when we first read the page, rather than checking them one at a time.
This allows us to take and release the buffer content lock just once
per page, instead of once per tuple.  Since it's a shared lock the
contention penalty for holding the lock longer shouldn't be too bad.
We can safely do this only when using an MVCC snapshot; else the
assumption that visibility won't change over time is uncool.  Therefore
there are now two code paths depending on the snapshot type.  I also
made the same change in nodeBitmapHeapscan.c, where it can be done always
because we only support MVCC snapshots for bitmap scans anyway.
Also make some incidental cleanups in the APIs of these functions.
Per a suggestion from Qingqing Zhou.

insufficient paranoia in code that follows t_ctid links.  (We must do both
because even with VACUUM doing it properly, the intermediate state with
a dangling t_ctid link is visible concurrently during lazy VACUUM, and
could be seen afterwards if either type of VACUUM crashes partway through.)
Also try to improve documentation about what's going on.  Patch is a bit
bulky because passing the XMAX information around required changing the
APIs of some low-level heapam.c routines, but it's not conceptually very
complicated.  Per trouble report from Teodor and subsequent analysis.
This needs to be back-patched, but I'll do that after 8.1 beta is out.

communication structure, and make it its own module with its own lock.
This should reduce contention at least a little, and it definitely makes
the code seem cleaner.  Per my recent proposal.

rather than an integer, and fix the associated fallout. From Alvaro
Herrera.

Tag appropriate files for rc3

Also performed an initial run through of upgrading our Copyright date to
extend to 2005 ... first run here was very simple ... change everything
where: grep 1996-2004 && the word 'Copyright' ... scanned through the
generated list with 'less' first, and after, to make sure that I only
picked up the right entries ...

http://archives.postgresql.org/pgsql-hackers/2004-10/msg00464.php.
This fix is intended to be permanent: it moves the responsibility for
calling SetBufferCommitInfoNeedsSave() into the tqual.c routines,
eliminating the requirement for callers to test whether t_infomask changed.
Also, tighten validity checking on buffer IDs in bufmgr.c --- several
routines were paranoid about out-of-range shared buffer numbers but not
about out-of-range local ones, which seems a tad pointless.

pg_subtrans --- what we need is the oldest xmin of any snapshot in use
in the current top transaction.  Introduce a new variable TransactionXmin
to play this role.  Fixes intermittent regression failure reported by
Neil Conway.

mode see a fresh snapshot for each command in the function, rather than
using the latest interactive command's snapshot.  Also, suppress fresh
snapshots as well as CommandCounterIncrement inside STABLE and IMMUTABLE
functions, instead using the snapshot taken for the most closely nested
regular query.  (This behavior is only sane for read-only functions, so
the patch also enforces that such functions contain only SELECT commands.)
As per my proposal of 6-Sep-2004; I note that I floated essentially the
same proposal on 19-Jun-2002, but that discussion tailed off without any
action.  Since 8.0 seems like the right place to be taking possibly
nontrivial backwards compatibility hits, let's get it done now.

((Snapshot) NULL) can no longer be confused with a valid snapshot,
as per my recent suggestion.  Define a macro InvalidSnapshot for 0.
Use InvalidSnapshot instead of SnapshotAny as the do-nothing special
case for heap_update and heap_delete crosschecks; this seems a little
cleaner even though the behavior is really the same.

make sure the $Id tags are converted to $PostgreSQL as well ...

discussion on pgsql-hackers: in READ COMMITTED mode we just have to force
a QuerySnapshot update in the trigger, but in SERIALIZABLE mode we have
to run the scan under a current snapshot and then complain if any rows
would be updated/deleted that are not visible in the transaction snapshot.

to allow es_snapshot to be set to SnapshotNow rather than a query snapshot.
This solves a bug reported by Wade Klaver, wherein triggers fired as a
result of RI cascade updates could misbehave.

free'd for every transaction or statement, respectively.  This patch
puts these data structures into static memory, thus saving a few CPU
cycles and two malloc calls per transaction or (in isolation level
READ COMMITTED) per query.

Manfred Koizar

older than current Xmin; we don't have to wait till it's older than
GlobalXmin.

transaction, so as to avoid returning them out of the index AM.  Saves
repeated heap_fetch operations on frequently-updated rows.  Also detect
queries on unique keys (equality to all columns of a unique index), and
don't bother continuing scan once we have found first match.

Killing is implemented in the btree and hash AMs, but not yet in rtree
or gist, because there isn't an equally convenient place to do it in
those AMs (the outer amgetnext routine can't do it without re-pinning
the index page).

Did some small cleanup on APIs of HeapTupleSatisfies, heap_fetch, and
index_insert to make this a little easier.

a frozen (copied) snapshot too.  Move execMain's snapshot copying code
out into a subroutine in case we find other places that need it.

in snapshots, per my proposal of a few days ago.  Also, tweak heapam.c
routines (heap_insert, heap_update, heap_delete, heap_mark4update) to
be passed the command ID to use, instead of doing GetCurrentCommandID.
For catalog updates they'll still get passed current command ID, but
for updates generated from the main executor they'll get passed the
command ID saved in the snapshot the query is using.  This should fix
some corner cases associated with functions and triggers that advance
current command ID while an outer query is still in progress.

mess up after an aborted VACUUM FULL, per today's pghackers discussion.
Add a suitable HeapTupleSatisfiesToast routine.  Remove useless special-
case test in HeapTupleSatisfiesVisibility macro for xmax =
BootstrapTransactionId; perhaps that was needed at one time, but it's
a waste of cycles now, not to mention actively wrong for SnapshotAny.
Along the way, add some much-needed comments to tqual.c, and simplify
toast_fetch_datum, which no longer needs to assume it may see chunks
out-of-order.

initdb/regression tests pass.

spacing.  Also adds space for one-line comments.

tests pass.

documentation to come, but the code is all here.  initdb forced.

(TransactionIdPrecedes, TransactionIdFollows, etc).  First step on the
way to transaction ID wrap solution ...

validity checking rules for VACUUM.  Make some other rearrangements of the
VACUUM code to allow more code to be shared between full and lazy VACUUM.
Minor code cleanups and added comments for TransactionId manipulations.

Cygwin with the possible exception of mSQL-interface.  Since I don't
have mSQL installed, I skipped this tool.

Except for dealing with a missing getopt.h (oid2name) and HUGE (seg),
the bulk of the patch uses the standard PostgreSQL approach to deal with
Windows DLL issues.

I tested the build aspect of this patch under Cygwin and Linux without
any ill affects.  Note that I did not actually attempt to test the code
for functionality.

The procedure to apply the patch is as follows:

    $ # save the attachment as /tmp/contrib.patch
    $ # change directory to the top of the PostgreSQL source tree
    $ patch -p0 </tmp/contrib.patch

Jason

  * Portions Copyright (c) 1996-2000, PostgreSQL, Inc

to all files copyright Regents of Berkeley.  Man, that's a lot of files.

where necessary --- several of them didn't really need it, though.
tqual-checking macros simplified accordingly.

time qualification of HeapTupleSatisfiesSnapshot()

Jan

Implements the CREATE CONSTRAINT TRIGGER and SET CONSTRAINTS commands.

TODO:
    Generic builtin trigger procedures
    Automatic execution of appropriate CREATE CONSTRAINT... at CREATE TABLE
    Support of new trigger type in pg_dump
    Swapping of huge # of events to disk

Jan