PDI: Clone your data in Kettle! (Video Tutorial)

In this tutorial we look at the cloning feature of Pentaho Data Integration/Kettle and use the power of the JavaScript step. Please watch the video here:


Part 1:

Part 2:

Part 3:

The files for this tutorial: Download the budget data here and the PDI/Kettle file here.


You can find the video's also on YouTube:

Video Part 1: click here

Video Part 2: click here

Video Part 3: click here

Please find below some more information:

Code for 1st JavaScript step:

function daysInMonth(iMonth, iYear)
{
iMonth=iMonth-1;
return 32 - new Date(iYear, iMonth, 32).getDate();
}

var days_in_month=daysInMonth(month,year);
var days_loop_nr=days_in_month-1;

var year=2010;

var bdgt_unsubs=bdgt_sub_base_start+bdgt_new_subs-bdgt_sub_base_end;




I found a nifty function (”daysInMonth”) on the internet that calculates the days of a particular month (we are neither JavaScript heros nor do we have time). This function provides us with the required number of days in a month, which we assign to the days_in_month variable. Important thing to remember is that we already have one row of data for each month, hence we have to deduct 1 from the days_in_month. We store this value in the “days_loop_nr” variable which we will use for the clone step.

We also add a default year and calculate how many users unsubscribed from our service (”bdgt_unsubs”). We need this figure as we want to calculate later on a daily figure for the subscription base (users subscribe and unsubscribe all the time).



Code for the 2nd JavaScript step:

var day_of_month;
// used to hold value of previous row:
var year_month_old;
var bdgt_sub_base_start_old;
var bdgt_new_subs_daily_old;
var bdgt_unsubs_daily_old;


//define day of month
var year_month=(year+"")+(month+"");

if(year_month!=year_month_old){
day_of_month=1;
}
else {
day_of_month=day_of_month+1;
}


//calculate the daily sub base at the start of the day
if(month==1 && day_of_month==1){
var bdgt_sub_base_start_daily=bdgt_sub_base_start;
}
else {
var bdgt_sub_base_start_daily=bdgt_sub_base_start_daily_old+bdgt_new_subs_daily_old-bdgt_unsubs_daily_old;
}


//keep value of current fields for next iteration
//assign them to a new variable so that they are available in the next iteration
//it is important that you only save the new value of year_month
//here as you want to work with the old value in the if statement
//above
year_month_old=year_month;
bdgt_sub_base_start_daily_old=bdgt_sub_base_start_daily;
bdgt_new_subs_daily_old=bdgt_new_subs_daily;
bdgt_unsubs_daily_old=bdgt_unsubs_daily;





We declare some variables first. Then we create the day number for each row: We use an if condition therefore. We have to start with 1 when a new month begins and then increase the number by 1.

It is important to understand the condition:
if(year_month!=year_month_old)

For the very first row of our dataset, the variable year_month_old won’t have a value. Hence, if(year_month!=year_month_old) will be true.

At the very end of the script we create a new variable call year_month_old which stores the current value of year_month for the next iteration. We only create this variable at the end of the script, so that we can use it in the next iteration for the condition before we overwrite it again.

A variable will be only overwritten if a new value is available.

So imagine we are in the second row of our dataset, the if(year_month!=year_month_old) condition will look like this: if(201001!=201001), hence the script will increase the value of the day by 1.  Once the month changes (i.e. if(201002!=201001)) then we have to start with 1 again.

That’s quite a nice solution. Again the javascript code might not be the best one, but it works. Please feel free to improve it.

We also have figures that we cannot just divide by the number of days in a month. The subscription base has to be calculated in a more complex way (well, not that complex). The calculation uses the same concept as above: saving the field value of the previous row in a new variable so that you can use it again in the current row.

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PDI: Full Outer Joins

Pentaho Data Integration: Full Outer Joins

Creating full outer joins in Pentaho Data Integartion (PDI aka Kettle) is a fairly straight forward approach ... let’s have a look at it:

In this example we will be looking at data of an online acquisition process. We are facing the problem that the tracking hasn’t been implemented correctly, hence it can happen, that in a few cases we have pin insertions but no page impressions.

This is a good example to use a full outer join, as we will preserve all the data and can demonstrate to management that there is indeed a problem with the tracking setup.

Imagine we have two simple data sets:

Page Impressions

date	service	mk	page impressions
2010-05-01	serv1	123	231
2010-05-01	serv2	443	2
2010-05-01	serv3	234	33

PIN Insertions

date	service	mk	pin insertions
2010-05-01	serv5	33	231
2010-05-01	serv2	443	1
2010-05-01	serv1	123	55

Ok, let’s get started: Copy the above data sets into two separate Excel spreadsheets, save the file and fire up PDI/Kettle.

Create a new transformation. First thing to do in Kettle is to drag and drop an Excel Input step (you can find in in the Input folder in the Design tab on the left hand side). Double click on it. Click on “Browse” and choose the file that we just saved. Click “Open”. The file dialog closes, then click on “Add” (next to “Browse”).

Next click on the “!Sheets” tab followed by clicking on “Get Sheetnames”. Mark the sheet name that contains the page impressions, then click “>” to add it to your selections. It should look like this now:

 

Click “ok”.

Go to the “!Fields” tab and click on “Get fields from header row(s) ...”:

Now we are ready to view the data: Click on “Preview Rows” and check if everything is alright.

Close the preview window and click “ok” to close the step window.

Now mark the “Excel Input” step and copy and paste it. Open the new step and change it so that it imports the other spreadsheet. Make sure that you change the sheet name and the field names! Preview the data to see if everything is ok.

We now add a sort step for each of the Excel Input steps. Connect the Excel Input steps and the Sort Steps with a hop by holding down SHIFT and drawing a line from one step to the other.

 

Open the Sort Step and click on “Get fields ...”. Mark the row that contains “page impressions” or “pin insertions” and press DELETE (we obviously don’t want to sort by the measure). Click “Ok”. Do exactly the same for the other Sort Step.

As we have now sorted our data sets, we can join them. Drag and drop a Merge Join Step onto the canvas and connect both Sort Steps to it.

Open the Merge Join Steps, set the first step to “Sort Rows” and the second step to “Sort Rows 2” and join type to “Full Outer”. As we use a full outer join, it isn’t really important which step you mention in first step or second step.

Now click on “get key fields” and delete the measures. It should look like this now:

Now it is a good idea to preview the data again. Mark the Merge Join step and press F10. In the “Transformation Debug Dialog” click on “Quick Launch”.

You see that Kettle has successfully joined the data sets. As we chose “Full Outer” as join type, we can see all the data from each input data set. You will also realize, that both data sets had field names in common, so Kettle added “_1” to the field names of the second data set to avoid any confusion.

So now let’s clean up this result set a bit, to make it look nicer. We will add new fields called date_king, service_king and mk_king, and will use the values date or date_1 ( and so on) to populate it. The goal is to have for each row a proper date, service and mk value.

Add a Formula step and connect the Merge Join step to it. Fill out the Formula step as shown in the screenshot below:

Here the formulas to copy:

IF(ISBLANK([date]);[date_1];[date])

IF(ISBLANK([service]);[service_1];[service])

IF(ISBLANK([mk]);[mk_1];[mk])

What we do here is to check if one of the fields is empty and if yes, we use the value of the other one.

Click “Ok” to close the step configuration.

Now do a quick preview by clicking on the step and pressing F10.

As we don’t want to have all the unnecessary data in our final result set, add a “Select values ...” step, create the hob and open the configuration window of this step. Click on “Get fields to select” and delete all fields except the ones shown in the screenshot below:

 

We also rename some of the fields and put them in a different order. Ordering works like this: Mark the row, press ALT and use the arrows to move the row to another position.

Press F10 again and now the result set should look like this:

Now everything looks pretty and nice. If you want to export the result set somewhere, feel free now to add one of the many export steps.

This is how to create an Outer Join in Kettle in a nutshell. I think you will agree with me in saying that this is fairly easy to achieve.

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Pentaho 3.2 Data Integration: Beginne...

Pentaho 3.2 Data Integration: Beginner's Guide

I received a free copy of this book from the publisher Pakt for this review. You can buy the book directly from Packt as a print or download a PDF version of it.

http://www.packtpub.com/pentaho-3-2-data-integration-beginners-guide/book?utm_source=diethardsteiner.blogspot.com&utm_medium=bookrev&utm_content=blog&utm_campaign=mdb_003011

I first got to know about Kettle/PDI back in 2008. I was looking for an open source tool that would allow me to introduce better BI for my company: A tool that would allow me to focus on working with the actual data instead of trying to build a tool myself and having a minimum amount of time left to deal with the data.

In all honesty I have to say that Kettle/PDI had a huge and positive impact on the way I work. At the time when I was starting with Kettle any documentation was scarce. I did a lot of trail and error, forum search, google search etc. This approach asked for a lot of patience and time. 

I am very pleased that there is finally a book about Kettle/PDI available, especially for all those people that are about to start working with Kettle/PDI. In a nutshell, this book will give you all the information that you need to get started with Kettle/PDI quickly and efficiently. 

So let's have a look at the book's content:

In the foreword we learn about the history of the Kettle project. Most of this was quite new to me. Did you know that Kettle actually was an acronym for KDE Extraction Transformation and Loading Environment? Anyways, this is just one of the exciting facts.

The first chapter describes the purpose of PDI, its components, the UI, how to install it and a very simple transformation. Moreover, the last part tells you step by step how to install MySQL on Windows and Ubuntu. 

It's just what you want to know when you touch PDI for the first time. The instructions are easy to follow and understand and should help you to get started in no time. I honestly quite like the structure of the book: Whenever you are learning something new, it is followed by a section that just recaps everything. So it will help you to remember everything much easier. 

Maria focuses on using PDI with files instead of the repository, but she offers a description on how to work with the repository in the appendix of the book.

Chapter 2: You will learn how to reading data from a text file and how to handle header and footer lines. Next up is a description of the "Select values ..." step which allows you to apply special formatting to the input fields, select the fields that you want to keep or remove. You will create a transformation that reads multiple text fields at once by using regular expressions in the text input step. This is followed by a troubleshooting section that describes all kind of problems that might happen in the setup and how to solve them.

The last step of the sample transformation is the text file output step.

Then you improve this transformation by adding the "Get system info" step, which will allow you to pass parameters to this transformation on execution. This is followed by a detailed description of the data types (I wish I had all this formatting info when I started so easily at hand). And then it even gets more exciting: Maria talks you through the setup of a batch process (scheduling a Kettle transformation).

The last part of this chapter describes how to read XML files with the XML file input step. There is a short description of XPath which should help you to get going with this particular step easily.

Chapter 3 walks you through the basic data manipulation steps. You set up a transformation that makes use of the calculator step (loads of fancy calculation examples here). For more complicated formulas Maria also introduces the formula step. Next in line are the Sort By and Group By step to create some summaries. 

In the next transformation you import a text file and use the Split field to rows step. You then apply the filter step on the output to get a subset of the data. Maria demonstrates various example on how to use the filter step effectively. 

At the end of the chapter you learn how to lookup data by using the "Stream Lookup" step. Maria describes very well how this step works (even visualizing the concept). So it should be really easy for everybody to understand the concept.

Chapter 4 is all about controlling the flow of data: You learn how to split the data stream by distributing or copying the data to two or more steps (this is based on a good example: You start with a task list that contains records for various people. You then distribute the tasks to different output fields for each of these people). Maria explains properly how "distribute" and "copy" work. The concept is very easy to understand following her examples.

In another example Maria demonstrates how you can use the filter step to send the data to different steps based on a condition. In some cases, the filter step will not be enough, hence Maria also introduces the "Switch/Case" step that you can use to create more complex conditions for your data flow.

Finally Maria tells you all about merging streams and which approach/step best to use in which scenario.

In Chapter 5 it gets really interesting: Maria walks you through the JavaScript step. In the first example you use the JavaScript step for complex calculations. Maria provides an overview of the available functions (String, Numeric, Date, Logic and Special functions) that you can use to quickly create your scripts by dragging and dropping them onto the canvas. 

In the following example you use the JavaScript step to modify existing data and add new fields. You also learn how to test your code from within this step. Next up (and very interesting) Maria tells you how to create special start and end scripts (which are only executed one time as opposed to the normal script which is executed for every input row). We then learn how to use the transformation constants (SKIP_TRANSFORMATION, CONTINUE_TRANSFORMATION, etc) to control what happens to the rows (very impressive!). 

In the last example of the chapter you use the JavaScript step to transform a unstructured text file. This chapter offered quite some in-depth information and I have to say that there were actually some things that I didn't know.

In the real world you will not always get the dataset structure in the way that you need it for processing. Hence, chapter 6 tells you how you can normalise and denormalise datasets. I have to say that Maria took really huge effort in visualizing how these processes work. Hence, this really helps to understand the theory behind these processes. Maria also provides two good examples that you work through.

In the last example of this chapter you create a date dimension (very useful, as everyone of us will have to create on at some point).

Validating data and handling errors is the focus of chapter 7. This is quite an important topic, as when you automate transformation, you will have to find a way on how to deal with errors (so that they don't crash the transformation). Writing erros to the log, aborting a transformation, fixing captured errors and validating data are some of the steps you go through.

Chapter 8 is focusing on importing data from databases. Readers with no SQL experience will find a section covering the basics of SQL. You will work with both the Hypersonic database and MySQL. Moreover Maria introduces you to the Pentaho sample database called "Steel Wheels", which you use for the first example. 

You learn how to set up a connection to the database and how to explore it. You will use the "Table Input" to read from the database as well as the "Table Output" step to export the data to a database. Maria also describes how to parameterize SQL queries, which you will definitely need to do at some point in real world scenarios. 

In next tutorials you use the Insert/Update step as well as the Delete step to work with tables on the database.

In chapter 9 you learn about more advance database topics: Maria gives an introduction on data modelling, so you will soon know what fact tables, dimensions and star schemas are. You use various steps to lookup data from the database (i.e. Database lookup step, Combination lookup/update, etc). You learn how to load slowly changing dimensions Type 1, 2 and 3. All these topics are excellently illustrated, so it's really easy to follow, even for a person which never heard about these topics before.

Chapter 10 is all about creating jobs. You start off by creating a simple job and later learn more about on how to use parameters and arguments in a job, running jobs from the terminal window and how to run job entries under conditions.

In chapter 11 you learn how to improve your processes by using variables, subtransformations (very interesting topic!), transferring data between transformations, nesting jobs and creating a loop process. These are all more complex topics which Maria managed to illustrate excellently.

Chapter 12 is the last practical chapter: You develop and load a datamart.  I would consider this a very essential chapter if you want to learn something about data warehousing. The last chapter 13 gives you some ideas on how to take it even further (Plugins, Carte, PDI as process action, etc) with Kettle/PDI.

In the appendix you also find a section that tells you all about working with repositories, pan and kitchen, a quick reference guide to steps and job entries and the new features in Kettle 4.

Conclusion: 

This book certainly fills a gap: It is the first book on the market that focuses solely on PDI. From my point of view, Maria's book is excellent for anyone who wants to start working with Kettle and even those ones that are on an intermediate level. This book takes a very practical approach: The book is full of interesting tutorials/examples (you can download the data/code from the Pakt website), which is probably the best way to learn about something new. Maria also made a huge effort on illustrating the more complex topics, which helps the reader to understand the step/process easily.

All in all, I can only recommend this book. It is the easiest way to start with PDI/Kettle and you will be able to create complex transformations/jobs in no time!

You can buy the book on the Pakt website.

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Pentaho Community Data Access (CDA)

Pedro Alves did some impressive work on the new CDA (Community Data Access):

CDA allows you to access any of the various Pentaho data sources without worrying about the details. It can be used as a standalone plugin on the Pentaho BI server that can output the result in several formats or it can be used in combination with the Dashboard Editor and the CDF.

It basically covers any source that you can use within PRD (Pentaho Report Designer). Additionally it has a security layer that prevents code injection.

Moreover it has a caching layer (only Mondrian provides caching out of the box).

CDA also offers unions, joins (full outer join), column selection, formula additon and column renaming. Following output formats are available: JSON, XML, CSV and XSL.

CDA uses XML files to define the access data, which can be created/edited in the CDA Editor (The Editor doesn't work in IE). Results can be previewed via the CDA Previewer.

A CDA file consists two parts: the connection details and the query itself.

By using JNDI you can use the connections that you set up on the Pentaho Admin Panel.

CDA can be used then as input for the Dashboard Editor.

For all charts that are displayed within the CDA plugin pages, CDF is actually called to generate them.

Pedro is working on releasing a new version on CDF with CDA completely integrated.

Watch the webcast on for more details.

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Review coming for "Pentaho 3.2 Data Integration: Beginner's Guide"

I am quite excited to let you know that Packt will kindly send me a copy of their new book "Pentaho 3.2 Data Integration: Beginner's Guide" (by María Carina Roldán) to review it. I should have it in my post box in the next few days and then I'll focus on it. So stay tuned!

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New books on Pentaho Data Integration (Kettle)

Good news for everybody who wants to get started with Pentaho Data Integration: 2 books are in the pipeline.

The first one "Pentaho 3.2 Data Integration: Beginner's Guide" by María Carina Roldán will be published in the next few days. I'll try to get a copy of it. The TOC promises a quite interesting book!

Later this year "Pentaho Kettle Solutions" will be available. This books will be based on the forthcoming PDI 4. It's written by the same team (Roland Bouman, Jos van Dongen) that brought you the excellent "Pentaho Solutions".

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MySQL breakfast presentation on data warehousing

Today I attended a Sun/MySQL presentation in London that focused on data warehousing with MySQL, Infobright and Talend. Overall the presentation gave quite a good overview. The concept of packaging and knowledge layer in Infobright seem quite interesting; and not to worry about indexing is another nice point. I have to look how it compares to Lucid DB or Monet DB at some point when I find some time. I might give the Infobright Community Edition a try.

It was also interesting to see another open source ETL tool. From my point of view the interface of Talend doesn't look as user friendly as Pentaho Kettle, but maybe that's down to the fact that I have been working with Kettle for a long time now. In essence, Kettle will still be my ETL tool of choice.

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