On 25-07-2013 05:32, suresh.balasubra wrote:
Disclaimer: I am no hacker, just a PostGreSQL user, trying to provide a user scenario where DISCARD SEQUENCES functionality is required.We have designed a developed a small Application Development platform for which the backend is PostGreSQL. There is a DBLayer which is responsible in generating SQL statements for all the INSERT, UPDATE, DELETE operations. Data can be pushed into multiple tables using this layer. What we provide to this layer is just a DataSet (.NET). DataTables in the DataSet will be named after their respective tables. We also use DataColumn extended properties to push in additional logic. All these happen with in a transaction and also in one shot, just one hit to the DB by appending SQL statements in proper order. There is an interesting feature that we have built into this DBlayer which is auto linking. All tables in our system will have a serial field 'id'. Suppose there is a master table (let us call it 'voucher') and a detail table ('voucher_lines'), and we are using the layer to push one record to the master table and 50 records to the detail table. 'voucher_lines' table will have a integer column 'voucher_id'. '*_id' fields are automatically populated with 'currval('*_id_seq'). All this works like a charm. Now, imagine we want to push data into another table (say 'invoice') which also has a field 'voucher_id'. This is a different activity not connected with the above mentioned transaction. In this scenario this field will get updated as currval('voucher_id_seq') returns a value. But we do not want that to be updated. What we want is to resolve '*_id' fields into values only within a transaction. After the transaction we want to get away with the session. If we could have cleared the session someway (DISCARD ALL does it, but not the currval sequence info) after the first transaction it would have worked for us.
I already sent a patch to implement DISCARD SEQUENCES [1] that I expect to be part of 9.4 version.
Regards, [1] https://commitfest.postgresql.org/action/patch_view?id=1171 -- Fabrízio de Royes Mello Timbira - http://www.timbira.com.br/ PostgreSQL: Consultoria, Desenvolvimento, Suporte 24x7 e Treinamento -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
