Thread: user defined types and strings
Hi I have made a user defined type which has a string of variable length and and an integer value. Since the string is of variable length i have used a pointer for the string. When i use this type as a column in a table and inserts values into it, the string will go away. I understand that this is because i am pointing to a place in memory for the string, and that this wont last for a very long time. So i am wondering how i am supposed to use strings in a user defined type so they will be saved in the database when the type is inserted in a table? -Kjetil
On Wed, Feb 23, 2005 at 02:01:36PM +0100, Kjetil Haaland wrote: > I have made a user defined type which has a string of variable length and and > an integer value. Since the string is of variable length i have used a > pointer for the string. When i use this type as a column in a table and > inserts values into it, the string will go away. I understand that this is > because i am pointing to a place in memory for the string, and that this wont > last for a very long time. So i am wondering how i am supposed to use strings > in a user defined type so they will be saved in the database when the type is > inserted in a table? Hmmm...haven't we already had this conversation? :-) http://archives.postgresql.org/pgsql-novice/2004-11/msg00096.php http://archives.postgresql.org/pgsql-novice/2004-11/msg00106.php The type's data needs to be a contiguous block of memory, preceded by four bytes (int32) indicating the total length (including the four bytes). You should also be aware of how TOAST works and the need to use PG_DETOAST_DATUM in certain places. http://www.postgresql.org/docs/8.0/static/xtypes.html http://www.postgresql.org/docs/8.0/static/storage-toast.html Or have I misunderstood what you're asking? -- Michael Fuhr http://www.fuhr.org/~mfuhr/
On Wednesday 23 February 2005 18:23, Michael Fuhr wrote: > Hmmm...haven't we already had this conversation? :-) > > http://archives.postgresql.org/pgsql-novice/2004-11/msg00096.php > http://archives.postgresql.org/pgsql-novice/2004-11/msg00106.php > > The type's data needs to be a contiguous block of memory, preceded > by four bytes (int32) indicating the total length (including the > four bytes). You should also be aware of how TOAST works and the > need to use PG_DETOAST_DATUM in certain places. > > http://www.postgresql.org/docs/8.0/static/xtypes.html > http://www.postgresql.org/docs/8.0/static/storage-toast.html > > Or have I misunderstood what you're asking? We have had almost the same conversation before. The type works in my functions, but since the string is just a pointer to a memory place it goes away when the type is stored in tables in the database. I have read about the TOAST stuff, and think i have to use this because i have a pointer, and that the actual values have to be found elsewhere. Is this correct? But i don't understand how this is used. I have tried to add the line pg_detoast_datum((struct varlena*) DatumGetPointer(result)); in my input function after i have allocated the memory for the structure and the string. I also set the length variable before i do this. But it still want save what's in the string. I have also tried to add it in the output function right after i have recieved the argument. But this doesn't help. Is there any examples i can look at to see how TOAST is used? thanks for all the help so far! -Kjetil
i use the following commands to start the postmaster on my development winxp / cygwin / pgsql 7.4.5 setup... 1. /usr/sbin/cygserver & 2. postmaster -i -D /usr/share/postgresql/data & before getting to my real question, what do the "&" characters do? now to the real question... how do i shut down the postmaster? i checked the docs bu it wasn't clear. i tried their example and it didn't work. i read about the signals... SIGTERM, SIGINT, or SIGQUIT, but i don't how to implement them since the example given didn't work. any help woul dbe greatly appreciated. i have been shutting down cygwin to end pgsql, but my guess is that isn't the best way to shut it down. tia... __________________________________ Do you Yahoo!? Take Yahoo! Mail with you! Get it on your mobile phone. http://mobile.yahoo.com/maildemo
You might find starting and stopping postmaster easier by using pg_ctl. Eg in a batch file the following will stop the server: bash pg_ctl stop -D /usr/share/postgresql/data Regards, George ----- Original Message ----- From: <operationsengineer1@yahoo.com> To: <pgsql-novice@postgresql.org> Sent: Wednesday, February 23, 2005 3:17 PM Subject: [NOVICE] shutdown postmaster question >i use the following commands to start the postmaster > on my development winxp / cygwin / pgsql 7.4.5 > setup... > > 1. > > /usr/sbin/cygserver & > > 2. > > postmaster -i -D /usr/share/postgresql/data & > > before getting to my real question, what do the "&" > characters do? > > now to the real question... how do i shut down the > postmaster? i checked the docs bu it wasn't clear. i > tried their example and it didn't work. > > i read about the signals... SIGTERM, SIGINT, or > SIGQUIT, but i don't how to implement them since the > example given didn't work. any help woul dbe greatly > appreciated. > > i have been shutting down cygwin to end pgsql, but my > guess is that isn't the best way to shut it down. > > tia... > > > > __________________________________ > Do you Yahoo!? > Take Yahoo! Mail with you! Get it on your mobile phone. > http://mobile.yahoo.com/maildemo > > ---------------------------(end of broadcast)--------------------------- > TIP 2: you can get off all lists at once with the unregister command > (send "unregister YourEmailAddressHere" to majordomo@postgresql.org) >
Kjetil Haaland <kjetil.haaland@student.uib.no> writes:
> On Wednesday 23 February 2005 18:23, Michael Fuhr wrote:
>> Hmmm...haven't we already had this conversation? :-)
> We have had almost the same conversation before. The type works in my
> functions, but since the string is just a pointer to a memory place it goes
> away when the type is stored in tables in the database.
The point here is that you've built a two-part structure:
<length> <pointer to string> <some other fields>
|
+------------> text of string
and this is fundamentally not going to work. A datum has to be one
piece of memory. Consider something like
<length> <some other fields> <text of string>
where the length is now variable.
regards, tom lane
--- George Weaver <gweaver@shaw.ca> wrote: > > You might find starting and stopping postmaster > easier by using pg_ctl. Eg > in a batch file the following will stop the server: > > bash pg_ctl stop -D /usr/share/postgresql/data > > Regards, > George > > > ----- Original Message ----- > From: <operationsengineer1@yahoo.com> > To: <pgsql-novice@postgresql.org> > Sent: Wednesday, February 23, 2005 3:17 PM > Subject: [NOVICE] shutdown postmaster question > > > >i use the following commands to start the > postmaster > > on my development winxp / cygwin / pgsql 7.4.5 > > setup... > > > > 1. > > > > /usr/sbin/cygserver & > > > > 2. > > > > postmaster -i -D /usr/share/postgresql/data & > > > > before getting to my real question, what do the > "&" > > characters do? > > > > now to the real question... how do i shut down > the > > postmaster? i checked the docs bu it wasn't > clear. i > > tried their example and it didn't work. > > > > i read about the signals... SIGTERM, SIGINT, or > > SIGQUIT, but i don't how to implement them since > the > > example given didn't work. any help woul dbe > greatly > > appreciated. > > > > i have been shutting down cygwin to end pgsql, but > my > > guess is that isn't the best way to shut it down. > > > > tia... > > > > > > > > __________________________________ > > Do you Yahoo!? > > Take Yahoo! Mail with you! Get it on your mobile > phone. > > http://mobile.yahoo.com/maildemo > > > > ---------------------------(end of > broadcast)--------------------------- > > TIP 2: you can get off all lists at once with the > unregister command > > (send "unregister YourEmailAddressHere" to > majordomo@postgresql.org) i tried pg_ctl with no luck. i started with pg_ctl start but my pgdata environment variable wasn't set and i couldn't quickly find out how to set it via the docs. i then tried pg_ctl /usr/share/postgresql/data start and received an invalid operation mode error. i'm not sure how pg_ctl handles the "-i" issue (tcp/ip connections) and whether the trailing "&" is required using pg_ctl. the docs and my php/pgsql book were unclear after an admittedly quick review. __________________________________ Do you Yahoo!? Yahoo! Mail - Helps protect you from nasty viruses. http://promotions.yahoo.com/new_mail
I have used 2 batch files in the past.
The first was start.bat with the lines
bash pg_ctl start -D /usr/share/postgresql/data -o -i
pause
stop.bat contained:
bash pg_ctl stop -D /usr/share/postgresql/data
----- Original Message -----
From: <operationsengineer1@yahoo.com>
To: "George Weaver" <gweaver@shaw.ca>; <pgsql-novice@postgresql.org>
Sent: Thursday, February 24, 2005 12:27 PM
Subject: Re: [NOVICE] shutdown postmaster question
>
> --- George Weaver <gweaver@shaw.ca> wrote:
>
>>
>> You might find starting and stopping postmaster
>> easier by using pg_ctl. Eg
>> in a batch file the following will stop the server:
>>
>> bash pg_ctl stop -D /usr/share/postgresql/data
>>
>> Regards,
>> George
>
> i tried pg_ctl with no luck. i started with
>
> pg_ctl start
>
> but my pgdata environment variable wasn't set and i
> couldn't quickly find out how to set it via the docs.
See -D abvove
> i then tried
>
> pg_ctl /usr/share/postgresql/data start
>
> and received an invalid operation mode error.
>
> i'm not sure how pg_ctl handles the "-i" issue (tcp/ip
> connections) and whether the trailing "&" is required
> using pg_ctl. the docs and my php/pgsql book were
> unclear after an admittedly quick review.
-o is needed to pass options directly to the postmaster e.g. -i
Regards,
Geroge