i'm working in a symfony project and using sfPropelPager to show a paged list of elements.
The problem is that with a great amount of data to list (i.e. thousands of registers) it makes a query to the database for each page to show!!!! That means about 100 extra queries in my case, and that is unacceptable.
Showing some of my code: the function that returns the pager object
$pager = new sfPropelPager('MyTable',sfConfig::get('sfPropelPagerLines'));
$c = new Criteria();
$c->add('my_table_field',$value);
$c->addDescendingOrderByColumn('date');
$pager->setCriteria($c);
$pager->init();
return $pager;
So, please, if you know a way to get all the results with only one query, it would be a great solution for my problem. Otherwise i must implement that list with an ajax call for every page the user wants to see
Thank you very much for your time.
I'm not sure to get your problem but, anyway, avoid the use of Criteria. Try to make queries with the ModelCriteria API: http://www.propelorm.org/reference/model-criteria.html.
For each paginated page, a query to the database will be done, this is the standard behavior for all pagers I know. If it's related to related objects (assuming you want to display information from relations), you may want to create a query that links those objects before to paginate, that way you'll get one query per page for all your data to display.
Read this doc for instance: http://www.propelorm.org/documentation/03-basic-crud.html#query_termination_methods
At last i did'nt get a solution for the problem, i had to implement the list via AJAX call, calling to a function that returns the requested page, so at the load of the page, no query for this list is slowing the user experience.
Thank you anyway to help me :)
Related
My goal is very simple and I would guess it is a very common goal among web developers.
I am creating a Rails (5.1) application, and I simply want to use AJAX to get the value of a specific cell in a specific row of a specific table in my database (later I am going to use that value to highlight some text on the current page in the user's browser).
I have not been able to find any documentation online explaining how to do this. As I said, it seems like a basic task to ask of jquery and ajax, so I'm confused as to why I'm having so much trouble figuring it out.
For concreteness, say I have a table called 'animals', and I want to get the value of the column 'species' for the animal with 'id' = 99.
How can I construct an AJAX call to query the database for the value of 'species' for the 'animal' with 'id' = 99 .
Though some DBs provide a REST API, what we commonly do is define a route in the app to pull and return data from the DB.
So:
Add a route
Add a controller/action for that route
In that action, fetch the data from the DB and render it in your preferred format
On the client-side, make the AJAX call to that controller/action and do something with the response.
I am trying to get either a dropdown or selection box(prefer the later, because of the possibility to choose multiple values at once) in a webform.
In this case i already got the dropdown working, based on measures.measurement_type. The second needs to be measures.measurement, filtered by the type selected in the first dropdown.
I can not seem to get this working. I tried googling, but without succes. Can anyone help me get on the right track?
I found solutions using Arrays, but no working solution using 1 database table.
using ruby 4.2
Thanks
There are two options for this.
Using AJAX calls. Like #Ronan said in his answer, you need to make an AJAX call on the selection of first drop down (on change method). In the rails action method, you can render a JS partial where you can set the filtered items for second drop down.
Another one is totally client side. Like render all the possible items of both drop downs to client side. Meaning both type and measurements as javascript array. Then when changing the type drop down, filter the measurements array using jQuery and populate in the second drop down.
You gotta use some ajax for doing that, can't see other way. When your measures.measurement_type changes, you send a request passing that measurement_type as param for your action. In that action, you retrieve the collection of measurements based on the measurement_type passed in the param, and then return that data to be handled on your success ajax callback. On that method, with some jquery you should populate the second input with the options returned.
This is some simpler explanation... you should take some look at a more complete article for understanding step-by-step. Would suggest this one, for example: https://remysharp.com/2007/01/20/auto-populating-select-boxes-using-jquery-ajax. Good luck!
I am currently designing a Rest API and is a little stuck on performance matters for 2 of the use cases in the system:
List all campaigns (api/campaigns) - needs to return campaign data needed for listing and paging campaigns. Maybe return up to 1000 records and would take ages to retreive and return detailed data. The needed data can be returned in a single DB call.
Retrieve campaign item (api/campaigns/id) - need to return all data about the campaign and may take up to a second to run. Multiple DB calls is needed to get all campaign data for a single campaign.
My question is: Is it valid to return different json-responses to those 2 calls (if well documented) even if it regards the same resource? I am thinking that the list response is a sub set of the retreive-response. The reason for this is to make to save DB calls and bandwitdh + parsing.
Thanks in advance!
I think it's both fine and expected for /campaigns and /campaigns/{id} to return different information. I would suggest using query parameters to limit the amount of information you need to return. For instance, only return a URI to each player unless you see a ?expand=players query parameter, in which case you return detailed player information.
When I query some view in Couchbase I get the response that has following structure:
{
"total_rows":100,
"rows":[...]
}
'total_rows' is very useful property that I can use for paging.
But lets say I select only a subset of view using 'start_key' and 'end_key' and of course I don't know how big this subset will be. 'total_rows' is still the same number (as I understand it's just total of whole view). Is there any easy way to know how many rows was selected in subset?
You can use the in-built reduce function _count to get the total count of your query.
Just add _count as reduce function for your view. After that, you will need to make two calls to couchbase:
In one call, you'll set the query param reduce=true (along with either group=true or group_level=n, depending upon how you're sending your key(s)). This will give you the total count of your filtered rows.
In the other call, you'll disable the reduce function with reduce=false because you now need the actual rows.
You can find more details about map and reduce at http://docs.couchbase.com/admin/admin/Views/views-writing.html
You can just use an array count/total/length in whatever language you are using.
For example in PHP:
$result = $cb->view("dev_beer", "beer_by_name", array('startkey' => 'O', 'endkey'=>'P'));
echo "total = >>".count($result["rows"])
If you're actually wanting to paginate your data then you should use limit and skip:
http://www.couchbase.com/docs/couchbase-manual-2.0/couchbase-views-writing-querying-pagination.html
If you have to paginate the view in the efficient way, you actually don't need to specify both start and the end.
Generally it is possible to use startkey/startkey_id and limit. In this case the limit will tell you that the page won't be bigger than known size.
Both cases are described in CouchDB book: http://guide.couchdb.org/draft/recipes.html#pagination
Here is how it works:
Request rows_per_page + 1 rows from the view
Display rows_per_page rows, store + 1 row as next_startkey and next_startkey_docid
As page information, keep startkey and next_startkey
Use the next_* values to create the next link, and use the others to create the previous link
I had a question here Mysql select speed
I figure that select of mysql is fast, but
My problem is when the ajax is generating a huge select and option of cities, for example BRAZIL.
Is there a way to generate the ajax select faster? Because if it's too big, the browser lag and waits to load full content of select. I want it smoother.
Can anyone help me please ? :(
Try to cache your query result. That means, run the query on a regular base, save the result (for example in another table or in an xml file), then send the precached data to the browser on request.
You may want to preload the whole lists into your document and hide them by the display: none; property. Then you do not need to AJAX pull the contents of your select box. Instead, just show the list you need if a user selects a specific entry and hide the others.
Is you problem is in server or in client?
Fiddler or Firebug can help you to know how much time spent by processing in server and by transfering to client.
I think you need to change your server side, and return small strings, like this:
1,Jerusalem|2,Tel Aviv|3,Ariel
In client side, you need to split by "|" and then by ",", and use an JS array to build HTML:
//not tested
var a = string.split("|"),s=[]
for (var i=0;i"+b[1]+"");
}
$("#div").html(s.join(" "));
JSON is easier to use, but will make the response larger and slowly.