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  • Best way to fetch data from a single database table with multiple threads?

    - by Ravi Bhatt
    Hi, we have a system where we collect data every second on user activity on multiple web sites. we dump that data into a database X (say MS SQL Server). we now need to fetch data from this single table from daatbase X and insert into database Y (say mySql). we want to fetch time based data from database X through multiple threads so that we fetch as fast as we can. Once fetched and stored in database Y, we will delete data from database X. Are there any best practices on this sort of design? any specific things to take care on table design like sharing or something? Are there any other things that we need to take care to make sure we fetch it as fast as we can from threads running on multiple machines? Thanks in advance! Ravi

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  • Updating multiple tables with LinqToSql in one unit of work

    - by zsharp
    Table 1: int ID-a(pk) Table 2: int ID-a(pk), int ID-b(pk) Table 3: int ID-b(pk), string C I have the data to insert into Table 1. But I do not have the ID-a, which is autogenerated. I have many string C to insert in Table 3. I am trying to insert row into Table 1, get the ID-a to insert in Table 2 along with the ID-b that is auto-Generated in Table 3 when I submit each string C, all in one submission to db. Right now I am calling dc.SubmitChanges twice in same call. Is it efficient to have to submit changes twice on same DataContext or can this be combined further?

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  • Database layout tagging system

    - by Kurresmack
    I am creating a web site for a customer and they want to be able to create articles. My idea is to tag them so I am going to implement the system. What is the best design, both from an architectural and a perfomance perspective: 1. To have table with all tags and then have a one to many relationship table that links a tag like this: articles table with ID tags table with ID one to many table with columns Article.ID and Tags.ID 2. To have one table with articles and one with tags for articles like this: articles table with ID tags table with Article.ID and tag text Thanks in advance!

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  • Database localization

    - by Don
    Hi, I have a number of database tables that contain name and description columns which need to be localized. My initial attempt at designing a DB schema that would support this was something like: product ------- id name description local_product ------- id product_id local_name local_description locale_id locale ------ id locale However, this solution requires a new local_ table for every table that contains name and description columns that require localization. In an attempt to avoid this overhead I redesigned the schema so that only a single localization table is needed product ------- id localization_id localization ------- id local_name local_description locale_id locale ------ id locale Here's an example of the data which would be stored in this schema when there are 2 tables (product and country) requiring localization: country id, localization_id ----------------------- 1, 5 product id, localization_id ----------------------- 1, 2 localization id, local_name, local_description, locale_id ------------------------------------------------------ 2, apple, a delicious fruit, 2 2, pomme, un fruit délicieux, 3 2, apfel, ein köstliches Obst, 4 5, ireland, a small country, 2 5, irlande, un petite pay, 3 locale id, locale -------------- 2, en 3, fr 4, de Notice that the compound primary key of the localization table is (id, locale_id), but the foreign key in the product table only refers to the first element of this compound PK. This seems like 'a bad thing' from the POV of normalization. Is there any way I can fix this problem, or alternatively, is there a completely different schema that supports localization without creating a separate table for each localizable table? Update: A number of respondents have proposed a solution that requires creating a separate table for each localizable table. However, this is precisely what I'm trying to avoid. The schema I've proposed above almost solves the problem to my satisfaction, but I'm unhappy about the fact that the localization_id foreign keys only refer to part of the corresponding primary key in the localization table. Thanks, Don

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  • Whats the best way to design this database scenario?

    - by ankimal
    I want to setup 2 MySQL databases which differ in schema in that, one is normalized and the other is flat for quicker reads and writes. The information being stored in both DBs is the same, but the representation is obviously different owing to the different design approaches. I need to find a robust solution to sync information in real time from my normalized version to my flatter version.

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  • What method do you use to identify the Aggregate Roots in Domain Drive Design?

    - by Robert
    When applying Domain Driven Design to a project, how do you identify the Aggregate Roots? For example, in a standard E-Commerce website, you might say that the Order is one, and the User is the other. But what if your Users belong to a Company? Does that make your Company the aggregate root? I'm interested in hearing people's approaches to working out the Aggregate roots, and how to identify poorly chosen aggregate roots.

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  • ResourceSerializable: an alternate to ORM and ActiveRecord

    - by Levi Morrison
    A few opinionated reasons I don't like the traditional ORM and ActiveRecord patterns: They work only with a database. Sometimes I'm dealing with objects from an API and other objects from a database. All the implementations I have seen don't allow for that. Feel free to clue me in if I'm wrong on this. They are brittle. Changes in the database will likely break your implemenation. Some implementations can help reduce this, but a few of the ones I've seen don't. Their very design is influenced by the database. If I want to switch to using an API, I'll have to redesign the object to get it to work (likely). It seems to violate the single-responsibility pattern. They know what they are and how they act, but they also know how they are created, destroyed and saved? Seems a bit much. What about an approach that is somewhat more familiar in PHP: implementing an interface? In php 5.4, we'll have the JsonSerializable interface that defines the data to be json_encoded, so users will become accustomed to this type of thing. What if there was a ResourceSerializable interface? This is still an ORM by name, but certainly not by tradition. interface ResourceSerializable { /** * Returns the id that identifies the resource. */ function resourceId(); /** * Returns the 'type' of the resource. */ function resourceType(); /** * Returns the data to be serialized. */ function resourceSerialize(); } Things might be poorly named, I'll take suggestions. Notes: ResourceId will work for API's and databases. As long as your primary key in the database is the same as the resource ID in the API, there is no conflict. All of the API's I've worked with have a unique ID for the resource, so I don't see any issues there. ResourceType is the group or type associated with the resource. You can use this to map the resource to an API call or a database table. If the ResourceType was person, it could map to /api/1/person/{resourceId} and the table persons (or people, if it's smart enough). resourceSerialize() returns the data to be stored. Keys would identify API parameters and database table columns. This also seems easier to test than ActiveRecord / Orm implemenations. I haven't done much automated testing on traditional ActiveRecord/ORM implemenations, so this is merely a guess. But it seems that I being able to create objects independently of the library helps me. I don't have to use load() to get an existing resource, I can simply create one and set all the right properties. This is not so easy in the ActiveRecord / Orm implemenations I've dealt with. Downsides: You need another object to serialize it. This also means you have more code in general as you have to use more objects. You have to map resource types to API calls and database tables. This is even more work, but some ORMs and ActiveRecord implementations require you to map objects to table names anyway. Are there other downsides that you see? Does this seem feasible to you? How would you improve it? Note: I almost asked this on StackOverflow because it might be too vague for their standards, but I'm still not really familiar with programmers.stackexchange.com, so please help me improve my question if it doesn't shape up to standards here.

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  • Getting an Access 2007 table (.accdb extension) in ArcMap programmatically

    - by Adrian
    I have recently found a script from ArcScripts on how to get an Access table in ArcGIS programmatically and it works well. But this is for Access 2003 (.mdb extension) and earlier. The code is posted below, and I want to know how to modify it for using Access 2007 (.accdb extension) and later databases. Attribute VB_Name = "Access_connect" Sub Open_Access_Connect() 'V. Guissard Jan. 2007 On Error GoTo EH Dim data_source As String Dim pTable As ITable Dim TableName As String Dim pFeatWorkspace As IFeatureWorkspace Dim pMap As IMap Dim mxDoc As IMxDocument Dim pPropset As IPropertySet Dim pStTab As IStandaloneTable Dim pStTabColl As IStandaloneTableCollection Dim pWorkspace As IWorkspace Dim pWorkspaceFact As IWorkspaceFactory Set pPropset = New PropertySet ' Get MDB file name data_source = GetFolder("mdb") ' Connect to the MDB database pPropset.SetProperty "CONNECTSTRING", "Provider=Microsoft.Jet.OLEDB.4.0;" _ & "Data source=" & data_source & ";User ID=Admin;Password=" Set pWorkspaceFact = New OLEDBWorkspaceFactory Set pWorkspace = pWorkspaceFact.Open(pPropset, 0) Set pFeatWorkspace = pWorkspace ' Get table name TableName = SelectDataSet(pFeatWorkspace, "Table") ' Open the table Set pTable = pFeatWorkspace.OpenTable(TableName) 'Create Table collection and add the table to ArcMap Set mxDoc = ThisDocument Set pMap = mxDoc.FocusMap Set pStTab = New StandaloneTable Set pStTab.Table = pTable Set pStTabColl = pMap pStTabColl.AddStandaloneTable pStTab ' Update ArcMap Source TOC mxDoc.UpdateContents Exit Sub EH: MsgBox "Access connect: " & Err.Number & " " & Err.Description End Sub Public Function GetFolder(Optional aFilter As String) As String ' Open a GUI to let the user select a Folder path name (by default) or : ' Set aFilter = "shp" to get a shapefile name ' Set aFilter = "mdb" to get an MS Access file name ' Return the Folder Path or phath & file name As String ' V. Guissard Jan. 2007 Dim pGxDialog As IGxDialog Dim pFilterCol As IGxObjectFilterCollection Dim pCurrentFilter As IGxObjectFilter Dim pEnumGx As IEnumGxObject Select Case aFilter Case "shp" Set pCurrentFilter = New GxFilterShapefiles aTitle = "Select Shapefile" Case "mdb" Set pCurrentFilter = New GxFilterContainers aTitle = "Select MS Access database" Case Else Set pCurrentFilter = New GxFilterBasicTypes aTitle = "Select Folder" End Select Set pGxDialog = New GxDialog Set pFilterCol = pGxDialog With pFilterCol .AddFilter pCurrentFilter, True End With With pGxDialog .Title = aTitle .ButtonCaption = "Select" End With If Not pGxDialog.DoModalOpen(0, pEnumGx) Then Smp = MsgBox("No selection : Exit", vbCritical) End 'Exit Function 'Exit if user press Cancel End If GetFolder = pEnumGx.Next.FullName End Function Public Function SelectDataSet(pWorkspace As IWorkspace, Optional theDataType As String) As String ' Open a GUI to let the user select a DataSet into a Workspace ' (Table or Request into an MS Access Database or a Geodatabase File) ' Set pWorkspace to the DataSet IWorkspace ' Set theDataType = "Table" to select a Table name of the DataSet ' Return the selected Table or Request Table name As String ' V. Guissard Jan. 2007 Dim aDataset As Boolean Dim boolOK As Boolean Dim DataSetList As New Collection Dim datasetType As Integer Dim n As Integer Dim pDataSetName As IDatasetName Dim pListDlg As IListDialog Dim pEnumDatasetName As IEnumDatasetName ' Set the Dataset Type Select Case theDataType Case "Table" datasetType = 10 Case Else Answ = MsgBox("Need a Dataset Type : Exit", vbCritical, "SelectDataset") End End Select ' Get the Dataset Names included in the workspace Set pEnumDatasetName = pWorkspace.DatasetNames(datasetType) ' Create the Dataset Names List Dialog aDataset = False Set pListDlg = New ListDialog pEnumDatasetName.Reset Set pDataSetName = pEnumDatasetName.Next Do While Not pDataSetName Is Nothing pListDlg.AddString pDataSetName.name DataSetList.Add (pDataSetName.name) Set pDataSetName = pEnumDatasetName.Next aDataset = True Loop ' Open a GUI for the user to select a dataset If aDataset Then boolOK = pListDlg.DoModal("Select a " & theDataType, 0, Application.hwnd) n = pListDlg.choice If (n <> -1) Then SelectDataSet = DataSetList(n + 1) Else Sup = MsgBox("No DataSet selected : EXIT", vbCritical, "SelectDataset") End End If End If End Function Here is the link to the ArcScript: http://arcscripts.esri.com/Data/AS14882.bas PS I know this code is written in VBA and I don't know if a modified version is in VB.NET or whatever else language. Thanks, Adrian

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  • Perl: implementing a dispatch table in an OO module?

    - by Iain
    I want to put some subs that are within an OO package into an array - also within the package - to use as a dispatch table. Something like this package Blah::Blah; use fields 'tests'; sub new { my($class )= @_; my $self = fields::new($class); $self->{'tests'} = [ $self->_sub1 ,$self->_sub2 ]; return $self; } _sub1 { ... }; _sub2 { ... }; I'm not entirely sure on the syntax for this? $self->{'tests'} = [ $self->_sub1 ,$self->_sub2 ]; or $self->{'tests'} = [ \&{$self->_sub1} ,\&{$self->_sub2} ]; or $self->{'tests'} = [ \&{_sub1} ,\&{_sub2} ]; I don't seem to be able to get this to work within an OO package, whereas it's quite straightforward in a procedural fashion, and I haven't found any examples for OO. Any help is much appreciated, Iain

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  • How to draw diagonal table borders in latex, like in excel ?

    - by Amyn Bennamane
    Is it possible to draw diagonal (parallelogram) cells in LaTeX: the cell content is diagonal, and the cell's originally vertical borders are also diagonal. Here is what I managed to do using the rotating package: \begin{tabular}{|r|c|c|} \hline \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ & \begin{rotate}{45}Trying to save some horizontal space\end{rotate} & \begin{rotate}{45}While keeping headers readable\end{rotate} \\ \hline this & is & a \\ \hline sample & latex & table \\ \hline \end{tabular} Here is a screenshot of the output vs what is possible using excel: Thanks.

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