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Thread: How can I retrieve attribute category with attribute Oid in C function?

How can I retrieve attribute category with attribute Oid in C function?

From
"a"
Date:
Hi I am writing something that would need to identify the attribute category inside a C function, now I may need a way of fast access it, but the information is not stored in FormData_pg_attribute structure.

Can anyone help? Thanks a lot!!!

Shore

Re: How can I retrieve attribute category with attribute Oid in Cfunction?

From
Laurenz Albe
Date:
a wrote:
> Hi I am writing something that would need to identify the attribute category inside a C function,
> now I may need a way of fast access it, but the information is not stored in FormData_pg_attribute structure.

Are you talking about pg_type.typcategory?

That is accessible from FormData_pg_type.
You'd have to look up atttypid in the TYPEOID cache.

Yours,
Laurenz Albe
-- 
Cybertec | https://www.cybertec-postgresql.com

Re: How can I retrieve attribute category with attribute Oid in Cfunction?

From
"a"
Date:
hey thank you!!

could you provide some more detail information??

What function should I use to get FormData_pg_type structure??

thanks a lot


------------------ Original message ------------------
From: "Laurenz Albe";
Sendtime: Monday, May 14, 2018 4:11 PM
To: "a"<372660931@qq.com>; "pgsql-general";
Subject: Re: How can I retrieve attribute category with attribute Oid in Cfunction?

a wrote:
> Hi I am writing something that would need to identify the attribute category inside a C function,
> now I may need a way of fast access it, but the information is not stored in FormData_pg_attribute structure.

Are you talking about pg_type.typcategory?

That is accessible from FormData_pg_type.
You'd have to look up atttypid in the TYPEOID cache.

Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com

Re: How can I retrieve attribute category with attribute Oid in Cfunction?

From
"a"
Date:
BTW, I searched another function called "lookup_type_cache", which will return a pointer of structure of "TypeCacheEntry".

The structure contains "TypeCacheEntry.typtype" that may also help to identify the type.

But I'm concerning about possible memory leak and allocation stuff. Is it safe to just declare a pointer and call this function??


------------------ Original ------------------
From:  "372660931@qq.com";<372660931@qq.com>;
Date:  May 14, 2018
To:  "Laurenz Albe"<laurenz.albe@cybertec.at>; "pgsql-general"<pgsql-general@postgresql.org>;
Subject:  Re: How can I retrieve attribute category with attribute Oid in Cfunction?

hey thank you!!

could you provide some more detail information??

What function should I use to get FormData_pg_type structure??

thanks a lot


------------------ Original message ------------------
From: "Laurenz Albe";
Sendtime: Monday, May 14, 2018 4:11 PM
To: "a"<372660931@qq.com>; "pgsql-general";
Subject: Re: How can I retrieve attribute category with attribute Oid in Cfunction?

a wrote:
> Hi I am writing something that would need to identify the attribute category inside a C function,
> now I may need a way of fast access it, but the information is not stored in FormData_pg_attribute structure.

Are you talking about pg_type.typcategory?

That is accessible from FormData_pg_type.
You'd have to look up atttypid in the TYPEOID cache.

Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com

Re: How can I retrieve attribute category with attribute Oid inCfunction?

From
Laurenz Albe
Date:
a wrote:

> could you provide some more detail information??
> 
> What function should I use to get FormData_pg_type structure??
> 
> BTW, I searched another function called "lookup_type_cache", which will return a pointer of structure of
"TypeCacheEntry".
> 
> The structure contains "TypeCacheEntry.typtype" that may also help to
identify the type.
> 
> But I'm concerning about possible memory leak and allocation stuff. Is it safe to just declare a pointer and call
thisfunction??
 

In "logicalrep_write_typ" in src/backend/replication/logical/proto.c
you can find an example how to get the pg_type values from the OID.

Yours,
Laurenz Albe
-- 
Cybertec | https://www.cybertec-postgresql.com