split
* remove 'bytes' field from GISTENTRY: in any case size of
value is defined by it's type.
* split GIST_SPLITVEC to two structures: one for using in picksplit
and second - for internal use.
* some code refactoring
* support of subsplit to rtree opclasses
TODO: add support of subsplit to contrib modules
* some refactoring and simplify code int gistutil.c and gist.c
* now in some cases it can be called used-defined
picksplit method for non-first column in index, but here
is a place to do more.
* small fix of docs related to support NULL.
sections now isn't nested. All user-defined functions now is
called outside critsections. Small improvements in WAL
protocol.
TODO: improve XLOG replay
(relpages/reltuples). To do this, create formal support in heapam.c for
"overwrite" tuple updates (including xlog replay capability) and use that
instead of the ad-hoc overwrites we'd been using in VACUUM and CREATE INDEX.
Take the responsibility for updating stats during CREATE INDEX out of the
individual index AMs, and do it where it belongs, in catalog/index.c. Aside
from being more modular, this avoids having to update the same tuple twice in
some paths through CREATE INDEX. It's probably not measurably faster, but
for sure it's a lot cleaner than before.
This formulation requires every AM to provide amvacuumcleanup, unlike before,
but it's surely a whole lot cleaner. Also, add an 'amstorage' column to
pg_am so that we can get rid of hardwired knowledge in DefineOpClass().
misleadingly-named WriteBuffer routine, and instead require routines that
change buffer pages to call MarkBufferDirty (which does exactly what it says).
We also require that they do so before calling XLogInsert; this takes care of
the synchronization requirement documented in SyncOneBuffer. Note that
because bufmgr takes the buffer content lock (in shared mode) while writing
out any buffer, it doesn't matter whether MarkBufferDirty is executed before
the buffer content change is complete, so long as the content change is
completed before releasing exclusive lock on the buffer. So it's OK to set
the dirtybit before we fill in the LSN.
This eliminates the former kluge of needing to set the dirtybit in LockBuffer.
Aside from making the code more transparent, we can also add some new
debugging assertions, in particular that the caller of MarkBufferDirty must
hold the buffer content lock, not merely a pin.
torn-page problems. This introduces some issues of its own, mainly
that there are now some critical sections of unreasonably broad scope,
but it's a step forward anyway. Further cleanup will require some
code refactoring that I'd prefer to get Oleg and Teodor involved in.
This commit doesn't make much functional change, but it does eliminate some
duplicated code --- for instance, PageIsNew tests are now done inside
XLogReadBuffer rather than by each caller.
The GIST xlog code still needs a lot of love, but I'll worry about that
separately.
when an error occurs during xlog replay. Also, replace the former risky
'write into a fixed-size buffer with no overflow detection' API for XLOG
record description routines; use an expansible StringInfo instead. (The
latter accounts for most of the patch bulk.)
Qingqing Zhou
partial. None of the existing AMs do anything useful except counting
tuples when there's nothing to delete, and we can get a tuple count
from the heap as long as it's not a partial index. (hash actually can
skip anyway because it maintains a tuple count in the index metapage.)
GIST is not currently able to exploit this optimization because, due to
failure to index NULLs, GIST is always effectively partial. Possibly
we should fix that sometime.
Simon Riggs w/ some review by Tom Lane.
isn't being used anywhere anymore, and there seems no point in a generic
index_keytest() routine when two out of three remaining access methods
aren't using it. Also, add a comment documenting a convention for
letting access methods define private flag bits in ScanKey sk_flags.
There are no such flags at the moment but I'm thinking about changing
btree's handling of "required keys" to use flag bits in the keys
rather than a count of required key positions. Also, if some AM did
still want SK_NEGATE then it would be reasonable to treat it as a private
flag bit.
comment line where output as too long, and update typedefs for /lib
directory. Also fix case where identifiers were used as variable names
in the backend, but as typedefs in ecpg (favor the backend for
indenting).
Backpatch to 8.1.X.
generated by bitmap index scans. Along the way, simplify and speed up
the code for counting sequential and index scans; it was both confusing
and inefficient to be taking care of that in the per-tuple loops, IMHO.
initdb forced because of internal changes in pg_stat view definitions.
on a page, as suggested by ITAGAKI Takahiro. Also, change a few places
that were using some other estimates of max-items-per-page to consistently
use MaxOffsetNumber. This is conservatively large --- we could have used
the new MaxHeapTuplesPerPage macro, or a similar one for index tuples ---
but those places are simply declaring a fixed-size buffer and assuming it
will work, rather than actively testing for overrun. It seems safer to
size these buffers in a way that can't overflow even if the page is
corrupt.
basic regression tests for GiST to the standard regression tests.
I took the opportunity to add an rtree-equivalent gist opclass for
circles; the contrib version only covered boxes and polygons, but
indexing circles is very handy for distance searches.
