Re: [SQL] Does PG have a database
Mark Fenbers ha scritto: > I have working PostgreSQL databases on 3 of my ~30 Linux boxes. I want > my software to be able to determine which of my 30 boxes have functional > databases on them. Since Pg is part of the baseline distro, merely > checking for the existence of an executable doesn't solve my problem. > > I tried looping through my list of hosts and running the command: >psql -h $host --list > but this fails on a box with a database with the same error code as on a > box that doesn't have a database, if my PGUSER isn't set and my login ID > is not the username of the database. The PGUSER setting might differ > for each host, so specifying this in the software is not practical. > > Bottom line: What trick can I use to determine whether a box has a > living, breathing Pg database if I don't know the DB owner? > Mark > Just write a custom client that connects to the given host, on some standard ports. If the connection is accepted, there is a possibility that on the other side there is a PostgreSQL server. To make sure send a StartupMessage http://www.postgresql.org/docs/8.1/static/protocol-message-formats.html You can reuse some code of a library I have written: pglib. http://developer.berlios.de/projects/pglib/ It is released under the MIT license, and it is written in Python and Twisted (a framework for writing asynchronous applications). By the way: pglib aims to be a complete replacement for libpq. Regards Manlio Perillo ---(end of broadcast)--- TIP 5: don't forget to increase your free space map settings
[SQL] primary keys as TEXT
Hi. There can be performancs problems in having primary keys of type TEXT? What about having a primary key of 3 columns (all of type TEXT)? Regards Manlio Perillo ---(end of broadcast)--- TIP 2: Don't 'kill -9' the postmaster
Re: [SQL] primary keys as TEXT
Michael Glaesemann ha scritto: > > On Jul 28, 2006, at 17:37 , Manlio Perillo wrote: > >> There can be performancs problems in having primary keys of type TEXT? >> What about having a primary key of 3 columns (all of type TEXT)? > > What defines a problem in terms of performance is heavily dependent on > your particular needs and requirements. What are your requirements? What > profiling have you done to see where your performance bottlenecks may be? > I still don't have done profiling. Simply in the first version of my schema I used serial keys but the result is ugly and it force me to do a lot of joins. Thanks and regards Manlio Perillo ---(end of broadcast)--- TIP 6: explain analyze is your friend
Re: [SQL] primary keys as TEXT
Aaron Bono ha scritto: > On 7/28/06, *Manlio Perillo* <[EMAIL PROTECTED] > <mailto:[EMAIL PROTECTED]>> wrote: > > Michael Glaesemann ha scritto: > > > > On Jul 28, 2006, at 17:37 , Manlio Perillo wrote: > > > >> There can be performancs problems in having primary keys of type > TEXT? > >> What about having a primary key of 3 columns (all of type TEXT)? > > > > What defines a problem in terms of performance is heavily dependent on > > your particular needs and requirements. What are your > requirements? What > > profiling have you done to see where your performance bottlenecks > may be? > > > > I still don't have done profiling. > > Simply in the first version of my schema I used serial keys but the > result is ugly and it force me to do a lot of joins. > > > > Ugly? Not sure what you mean by that. > Because serial ids are only surrogate keys. My tables have well definited primary keys, the only problem is that they are of type TEXT (and spawn up to 3 columns). My concern is: how bad can be performance? > I do understand the problem with so many joins. I use views so that the > joins are only delt with once (in the database) and then all my > applications run off the views. That way, the applications use very > simple queries. The views also allow me to change the table structure > (column names, more table normalization, etc.) without having to make > changes to the application. > View are a good idea, thanks. Regards Manlio Perillo ---(end of broadcast)--- TIP 5: don't forget to increase your free space map settings
