Re: How to use JDBC to update LargeObject - Mailing list pgsql-jdbc
From | Satish Burnwal (sburnwal) |
---|---|
Subject | Re: How to use JDBC to update LargeObject |
Date | |
Msg-id | 3A8C969225424C4D8E6BEE65ED8552DA89D6E5@XMB-BGL-41C.cisco.com Whole thread Raw |
In response to | Re: How to use JDBC to update LargeObject (Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>) |
Responses |
Re: How to use JDBC to update LargeObject
(Kris Jurka <books@ejurka.com>)
|
List | pgsql-jdbc |
Even setBlob() method seems to be updating large object only partially. This is my code: CREATE TABLE image (name TEXT, oid OID); select * from image; name | oid -----------------+------- bigfile | 17416 (1 rows) //update the blob in the database org.postgresql.jdbc3.Jdbc3Blob blob = new org.postgresql.jdbc3.Jdbc3Blob((org.postgresql.PGConnection)con, 17416); InputStream is = new FileInputStream("/root/myfile"); byte[] bytes = new byte[128]; int n = 0, pos = 1; while ((n = is.read(bytes)) >= 1) { blob.setBytes(pos, bytes, 0, n); pos = pos + n; } is.close(); PreparedStatement sst = con.prepareStatement("update image set oid = ? where name = ?"); sst.setString(2, "bigfile"); sst.setBlob(1, blob); int count = sst.executeUpdate(); This updates only partially the existing blob. I want the file contents to be changed (from 1 Mb to 100 kb). Tell me if thereis a way (without changing the OID of the large object). Satish ------------------------ -----Original Message----- From: Heikki Linnakangas [mailto:heikki.linnakangas@enterprisedb.com] Sent: Thursday, January 21, 2010 1:27 PM To: Satish Burnwal (sburnwal) Cc: pgsql-jdbc@postgresql.org Subject: Re: [JDBC] How to use JDBC to update LargeObject Satish Burnwal (sburnwal) wrote: > I am using 8.1 Postgre JDBC. I want to know how can I use JDBC to > update the contents of a LargeObject. For example, say I have created > a LO for a file with 1 Mb of data. Later on, file contents have > changed and are now just 100 kb and I want to update the LO. When I > try to write to a large object using the method largeObject.write(byte > [], off, len), it seems to be updating the first 100 kb data, not > really replacing the existing 100 MB with the new data. pg_largeobject > table still shows the same number of rows. Any idea how can I update > the contents of a large object. See manual, http://jdbc.postgresql.org/documentation/84/binary-data.html: " To use the Large Object functionality you can use either the LargeObject class provided by the PostgreSQL™ JDBC driver, or by using the getBLOB() and setBLOB() methods. Important You must access Large Objects within an SQL transaction block. You can start a transaction block by calling setAutoCommit(false). " -- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com
pgsql-jdbc by date: