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* types oids @ 1999-08-16 23:18 Nicolas Aragon <nyco@jet.es> 1999-08-17 00:23 ` Re: [INTERFACES] types oids Tom Lane <tgl@sss.pgh.pa.us> 0 siblings, 1 reply; 2+ messages in thread From: Nicolas Aragon @ 1999-08-16 23:18 UTC (permalink / raw) To: pgsql-interfaces Hello, I'm programming with pqlib from Pascal (FPC) and trying to build some classes to encapsulate result sets in a similar way as Delphi. I need to know the type of every field and I've found that PQftype returns an OID. OK, I can query pg_type system table and find out type information. But this leads me to new questions because it seems that standard types aren't hardcoded anywhere. pg_type tells me the name, size and some other information about the type. But what about the "kind" of the type (numeric, text, date...)? I can only think of comparing the name with a list of names for standard types. Is there another simpler method? A standard relation between standard types and their OIDs? If the answer to last question is "no", can I really trust at least the name? If so, since I don't want to make the metadata query before each "regular" query, I'll have to cache it. Is it OK to do it once per connection? I can even think that.... is the user (admin) allowed to change the names of standard types? Another, more trivial question: do you know where to find nice logos for postgres? Thanks in advance Nico http://www.clubdelphi.com/nico/ ^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: [INTERFACES] types oids 1999-08-16 23:18 types oids Nicolas Aragon <nyco@jet.es> @ 1999-08-17 00:23 ` Tom Lane <tgl@sss.pgh.pa.us> 0 siblings, 0 replies; 2+ messages in thread From: Tom Lane @ 1999-08-17 00:23 UTC (permalink / raw) To: Nicolas Aragon <nyco@jet.es>; +Cc: pgsql-interfaces Nicolas Aragon <nyco@jet.es> writes: > But this leads me to new questions because it seems that standard types > aren't hardcoded anywhere. pg_type tells me the name, size and some other > information about the type. But what about the "kind" of the type (numeric, > text, date...)? You pretty much have to know from the name what the datatype is. Postgres doesn't have any type categorization like that. (Maybe it should ... I think there are some hacks in the parser that amount to categorizing the standard datatypes, but that knowledge is not visible outside the parser.) > I can only think of comparing the name with a list of names for standard > types. Is there another simpler method? A standard relation between standard > types and their OIDs? In reality, the OIDs assigned to standard types like "bool" and "int4" are unlikely ever to change; they certainly will not change faster than once per Postgres major release. You could probably get away with hard-wiring the knowledge that OID 16 == bool, say. If that seems a little too ugly, reading the OIDs for known types during startup is plenty good enough. If you are dealing with user-defined types, looking up the OIDs at startup is the way to go. (User type OIDs could change across a database dump/reload, so hardwiring those would be a bad idea.) > I can even think that.... is the user (admin) allowed to change the names > of standard types? Not if he wants things to keep working ;-) > Another, more trivial question: do you know where to find nice logos > for postgres? See the website. regards, tom lane ^ permalink raw reply [nested|flat] 2+ messages in thread
end of thread, other threads:[~1999-08-17 00:23 UTC | newest] Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 1999-08-16 23:18 types oids Nicolas Aragon <nyco@jet.es> 1999-08-17 00:23 ` Tom Lane <tgl@sss.pgh.pa.us>
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