Secret Santa Generator

It’s Christmas! And with Christmas comes Secret Santa! We replicated the names in a hat process which is normally used for this kind of thing: write all the names in pieces of paper and put them in a hat; each person takes one, if you drew your own name, you put it back and draw another. If the last person draws his own name, the whole process is repeated. We know it’s not the most efficient way to do it but is an interesting challenge to implement in PDI. You can find it here.

We start with a list of names and emails in a CSV file. PDI reads them, generates two sets of random numbers, builds the pairings and checks if in any pair there’s a repeated name. If so, it repeats the process again, until we have a valid list of pairs of names and then it emails everyone with the names of the recipient they were assigned.

Using loops in PDI is a powerful pattern but a dangerous one. One should always guarantee that the job will not loop indefinitely, eventually blowing up with an out of memory error. In our case this would happen if the list provided has only one name on it, but we trust the user not to misuse the program (besides, what’ the point of having a secret Santa if there’s only one Santa to assign, anyway?).

Ctools table component tweaks

(tl;dr: jump straight to section 3 below if you already know about scrolling tables)

Tables in Ctools are implemented by, a jQuery plugin to… well, display tables. However, as it normally is the case with Ctools, not all features are exposed via the CDE interface. And how could they, given the astounding number of features available plus the ever growing list of DataTables plugins out there. Implementing that extra bit of behaviour the users really love ends up being more an exercise in googling and finding the right plugin or trick to do the task than exploring the list of available properties in the Advanced column of CDE.

And that is the subject of today’s post. A specific tweak to the DataTables component that may be quite handy to know about.

1. To paginate or not to paginate.
By default tables are paginated in DataTables and, therefore, in CDE. However, especially if the result set is not very large, users may prefer a single page table to be displayed. Ok, that’s easy, just go to your Advanced properties tab and set pagination to False. Done, easy.

2. Don’t paginate, but scroll
However, single page tables are really only useful if your table is displaying a handful of rows. If you’re displaying some 20-30 records, for example, they may not be enough to justify pagination, but they’re way too many to display in a single page. One way around it is via CSS: just set its parent div height to be of a fixed size and set its overflow property to scroll. Again, done, easy.

Ah, except that now the table headers, filter box, etc. disappear when you scroll. And you can’t just set the scroll on the tbody element (ok, maybe you can with some really clever CSS hack). Fortunately, there’s an easy way around. A quick google search brings us to an example showing a scrollable table. The relevant property is scrollY, which can be set to any meaningful unit (e.g., 200px; vh and vw are units proportional to the viewpoort). To use it in CDE all we need is to add a new Extra option on the Advanced properties panel and set the property scrollY to whatever value we want.

Ok, but this is all relatively old news. If you have some experience with CDE and tables you may already know all this. So lets move on to something cooler.

3. But when the table refreshes, the scrollable area goes back to the top
Ah, so now your table scrolls up and down, but it has a major issue: the user wants the table to remember where it was. Namely, when the table refreshes because some parameter changed, the table should keep the search string and the scroll position and go back to the previous state.

For that, unfortunately, there’s no option in DataTables we can use, at least none we know about. So we need to implement it. Fortunately, it’s not that complex and the idea can be generalized for other properties we want to keep across component updates.

Step 1: add the following to the table’s preExecution function:

if( typeof this.tableState == "undefined"){
this.tableState = {
search: '',
scroll: 0
return true;

This creates the tableState property where we can store the two values we want to keep.

Step 2: add the following on the preChange of any selector that changes a parameter the table listens to:

var t = render_customerTable;
if( typeof t.tableState != "undefined"){ = $("#" + t.htmlObject + " div.dataTables_filter input").val();
t.tableState.scroll = $("#" + t.htmlObject + " .dataTables_scrollBody" ).scrollTop();

(we need the condition just in case the selector renders before the table itself, which is the case in the sample provided)

This retrieves the two values we want to keep and updates the tableState to reflect them.

Step 3: add this to the postExecution of the table:

var e = this.placeholder().find("div.dataTables_filter input");
this.placeholder().find(" .dataTables_scrollBody" ).scrollTop(this.tableState.scroll);

This will restore the contents of the search box, force the table to draw itself again (by calling the keyup event) and then scroll the table body.

And that’s it. The table now does what we needed with relatively low effort.

Note that the code was written in the pre-require framework. If your dashboard has support for require.js the code should still work, but there are probably better ways to interact with the table, other than jQuerying its HTML target.

If you want to try it, download the sample we created.

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Ctools now supports Require.js – But… what about jQuery plugins?

Great news from the Pentaho Community Dashboards front. As of the current version (15.06.30), there’s support for Require.js, which greatly streamlines the javascript downloaded when rendering a dashboard, cleans up the global scope and provides a proper management of modules and dependencies. I won’t bother you with the details, you can read more about it in Pedro Alves’s post.

This is truly a game changer when it comes to developing CDF/CDE dashboards. We have to write our code better, with a proper architecture in place to make all the pieces talk to each other, we need to use the proper methods to set or get parameter values, to run custom functions in pre-execution or post-execution code snippets, etc.

This is not a bad thing, far from it. But it doesn’t come without its challenges. We’ve started playing with the new require.js framework here at Ubiquis and we’ve learned useful tricks already.

Here’s one: remember how easy it was to upload that myAwesomeJqueryPlugin that you found on some github repository and allowed you to implement that super-duper feature on your dashboard? Well, it won’t work anymore. Not without a bit of work, at least. Here’s why: your typical jQuery plugin is a function of the type

(function ($) {
// your awesome code goes here

But now it will fail. The reason is that $ is no longer defined in the global scope. It’s still exposed and you can access it as usual from within any component’s internal methods, but not when you’re loading your jQuery plugins.

So, after some reading we got to a very interesting Stack Overflow post (see , that pretty much solves the problem. We just need some tweaks on the plugin code to make it require friendly:

(function (factory) {
if (typeof define === 'function' && define.amd) {
// AMD. Register as an anonymous module depending on jQuery.
define(['jquery'], factory);
} else {
// No AMD. Register plugin with global jQuery object.
}(function ($) {
// your awesome code goes here

(note that the whole jQuery plugin is passed as a parameter to the factory function)

And there you have it, you can continue to use all the jQuery plugins you want, which are now loaded as require.js modules.

PDI: getting the previous value of a field, but only sometimes

In PDI we can easily retrieve the previous (or next) value of a field easily, by using the Transformation step Analytical Query. It allows us to fetch the value of a given field or fields N rows back or N rows forward. Quite useful for things like cumulative sums (although for that we could just use a Group by step), getting the previous attribute values of a SCD, etc to map a SCD of type II to a SCD of type III, etc.

However, this is a rather limited step:

  • The number of rows back or forth is fixed; it can be a variable, but can’t be dynamically changed;
  • We can only get a field’s value, not anything more complex, like operations on fields;
  • We can’t get values based on a condition (e.g., if customer number is null, take the previous customer number; otherwise, build it using some algorithm)

We were facing a problem where the answer seemed to be the Analytical Query step… only that it wasn’t. Here’s the problem: on an event tracking database we have a category_raw field; as a general rule, this is the value we want to use as the true category of the object, let’s call it category_new. However, if the category_raw field value is ‘X’, we should ignore it and instead use the previous category_new value. Sounds simple, right?

Here’s a sample of the data and the desired output:


From here it seems quite obvious: we use the Analytical Query step, fetch the category_raw value of the previous row and with a simple condition we evaluate

category_raw == “X” ? prev_category_raw : category_raw

However, if we have various consecutive exceptions,


This approach doesn’t work: the 3rd row would fetch “X”, the value of the previous row, not “A” which occurred 2 rows before.

We tried to trick the Analytical Query step into fetching the value of the same field it’s creating, but that doesn’t work either. The step has to read values from one field and write a new field, but they must be different.

In the end we decided to go with a simple Java Script step, not so much because it’s the only way to go (you can quite easily fetch the objects you need using a Java class, Java expression, etc.), but because it’s simple.

Here’s a Javascript code:

var category_new;
if( category_raw == “X”){
category_new = getVariable( “prev_category_new”, “”);
category_new = category_raw;
setVariable( “prev_category_new”, category_new, “s”);

We know we’re setting a variable and using it in the same transformation, which is something we were always told is wrong. And usually, it is. However, as setting and getting the variable both happen inside the same step, it’s actually harmless: the variable is set for row 1 before it’s called on row 2, and so on…

Here’s a sample of the result:


Each row picks up the correct category_new value, taking into account the handling of the excepcional “X” values.

Hello world, again

Well, we finally got round to upgrade our Pentaho installation to 5.2 and decided to revamp our World Population dashboard in the process.

First thing you may notice: it’s called World Data now, not World Population. This is because we plugged in data available at the Gapminder and add a few selectors to allow you to choose different metrics. Anything from Overall population to GDP/capita in inflation-adjusted PPP dollars, to percentage of renewable energies, you name it and probably Gapminder has it.

The best part: there’s time series data, sometimes dating as far back as the Middle Ages, which allows us to show how those indicators evolved for any particular country. Just click on a country and you’ll see.

We also added a switch to allow you to change the color scale from linear to log (the algorithm decided automatically which one to use, but sometimes it may choose unwisely).

Here, enjoy it: World Data demo dashboard.

Reading/Writing files from a Kettle CDA datasource in Pentaho 5.x

Kettle datasources in CDA are the most versatile way of getting data from disparate systems into a dashboard or report. Both C-tools and PRD expose Kettle as a datasource, so we can call a transformation that queries several different systems (databases, web services, etc.), do some Kettle magic on the results and then ship the final resultset back to the server.

However… there’s no way out of the box to reference sub-transformations in Pentaho 5.x. Solution files are now hosted on Jackrabbit and not on the file system and ${Internal.Transformation.Filename.Directory} just doesn’t work. If you have a transformation calling a sub-transformation and upload both to the repository, when you run it you get an error message saying that it cannot find the file.

Although this usually isn’t a problem, as most Kettle transformations used by dashboards are relatively simple, for more complex tasks you may want to use mappings (sub-transformations), call a job or transformation executor or, and perhaps the best use case, use metadata injection. In these scenarios you _really_ need to be able to call ktr files from the BA server context, and as it happens you can’t.

Well, sort of. As it turns out, you can.

The problem: lets say you have your server installed in /opt/pentaho/biserver-ce (or biserver-ee, we at Ubiquis don’t discriminate), and your kettle file is in your repository in /public/myDashboard/files/kettle/myTransformation.ktr. You want to use Metadata injection on a transformation called myTemplate.ktr and so you reference it by ${Internal.Transformation.Filename.Directory}/myTemplate.ktr in your metadata injection step. When you run your datasource, your error message will say something like

Cannot read from file /opt/pentaho/biserver-ce/pentaho-solutions/public/myDashboard/files/kettle/myTemplate.ktr because it’s not a file.

So what seems to be happening is that Kettle is using your pentaho-solutions folder as the root folder and it just appends the JCR path to it. Which obviously fails, as there’s no physical counterpart in your filesystem for the JCR files.

But, if you use the Pentaho Repository Synchronizer plugin to copy the contents of JCR to the filesystem and vice-versa (which is perhaps the simplest way to have your solution files under GIT or SVN, at least until the Ivy GS plugin becomes fully functional), then the synchronisation process will create a folder repositorySynchronizer inside your pentaho-solutions folder and use it to create the copies of every JCR file.

So, after synchronising JCR with the file system, your template transformation can be found in /opt/pentaho/biserver-ce/pentaho-solutions/repositorySynchronizer/public/myDashboard/files/kettle.

And now, the funny bit: to get it working, just create a symbolic link to remove the extra repositorySynchronizer element from your path: go to your pentaho-solutions folder and just type ln -s repositorySynchronizer/public public.

Now the template transformation is found and you can reference it from a transformation called by a dashboard.

Credit for the discovery goes to Miguel Cunhal, our junior consultant, that had the tough task of getting our metadata injection transformation running inside a demo dashboard. But more on that in another post.

Dynamic date ranges in MDX: what happens if there’s no data?

Imagine the following scenario: a user wants a query to return the sales value from the past N years (lets say 5). It’s quite an easy query, your rows clause would look like this:

SELECT {[Measures].[Sales]} ON COLUMNS,
([Time].[2005].Lag(4) : [Time].[2005]) ON ROWS
FROM [SteelWheelsSales]

(As we’re using our good old friend SteelWheelsSales, lets pretend we’re back in 2005; If you’d like to have SteelWheelsSales updated, say to cover 2013-2015, please vote on the JIRA we created)

Here lies the problem: SteelWheelsSales only has data from 2003 to 2005, so the member [Time].[2005].Lag(4), which would be 2001, doesn’t exist. As such, the first member of that range doesn’t exist and the row set is empty.

And that’s not nice. It would be good to have a query that goes back N years in time but if there’s not enough data it still displays something.

What we need is a dynamic date range. It goes as far back as 4 years ago or, if there aren’t enough years in your database, shows all years.

Here’s what such a query would look like:

Set YEARS as [Time].[Years].Members
Member [Measures].[Year Number] as Rank([Time].[2005], YEARS ) - 1
Member [Measures].[Lag] as Iif( [Measures].[Year Number]<4, [Measures].[Year Number], 4) SELECT [Time].[2005].Lag( [Measures].[Lag] ) : [Time].[2005] ON ROWS, [Measures].[Sales] ON COLUMNS FROM [SteelWheelsSales]

Here's how it works:

  • The Year Number measure determines the rank of the last year of the date range; we subtract 1 to make it zero based;
  • The Lag measure checks whether the last year's rank is at least 4. If it's not, it takes the zero based rank (which means, it takes the first available year as the start of the date range
  • The date range on Rows takes this Lag measure to set the beginning of the range

This query returns all three years available in SteelWheelsSales. However, if more periods are available, it'll display up to 5 years of data.

And we can parametrize the query to take a year number:

Set YEARS as [Time].[Years].Members
Member [Measures].[Year Number] as Rank([Time].[${year}], YEARS ) - 1
Member [Measures].[Lag] as Iif( [Measures].[Year Number]<4, [Measures].[Year Number], 4) SELECT [Time].[${year}].Lag( [Measures].[Lag] ) : [Time].[${year}] ON ROWS, [Measures].[Sales] ON COLUMNS FROM [SteelWheelsSales]

Bonus points: make it smarter, that is, make the query dinamycally return a range of members of the time dimension, regardless of the level of the parameter:

Set MEMBERS as ${timeParameter}.Level.Members
Member [Measures].[Member Number] as (Rank(${timeParameter}, MEMBERS) - 1)
Member [Measures].[Lag] as IIf(([Measures].[Member Number] < 4), [Measures].[Member Number], 4) SELECT {[Measures].[Sales]} ON COLUMNS, (${timeParameter}.Lag([Measures].[Lag]) : ${timeParameter}) ON ROWS FROM [SteelWheelsSales]

This query takes a parameter ${timeParameter} as a fully qualified MDX member, e.g. [Time].[2004] or [Time].[2004].[QTR1] or [Time].[2004].[QTR1].[Jan] and returns a row set with 5 time periods, or a smaller range if we don't have that much data in the past.

GEM, a Generic ETL Machine

It’s finally here. After a few months of work, a lot of bugs fixed and a last minute refactor of all database connections, we are proud to release the first version of GEM, Generic ETL Machine.

It’s an ETL framework based on Pentaho Data Integration, to automate most of the common tasks that take time to develop, are essential to ensure a proper maintainable ETL, but that are hard to explain when the project’s stakeholders want to see their data. Things like enabling a solid logging mechanism with email alerts; data lineage to allow us to trace the data from the reports and dashboards, to the cube, then the fact table, then the staging tables, then the source files or databases, complete with line numbers, date the record was extracted, etc; a way (still very archaic) to define the order in which several tasks should run; a way to quickly deploy from the development laptop to a server and switch environments, from dev to test, to prod; and all this, of course, configurable.

This is still the first version and a lot of work is left to do. For the time being there’s no user interface to display the status of each ETL run or the results, all rollbacks must be performed manually in the database and there’s no way to schedule different tasks at different intervals. That’s all on the roadmap, time permitting, together with increasing the number of available samples (CSV files and web services to name a couple), support for PDI clusters, output and input directly into Hadoop in its multiple shapes and forms.

But it’s usable as it is (well, sort of – we only support a couple databases on each stage for the time being) and it’s been allowing us to spend a significant larger amount of time dealing with what really matters when we have to develop an ETL from scratch: the data analysis and the design of the data model. Not enabling file or DB logging, or setting up the email step for the 500th time.

Clone it, fork it, commit to it, enjoy!

source code on Github

Pentaho Community Meeting 2014, Antwerp

Wow, what a ride!

Last week-end (part of) the Pentaho Community gathered in Antwerp for the 7th (8th?) annual Pentaho Community Meeting. This year the location was Antwerp in Belgium, hosted by our friends at Know BI and sponsored by Pentaho.

And it was unanimously considered the best PCM ever, if not by anything else, by the sheer quality of the presentations. We had tons of cool stuff being presented, a lot of new Sparkl plugins, PDI plugins and al in all, interesting tricks learnt from people across a wide range of specialities and roles in the Pentaho world.

In case you missed it, it’s rumoured next year PCM will be held in London (and Ubiquis is keen to help organising it) but, most importantly, you should check the Pentaho London User Group, which will meet again on 2 December at Skills Matter. Among other interesting topics, Dan Keeley (@codek1) will be presenting a talk covering the last PCM.

See you there!