ECL - Part II (ECL IDE Basics and Transformations)

In Part I of the ECL blog series we were introduced to the HPCC platform, how to load a data file and display the contents using ECL. In Part II, we will continue from where we left off and learn about transformations in ECL. This will give you a glimpse of the power of the ECL language and why it is the best language to handle data  (Big or Small) manipulation.

Before we begin to code transformations, let us spend some time understanding the features/views available in the ECL IDE, the tool used to write ECL code:

• Builder - Use the builder to edit your ECL code, build and submit it for execution.
• Submit/Compile - Is used to compile an ECL code file and submit it as a job for execution on the cluster
• Output Results - Executed ECL code results can be viewed here.
• Syntax Errors - Check if your ECL code is free of syntax errors using the compile option (F7). The Syntax Errors view displays design time syntax errors.
• Runtime Errors - The error log view  displays the errors that occur when ECL code is executed on the cluster.
• Workunits - Displays all the ECL jobs that have been executed on a cluster. It is conveniently categorized by days, months and years. 
• Repository - This synonymous to projects in other IDEs. Shows location of files on local storage. For me, it can we found on the hard disk at "C:\Users\Public\Documents\HPCC Systems". It can be configured to point elsewhere by changing the IDE preferences.
• Workspace - Is a logical work environment that can be used to enhance your programming experience. 
• Datasets - List the available data sets on the cluster. It is convent to select the data set and copy the label so as to use it in the code

Read more about the ECL IDE and Client Tools here. 

Now back to coding transformations.  For the transformation example, we are going to work with the OriginalPerson dataset from Part I and transform the data to create a new TransformedPerson dataset, which is a copy of the OriginalPerson dataset with the First, Middle and Last names converted to upper case.

Open a new builder window (CTRL+N) and type in the following code: 

---

IMPORT Std;
//Declare the format of the source and destination record
Layout_People := RECORD
  STRING15 FirstName;
  STRING25 LastName;
  STRING15 MiddleName;
  STRING5 Zip;
  STRING42 Street;
  STRING20 City;
  STRING2 State;
END;

//Declare reference to source file
File_OriginalPerson :=
DATASET('~tutorial::AC::OriginalPerson',Layout_People,THOR); 

//Write the Transform code
Layout_People toUpperPlease(Layout_People pInput)
:= TRANSFORM
  SELF.FirstName := Std.Str.ToUpperCase(pInput.FirstName);
  SELF.LastName := Std.Str.ToUpperCase(pInput.LastName);
  SELF.MiddleName := Std.Str.ToUpperCase(pInput.MiddleName);
  SELF.Zip := pInput.Zip;
  SELF.Street := pInput.Street;
  SELF.City := pInput.City;
  SELF.State := pInput.State;
END ; 

//Apply the transformation
TransformedPersonDataset := 
   PROJECT(File_OriginalPerson,toUpperPlease(LEFT)); 

//Output it as a new Dataset
OUTPUT(TransformedPersonDataset,,'~tutorial::AC::TransformedPerson',
       OVERWRITE);

---

The important step is a call to the Project function. In this particular case it means:

"Transform Dataset File_OriginalPerson to TransformedPersonDataset By applying  transformation toUpperPlease for each record of LEFT dataset = File_OriginalPerson"

LEFT is analogous to the LEFT join syntax in SQL. In this case it is the File_OriginalPerson.

Compile and Submit the code. View the results in the Output Results view.

This is some powerful code. ECL lets you solve complex data manipulation problems using simple and concise code. This is only tip of the iceberg. Read the ECL programmers guide and ECL Language reference to discover ECLs immense power.

ECL - Part I (loading data)

One of the cool features of the HPCC platform is its ability to extract, transform and load Big Data (tera bytes to peta bytes). At the core of the HPCC platform is the powerful and simple ECL (Enterprise Control Language) programming language. Part I of the ECL blog, shows you how to load data and display the contents. In essence, have the data ready for further data manipulation.

Before we begin to get our feet wet and drool over the code, it is imperative to spend a few minutes understanding the HPCC platform architecture. The following high level architecture diagram, provides you with a view of the important components:



THOR - The Thor cluster performs the Loading, Extraction and Transformation of the data. It is used to load Big Data (unstructured, semi-structured or structured), transform it and optimize it for querying.

ROXIE - The Roxie cluster is optimized to perform queries with very high concurrency. Typically, processed data from a Thor cluster is exported to a Roxie cluster to enable real time, fast and highly concurrent query processing.

ESP - The ESP provides you with a simple web services interface, that is used to access the Roxie queries.

Now back to the coding. How do we load the data? The HPCC Platform has a built in utility called ECL Watch. Data loading is one of the functions (among many) that ECL Watch provides. The following step by step tutorial takes you through the process:

1) For the sake of sanity, we will assume that you have been able to download and install the HPCC VM. If not, please proceed to do so and read the HPCC VM Install Guide.

2) Now download the sample data file containing person information data- first name, last name etc. Once downloaded, extract the contents of the zip file and store it at a known location.

3) Point your browser to the ECL Watch and use the upload/download file link to upload the file to the landing zone



Browse to the sample person file you downloaded, select and upload.

4) Spray the file contents to all the nodes across the cluster. Again, use the ECL Watch utility to do this.




The label is a logical name, AC stands for my initials. It really can be anything. Choose the file that you uploaded in step 3, set the record size to 124 (record size of the person file) and submit for it to be sprayed.

If successful, you should see a results page that looks like:



Click on the View Progress to view the progress of the spray

5) Download, install and configure the ECL IDE if you have not done so already.

ECL IDE preferences:

Enter your VM IP in the "Server" input.



Save the preference

6) Now, you are ready to write ECL Code. While in the ECL IDE, press CTRL+N to open a new work unit. Type in the following code:

Layout_People := RECORD
STRING15 FirstName;
STRING25 LastName;
STRING15 MiddleName;
STRING5 Zip;
STRING42 Street;
STRING20 City;
STRING2 State;
END;


File_OriginalPerson :=
DATASET('~tutorial::AC::OriginalPerson', Layout_People, THOR);

//Here change the AC to whatever you used to name the label in step 4

OUTPUT(File_OriginalPerson);




7) Syntax check (f7) and Submit/Execute the code to see the following results





That is it for now. In my next blog post, we will be looking at some of the features of the ECL IDE and ECL Language. In the process, we will also expand upon the person example and learn about transformations, indexing and sorting.