I'm using Postgres 8.4 on RHEL 6 and I need to support inserting data into a table from multiple processes with there occasionally being duplicates from the different processes. Here's a simple example table:
CREATE TABLE test (tutc TIMESTAMP WITHOUT TIME ZONE, id INTEGER, value INTEGER, PRIMARY KEY (tutc, id));
If I do the following query from 2 processes, then it's fine:
INSERT INTO test (tutc, id, value) SELECT '2015-01-01 01:02:03', 4, 5 WHERE NOT EXISTS (SELECT 1 FROM test WHERE tutc='2015-01-01 01:02:03' AND id=4);
But if I put the operation in a transaction, then the second process will block until the transaction of the first is commited (which is fine) but then the insert fails with a "duplicate key value violation". I'm guessing that this is because the transaction is making it so that the SELECT only sees the values from before the transaction of the second process began.CREATE TABLE test (tutc TIMESTAMP WITHOUT TIME ZONE, id INTEGER, value INTEGER, PRIMARY KEY (tutc, id));
If I do the following query from 2 processes, then it's fine:
INSERT INTO test (tutc, id, value) SELECT '2015-01-01 01:02:03', 4, 5 WHERE NOT EXISTS (SELECT 1 FROM test WHERE tutc='2015-01-01 01:02:03' AND id=4);
Using an "upsert" type of function, like the one shown in the documentation ( see http://www.postgresql.org/docs/8.4/static/plpgsql-control-structures.html#PLPGSQL-UPSERT-EXAMPLE ) seems like it might work, but I don't need to support updating and was hoping to not have to use a custom function. So is there some way to catch the unique_violation exception without creating a function? Or some other solution to this?
Thanks,
Dave
