Guys,
I want to assure that a SQL statement is atomar. It trys to check if an
email address is already found in a table, if yes, it returns the id
field of the entry. If not found, it inserts the entry with the
previously generated increment id and returns - again - the id.
My concern: in a multi threaded environment, can a second thread
interrupt this statement and eventually insert the same email address in
the table with a different id? Or is this statement atomar?
Any help would be highely appreciated.
CODE: _id := nextval('email_id_increment');
INSERT INTO email_adr (email_id, email, lastupdate)
SELECT _id, 'sender@example.com', now()::timestamp
WHERE NOT EXISTS (SELECT * FROM email_adr WHERE
email='sender@example.com');
- Johann
