Обсуждение: large object support in PostGres 7.4

Hi,

We have API's in /usr/local/pgsql/include/libpq-fe.h which support large
objects in PostGres     extern int  lo_open(PGconn *conn, Oid lobjId, int mode);     extern int  lo_close(PGconn *conn,
intfd);     extern int  lo_read(PGconn *conn, int fd, char *buf, size_t len);     extern int  lo_write(PGconn *conn,
intfd, char *buf, size_t len);     extern int  lo_lseek(PGconn *conn, int fd, int offset, int whence);     extern Oid
lo_creat(PGconn*conn, int mode);     extern int  lo_tell(PGconn *conn, int fd);     extern int  lo_unlink(PGconn *conn,
OidlobjId);     extern Oid  lo_import(PGconn *conn, const char *filename);     extern int  lo_export(PGconn *conn, Oid
lobjId,const char
 
*filename);

My doubt is, do these API's operate on character data?   i.e., My table
schema is like this

table (name varchar, script varchar).  I have to store a large data(in
character form) in the script column (upto 3 MB).

As of my understanding the above mentioned API's work on the OID field.
i.e,.  table(name varchar, script oid).  Is that correct?
Please clarify this if anyone has already used this large object APIs and
specify if this has any limitation on the size?

thanks,
-Vadivel



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Hi,

On 6/7/05, Vadivel Subramaniam
<vadivel.subramaniam@flextronicssoftware.com> wrote:
> My doubt is, do these API's operate on character data?   i.e., My table
> schema is like this
>
> table (name varchar, script varchar).  I have to store a large data(in
> character form) in the script column (upto 3 MB).
>
> As of my understanding the above mentioned API's work on the OID field.
> i.e,.  table(name varchar, script oid).  Is that correct?

Yep. Large Objects are stored (and distributed between rows) in a
specific table: `pg_largeobject'. You can use these lo records by
referencing to their OIDs. Furthermore, you cannot (also shouldn't)
reach data on pg_largeobject with another function/routine out of
supplied lo_... functions by libpq.

> Please clarify this if anyone has already used this large object APIs and
> specify if this has any limitation on the size?

Yes, there's a limitation about 'em. (2GB) For more information please see:
http://www.postgresql.org/docs/7.4/interactive/largeobjects.html

Regards.