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[IMP] point_of_sale: added some comments about the localstorage db implementation and performance 

bzr revid: fva@openerp.com-20130111144108-5u4ie3p9ueoj6ulm
This commit is contained in:
Frédéric van der Essen 2013-01-11 15:41:08 +01:00
parent 493385f279
commit 81ffada41c
1 changed files with 31 additions and 3 deletions
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34
addons/point_of_sale/static/src/js/db.js
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@ -1,8 +1,34 @@
function openerp_pos_db(instance, module){
/* PosLS is a LocalStorage based implementation of the point of sale database,
it performs better for few products, but does not scale beyond 500 products.
*/
/* The db module was intended to be used to store all the data needed to run the Point
* of Sale in offline mode. (Products, Categories, Orders, ...) It would also use WebSQL
* or IndexedDB to make the searching and sorting products faster. It turned out not to be
* a so good idea after all.
*
* First it is difficult to make the Point of Sale truly independant of the server. A lot
* of functionality cannot realistically run offline, like generating invoices.
*
* IndexedDB turned out to be complicated and slow as hell, and loading all the data at the
* start made the point of sale take forever to load over small connections.
*
* LocalStorage has a hard 5.0MB on chrome. For those kind of sizes, it is just better
* to put the data in memory and it's not too big to download each time you launch the PoS.
*
* So at this point we are dropping the support for offline mode, and this module doesn't really
* make sense anymore. But if at some point you want to store millions of products and if at
* that point indexedDB has improved to the point it is usable, you can just implement this API.
*
* You would also need to change the way the models are loaded at the start to not reload all your
* product data.
*/
/* PosLS is a localstorage based implementation of the point of sale database.
* FIXME: The Products definitions and categories are stored on the locastorage even tough they're
* always reloaded at launch. This could induce a slowdown because the data needs to be reparsed from
* JSON before each operation. If you have a huge amount of products (around 25000) it can also
* blow the 5.0MB localstorage limit.
*/
module.PosLS = instance.web.Class.extend({
name: 'openerp_pos_ls', //the prefix of the localstorage data
limit: 100, // the maximum number of results returned by a search
@ -110,6 +136,8 @@ function openerp_pos_db(instance, module){
},
/* saves a record store to the database */
save: function(store,data){
var str_data = JSON.stringify(data);
console.log('Storing '+ Math.round(str_data.length/1024.0)+' KB of data to store: '+store);
localStorage[this.name + '_' + store] = JSON.stringify(data);
this.cache[store] = data;
},