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.
to the client before closing the connection. Before 7.2 this was done
correctly, but new code would simply close the connection with no report
to the client.
a get on a bytea value the code was running the raw value from the server
through character set conversion, which if the character set was SQL_ASCII
would cause all 8bit characters to become ?'s.
Fixes time zone problems introduced by Thomas' implementation of
TIMESTAMP WITHOUT TIME ZONE which caused the behavior of the previously
appropriate routine, timestamp_date(), to change for the worse in this
context.
Disallow CREATE INDEX on system catalogs, non-tables (views, sequences, etc).
Disallow CREATE/DROP TRIGGER on system catalogs, non-tables.
Disallow ALTER TABLE ADD/DROP CONSTRAINT on system catalogs.
Disallow FOREIGN KEY reference to non-table.
None of these things can actually work in the present system structure,
but the code was letting them pass without complaint.
macros, but only at explicit CHECK_FOR_INTERRUPTS() calls. Not clear
whether overenthusiastic acceptance of interrupts accounts for any real
bugs, but it definitely seems risky and unnecessary.
to insert the same key into a supposedly unique index. The bug is of
low probability, and may not explain any of the recent reports of
duplicated rows; but a bug is a bug.
cases which should have worked but did not.
Now supports julian day (J2452271), ISO time labels (T040506) and various
combinations of spaces and run-togethers of dates, times, and time zones.
All regression tests pass, and I have more tests to add after the 7.2
release (don't want to require changes to the ancillary horology result
files until after then).
'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.)
machines. I have just been observing some scenarios where set_ps_display
accounts for more than 10% of the backend CPU, and this loop has to be
the reason.
