Newer version On Thu, 2008-05-01 at 15:15 +0200, Philip Van Hoof wrote:
To Jamie, Martyn, Frade, Ottela, etc ... Here's some actual code. Please review this and let me know if you see dings different. On Tue, 2008-04-29 at 17:56 +0200, Philip Van Hoof wrote:Pre note: This is about the Xesam support being done (since this week) in the indexer-split. About: Xesam requires notifying live searches about changes that affect them. We plan to implement this with a "events" table that journals all creates, deletes and updates that the indexer causes. Periodically we will handle and then flush the items in that events table. I made a cracktasty diagram that contains the from-a-high-distance abstract proposal that we have in mind for this. This is pseudo code that illustrates the periodic handler: bool periodic_handler (...) { lock indexer update eventstable set beinghandled=1 where 1=1 (all items) unlock indexer foreach query in all livequeries added, modified, removed = query.execute-on (eventstable) query.emit_added (added) query.emit_removed (removed) query.emit_modified (modified) done lock indexer delete from eventstable where beinghandled = 1 unlock indexer return (!stopping) } Here's a piece of IRC log between me and jamiecc about the proposal: pvanhoof ping jamiemcc pvanhoof same thing pvanhoof I'll make a pdf jamiemcc oh ok pvanhoof Sending pvanhoof ok pvanhoof so pvanhoof it's about the hitsadded, hitsremoved and hitsmodified signals for xesam pvanhoof What we have in mind is using a "events" table that is a journal for all creates, deletes and updates pvanhoof Periodically we will flush that table, each create (insert), update and each delete we add a record in that table pvanhoof We'll make sure the table is queryable in a similar fashion as how the Xesam query will execute pvanhoof In the periodical handler we'll for each live search check whether it got affected by the items in the events table pvanhoof In pseudo, the handler: jamiemcc sounds feasible pvanhoof gboolean periodic_handler (void data) { pvanhoof lock indexer pvanhoof update eventstable set beinghandled=1 where 1=1 (all items) pvanhoof unlock indexer pvanhoof foreach query in all live queries pvanhoof added, modified, removed = query.execute-on (eventstable) pvanhoof query.emit_added (added) pvanhoof query.emit_removed (removed) pvanhoof query.emit_modified (modified) pvanhoof done pvanhoof lock indexer pvanhoof delete from eventstable where beinghandled = 1 pvanhoof unlock indexer pvanhoof } pvanhoof I've send you a diagram that you can look at as if it's a state-activity one, a ERD and a class diagram :) now how cool is that?? :) pvanhoof it's just three columns, although the ERD is quite simplistic of course jamiemcc yeah just go tit * fritschy (~fritschy 84 19 173 195) has left #tracker pvanhoof so, the current idea is to adapt those stored procedures into transactions that will also add this record to the "events" table * fritschy (~fritschy 84 19 173 195) has joined #tracker pvanhoof Which might not be sufficient, and we kinda lack the in-depth know-how of all the db handling of tracker pvanhoof So that's a first issue we want to discuss with you pvanhoof The other is stopping the indexing, restarting it (locking it, in the pseudo code): what you think about that jamiemcc ok I will need to think about it - I iwll probably reply later tonight and we can discuss tomorrow pvanhoof I adapted my initial proposal to have two short critical sections rather than letting the entire periodic handler be one critical section pvanhoof that way the lock is smaller jamiemcc the indexer will be seaparte process so will need to be locked via dbus signals pvanhoof by just adding a column to the events table pvanhoof yes but I guess we want any such locking to be short jamiemcc well yes pvanhoof then once the items that are to be handled are identified, we for each live-search check whether the live-search is affected pvanhoof and we perform the necessary hitsadded, hitsremoved and hitsmodified signals if needed pvanhoof if all is done, we simply purge the handled items from the events table jamiemcc the query results will be store din temp tables pvanhoof which is the second location where we want the indexer to be locked-out jamiemcc remember a query may be a cursor so wont include entire result set pvanhoof No okay, but that's something the check needs to worry about pvanhoof so ottela is working on a query for the live-search jamiemcc ok cool pvanhoof and if we only want to update if the client has the affected item visible, due to cursor-usage pvanhoof then i guess we'll somehow need to get that info into trackerd jamiemcc any reason we dont store whats change din memory rather than sqlite table? pvanhoof oh, that's abstract right now jamiemcc o jamiemcc ok pvanhoof "tracker's event table" can also be a hashtable for me .. jamiemcc yeah fine pvanhoof implementation detail pvanhoof since it doesn't need to be persistent ... pvanhoof difference is that either we use a memory table and still a transaction for the three stored procedures pvanhoof or we adapt code jamiemcc prefer hashtable as amount of data will be small jamiemcc can even be a list pvanhoof ok, your comments/ideas on this would of course be very useful btw jamiemcc yeah I will think about it more tonight and get back to you pvanhoof sounds great pvanhoof I'll make a mail about this to the mailing list? or I await your ideas tomorrow? pvanhoof I'll just wait for now jamiemcc you cna mail if you like jamiemcc I will reply to it _______________________________________________ tracker-list mailing list tracker-list gnome org http://mail.gnome.org/mailman/listinfo/tracker-list_______________________________________________ tracker-list mailing list tracker-list gnome org http://mail.gnome.org/mailman/listinfo/tracker-list
-- Philip Van Hoof, freelance software developer home: me at pvanhoof dot be gnome: pvanhoof at gnome dot org http://pvanhoof.be/blog http://codeminded.be
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