Large Objects

The Large Objects feature is a way of storing large files in a PostgreSQL database. Files can normally be stored in bytea columns but there are two downsides; a file can only be 1 GB and the backend buffers the whole file when reading or writing a column, which may use significant amounts of RAM on the backend.

With the Large Objects feature, objects are instead stored in a separate system table in smaller chunks and provides a streaming API for the user. Each object is given an integral identifier that is used for accessing the object, that can, for example, be stored in a user's table containing information about this object.

Example

// Retrieve a Large Object Manager for this connection
var manager = new NpgsqlLargeObjectManager(Conn);

// Create a new empty file, returning the identifier to later access it
uint oid = manager.Create();

// Reading and writing Large Objects requires the use of a transaction
using (var transaction = Conn.BeginTransaction())
{
    // Open the file for reading and writing
    using (var stream = manager.OpenReadWrite(oid))
    {
        var buf = new byte[] { 1, 2, 3 };
        stream.Write(buf, 0, buf.Length);
        stream.Seek(0, System.IO.SeekOrigin.Begin);

        var buf2 = new byte[buf.Length];
        stream.Read(buf2, 0, buf2.Length);

        // buf2 now contains 1, 2, 3
    }
    // Save the changes to the object
    transaction.Commit();
}

Table of Contents

Large Objects

Example

See also