removes any empty chunks, the chunk previously added won't be there
anymore, so it's possible there is zero free space in the rel's page list
afterwards. Must loop back and rerun the part that adds a chunk to
the list.
to prevent spreading of corruption when page header pointers are bad.
Merge PageZero into PageInit, since it was never used separately, and
remove separate memset calls used at most other PageInit call points.
Remove IndexPageCleanup, which wasn't used at all.
granted the lock when awakened; the signal now only means that the lock
is potentially available. The waiting process must retry its attempt
to get the lock when it gets to run. This allows the lock releasing
process to re-acquire the lock later in its timeslice. Since LWLocks
are usually held for short periods, it is possible for a process to
acquire and release the same lock many times in a timeslice. The old
spinlock-based implementation of these locks allowed for that; but the
original coding of LWLock would force a process swap for each acquisition
if there was any contention. Although this approach reopens the door to
process starvation (a waiter might repeatedly fail to get the lock),
the odds of that being a big problem seem low, and the performance cost
of the previous approach is considerable.
'volatile' pointers to access those structures, so that optimizing
compilers will not decide to move the structure accesses outside of the
spinlock-acquire-to-spinlock-release sequence. There are no known bugs
in these uses at present, but based on bad experience with lwlock.c,
it seems prudent to ensure that we protect these other uses too.
Per pghackers discussion around 12-Dec. (Note: it should not be
necessary to worry about structures protected by LWLocks, since the
LWLock acquire and release operations are not inline macros.)
should be accounted for in the PROC_SEM_MAP_ENTRIES() macro. Otherwise
the ports that rely on this macro to size data structures are broken.
Mea culpa.
so that only one signal number is used not three. Flags in shared
memory tell the reason(s) for the current signal. This method is
extensible to handle more signal reasons without chewing up even more
signal numbers, but the immediate reason is to keep pg_pwd reloads
separate from SIGHUP processing in the postmaster.
Also clean up some problems in the postmaster with delayed response to
checkpoint status changes --- basically, it wouldn't schedule a checkpoint
if it wasn't getting connection requests on a regular basis.
never overwrite adjacent pages with copied data, even if page header
and/or item pointers are already corrupt. Change inspired by trouble
report from Alvaro Herrera.
readability. Bizarre '(long *) TRUE' return convention is gone,
in favor of just raising an error internally in dynahash.c when
we detect hashtable corruption. HashTableWalk is gone, in favor
of using hash_seq_search directly, since it had no hope of working
with non-LONGALIGNable datatypes. Simplify some other code that was
made undesirably grotty by promixity to HashTableWalk.
portability issues). Caller-visible data structures are now allocated
on MAXALIGN boundaries, allowing safe use of datatypes wider than 'long'.
Rejigger hash_create API so that caller specifies size of key and
total size of entry, not size of key and size of rest of entry.
This simplifies life considerably since each number is just a sizeof(),
and padding issues etc. are taken care of automatically.
upper limit on what we will believe from sysconf(_SC_OPEN_MAX). The
default value is 1000, so that under ordinary conditions it won't
affect the behavior. But on platforms where the kernel promises far
more than it can deliver, this can be used to prevent running out of
file descriptors. See numerous past discussions, eg, pgsql-hackers
around 23-Dec-2000.
existing lock manager and spinlocks: it understands exclusive vs shared
lock but has few other fancy features. Replace most uses of spinlocks
with lightweight locks. All remaining uses of spinlocks have very short
lock hold times (a few dozen instructions), so tweak spinlock backoff
code to work efficiently given this assumption. All per my proposal on
pghackers 26-Sep-01.
a hung client or lost connection can't indefinitely block a postmaster
child (not to mention the possibility of deliberate DoS attacks).
Timeout is controlled by new authentication_timeout GUC variable,
which I set to 60 seconds by default ... does that seem reasonable?
for them, and making them just wastes time during backend startup/shutdown.
Also, remove compile-time MAXBACKENDS limit per long-ago proposal.
You can now set MaxBackends as high as your kernel can stand without
any reconfiguration/recompilation.
available in freeSemMap. As noted by Tatsuo, this is now a likely
scenario for detecting MaxBackends-exceeded; if MaxBackends is a multiple
of PROC_NSEMS_PER_SET then we will fail here and not in sinval.c. The
cleanup path did not work correctly before, anyway.
system. Some systems did not understand the 'l' section, and in general
it wasn't entirely appropriate.
On SCO OpenServer, the man pages won't be installed at all until someone
figures out their man system.
buffer manager with 'pg_clog', a specialized access method modeled
on pg_xlog. This simplifies startup (don't need to play games to
open pg_log; among other things, OverrideTransactionSystem goes away),
should improve performance a little, and opens the door to recycling
commit log space by removing no-longer-needed segments of the commit
log. Actual recycling is not there yet, but I felt I should commit
this part separately since it'd still be useful if we chose not to
do transaction ID wraparound.
cvs.
The Debian bug report says, "The upstream source makes use of NOFILE
unconditionalized. As the Hurd doesn't have an arbitrary limit on the
number of open files, this is not defined. But _SC_OPEN_MAX works fine
and returns 1024 (applications can increase this as they want), so I
suggest the below diff. Please forward this upstream, too."
Oliver Elphick
in GetSnapshotData, GetNewTransactionId, CommitTransaction, AbortTransaction,
etc. Correct race condition in transaction status testing in
HeapTupleSatisfiesVacuum --- this wasn't important for old VACUUM with
exclusive lock on its table, but it sure is important now. All per
pghackers discussion 7/11/01 and 7/12/01.
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.
