using
ports on FreeBSD is pretty painless (for that matter, so is keeping the
OS itself up-to-date).
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On Thu, Jul 31, 2003 at 04:59:21PM -0400, Andrew Sullivan wrote:
On Thu, Jul 31, 2003 at 02:51:45PM -0500, Jim C. Nasby wrote:
If you really needed to set enable_seqscan=false (did you really?
Are you sure that's not the cheapest way?), you might want to
investigate expainding the statistics
On Fri, Aug 01, 2003 at 08:16:12AM -0400, Andrew Sullivan wrote:
On Thu, Jul 31, 2003 at 05:59:59PM -0500, Jim C. Nasby wrote:
Well, if I don't do this it wants to seqscan a table that occupies 350k
pages, instead of pulling a couple thousand rows. I started running it
with the seqscan
process be at 100% CPU? It does seem a bit coincidental that the
two procs seem to be taking 100% of one CPU (top shows them running on
different CPUs though).
This is version 7.3.4.
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if you're paying per CPU!).
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.
Also, if I set enable_hashagg = false, it runs in less than a second.
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ms
Even though the second case is only a select, it seems clear that
something's wrong...
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Dammit, I somehow deleted a bunch of replies to this.
Did a TODO ever come out of this?
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, the same kind of reorganization you would normally expect in a
BTree index.
This isn't true, at least in 9i. You can create whatever indexes you
want on an index-organized table. I believe that the index stores the PK
value instead of the ROWID.
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.
I'm sure there's a ton of things I'm missing, especially since I'm not
familiar with the postgresql code, but hopefully others can explore this
further.
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the partitions to be
eliminated from the query, and so run for much longer.
Is there by any chance a set of functions to manage adding and removing
partitions? Certainly this can be done by hand, but having a set of
tools would make life much easier. I just looked but didn't see anything
on GBorg.
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that the table has over 130M rows right now. So it would be nice to have
an easy way to partition the table based on unique project_id's and not
waste space in the partition tables on a field that will be the same for
every row (in each partition).
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, we have a box with 8 drives, 2 in a mirror with the OS and
WAL and pg_temp; the rest in a raid10 with the database on it. Do you
think it would have been better to make one big raid10? What if it was
raid5? And what if it was only 6 drives total?
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setup is that the raid10 is almost always
the IO bottleneck, and not the mirror with everything else on it.
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is required. Even if locks were
required, they would be shared read locks which wouldn't block each
other.
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will swamp
the planning cost. This does not mean you have to use something like
pgpool (which makes some rather questionable claims IMO); any decent web
application language/environment will support connection pooling.
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Give your computer
is persistent (i.e. not dropped and remade for each
request), but not shared between processes, therefore not pooled.
OK, that'd work too... the point is if you're re-connecting all the time
it doesn't really matter what else you do for performance.
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is how much will be saved.
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licensing costs was usually enough to pay for the new hardware in
one year.
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on
process priority, while linux won't. This can be very handy for things
like vacuum.
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crude to detect.
Isn't that exactly what pg_stats.correlation is?
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On Thu, Oct 28, 2004 at 07:49:28PM -0400, Tom Lane wrote:
Jim C. Nasby [EMAIL PROTECTED] writes:
On Sun, Oct 24, 2004 at 04:11:53PM -0400, Tom Lane wrote:
The test case you are showing is probably suffering from nonrandom
placement of this particular data value; which is something
like to avoid putting a 'set enable_seqscan=false' in my
code, especially since this query only has a problem if it's run on a
large date/time window, which normally doesn't happen.
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date/time window, which normally doesn't happen.
Try increasing your statistics target for the column and then rerunning
analyze.
Sincerely,
Joshua D. Drake
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it'll be getting a unique value or a small set of
values even though stats indicates that it should be.
One final question... would there be interest in a process that would
dynamically update the histogram settings for tables based on how
distinct/unique each field was?
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://catalyst.net.nz/PHYS: Level 2, 150-154 Willis St
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These PRESERVES should be FORCE-FED to PENTAGON OFFICIALS!!
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be found at
http://minilink.org/cvs.distributed.net/l3.sql.
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can get through to the mailing list cleanly
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} | {0.461133,0.4455,0.0444333,0.0418667,0.0049,0.00216667} | |
0.703936
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real-world examples where you could do
something with a PostgreSQL procedural language that you couldn't do
with PL/SQL.
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it? I thought it did, I know it was
discussed w/ the guy from Cox Communications and I thought he was using
it :).
No, PostgreSQL doesn't support any kind of partitioning, unless you
write it yourself. I think there's some work being done in this area,
though.
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across machines. So you better have fast access to the drive array, and
the array better have caching of some kind.
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people willing to
work on it.
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: 299623.954 ms
Everything is analyzed, and the statistics target is set to 1000.
Basically, it seems that it doesn't understand that each row in log will
match up with at most one row in bucket. There is a unique index on
bucket(rrs_id, end_time), so it should be able to tell this.
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.
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On Sat, Jan 22, 2005 at 10:18:00PM -0500, Tom Lane wrote:
Jim C. Nasby [EMAIL PROTECTED] writes:
(SELECT b.bucket_id AS rrs_bucket_id, s.*
FROM rrs.bucket b
JOIN page_log.log s
of large tables would make for a significant
reduction in the cost of VACUUM.
FWIW, that's already on the TODO. See also
http://lnk.nu/archives.postgresql.org/142.php.
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valid to assume that minimizing the amount of work you do in
a transaction means better throughput without considering what it will
cost to do the work you're putting off until later.
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pg_stats_* or
explain analize and turn them into configuration settings (such and
random page cost)?
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. If you look in the archives
you'll find people running postgresql on 30 and 40 drive arrays.
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On Tue, Feb 01, 2005 at 12:06:27AM -0500, Tom Lane wrote:
Jim C. Nasby [EMAIL PROTECTED] writes:
On Mon, Jan 31, 2005 at 03:26:12PM -0500, Tom Lane wrote:
Preferably a whole lot of queries. All the measurement techniques I can
think of are going to have a great deal of noise, so you
you can lose half
your drives without any data loss (if each dead drive is part of a
different mirror). Recovery is also faster.
You'll almost certainly be much happier with hardware raid instead of
software raid. stats.distributed.net runs a 3ware controller and SATA
drives.
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of my head, but I think it was a
'wedge' that clients would connect to as if it was the database, and the
wedge would then find an available database process to use.
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not for memory size
but because of memory *bandwidth*).
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... WHERE customer_id = 1 would be a good example of such a query
(assuming the table is partitioned on something like invoice_date).
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to recognize if the
partition that tuple was in had been removed, and just ignore that index
entry. Granted, you'd need to clean the index up at some point
(presumably via vacuum), but it doesn't need to occur at partition drop
time.
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it's a more effective
means of limiting the impact of large queries. I don't know how other
OS's handle this.
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bound than CPU bound. And unlike the
base tables, you generally don't need to read the WAL, so you don't
really need to worry about not being able to quickly scan through the
data without decompressing it.
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to -admin about a database that's
doing 340M inserts a day in 300M transactions...
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at what b and c look like each time 'through
the loop'.
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give each drive it's own dedicated bandwidth).
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On Wed, Apr 06, 2005 at 06:35:10PM -0400, Tom Lane wrote:
Jim C. Nasby [EMAIL PROTECTED] writes:
On Wed, Apr 06, 2005 at 06:09:37PM -0400, Tom Lane wrote:
Can anyone suggest a more general rule? Do we need for example to
consider whether the relation membership is the same in two clauses
do not match
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(estimate_rows_for_sql(text)) would
probably be very useful to functions that wanted to support returning a
rows estimate.
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like you
could just put a compression routine between the log writer and the
filesystem.
Is this a TODO?
ISTM it's at least worth hacking something together and doing some
performance testing...
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the faster spindle speed of drive A?
The increased data density will help transfer speed off the platter, but
that's it. It won't help rotational latency.
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different RAID configurations using dbt2. I don't know if this is
something that the lab is setup for or capable of, though.
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or two very large tables,
the extra spindles won't help unless you break up the tables and
glue them together with query magic. But it's still a point to
consider.
Huh? Do you know how RAID10 works?
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Give your computer some
eager to find out how PG handles all this.
AFAIK PostgreSQL requests data one database page at a time (normally
8k). Of course the OS might do something different.
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and
not raw SCSI...
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You should re-run the function test using SQL as the function language
instead of plpgsql. There might be some performance to be had there.
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on how frequently a table is vacuumed, it will
settle down to a steady-state size that is greater than it's size after
a vacuum full.
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, probably can).
Actually, the planner (at least in 7.4) isn't smart enough to consider
if the sort would fit in memory or not. I'm running a test right now to
see if it's actually faster to use an index in this case.
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On Tue, Apr 19, 2005 at 11:01:26PM -0400, Tom Lane wrote:
Jim C. Nasby [EMAIL PROTECTED] writes:
Actually, the planner (at least in 7.4) isn't smart enough to consider
if the sort would fit in memory or not.
Really? Have you read cost_sort()?
It's certainly possible
No, this is a single process. And there's known issues with context
storms on Xeons, so that might be what you're seeing.
On Tue, Apr 19, 2005 at 09:37:21PM -0700, Mischa Sandberg wrote:
Quoting Tom Lane [EMAIL PROTECTED]:
Jim C. Nasby [EMAIL PROTECTED] writes:
A friend of mine has
No, he's using either COPY or \COPY.
On Wed, Apr 20, 2005 at 12:34:27AM -0400, Greg Stark wrote:
Jim C. Nasby [EMAIL PROTECTED] writes:
What's really odd is that neither the CPU or the disk are being
hammered. The box appears to be pretty idle; the postgresql proces is
using 4-5% CPU
could use \timing.
In any case, it's not valid to use pgadmin to time things.
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the wrong choice
here. BTW, changing random_page_cost to 3 or 4 doesn't change the plan.
On Tue, Apr 19, 2005 at 10:40:41PM -0500, Jim C. Nasby wrote:
On Tue, Apr 19, 2005 at 11:01:26PM -0400, Tom Lane wrote:
Jim C. Nasby [EMAIL PROTECTED] writes:
Actually, the planner (at least in 7.4) isn't smart
not a valid test case (and by the way, this is true no matter
what database you're looking at. Multiuser access is where you uncover
your real bottlenecks.)
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be thinking
wrong.
BTW, the column I'm indexing is a bigint with a low correlation.
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On Fri, Apr 22, 2005 at 10:08:06PM -0400, Tom Lane wrote:
Jim C. Nasby [EMAIL PROTECTED] writes:
I've run some performance tests. The actual test case is at
http://stats.distributed.net/~decibel/timing.sql, and the results are at
http://stats.distributed.net/~decibel/timing.log
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On Sat, Apr 23, 2005 at 01:00:40AM -0400, Tom Lane wrote:
Jim C. Nasby [EMAIL PROTECTED] writes:
Feel free to propose better cost equations.
Where would I look in code to see what's used now?
All the gold is hidden in src/backend/optimizer/path/costsize.c
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be set in /boot/loader.conf.
hw.ata.wc=0 is an example (which you want to set on any box with IDE
drives if you want fsync to actually do what it thinks it's doing).
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)
);
I'm not sure how standard that is or if other databases support it.
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, but it's been a few years...
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On Tue, May 10, 2005 at 02:38:41AM +1000, Neil Conway wrote:
Jim C. Nasby wrote:
Having indexes that people shouldn't be using does add confusion for
users, and presents the opportunity for foot-shooting.
Emitting a warning/notice on hash-index creation is something I've
suggested
On Tue, May 10, 2005 at 10:14:11AM +1000, Neil Conway wrote:
Jim C. Nasby wrote:
No, hash joins and hash indexes are unrelated.
I know they are now, but does that have to be the case?
I mean, the algorithms are fundamentally unrelated. They share a bit of
code such as the hash functions
the entire index every time it looks like a different bucket
size would help.)
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On Tue, May 10, 2005 at 11:49:50AM -0400, Tom Lane wrote:
Jim C. Nasby [EMAIL PROTECTED] writes:
What's the challange to making it adaptive, comming up with an algorithm
that gives you the optimal bucket size (which I would think there's
research on...) or allowing the index to accommodate
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contact the sender by reply email and delete and destroy
all copies of the original message, including attachments.
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: syncronous).
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out Bizgres.
(http://pgfoundry.org/projects/bizgres/) I'm sure your insights would be
most welcome.
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), but that
alone isn't enough to explain the difference.
On Wed, May 11, 2005 at 05:59:10PM +0200, Manfred Koizar wrote:
On Sun, 24 Apr 2005 17:01:46 -0500, Jim C. Nasby [EMAIL PROTECTED]
wrote:
Feel free to propose better cost equations.
I did. More than once.
estimated index scan cost
stays up and it's fast. Though granted, LJ
is quite a bit faster than it was 6 months ago.
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On Thu, May 12, 2005 at 08:54:48PM +0200, Manfred Koizar wrote:
On Wed, 11 May 2005 16:15:16 -0500, Jim C. Nasby [EMAIL PROTECTED]
wrote:
This is divided by the number of index columns, so the index correlation
is estimated to be 0.219.
That seems like a pretty bad assumption to make
or not.
Does this sound like a good way to determine actual costs for index
scans (and hopefully other access methods in the future)? If so, what
would be a good way to implement this?
--
Jim C. Nasby, Database Consultant [EMAIL PROTECTED]
Give your computer some brain candy
analyze) just to make
sure we knew what the optimizer was doing, but I think we shouldn't need
the info to produce cost estimates.
--
Jim C. Nasby, Database Consultant [EMAIL PROTECTED]
Give your computer some brain candy! www.distributed.net Team #1828
Windows: Where do you want to go
On Fri, May 20, 2005 at 04:47:38PM -0400, Tom Lane wrote:
Jim C. Nasby [EMAIL PROTECTED] writes:
On Thu, May 19, 2005 at 09:31:47AM -0700, Josh Berkus wrote:
can test our formula for accuracy and precision. However, such a formula
*does* need to take into account concurrent activity
step. I would argue
that doing it that way is actually more accurate, because the overhead
of explain analyze is huge and tends to swamp other factors out. As I
mentioned in my other email, my tests show explain analyze select * from
table is 5x slower than select count(*) from table.
--
Jim C
for that
tuple.
I looked on the TODO but didn't see this, maybe it fell through the
cracks?
--
Jim C. Nasby, Database Consultant [EMAIL PROTECTED]
Give your computer some brain candy! www.distributed.net Team #1828
Windows: Where do you want to go today?
Linux: Where do you want to go
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