Re: Postgres C-API: How to get the Oid for a custom type defined in a schema outside of the current search path

[Pavel Stehule <pavel.stehule@xxxxxxxxx>]

čt 3. 12. 2020 v 11:44 odesílatel Michael Krüger <michael@kruegers.email> napsal:

Hi,

Am 03.12.2020 um 11:01 schrieb Pavel Stehule <pavel.stehule@xxxxxxxxx>:

Hi

čt 3. 12. 2020 v 10:32 odesílatel Michael Krüger <michael@kruegers.email> napsal:

Dear all,

I need to find out the Oid of a custom type in C programming language. This type is defined in a schema, outside of the standard search path, e.g. public.

I know that I can call TypenameGetTypid to find out an Oid. But this is not working for me if the type is not in the public namespace.
How can I query a non-public Oid? Do I have to change the search path? If yes how do I do it? As mentioned I need to do this with the C interface. 

I looking to source code

Oid
TypenameGetTypidExtended(const char *typname, bool temp_ok)
{
<-->Oid><--><-->typid;
<-->ListCell   *l;

<-->recomputeNamespacePath();

<-->foreach(l, activeSearchPath)
<-->{
<--><-->Oid><--><-->namespaceId = lfirst_oid(l);

<--><-->if (!temp_ok && namespaceId == myTempNamespace)
<--><--><-->continue;<-><--><-->/* do not look in temp namespace */

<--><-->typid = GetSysCacheOid2(TYPENAMENSP, Anum_pg_type_oid,
<--><--><--><--><--><--><--><-->PointerGetDatum(typname),
<--><--><--><--><--><--><--><-->ObjectIdGetDatum(namespaceId));
<--><-->if (OidIsValid(typid))
<--><--><-->return typid;
<-->}

<-->/* Not found in path */
<-->return InvalidOid;
}

You can get the value from sys cache by call GetSysCacheOid2. It can looks like

<--><-->char<-->   *schemaname;
<--><-->char<-->   *typname;

<--><--><-->namespaceId = LookupExplicitNamespace(schemaname, missing_ok);
<--><--><-->if (OidIsValid(namespaceId))
<--><--><--><-->typoid = GetSysCacheOid2(TYPENAMENSP, Anum_pg_type_oid,
<--><--><--><--><--><--><--><--><--><--> PointerGetDatum(typname),
<--><--><--><--><--><--><--><--><--><--> ObjectIdGetDatum(namespaceId));
<--><--><-->else
<--><--><--><-->typoid = InvalidOid;

Thank you so much. That worked.

with pleasure.

When you write C extensions for Postgres, then PostgreSQL source code is the best source of inspiration.

Regards

Pavel

Regards,

Michael