SmartGWT RestDateSource and Paging (Large DataSet of) Dynamic Data

Question

Hello

I have a database table for log messages and at any time there can be inserted new rows. I want to show them in grid and when you scroll down I want to request more rows form this table (server side) but without to be affected from new added rows. The new rows only have to be visible if I refresh the whole grid.

I'm not sure how can I request rows in a range (from, to) using JDBC. I think there is no portable (across deferent databases) SQL query to do this? (I'm using MYSQL)

I think that after reading first page of this table I have to send to the client side the Max Id from log table and after that request new rows using this Max Id as parameter in SQL (WHERE id <= MAXID) but I'm not sure how I can pass this parameter from server to client and back using RestDateSource?

Do you have any better ideas how I can make this?

P.S. I'm using LGPL SmartGWT version and using my own servlets for server side.

Answer 1

SmartGWT Pro and better do this automatically. Even if you don't want to use Pro, you can download the evaluation (smartclient.com/builds) and watch the server-side console, where the SQL queries are logged.

Answer 2

Here is what I would do; I imagine that you either have a growing-number ID or a timestamp for each of your rows.

Before you start querying for data, you call a webservice to query the current id (eg last line insterted is 12345).

Then you add a Criteria object to your datasource that says "rowId <= 12345". At this point, you can use the grid freely - paging, sorting, etc will work automatically as new rows will automatically be excluded.

(Or if you use a personalized datasource and not the default RESTdataSource, you basically do the same thing without using Criteria explicitly).