Subject: [HACKERS] Small date patches (resubmitted)
Here a some small patches for the date/time code. They set the default
output format for the datetime type to the traditional Postgres
style, and fix a date debugging declaration. I submitted these
a couple of days ago, but they might have gotten lost...
NOTE: the second patch to dt.c is what I believe D'Arcy submitted as well,
that I claimed was taken out...sorry D'Arcy, my fault :(
Subject: Re: [HACKERS] abstime "now" broken
Yes, I broke 'now' :( with an attempt at a bug fix involving
servers running in the UTC/GMT timezone. These patches fix
the problem, and have been tested in GMT (+00 hours),
PST (-08), and NZT (+12) timezones which exercized the code for
various cases including across day boundaries. btw, this code
fixes the same type of problem for 'today', 'yesterday', 'tomorrow',
for DATETIME, ABSTIME, DATE and TIME types.
The bugfix itself is quite small, but I have accumulated other
changes in the datetime data type and include them here also.
One set of changes involves printing ISO-formatted dates and
is in response to the helpful information from Kurt Lidl regarding
ANSI SQL dates. I'll send another e-mail sometime soon discussing
more issues he has raised...
Reply-To: hackers@hub.org, Dan McGuirk <mcguirk@indirect.com>
To: hackers@hub.org
Subject: [HACKERS] tmin writeback optimization
I was doing some profiling of the backend, and noticed that during a certain
benchmark I was running somewhere between 30% and 75% of the backend's CPU
time was being spent in calls to TransactionIdDidCommit() from
HeapTupleSatisfiesNow() or HeapTupleSatisfiesItself() to determine that
changed rows' transactions had in fact been committed even though the rows'
tmin values had not yet been set.
When a query looks at a given row, it needs to figure out whether the
transaction that changed the row has been committed and hence it should pay
attention to the row, or whether on the other hand the transaction is still
in progress or has been aborted and hence the row should be ignored. If
a tmin value is set, it is known definitively that the row's transaction
has been committed. However, if tmin is not set, the transaction
referred to in xmin must be looked up in pg_log, and this is what the
backend was spending a lot of time doing during my benchmark.
So, implementing a method suggested by Vadim, I created the following
patch that, the first time a query finds a committed row whose tmin value
is not set, sets it, and marks the buffer where the row is stored as
dirty. (It works for tmax, too.) This doesn't result in the boost in
real time performance I was hoping for, however it does decrease backend
CPU usage by up to two-thirds in certain situations, so it could be
rather beneficial in high-concurrency settings.
Subject: [HACKERS] backend/utils/adt/timestamp.c
Back to this timezone stuff. The struct tm has a field (tm_gmtoff) which
is the offset from UTC (GMT is archaic BTW) in seconds. Is this the
value you are looking for when you use timezone? Note that this applies
to NetBSD but it does not appear to be in either ANSI C or POSIX. This
looks like one of those things that is just going to have to be hand
coded for each platform.
Why not just store the values in UTC and use localtime instead of
gmtime when retrieving the value?
Also, you assume the time is returned as a 4 byte integer. In fact,
there is not even any requirement that time be an integral value. You
should use time_t here.
The input function seems unduly restrictive. Somewhere in the sources
there is an input function that allows words for months. Can't we do
the same here?
There is a standard function, difftime, for subtracting two times. It
deals with cases where time_t is not integral. There is, however, a
small performance hit since it returns a double and I don't believe
there is any system currently which uses anything but an integral for
time_t. Still, this is technically the correct and portable thing to do.
The returns from the various comparisons should probably be a bool.
of endian.h. I figure that if it exists it's pretty sure that it has
the byte order information and we may catch some other ports without
any further testing.
From: "D'Arcy J.M. Cain" <darcy@druid.net>
Subject: [HACKERS] More patches for date/time
I have accumulated several patches to add functionality to the datetime
and timespan data types as well as to fix reported porting bugs on non-BSD
machines. These patches are:
dt.c.patch - add datetime_part(), fix bugs
dt.h.patch - add quarter and timezone support, add prototypes
globals.c.patch - add time and timezone variables
miscadmin.h.patch - add time and timezone variables
nabstime.c.patch - add datetime conversion routine
nabstime.h.patch - add prototypes
pg_operator.h.patch - add datetime operators, clean up formatting
pg_proc.h.patch - add datetime functions, reassign conflicting date OIDs
pg_type.h.patch - add datetime and timespan data types
The dt.c and pg_proc.h patches are fairly large; the latter mostly because I tried
to get some columns for existing entries to line up.
nicer. Also, I grabbed my copy of the Informix manual, and
added a couple of variables that make sense (formats for
money, time, a language setting, a timezone).
- New functions SetPGVariable() and GetPGVariable() in tcop/*.
These don't actually do anything for the moment, but should
be enough to implement the SET var_name TO var_val in the
parser?
SetPGVariable() expects just two strings, the var_name and
the var_value from above, and is expected to do the right thing.
Returns TRUE if everything okay.
From: "Martin J. Laubach" <mjl@wwx.vip.at>
Actually required by multi-column indices support.
We still don't use btree for 'A is (not) null', but
now btree keep items with NULL attrs using single rule
for placing/finding items on pages:
NULLs greater NOT_NULLs and NULL = NULL.
+ Bulkload code (nbtsort.c) support for multi-column indices
building and NULLs.
+ Fix for btendscan()->pfree(scanopaque) from Chris Dunlop.
Subject: [HACKERS] backend/utils/adt/nabstime.c
There is a problem with some of the calls to strftime. The second arg is
missing. In all cases the buffer is CTZName which, according to the
file init/globals.c, is char CTZName[8] so I have added this value.
I know there should be a #define set up for this but I wasn't sure
which header to put it in.
Subject: [HACKERS] libpq/pqcomm stuff and Solaris byte order
I decided to go ahead with the required changes since no one else seems
to. I don't guarantee that it is perfect but with these changes the
package actually compiles. While I was at it I added to the Sparc
Solaris header to define the byte order. Note that NetBSD sets this
in the system headers so it wasn't required there.
In particular, someone may want to check whether I removed the correct
84 lines from backend/libpq/pqcomprim.c.
Subject: [HACKERS] auth.c for kerberos.
I made pgsql with eBones(international version of Kerberos4). The
following modification was needed. And I added read permition for
group to srvtab instead of running postmaster as root.
According to man page under FreeBSD for sys_errlist[], strerror() should be
used instead...not sure if this will break other systems, so only changing
two files for now, and we'll see what "errors" it turns up
of common routines in pqcomprim.c (pq communication primitives).
Not all adapted to it yet, but it's a start.
- Rewritten some of those routines, to write/read bigger chunks of
data, precomputing stuff in buffers instead of sending out byte
by byte.
- As a consequence, I need to know the endianness of the machine.
Currently I rely on getting it from machine/endian.h, but this
may not be available everywhere? (Who the hell thought it was
a good idea to pass integers to the backend the other way around
than the normal network byte order? *argl*)
- Libpq looks in the environment for magic variables, and upon
establishing a connection to the backend, sends it queries
of the form "SET var_name TO 'var_value'". This needs a change
in the backend parser (Mr. Parser, are you there? :)
- Currently it looks for two Env-Vars, namely PG_DATEFORMAT
and PG_FLOATFORMAT. What else makes sense? PG_TIMEFORMAT?
PG_TIMEZONE?
From: "Martin J. Laubach" <mjl@wwx.vip.at>
Subject: [HACKERS] Patches for 970316 compilation
I made a small pre-emptive change in the new datetime code to eliminate
calls to infnan(). Hopefully this will make Solaris (and probably other
non-GNUlib) systems happier. Didn't find fe-connect.h in the 970316
distribution, so made one up. Also, one of the test routines needs an
update for the geo-decls.h -> geo_decls.h name change.
Patches appear below...
