Differences

This shows you the differences between two versions of the page.

--- pracro:database [2008/11/25 09:00] – created deva
+++ pracro:database [2010/06/07 11:17] (current) – deva
@@ Line 1: / Line 1: @@
 ======Pracro Database design======
-Nothing to see here, move along....
+Nothing to see here, move along...
+=====Persistent transactions=====
+When a new Pracro session is initiated, a connection to PostgreSQL is made.
+All commands (strings) issued to this connection, will be appended to a string contained in the session class.
+This string will be serialised with the rest of the session data upon pracrod shutdown and re-read on startup.
+The first SQL command issued is BEGIN;
+If a 'commit' is received by the pracro server, it is translated into a COMMIT; on the SQL connection and the command string is cleared.
+If the client disconnects without any actions, an ROLLBACK; is sent to the SQL server.
+On reconnect to the session, the entire command string is replayed as it is, and the session is ready to continue where it left off.
+On the Pracro 'discard' command, a ROLLBACK; is sent to the SQL server, and the command string is cleared.
+=====Journal uptodateness check=====
+  * Person A is working on a patient P.
+  * Person A commits the macro M, with data "data from A".
+  * Person A 'close no commit'.
+  * Person B starts working on patient P.
+  * Person B commits the macro M, with data "data from B".
+  * Person B 'close and commit'.
+  * Person A continues work on patient P.
+  * Person A sees the resume of M being "data from B", and acknowledges it.
+  * Person A 'close and commit'
+Person A now **thinks** that the journal contains "data from B". But in fact it contains
+<code>
+data from B
+data from A
+</code>
+This is due to two problems: The field shown on the active session is not nesecarily the one being commit, when the entire session is committed. Second person A cannot see what changes has been made by others.