Обсуждение: Not all functions in schema pg_catalog are "visible"

Hi,

I just noticed that that there are functions defined (such as pg_catalog.time(timestamp) that can only be called when
prefixedwith pg_catalog. However other functions (that are at first glance defined identically to time()) can be called
withoutprefixing them with pg_catalog. 

My understanding is that time(timestamp) is there to support the various CAST ( .. ) expressions, but why isn't it
exposedas a "regular" function as well (as it seems to work just fine when being called directly) 

So, just out of curiosity: how could I tell by looking at pg_proc (or other system tables) which of those functions is
"public"and which is not? 

Regards
Thomas

Thomas Kellerer wrote:
> Hi,
>
> I just noticed that that there are functions defined (such as pg_catalog.time(timestamp) that can only be called when
prefixedwith pg_catalog. However other functions (that are at first glance defined identically to time()) can be called
withoutprefixing them with pg_catalog. 

I think it's not that they are visible but rather that their names are
keywords.  So you could also call them by quoting them, e.g.
"time"(timestamp).  IIRC there's a view listing all keywords you can use
to figure this out.

--
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support