Introduction to Object-Relational Mapping for DBAs – Part 2

This is part two of a lighting talk I’m giving at the SQL Saturday Edmonton Speaker Idol Contest.   Imagine I’m actually speaking the words below and showing some of the images on slides and/or doing a demo.  Code can be found here.

If you don’t want to read Part 1 it basically started the ORM example and ended in a panic over indexes.  

This is a rough draft so constructive feedback at chris.cumming@saturdaymp.com is much appreciated.

Now that we have our initial panic out of our system lets get back to Bud.  The next thing he wants to do is link a logged in user to a player.  A player needs to have a name and be linked to the login.  Bud creates a model, really just a simple C# class, and puts in all the information he wants to store a player.

Player Model

Looks kind of like a database table.  The one question you might have is what is a ApplicationUser?  It turns out a ApplicationUser is another model in the project that was auto-created when we choose to have authentication in our application.  It’s the logged in user.

If we open that ApplicationUser class we see it does not define any fields.  It doesn’t define any fields in the child class but the parent class does.  I’m not going to explain inheritance here but rest assured the fields are defined as shown below.

Empty Application User Model

Application Model Parent With Fields

Because the relationship is one-to-one Bud does add a new property to the ApplicationUser model.

Application User Model Linked To Player

Now the application knows that ApplicationUser has a one-to-one relationship to Player.  One other thing Bud has to do is add his new class the DB context.  Entity Framework might find his new model but it’s best if it’s listed.

Player Model Added to DB Context

Now Bud can create a new migration for his new Player model.

Add-Migration CreatePlayerTable

 

Add Player Table Migration

This creates the <timestamp>_CreatePlayerTable file.  If we open it up we see it creates the Player table and also a foreign key relationship to the ApplicationUser which maps to the AspNetUsers table.

Player Migration Create Table

Player Migration Foreign Key To Application User

Now that the migration file is created Bud runs the migration to add the Players table to his database.

Update-Database

 

Update Database Add Player Table

Now if we look in the database we find the new Players table, notice it’s plural, and it has a foreign key to the AspNetUsers table.

Players Table In SQL Server

OK, enough of following Bud, we are running out of lightning time.  Lets talk about why Bud would want to use an ORM tool such as Entity Framework.

You can find part 1 here. and part 3 here.  You can find the code for this talk here.  As I said above, this is a rough draft so constructive feedback at chris.cumming@saturdaymp.com is much appreciated.

 

Posted in Code Examples, Software Development | Tagged , , , , | Comments Off on Introduction to Object-Relational Mapping for DBAs – Part 2

Introduction to Object-Relational Mapping for DBAs – Part 1

This is the part one of a lighting talk I’m giving at the SQL Saturday Edmonton Speaker Idol Contest.   Imagine I’m actually speaking the words below and showing some of the images on slides and/or doing a demo.  Code can be found here.

This is a rough draft so constructive feedback at chris.cumming@saturdaymp.com is much appreciated.

Skip ahead to Part 2 if don’t feel like reading all of part 1.

Developer Bud wants to create a new application to track the board games he and his friends play.  He wants a simple website where him and his buddies can login to update the results from the board games they have played.  Being a .NET Developer he creates a ASP.NET MVC Core application with individual authentication.

Creating New ASP .NET MVC

Creating New ASP .NET MVC Authentication

By default this new application uses Entity Framework which is a object-relational mapping (ORM) framework.  Since he picked to use authentication the default ASP.NET application has a migration file that defines the authentication tables.

Authentication Migration File Location

Authentication Migration File

Even if you don’t understand C# you can probably see the above is describing a database but is not the usual SQL DDL.  We will return to this file later, for now lets continue to follow Bud.

Next he compiles and runs the application to make sure it works.  It loads up and looks like the below.

App Running For First Time

Everything looks good but when he tries to create a new user he gets the following error:

Trying To Register

Apply Migrations Registration Error

 

Following the advice he runs the migration.  Actually before he runs the migration he changes the connection string to point to his SQL Server instance instead of the SQL Server local DB:

App Settings JSON Location

Connection String In App Settings

"Server=(localdb)\\mssqllocaldb;Database=aspnet-SaturdayMP.BuddiesGameTracker-1CDAB6F6-EB6A-4A5D-B6A9-8CD3DC4B3B07;Trusted_Connection=True;MultipleActiveResultSets=true"
"Server=localhost;Database=BuddiesGameTracker;Trusted_Connection=True;"

Then Bud runs the command to update the database:

Update-Database

 

Update Database Command

Update (Dec 5th, 2018): Added the Bud successfully runs the application section below and changed some text at the end or part 1.

Bud runs the application again and this time when he registers there are no errors and he is successfully registered.

Register Successful After Migration

 

Bud doesn’t care about the underlying database that was created.  Well, that is not true, he does care about it but the same way most of us care about our car engine.  We only care about our care engine if the car won’t start.  If the car gets us from point A to point B then we don’t really care about the engine.

Bud doesn’t do this but because we are omnipotent DBAs (are all DBAs omnipotent?) we will peek behind the curtains at the generated database.  And here it is, a new database with some authentication tables.

Buddies Game Tracker Tables Created

From a developer point of view this is great.  Bud didn’t have to write a single line of SQL.  He didn’t didn’t even have to open up SQL Server, the database was just magically created.

This is just the beginning.  Later Bud will create more tables in code to track what buddies have which played which games.  He will do this without writing DDL and access the data with little to no SQL.

I imagine from a DBAs point of view this is a bit strange.  Don’t you start a new application by creating the database ERD first?  How did Visual Studio create the database?  Is the created database any good?  What about the auto-generated CRUD SQL?  Wait, what about the indexes?

Won't Somebody Please Think of the Indexes

Continue to part two of the talk.  You can find the code for this talk here.  As I said above, this is a rough draft so constructive feedback at chris.cumming@saturdaymp.com is much appreciated.

 

 

Posted in Code Examples, Software Development | Tagged , , , , , | Comments Off on Introduction to Object-Relational Mapping for DBAs – Part 1

XPlugins.iOS.BEMCheckBox 1.4.3 Released

I’m happy to announce the release of XPlugins.iOS.BEMCheckBox 1.4.3.  The main feature of this release is exposing the DidTapCheckBox event in the underlying BEMCheckBox.  You can find a full list of issues fixed in this release here.

The easiest way to get this update is via NuGet:

Install-Package SaturdayMP.XPlugins.iOS.BEMCheckBox -Version 1.4.3 
dotnet add package SaturdayMP.XPlugins.iOS.BEMCheckBox --version 1.4.3 

Subscribe to the DidTapCheckBox event as you would any other C# event:

checkbox.DidTapCheckBox += DidTapCheckBoxEvent;

The event handler looks like:

// Fired before the checkbox animation completes but after the internal
// checkbox settings are updated with the new check/unchecked status (i.e.
// On property is updated).
private void DidTapCheckBoxEvent(object sender, EventArgs eventArgs)
{
  Console.WriteLine("In BeforeCheckBoxClickedEvent which is DidTapCheckBox in BEMCheckBox.");
}

Remember XPlugins.iOS.BEMCheckBox is just an Xamarin wrapper for objective-c BEMCheckBox.  For all the features of the checkbox checkout the BEMCheckBox website.

Thanks, as always, to Boris-Em for creating the excellent BEMCheckBox.

Posted in Software Development | Tagged , , , , | Comments Off on XPlugins.iOS.BEMCheckBox 1.4.3 Released

Happy Holidays and all the Best in 2018!

Wrapped Christmas Presents

Gift wrapping skill is inversely correlated to software development skills.

This morning I made my last shopping trip before Christmas, at least I hope it’s my last trip.

Pro tip: the Costco near us officially opens at 10am but if you show up at 9:45ish they will let you in.  At least they let me in.  Then you can run, grab the salmon, and get out before the hoards descend.

Now the salmon is becoming gravlax and the last of the gifts are wrapped.  All that’s left is to write this blog post.  Actually there are a couple other Christmas chores to finish up but not many and then I can kick back and enjoy the holidays with friends and family.

Please note that kicking back means Saturday Morning Productions will be slow to respond to phone calls, e-mails, etc over the holidays.  We appreciate your understanding.

We hope that you have also wrapped up your Christmas chores and gifts and can enjoy this holiday long weekend.  We also hope you are looking forward to the grande adventures you will have in 2018.

Happy holidays and all the best in 2018!

P.S. – Don’t forget this is the season of sharing.  If you are in a position to do so share some of your good fortune with others.  Like cooking the turkey for your wife while they are at the food bank.

 

Posted in Fun | Tagged | Comments Off on Happy Holidays and all the Best in 2018!

Today I Learned How to Fix Illegal Characters in Path Error with TeamCity and RealmDB

When building a Xamarin application one step is to build the Android APK file.  This is a MsBuild step in TeamCity that looks like:

TeamCity Create APK Package Build Step

This step generates the following error:

[15:55:53][Source\SmallVictories\SmallVictories.csproj] CopyRealmWeaver
[15:55:53][CopyRealmWeaver] CopyRealmWeaver
[15:55:53][CopyRealmWeaver] Copy
[15:55:53][Copy] Creating directory "*Undefined*Tools".
[15:55:53][Copy] C:\BuildAgent\temp\buildTmp\.nuget\packages\realm.database\2.1.0\build\Realm.Database.targets(28, 5): error MSB3021: Unable to copy file "C:\BuildAgent\temp\buildTmp\.nuget\packages\realm.database\2.1.0\build\..\tools\RealmWeaver.Fody.dll" to "*Undefined*Tools\RealmWeaver.Fody.dll". Illegal characters in path.
[15:55:53][Step 6/8] Error message is logged

Notice the “*Undefined*Tools” in the directory path.  To fix this step you need to add /p:SolutionDir=”/” to the command line.  So now the build step looks like:

TeamCity Create APK Package Build Step Fixed

You can find more about the bug in this GitHub issue and more about the fix in this blog post.

 

Posted in Software Development, Today I Learned | Tagged , , | Comments Off on Today I Learned How to Fix Illegal Characters in Path Error with TeamCity and RealmDB

Overlapping Segments Create Space Time Paradoxes

This post is part of a larger discussion about temporal databases.  Hopefully it stands on it’s own but for more context see the Temporal Database Design page.  You can read the official Wikipedia definition but for our purposes a Temporal Database is a database where you can query for historical data using SQL.  This is work in progress and constructive feedback via e-mail, at chris.cumming@saturdaymp.com, is most appreciated.

In the last Temporal Database post I introduced timelines.  In this post we will talk about the one rule you cannot break:

Timeline segments cannot overlap!

That’s it.  That is the one rule.  Breaking this rule leads to all sorts of problems when you try to actually implement timelines in a database.  Aside from creating problems at the database level it also creates theoretical headaches.  For example, if you have the following in your customer table:

Timelines - Overlapping Segments

What is Chronos’s name on December 20th?  Is it Chronos or Kronos?  That said it is possible for people to have two names at the same time.  We have nicknames, aliases, and the like.  If you need to create a database that supports multiple names, say a police database, you can have an Aliases table that hangs off the Offenders table.  For example:

Timelines - Aliases Table

Chronos has an offender record with the name but also has two timelines in the Alias table with his over names.  Notice that alias table has two timelines, not one segment with overlapping segments.

How you design your temporal database will depend on your business logic but you must remember that there is one rule you can’t break:

When this baby hits 88mph you are going to see some serious $#%!

Sorry, wrong timeline.  I meant:

Timeline segments cannot overlap!

Posted in Software Development | Tagged | Comments Off on Overlapping Segments Create Space Time Paradoxes

Temporal Database Timelines

This post is part of a larger discussion about temporal databases.  Hopefully it stands on it’s own but for more context see the Temporal Database Design page.  You can read the official Wikipedia definition but for our purposes a Temporal Database is a database where you can query for historical data using SQL.  This is work in progress and constructive feedback via e-mail (chris.cumming@saturdaymp.com) is most appreciated.

In a non-temporal database a record dose not change over time.  For example say you have a Contacts table with a name field.

Timelines - Contact Table no History

A record in that table does not change over time.  Record 100 either has the name Chronos of some other name.  If you think of this record from a temporal point of view it’s a record starts at the beginning of time and goes to infinity.  If we where to represent this record using a timeline it would look like:Timelines - Non-Temporal Timeline Example

Now lets make the table effective-temporal.  The technical details of how we do this in the database is not important right now.  For now lets just focus on the timeline.  Say Chronos changes his name to Kronos on January 1, 2017 then our timeline would look like:

Timelines - Temporal Timeline Example

We are going to assume gods aren’t born and don’t die so the timeline still goes from start of time to infinity.  However, the timeline now consists of two segment.  The first segment goes from the start of time to Dec 31, 2016.  The second segment goes from Jan 1, 2017 to infinity.

Notice that the ID does not change.  It’s still 100 in both segments.  Chronos changed his name to Kronos but he is still the same person, er god.

One more example.  In this case lets track where John Doe works as he goes through high school.  Lets start in grade 10 with his first job as a burger flipper.  He works in the weekend as he attends school.  The workplace timeline looks like:

Timelines - John Doe - Grade 10 Job

In the summer John continues to work at Bob’s Burgers but also gets a second job as a life guard at the water park Water Wizz.

Timelines - John Doe - Grade 10 to 11 Summer Jobs

Now John Doe has two timelines one for Bob’s Burgers and one for Water Wizz.  When summer ends John leaves Wizz World but keeps his burger flipping job in Grade 11 so now his employment timelines look like:

Timelines - John Doe - Grade 11 Jobs

Notice that the timeline for Wizz World has ended but Bob’s Burgers continues.  In the summer between grade 11 and 12 John is again hired by Wizz World because he such a good worker.  Now his employment timelines look like:

Timelines - John Doe - Grade 11 to 12 Summer Jobs

One of the challenges when creating a temporal database is deciding when to create new timelines and when to create new segments.  In this case we decided to use the existing Wizz World timeline and add a segment to it.  If the employer stays the same keep the timeline, if the employer is different create a new timeline.

Also notice that the Wizz World timeline has a gap in the segments, which is just fine.  What you can’t have is a timeline with overlapping segments.  You can have timelines that overlap but a timeline can’t have overlapping segments.

Let’s talk more about overlapping segments and other stuff in a future segment.  Ah, time jokes, they never get old.

Posted in Software Development | Tagged | Comments Off on Temporal Database Timelines

Notes on Fixing Incomplete Bitcode Error in TeamCity Automated Objective-c Builds

Notes I took while trying to fix the Incomplete Bitcode error in submission bug.  Not sure if it’s fixed yet as I haven’t tried submitting an app to the App Store yet.  Hopefully someone else will try it and confirm it’s fixed.

In summary when submitting an app to iTunes Connect that has the XPlugins.iOS.BEMCheckBox the user got the following error:

ERROR ITMS-90668: “Invalid Bundle Executable. The executable file ‘InstantApp.BoostOrder.Customer.Touch.app/Frameworks/BEMCheckBox.framework/BEMCheckBox’ contains incomplete bitcode. To compile binaries with complete bitcode, open Xcode and choose Archive in the Product menu.”

For some more background please see the previous post Today I Learned How to Automate Objective-c Builds in TeamCity for more information about how built the BEMCheckBox framework.

Current Build Settings

My build settings for compiling the BEMCheckBox framework look like:

TeamCity BEMCheckBox Current Build Actions

The look the same for compiling for both the device (ARM architecture) and the simulator (x86/x64 architecture).  I started with the build step that compiled the device and after some research I figured the problem was the build actions.  Instead of doing build I should do an archive.

Updating Compile for Device Settings

To create an archive requires change the build from Target-based to Schema-based.  There was a couple other changes required which are outlined below.

TeamCity BEMCheckBox Updated Build Actions

  1. Make sure the project build settings are up to date by clicking the Check/Reparse Project.
  2. Change to Scheme-based.
  3. Set the scheme to BEMCheckBox.
  4. Use the output directory or xCode will put the build god-knows-where.
  5. Change the build action from build to archive.

Did a build and everything compiled.  Lets do the same for the simulator build.

Updating Compile for Simulator Settings

Actually you don’t need to change anything for the simulator build.  You can’t create an archive for simulators.  As usual it took me some time to figure out nothing needs to be done.  Aren’t you glad you are reading this instead of wasting time like I did?

Update Script that Combines the Builds

After compiling for the device and the simulator the builds need to be combined into one package.  In my build this is done via a script and a minor update was required because the path changed when we built the archive for the device.

The current script looks like:

cp -r Sample\ Project/build/Release-iphoneos/BEMCheckBox.framework .
lipo -create -output BEMCheckBox.framework/BEMCheckBox Sample\ Project/build/Release-iphoneos/BEMCheckBox.framework/BEMCheckBox Sample\ Project/build/Release-iphonesimulator/BEMCheckBox.framework/BEMCheckBox

It now looks like:

cp -r build/Release-iphoneos/BEMCheckBox.framework .
lipo -create -output BEMCheckBox.framework/BEMCheckBox build/Release-iphoneos/BEMCheckBox.framework/BEMCheckBox Sample\ Project/build/Release-iphonesimulator/BEMCheckBox.framework/BEMCheckBox

Notice the path for the device build has been changed.  It no longer gets put in the Sample Project folder.  I couldn’t figure out a way to get the paths the same for both build so I just gave up.

Anyway, there are my notes on the changes I did.  Not sure if my changes fixed the orginial problem.  If you use XPlugins.iOS.BEMCheckBox please let me know either way.  Thank you to jjchoo for originally reporting the problem.

Posted in Notes, Software Development | Tagged , , , , | Comments Off on Notes on Fixing Incomplete Bitcode Error in TeamCity Automated Objective-c Builds

Family Vacation is Over

Our family vacation is over and the basement is back open for business.  Actually we where open on Monday but I forgot to remove the digital closed signed.  Sorry about that.

On this trip we visited Hong Kong and Shanghai, spending about a week in each city.  This is our second time to Honk Kong and we got to see and do things we missed on our first visit.  This includes hanging out at a beach and swimming, hiking the highest mountain in Hong Kong, a helicopter ride (sponsored by our daughter who saved her money for a year), and visiting the highest building in Hong Kong.

This was our first time to Shanghai and it contrasts nicely with Hong Kong.  Hong Kong is hilly and the population is concentrated in small pockets on the flatter parts.  Shanghai is flat with less hi-rises.  It reminds me of LA, a flat city that stretches for miles.

We stayed near the historic Old Town and did the usual tourist things like visiting People’s Square, toured The Bund, and looked out over Shanghai half a kilometer in the sky in the Shanghai Tower (the second highest building in the world).

Finally we visited both Hong Kong Disneyland, for a second time, and Shanghai Disneyland.  That means we have visited three of the six Disney Resorts having visited the original Disneyland in California in the past.  We have a family goal to visit all six Disney Resorts before my darling daughter turns 18 to help her become an Imagineer.  That and we really like the Disney parks.

Walt Disney Imagineering Logo

Thank you for your patience during our absence.  We have settled into our normal routine and look forward to serving you with refreshed enthusiasm.

Posted in Uncategorized | Comments Off on Family Vacation is Over

Closed for Family Vacation

Basement Office Closed SignSaturday MP is a small family business and like your local family run restaurant the entire family is involved in some way.  Currently it’s mostly me working at Saturday MP but Ada helps with some book keeping and in the past was a consultant.  Our daughter also used to clean the basement office and shred papers.

Also, like your local family restaurant, when we take a vacation the entire business closes.  Well, mostly closes, we can still be reached virtually but please expect delays in our response.  Thank you for your patience and we look forward to serving you when we get back to the basement on November 27th.

Posted in Business Side, Fun | Tagged , | Comments Off on Closed for Family Vacation