Обсуждение: CREATE TABLE with a name derived from a string
I am creating a DB for a multi user IM system. Each user can store their history. Each user also has a unique ID. There will be many users and a lot of history will be generated by each user, so we are going to create a history table per user, with a tablename that is derived from the unique userid. I've hit a problem implementing this scheme. I want to be able to write a stored procedure in postgres that takes an integer userid as a param and creates a table called History.<userid>. (e.g. History.695). My dream is: CREATE TABLE 'History' || $1 (...); but this won't work. I dabbled with plpgsql but didn't get very far (I'm not an expert at this stuff :( ). I also tried the ALTER TABLE XX RENAME TO YY but this won't allow strings for the table names either :(. I know that this could be done relatively easily be creating the queries in C++ and executing them, but I want to do as much as possible in stored procedures for many reasons (performance, reuse, abstraction from DB changes...). Has anyone any experience doing something similar? Any help or pointers would be appreciated. Thanks, John
On 12 Feb 2003, Savage wrote: > I am creating a DB for a multi user IM system. Each user can store > their history. Each user also has a unique ID. There will be many > users and a lot of history will be generated by each user, so we are > going to create a history table per user, with a tablename that is > derived from the unique userid. I've hit a problem implementing this > scheme. > > I want to be able to write a stored procedure in postgres that takes > an integer userid as a param and creates a table called > History.<userid>. (e.g. History.695). My dream is: > > CREATE TABLE 'History' || $1 (...); I think using execute might work: EXECUTE ''CREATE TABLE History'' || $1 || '' (...);'';
On Fri, 14 Feb 2003, John Savage wrote: > I came across the EXECUTE command while googling for a solution to this > problem but found > a) it was incredibly hard to read because of all the quotes and > b) I couldn't find much documentation for it. It isn't mentioned on the main > red hat postgreSQL manual pages at all > (http://www.redhat.com/docs/manuals/database/) and the word EXECUTE isn't > the best word to google on :). The best resource for plpgsql I could find is > at http://www.phpfreaks.com/postgresqlmanual/page/plpgsql.html but I wasn't > sure if this was going to help me. Are there any better resources for > plpgsql? I'll look into it more now anyway. Thanks. I don't know if techdocs has anything more useful, otherwise the official interactive docs have a short section. (Programmer's Guide) The short form is that for most general queries you want to run you can make a string that contains the full query and then EXECUTE that string.
JSavage@data-mate.com (Savage) writes: > I am creating a DB for a multi user IM system. Each user can store > their history. Each user also has a unique ID. There will be many > users and a lot of history will be generated by each user, so we are > going to create a history table per user, with a tablename that is > derived from the unique userid. As others have mentioned this is a bad idea. A really really bad idea. On option is to just put userid first in your primary key and use it on all lookups. That's what indexes are for. -- greg
I came across the EXECUTE command while googling for a solution to this problem but found a) it was incredibly hard to read because of all the quotes and b) I couldn't find much documentation for it. It isn't mentioned on the main red hat postgreSQL manual pages at all (http://www.redhat.com/docs/manuals/database/) and the word EXECUTE isn't the best word to google on :). The best resource for plpgsql I could find is at http://www.phpfreaks.com/postgresqlmanual/page/plpgsql.html but I wasn't sure if this was going to help me. Are there any better resources for plpgsql? I'll look into it more now anyway. Thanks. Meantime, I got a reply from Dmitry Tkach yesterday that made me reconsider why we are taking this approach. Short term I no longer need this functionality, but will be needing it over the coming weeks for definite. Thanks, John _____ John Savage <mailto:jsavage@data-mate.com> Software Engineer DataMate Global Communications Tel: +1 818 487 3900 ext105 _____ -----Original Message----- From: Stephan Szabo [mailto:sszabo@megazone23.bigpanda.com] Sent: Friday, February 14, 2003 10:36 AM To: Savage Cc: pgsql-general@postgresql.org Subject: Re: [GENERAL] CREATE TABLE with a name derived from a string On 12 Feb 2003, Savage wrote: > I am creating a DB for a multi user IM system. Each user can store > their history. Each user also has a unique ID. There will be many > users and a lot of history will be generated by each user, so we are > going to create a history table per user, with a tablename that is > derived from the unique userid. I've hit a problem implementing this > scheme. > > I want to be able to write a stored procedure in postgres that takes > an integer userid as a param and creates a table called > History.<userid>. (e.g. History.695). My dream is: > > CREATE TABLE 'History' || $1 (...); I think using execute might work: EXECUTE ''CREATE TABLE History'' || $1 || '' (...);'';