using POSIX semaphores more robust on Darwin 1.2/Mac OS X
Public Beta. this is for the version of 7.1 available
via anon cvs as of Jan 14 2001 14:00 PST.
since the semaphores and shared memory created by this
emulator are shared with the backends via fork(), their
persistent names are not necessary. removing their
names with shm_unlink() and sem_unlink() after creation
obviates the need for any "ipcclean" function. further,
without these changes, the shared memory (and, therefore,
the semaphores) will not be re-initialized/re-created after
the first execution of the postmaster, until reboot
or until some (non-existent) ipcclean function is executed.
this patch does the following:
1) if the shared memory segment "SysV_Sem_Info" already
existed, it is cleaned up. it shouldn't be there anyways.
2) the real indicator for whether the shared memory/semaphore
emulator has been initialized is if "SemInfo" has been
initialized. the shared memory and semaphores must be
initialized regardless of whether there was a garbage shared
memory segment lying around.
3) the shared memory segment "SysV_Sem_Info" is created with "O_EXCL"
to catch the case where two postmasters might be starting
simultaneously, so they don't both end up with the same shared
memory (one will fail). note that this can't be done with the
semaphores because Darwin 1.2 has a bug where attempting to
open an existing semaphore with "O_EXCL" set will ruin the
semaphore until the next reboot.
4) the shared memory segment "SysV_Sem_Info" is unlinked after
it is created. it will then exist without a name until the
postmaster and all backend children exit.
5) all semaphores are unlinked after they are created. they'll
then exist without names until the postmaster and all backend
children exit.
-michael thornburgh, zenomt@armory.com
Not sure why some were this way, and others were already correct, but it
seems to have been like this for several years.
This caused problems on a few damaged platforms like AIX and IRIX which do
not support DST calculations for years before 1970.
Thanks to Andreas Zeugswetter <ZeugswetterA@wien.spardat.at> for finding
the problem.
Chapter 10. PL/pgSQL - SQL Procedural Language (c40914117.htm)
Statements
...
(resulting in a PL/pgSQL internal SELECT).
But there are cases where someone isn't interested int
-----------------------------------------(have to be)-->
But there are cases where someone isn't interested in
the functions result.
RAISE level format''
--(have to be)-->
RAISE level 'format'
I hope. I finally realized that we were going at it backwards: when
there are excess parentheses, they need to be treated as part of the
sub-SELECT, not as part of the surrounding expression. Although either
choice yields an unambiguous grammar, only this way produces a grammar
that is LALR(1). With the old approach we were guaranteed to fail on
either 'SELECT (((SELECT 2)) + 3)' or
'SELECT (((SELECT 2)) UNION SELECT 2)' depending on which way we
resolve the initial shift/reduce conflict. With the new way, the same
reduction track can be followed in both cases until we have advanced
far enough to know whether we are done with the sub-SELECT or not.
given the fundamental restriction of not looking at transaction commit
data in pg_log. Use code that is actually based on tqual.c rather than
ad-hoc tests. Also write the tuple fetch loop using standard access
macros rather than ad-hoc code.
GetRawDatabaseInfo() won't cope with a compressed path spec (much less
a moved-off one). I'm not going to force an initdb for this change,
because it's noncritical --- we're not actually using datpath at all
right now. But it seems a good idea to apply the fix while I'm thinking
about it.
are treated more like 'cancel' interrupts: the signal handler sets a
flag that is examined at well-defined spots, rather than trying to cope
with an interrupt that might happen anywhere. See pghackers discussion
of 1/12/01.
---------------------------------------------------------------------------
Attached is a set of patches for a couple of bugs dealing with
timestamps in JDBC.
Bug#1) Incorrect timestamp stored in DB if client timezone different
than DB.
timestamps in JDBC.
Bug#1) Incorrect timestamp stored in DB if client timezone different
than DB.
The buggy implementation of setTimestamp() in PreparedStatement simply
used the toString() method of the java.sql.Timestamp object to convert
to a string to send to the database. The format of this is yyyy-MM-dd
hh:mm:ss.SSS which doesn't include any timezone information. Therefore
the DB assumes its timezone since none is specified. That is OK if the
timezone of the client and server are the same, however if they are
different the wrong timestamp is received by the server. For example if
the client is running in timezone GMT and wants to send the timestamp
for noon to a server running in PST (GMT-8 hours), then the server will
receive 2000-01-12 12:00:00.0 and interprete it as 2000-01-12
12:00:00-08 which is 2000-01-12 04:00:00 in GMT. The fix is to send a
format to the server that includes the timezone offset. For simplicity
sake the fix uses a SimpleDateFormat object with its timezone set to GMT
so that '+00' can be used as the timezone for postgresql. This is done
as SimpleDateFormat doesn't support formating timezones in the way
postgresql expects.
Bug#2) Incorrect handling of partial seconds in getting timestamps from
the DB
When the SimpleDateFormat object parses a string with a format like
yyyy-MM-dd hh:mm:ss.SS it expects the fractional seconds to be three
decimal places (time precision in java is miliseconds = three decimal
places). This seems like a bug in java to me, but it is unlikely to be
fixed anytime soon, so the postgresql code needed modification to
support the java behaviour. So for example a string of '2000-01-12
12:00:00.12-08' coming from the database was being converted to a
timestamp object with a value of 2000-01-12 12:00:00.012GMT-08:00. The
fix was to check for a '.' in the string and if one is found append on
an extra zero to the fractional seconds part.
Bug#3) Performance problems
In fixing the above two bugs, I noticed some things that could be
improved. In PreparedStatement.setTimestamp(),
PreparedStatement.setDate(), ResultSet.getTimestamp(), and
ResultSet.getDate() these methods were creating a new SimpleDateFormat
object everytime they were called. To avoid this unnecessary object
creation overhead, I changed the code to use static variables for
keeping a single instance of the needed formating objects.
Also the code used the + operator for string concatenation. As everyone
should know this is very inefficient and the use of StringBuffers is
prefered.
I also did some cleanup in ResultSet.getTimestamp(). This method has
had multiple patches applied some of which resulted in code that was no
longer needed. For example the ISO timestamp format that postgresql
uses specifies the timezone as an offset like '-08'. Code was added at
one point to convert the postgresql format to the java one which is
GMT-08:00, however the old code was left around which did nothing. So
there was code that looked for yyyy-MM-dd hh:mm:sszzzzzzzzz and
yyyy-MM-dd hh:mm:sszzz. This second format would never be encountered
because zzz (i.e. -08) would be converted into the former (also note
that the SimpleDateFormat object treats zzzzzzzzz and zzz the same, the
number of z's does not matter).
There was another problem/fix mentioned on the email lists today by
mcannon@internet.com which is also fixed by this patch:
Bug#4) Fractional seconds lost when getting timestamp from the DB
A patch by Jan Thomea handled the case of yyyy-MM-dd hh:mm:sszzzzzzzzz
but not the fractional seconds version yyyy-MM-dd hh:mm:ss.SSzzzzzzzzz.
The code is fixed to handle this case as well.
Barry Lind
are now critical sections, so as to ensure die() won't interrupt us while
we are munging shared-memory data structures. Avoid insecure intermediate
states in some code that proc_exit will call, like palloc/pfree. Rename
START/END_CRIT_CODE to START/END_CRIT_SECTION, since that seems to be
what people tend to call them anyway, and make them be called with () like
a function call, in hopes of not confusing pg_indent.
I doubt that this is sufficient to make SIGTERM safe anywhere; there's
just too much code that could get invoked during proc_exit().
- Fix handling of --tables=* (multiple tables never worked properly, AFAICT)
- strdup() the current user in DB routines
- Check results of IO routines more carefully.
- Check results of PQ routines more carefully.
Have not fixed index output yet.
1. Support of variable size keys - new algorithm of insertion to tree
(GLI - gist layrered insertion). Previous algorithm was implemented
as described in paper by Joseph M. Hellerstein et.al
"Generalized Search Trees for Database Systems". This (old)
algorithm was not suitable for variable size keys and could be
not effective ( walking up-down ) in case of multiple levels split
Bug fixed:
1. fixed bug in gistPageAddItem - key values were written to disk
uncompressed. This caused failure if decompression function
does real job.
2. NULLs handling - we keep NULLs in tree. Right way is to remove them,
but we don't know how to inform vacuum about index statistics. This is
just cosmetic warning message (like in case with R-Tree),
but I'm not sure how to recognize real problem if we remove NULLs
and suppress this warning as Tom suggested.
3. various memory leaks
This work was done by Teodor Sigaev (teodor@stack.net) and
Oleg Bartunov (oleg@sai.msu.su).
Bruce Momjian
Thomas G. Lockhart
Tom Lane
Peter Eisentraut
Marc G. Fournier
Philip Warner