Re: Tuple concurrency issue in large objects

Hi all,

I am working on a project which allows multiple users to work on single
large text document. I am using lo_put to apply only the diff into the
large object without replacing it with a new lob. While working on it, I
encountered an error "Tuple concurrently updated".
The error can be reproduced with two psql clients.

Setup:

mydb=# create table text_docs(id serial primary key, data oid);
CREATE TABLE
mydb=# insert into text_docs(data) select lo_import('./upload.txt');
INSERT 0 1
mydb=# select * from text_docs;
  id |  data
----+---------
   1 | 5810130
(1 rows)

Now, if we open two psql clients and execute the following commands:

Client 1:

mydb=# begin;
BEGIN
mydb=# select lo_put(5810130, 10, '\xaa');
UPDATE 1

Client 2:

mydb=# select lo_put(5810130, 10, '\xaa');

Client 1:
mydb=# commit;
COMMIT

Client 2:
mydb=# select lo_put(5810130, 10, '\xaa');
ERROR:  tuple concurrently updated

Is there a workaround to this concurrency issue without creating a new
large object?

Regards
Shalini