Using binary large objects

What if someone wants to store a picture, Word document, or PDF, in a database? For this, PostgreSQL has a large object facility that provides stream-style access to user data, which is stored in a special large-object structure. Streaming access is useful when you are working with data values that are too large to manipulate conveniently as a whole.

The large object implementation breaks large objects into chunks and stores them in rows in the database. A B-tree index guarantees fast searches for the correct chunk number when doing random-access reads and writes.

How do we implement it? As this book is intended to teach you the basics, let's look at how to create/implement large objects:

Creating a large object

You can use the lo_creat function to create a large object. The syntax is as follows:

Oid lo_creat(PGconn *conn, int mode);

The return value is Oid.

Here's an example:

inv_oid = lo_creat(conn, INV_READ|INV_WRITE);

The Oid lo_create(PGconn *conn, Oid lobjId)...