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arilotta

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Posts posted by arilotta

    New TUniCheckListBox component

    in Components and Code Samples

    Posted

    It is something related to the way events are treated in Unigui.

    Either:

     

    - populate the CheckListBox at design time or at runtme in the FormCreate event; then handle just the initialization of Selected in the another event

     

    - set EnableSynchronousOperations to TRUE in UniMainModule, then adjust your code in this way:

     

    procedure TMainForm.testcl(Sender: TObject);
    begin
      UniCheckListBox1.Items.Add('Item 1');
      UniCheckListBox1.Items.Add('Item 2');
      UniCheckListBox1.Items.Add('Item 3');
      UniSession.Synchronize;
      UniCheckListBox1.Selected[1]:=true;
    end;

    UniDbGrid - fetching considerations

    in General

    Posted

    Glad to post the code (MOGSY, my name's Andrea :-)

    Here you can download the whole app:

     

    https://drive.google.com/file/d/1p09s2H3-gky58SZ8VglohjtZjJD81sM6/view?usp=sharing

     

    - to customize the grid (hide refresh button and add "More pages..." button) I've used some code that I've found on this forum and it's not mine:

    GRD.ClientEvents.UniEvents 

    Ext.toolbar.Paging [pagingBar]

    pagingBar.afterCreate

     

    function pagingBar.afterCreate(sender)
    {
      sender.items.items[10].hide();
      sender.add([{
                   xtype: 'button',
                   text: 'More pages...',
                   handler: function() {             
                     ajaxRequest(sender, 'morePages',[]);                 
                   }
                  }]);
    }
     
    - to support the incremental fetching your tdataset descendent (and your RDBMS) should support the following propertes:
    * FetchRows (or similar, number of rows to fetch each time)
    * RecordCount
    * RecNo
     
    I use Oracle and ODAC components from DevArt, in a previous post Volk65 said that even FireDac components should work,
    you can check the following link:
     

    UniDbGrid - fetching considerations

    in General

    Posted

    Hi all, I've developed a small app that shows better the idea, it is published at the following address (I will keep it online for a week):

     

    http://188.11.1.245:8746/FetchingDemo.dll

     

    - In the main page, it is possible to choose:

        - the grid page size

        - the maximum number of rows to fetch (this limits the rows manipulating the SQL in the query)

        - whether fetch all the rows or not

    - The actual table contains more than 6 million records

    - Clicking the "Open" button the secondary form with the UniDbgrid (FRMGrid) is opened with the settings specified in the main form

    - The grid contains a new button in the paging bar: "More pages..."; by clicking it an additional page (pagesize rows) is fetched from

      the opened query if available, and the grid and the paging bat is updated accordingly

    - The secondary form contains also a couple of buttons to show the rows fetched so far (Fetched row count) and the possibility to

      select a row given its absolute position (RecNo)

     

    Now let's tets the following scenarios:

    1. pagesize:10; #rows: 100000; fetch all rows: TRUE

        This is the current suggested configuration for large datasets: pagination+fetch all. 

        It takes more or less 5 seconds on my web server to fetch 100000 rows from the DB server, to paginate them and to send the fisrt page back

        to the browser. The memory consumption on the web server is huge, as all the 100000 are kept in memory.

        It is almost impossible to use this approach to fetch 1 million rows.

    2. pagesize:10; #rows: 100000; fetch all rows: FALSE

        This is the implementation I'm suggesting for big datasets. 

        It takes nothing to open the secondary form (in fact it is opened immediately), and the memory consumption is minimized

        as only the first 10 rows are fetched from the DB server. If the user wants to fetch additional pages, it can click on the

       "More pages..." button and fetch them one by one (it takes nothing to fetch additional pages, 10 at a time).

        Memory consumption is minimized on DB server and web server, network traffic highly reduced, web site more responsive....

     

    In my original post, I told I would prefer additional rows fetched from the DB to be appended to the bottom of the grid rather than

    being put in an additional page, but I was not able to achieve this behaviour with my limited knowledge of Ext JS...

    For the moment, I think that this solution is acceptable for my needs.

     

    I would really like to know your opinion.

     

    Andrea

    Object reference between different forms at design time

    in General

    Posted

    Sorry to say, but it is not happening with usual VCL TForms.

    Just create a simple project with 2 forms, place a tdatasource in Form1, place a dbgrid in form2, 

    add Form1 in the uses of Form2, set the DBGrid's datasource property to the datasource in form1.

    The close Form2, or close the project, and reopen it: the link is manteined.

     

    This does not happens between TUniForms, only between TUniMainModule and TUniForms...

    Object reference between different forms at design time

    in General

    Posted

    Hi all,

    I'm having some troubles setting object references between different forms at design time; reference is not kept when forms are closed

    and reopened.

    For example, setting the TDataSource property for a TUniDbGrid when the two objects belong to different forms

    (TUniForm descendents).

    However, if I place the TDataSource on the UniMainModule, it works.

     

    Is anyone else experiencing the same problems ?

     

    Thanks

    Andrea

    UniDbGrid - fetching considerations

    in General

    Posted

    Hi Stefano, I see your concerns about scrolling (down) the grid and the consequent fetching of additional rows, but this should be limited in one of the following ways:

     

    - the users scrolls down the grid to the last row, and they can fetch and additional page (N rows) using a dedicated button "Load more rows" that could be 

      placed on the navigation bar, instead of the current previous/next/first/last page buttons

    - the user scrolls down the grid to the last row, and automatically (ajax event ?) and additional page (N rows) is fetched from the opened query and added to the UniDbGrid

     

    So no way for the end user to move to the last row and fetch all the rows from the dataset as a whole.

    After a few page fetches without finding what they are looking for, the users would tipically refine the filter to get the data he really wants.

    Memory occupation, CPU, network usage minimized on the DB side and web server (UniGUI).

     

    Andrea

    UniDbGrid - fetching considerations

    in General

    Posted

    Hi Volk65, I think you are right regarding the fact that not all TDataSet descendents support incremental fetching.

    For example, the TClientDataSet or TVirtualTable, which are not bound to a DB server, obviously do not support it.

    Even the general TDataSet does not support it.

    But I think there are many other specialized descendent that support it instead.

    I am using DevArt components to connect to Oracle DB, and I can finely tune the following fetching options:

     

    - FetchAll (boolean: fetch all rows or not )

    - FetchRows (number or rows to fetch in a bunch)

     

    FireDac, as you say, can do it.

    Implementing the "incremental fetch" with UniDbGrids, and using a TDataSet that does not support it, would give the same result

    as today.

    But if used with TOraQuery (or FireDac), would give the same user experience as VCL in a web application: amazing !

     

    Of course using the Locate (or Last command) would break the rule, but it is something that the developer should be aware of,

    as the behaviour is well known. It is sufficient to avoid local filtering options with big datasets and this kind of "incremental fetching grids"

    (and reopen the queryinstead with changed conditions).

     

    To make a comparison with VCL, it is the same as using the vertical scrollbar on a DBGrid filled with 1 million rows, and dragging it

    to the bottom: the system hangs.

    It is up to the developer to block such a bad behaviour.

     

    Thank you for sharing your opinion.

    Anyone else ?

    Andrea

    UniDbGrid - fetching considerations

    in General

    Posted

    Hi all,

    as far as I have read from the forum the only way to deal with big datasets and uniDbGrids is paging.

    This works quite well, but I would prefer another option, let me explain better.

     

    Without paging, the web server fetches the whole dataset and it gives back it to the client:

     

    DB server --> Web server (Unigui) : whole dataset

    Web Server (UniGUI) --> Browser: whole dataset

     

    This is the worst situation, as it implies a lot of overhead for all the actors (DB Server, Web Server, 

    Browser, network, etc.). It should not be used for large datasets.

     

     

    With paging, the web server fetches the whole dataset (this is why the option FetchAll shall be set),

    and it gives back to the client (browser) just the current page. Therefore:

     

    DB server --> Web server (Unigui) : whole dataset

    Web Server (UniGUI) --> Browser: partial dataset/ curent page

     

    This is better, as it minimizes the overhead on the client side (browser), but the Web Server (UniGUI) still

    has to deal with a large dataset that has to be fetched entirely from the DB server and to be kept in memory.

     

     

    The last option, that I really miss with UniGUI, is the way that VCL DBGrid works, but it is common to find it

    on many websites. This is the reason why I'm asking about it, I'm confident there should be a way to work it out

    with UniGUI.I think that it could be called "incremental fetch".

     

    Practically, UniGUI should fetch just the first N rows and show them on the UniDbGrid component, letting the user know

    that there are more rows than the ones actually visible. It could be a button on the paging bar called "Load more rows".

    If the user clicks on that button, UniGUI should fetch N additional rows from the dataset, and then display N*2 total

    rows. This approach can be iterated till the whole dataset is fetched.

    Alternatively, without using the "Load more rows" button, it could be possible to do it in the VCL way:

    when the user scrolls down the grid and he reaches the last line, the "give me more lines" could be automatically

    fired.

    The "incremental fetch" solution would be the best in my opinion, as the user does not really care to know the number of pages in the grid,

    nor he needs to skip randonly on different pages. Usually he does want quickly the first N rows, and then the possibility

    to look up another N rows for a fe times. Then, if the data is not found, he would change the actual filter/selection.

    This would bring the following situation:

     

    DB server --> Web server (Unigui) : partial dataset

    Web Server (UniGUI) --> Browser: partial dataset

     
     
     
    Sorry for the long post, hoping that I was clear, thank you all.
    Andrea
    • Upvote 2

    Dock and Align layout and ScreenMask

    in General

    Posted

    Thank you Delphi Dev super as always.

    For anyone interested, to applyt the mask to a form different than the main form:

     

    UniSession.AddJS(self.Name+'.form.mask("'+UniServerModule.ServerMessages.LoadingMessage+'")');
     
    And to unmask:
     
    UniSession.AddJS(self.Name+'.form.unmask()');

    Dock and Align layout and ScreenMask

    in General

    Posted

    Hi all,

    I'm trying to show the screen mask on a form with the Dock and Align layout. It seems that the screen mask covers just

    the panel aligned to Client (alClient).

    To reproduce just add the following event to the UniPanelClient panel (UniPanel2) on the Dock&Align demo:

     

    procedure TMainForm.UniPanel2Click(Sender: TObject);
    begin
      self.ShowMask('test');
    end;
     
    Is there a workaround ?
     
    Thanks
    Andrea

     

     

    UniDbGrid - RefreshRecord support

    in Feature Requests

    Posted

    Hi,

    I'm using the DevArt components to access the DB (Oracle). They feature the RefresRecord command, a very useful statement that ca be used to refetch just the current record from the DB, without the need to refetch the whole dataset, which can be very time-consuming.

    For example, I use it extensively on VCL to get the fields that are updated by some DB triggers, or to get back the changes performed by DB stored procedures.

    It seems that this command is not supported by UniGUI, issuing a RefreshRecord on a dataset does not updates the DbGrid, even though the underlying data changes.

    Is there something I could use to force the DBGrid to update ?

     

    Thank you

    Andrea

     

    DBGrid editing - OnEditButtonClick

    in Feature Requests

    Posted

    Hi, in VCL DbGrid there is the possibility for a column to pick up a customized editor (a dialog), by setting the column ButtonStyle to cbsEllipsis and managing the OnEditButtonClick event.

    UniGUI already implements various DbGrid editors (UniEdit, UniCombo, UniDBLoockUpComboBox, NumEdit, etc.).

     

    In some cases, especially when there are many values to choose from, I think that the ellipsis button that could open a specialized dialog is the best solution. (and maybe it is not too difficult to implement...)

     

    Thanks

    Andrea

     

    DBGrid - filter multiple values

    in Feature Requests

    Posted

    Hi,

    I think that UniDbGrid filtering features are really powerful.

    In certain cases, however, there is the need to filter multiple values from a list (DBLookup combo), as can be done in MS Excel (see attachment).

    Currently, with a DBLookupComboBox filter editor, there is the possibility to filter just one value.

    Is there the possibility to develop such an enhancement ?

     

    Thanks for your work.

    Andrea

    How to cancel "×" on the lookup field when dropdown

    in General

    Posted

    Thank you for the reply. The demo shows a situation a bit different, and in fact not very common.

    In the demo the field posted is "Name", while commonly in a lookup situation it is a numeric identifier (ID).

     

    In this situation, to have the user see the name rather than the identifier, the grid column should be bound to a lookup field

    to decode the identifier and show the value, correct ?

     

    Thank you

    Dbgrids - change dgRowSelect at runtime

    in General

    Posted

    It is not so important at the moment, maybe I'll have 2 grids with the 2 different settings and switch between them at run time.

     

    Delphi Dev, please could you hava a look at the post "How to cancel "×" on the lookup field when dropdown" ?

     

    This is very important and urgent to me, I need just your opinion.

    Thank you

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