Category Archives: Scripting

qcb-qlik-sse, A General Purpose SSE

In Qlikview we have the ability to add function to the scripting language by writing VbScript in the document module (sometime called the “macro module”).  Typical  additions included regular expression matching & parsing,

Qlik Sense does not have the module feature, but both Sense and QlikView share a similar feature,  Server Side Extension (SSE).  SSE is typically positioned as a method to leverage an external calculation engine such as R or Python  from within Qlik script or charts.   The Qlik OSS team has produced a number of SSE examples in various languages.

SSE seems to be a good fit for building the “extra” functions (such as regex) that I am missing in Sense.  The same SSE can serve both Sense and QlikView.

Installing and managing a SSE takes some effort  so I’m  clear I don’t want to create a new SSE for every new small function addition.  What I want is a general purpose SSE where I can easily add new function, similar to the way QlikView Components does for scripting.

Miralem Drek has created a package, qlik-sse,  that makes for easy work of implementing an SSE using nodejs.  What I’ve done is use qlik-sse to create qcb-qlik-sse,  a general purpose SSE that allows functions to be written in javascript and added in a “plugin” fashion.

My motivating  principles for qcb-qlik-sse:

  • Customers set up the infrastructure — Qlik config & SSE task — once.
  • Allow function authors to focus on creating function and not SSE details.
  • Leverage community through a shared function repository.

I’ve implemented a number of functions already.  You can see the current list here. Most of the functions thus far are string functions like RegexTest and HtmlExtract that I frequently have implemented in  QlikView module or I’ve missed from other languages.

One of the more interesting functions I’ve implemented is CreateMeasure(), which allows you to create Master Measures from load script.  This is a problem I’ve been thinking about for some time and qcb-qlik-sse seemed to be a natural place to implement.

If you want to give qcb-qlik-sse a try, download or clone the project. Nodejs 8+ is required.  Some people report problems trying to install grpc using node 12, so if you are new to all this I recommend you install nodejs v10 instead of the latest v12.

If you are familiar with github and npm, you will hopefully find enough information in the readme(s) to get going. If not, here’s a quickstart.

  1. Install nodejs if not already present.  To check the version of nodejs on your machine, type at a command prompt:
    node --version
  2. Download and extract qcb-qlik-sse on the same machine as your Qlik desktop or server.
  3. From a command prompt in the qcb-qlik-sse-master directory install the dependent packages:
    npm install
  4. Configure the SSE plugin in Qlik.  Recommend prefix is QCB. If configuring in QlikView or Qlik Sense Desktop the ini statement will be:
     SSEPlugin=QCB,localhost:50051
  5. Start the SSE:
     ./runserver.cmd

The “apps” folder in the distribution contains a sample qvf/qvw that exercises the functions.

I’d love to get your feedback and suggestions on usage or installation.

-Rob

 

Share

A Common SSE Plugin Project

Summary: I introduce qcb-qlik-sse, a community Server Side Extension to share custom Qlik functions. 

At the Masters Summit for Qlik, I dive into several different methods of creating reusable script and custom functions.  In QlikView we have the ability to write custom functions using VbScript/Jscript in the qvw Module.

Custom functions have been useful for things like regular expressions, geo calculations, url encoding, encryption and others.  I’ll call them “edge functions” — some of us need them, some of us don’t.

Qlik Sense does not have the module facility. How can we satisfy the requirement for custom function in Qlik Sense?  The Server Side Extension (SSE) facility can fill the need and is available to both Qlik Sense and QlikView.

An SSE Plugin runs as a separate task and provides communication with a Qlik Script or chart Expression via a TCP port. The same SSE Plugin can serve both QS and QV.

Anyone can write an SSE. The Qlik team provides the SSE base and you write a plugin that wires your new functions to Qlik. The new functions can be used in both Script and Charts.  A number of plugins have already been produced.

SSE seems to be the ideal place to provide a collection of edge functions.  Rather than a bunch of one-offs, I’m thinking a good idea would be to pool resources into a single effort that could be shared, much like QlikView Components did for Script.

I’ve implemented this idea as qcb-qlik-sse.  This server uses as it’s base the qlik-sse package created by Miralem Drek.

qcb-qlik-sse is written in javascript and runs in node.js.  At startup, the server scans it’s “/functions” directory and discovers what functions are available.  The general idea is that you can add new function by creating a new js file.  You can remove function you don’t want available by deleting the corresponding js file.

See what functions I’ve already implemented in the doc here. I’ve also provided an example qvf and qvw that exercise the functions.

If you want to try it out,  download the project and define the plugin to QS or QV as documented here.  You will also need node.js 8 or later installed.

Defined functions will show up in the suggestion list in both the script and expression editors.

 

If you want to add functions, some javascript skills are required.  Follow the directions in the readme and submit a PR.

I’ve labeled the project as “experimental” at this stage because I anticipate there could be some significant restructuring as I get feedback.

Let me know your ideas and if you find this useful!

-Rob

Want to kick the tires on reusable code and make your Qlik team more efficient? Come to the Masters Summit for Qlik, a three day advanced training event for Qlik Developers. 

 

 

Share

Script Interpretation and Evaluation

Summary: Qlik Script is both interpreted and evaluated. Understanding the meaning of these terms is useful in writing advanced script and understanding why some script “tricks” work and others don’t.

In my Advanced Scripting session at the Masters Summit for Qlik, I sometimes begin with the question “What does $() do in script?”.  A common answer I hear is “it causes the variable contents to be treated as an expression and evaluated”.  While in some cases this is the practical result, the answer is incorrect.

$() “Dollar Sign Expansion or DSE”, which takes place during interpretation, replaces the variable name with the value of the variable.  This process is called “expansion” or “substitution”. The new value may subsequently get evaluated as an expression during the evaluation phase, but only if an expression is expected in that specific script statement.  Let’s take a look.

SET vVal = 1 + 1; // expecting "1 + 1"
LET v1 = $(vVal); // expecting "2"
SET v2 = $(vVal); // expecting "1 + 1"

$(vVal) will substitute the contents of the vVal variable which is the string “1 + 1”.   After execution, we expect v1 to be “2” because the behavior of a LET statement is to evaluate what is to the right of the equal sign as an expression.  We expect v2 will be “1 + 1” because the documented behavior of the SET statement is to treat the value to the right of equals as a literal string, not an expression.

The individual pieces of a script statement are carved up by the script parser into “symbols” or tokens. The script language definition defines what types — Expressions, Literals, Numbers, etc. — are valid for each symbol.  Only symbols defined as Expressions will be evaluated as such.

The TRACE statement expects a String as it’s symbol.  We can’t calculate a dynamic value within the TRACE statement itself.  We must calculate the value into a variable and then reference the variable like this:

LET vRows = NoOfRows('Orders');
Trace Orders has $(vRows) rows;

It would be useful if script supported the “$(=)” DSE form, like Set Analysis. Then we could do something like this.

Trace Orders has $(=NoOfRows('Orders')) rows;

Simple enough so far.  Let’s look at some more subtle examples.  A user on Qlik Community posted  a requirement to dynamically form several fieldnames in a load statement based off the current date.  She wanted to load a specific field as ‘Month_MMM’ where MMM is the current month-1, another field as current month-2 and so on.  She created a reusable (good idea) variable-with-parameter to create the names:

SET vMonthFieldname = 'Month_' & Date(AddMonths(today(),$1),'MMM');

If called in July as $(vMonthFieldname(-1)) the expected return value would be “Month_Jun”.  The LOAD statement would look something like:

LOAD
  Key,
  field1 as [$(vMonthField(-1))],
  field2 as [$(vMonthField(-2))]

This script executed without error, but to her surprise the final table had unexpected field names:

The variable expansion took place during interpretation, returning the expression string that was intended to form the fieldname.  However, the “as aliasname” clause only expects a literal so no evaluation took place and the string was used as-is for the fieldname.  Like the TRACE example, the workaround would be to first build the values  using LET:

LET vMonth1=$(vMonthField(-1));
LET vMonth2=$(vMonthField(-2));
Data:
LOAD
  Key,
  field1 as [$(vMonth1)],
  field2 as [$(vMonth2)]

How about if we used vMonthField  as the fieldref parameter (to the left of the “as” keyword)?

LOAD
  Key,
  $(vMonthField(-1)) as Month1,
  $(vMonthField(-2)) as Month2

The symbol to the left of “as” may be an Expression, so this would generate expected values. (Admittedly, this is not what the poster asked for, I include it only for illustration).

Let’s visit another illustration of interpretation and evaluation.  How many times will this loop execute?

SET vCounter = 1;
Do While $(vCounter) <= 3
  TRACE Counter is $(vCounter);
  LET vCounter = $(vCounter)+1;
Loop

If your answer is “forever”, you are correct.  Looking at the progress window, we can see  the counter increments beyond 3 but the script continues running.

The script execution log is where we can see what script looks like after interpretation and DSE.

2019-07-25 00:48:17 0021 Do While 1 <= 3
2019-07-25 00:48:17 0022 TRACE Counter is 1
2019-07-25 00:48:17 0022 Counter is 1
2019-07-25 00:48:17 0023 LET vCounter = 1+1
2019-07-25 00:48:18 0025 Loop
2019-07-25 00:48:18 0022 TRACE Counter is 2
2019-07-25 00:48:18 0022 Counter is 2
2019-07-25 00:48:18 0023 LET vCounter = 2+1
2019-07-25 00:48:19 0025 Loop
2019-07-25 00:48:19 0022 TRACE Counter is 3
2019-07-25 00:48:19 0022 Counter is 3
2019-07-25 00:48:19 0023 LET vCounter = 3+1

The Do While condition is fixed at “1 <= 3” which will always be true!  According to the documentation for Do While:

The while or until conditional clause must only appear once in any do..loop statement, i.e. either after do or after loop. Each condition is interpreted only the first time it is encountered but is evaluated for every time it is encountered in the loop.

The doc tells us our $() expansion — which is interpretation — will happen only once.  Evaluation, on the other hand, will be done repeatedly.  The correction to the loop will be to remove $() so our statement looks like this:

Do While vCounter <= 3

This is a valid expression and the loop will execute only 3 times.

So where do we need $() in this loop? We need it in the TRACE because we do not have evaluation, only interpretation.  The While condition and the LET symbol both allow Expressions, therefore we can count on evaluation to get the current variable value.

Do While vCounter <= 3
  TRACE Counter is $(vCounter);
  LET vCounter = vCounter + 1;
Loop

I hope this discussion and examples help you to understand script  interpretation and evaluation, especially in the context of $().

Share

Loading Varying Column Names

Summary:  A script pattern to wildcard load from multiple files when the column names vary and you want to harmonize the final fieldnames.  Download example file here.

I’m sometimes wondering “what’s the use case for the script ALIAS statement?”.  Here’s a useful example.

Imagine you have a number of text files to load; for example extract files from different regions.  The files are similar but have slight differences in field name spelling.   For example the US-English files use “Address” for a field name, the German file “Adresse” to represent the same field and the Spanish file “Dirección”.

We want to harmonize these different spellings so we have a single field in our final loaded table.  While we could code up individual load statements with “as xxx” clause to handle the rename, that approach could be difficult to maintain with many variations.  Ideally we want to load all files in a single load statement and describe any differences in a clear structure.  That’s where ALIAS is useful.  Before we load the files, use a set of ALIAS statements only for the fields we need to rename.

ALIAS Adresse as Address;
ALIAS Dirección as Address;
ALIAS Estado as Status;

The ALIAS will apply the equivalent “as” clause to those fields if found in a Load.

We can now load the files using wildcard “*” for both the fieldlist and the filename:

Clients:
LOAD *
FROM addr*.csv (ansi, txt, delimiter is ',', embedded labels, msq)
;

It’s magic I tell you!

What if the files have some extra fields picked up by “LOAD *” that we don’t want?  It’s also possible that the files have different numbers of fields in which case automatic concatenation won’t work.  We would get some number of “Client-n” tables which is incorrect.

First we will add the Concatenate keyword to force all files to be loaded into a single table.   As the table doesn’t exist, the script will error with “table not found” unless we are clever.  Here is my workaround for that problem.

Clients:
LOAD 0 as DummyField AutoGenerate 0;
Concatenate (Clients)
LOAD *
FROM addr*.csv (ansi, txt, delimiter is ',', embedded labels, msq)
;
DROP Field DummyField;

Now let’s get rid of those extra fields we don’t want.  First build a mapping list of the fields we want to keep.

MapFieldsToKeep:
 Mapping
 LOAD *, 1 Inline [
 Fieldname
 Address
 Status
 Client
 ]
 ;

I’ll use a loop to DROP fields that are not in our “keep list”.

For idx = NoOfFields('Clients') to 1 step -1
  let vFieldName = FieldName($(idx), 'Clients');
  if not ApplyMap('MapFieldsToKeep', '$(vFieldName)',   0) THEN
    Drop Field [$(vFieldName)] From Clients;
EndIf
Next idx

The final “Clients” table contains only the fields we want, with consistent fieldnames.

Working examples of this code for both  Qlik Sense and QlikView  can be downloaded here.

I hope you find some useful tips in this post. Happy scripting.

-Rob

 

 

Share

Does Data Sort Order Impact Chart Calc Time?

Lately I’ve been digging into an old Qlik performance question.  How much impact, if any, does the order of Qlik data tables have on chart calc time?  My experience is that for a chart or aggr() cube with a lot of dimension values,  ordering of rows by dimension values can have a significant and measurable effect.

Mike Steedle of Axis Group blogged about the issue  a couple of years ago.  Mike’s post includes a useful subroutine to organize any table by a specific field.

I’ve added my own study and sample files on the topic in this QlikCommunity post.

Mike and I are are working together on the next update to Qlik Sense Document Analyzer.  Mike is keen on analyzing the data model and making useful recommendations.  One of the optimization questions we are studying is whether it is possible to make a solid recommendation on data table organization.

I’m curious to hear what others have discovered on the topic.  Do you have any rules you follow in ordering table rows?   Any thresholds or object/expression scenarios where you find it’s worth the trouble to manage the ordering?

-Rob

 

Share

Loading Variables From Another QVW

I just read a good post by Kamal Kumar Sanguri on QlikCommunity.  Kamal’s post reminded me that managing variables in QlikView has always presented some challenges and over the years various techniques and code snippets have been shared to address those challenges.

Most folks quickly find that maintaining variables in external files  loaded with a script loop is a good approach and resolves common concerns regarding shareability, dollar sign escaping and so on.

Sometimes you encounter a need for an adhoc import or export of variables. Kamal’s post offers some useful code snippets for that.  Several years ago my colleague Barry Harmsen  wrote a post on QlikFix.com that shows some useful macros to manipulate Variables.  Barry and I  subsequently collaborated on a desktop utility that handles both import and export from a menu.  While the download link on the blog is dead, I’ve reposted the utility on the QlikViewCookbook Tools section for download.

Kamal said that there is no way to directly load variables from one QlikView document to another.  That got me to thinking.  It is possible, but gee, no one has ever asked for it.

What’s the use case?  When I want to do an adhoc copy, I use the desktop utility referenced above.  I have seen a number of customers who generate complex calendars into QVDs followed  by  generation of variable for use with the calendar.  Calendar QVD consumers incorporate the variable generation logic with an include file. It works.

Would it be any better if calendar consumers loaded the variables directly from the calendar generating QVW?  I think not because there is possibility of a mismatch between the QVW source and the Calendar QVD.

All that said, maybe you have a use case for loading variables from a QVW?  No one asked, but for the record here is the script to load variables directly from another QVW.

VariableDescription:
LOAD 
 Name,
 RawValue
FROM [..\..\data\StudentFile.qvw] 
(XmlSimple, Table is [DocumentSummary/VariableDescription])
Where IsConfig = 'false' and IsReserved = 'false' // Exclude system vars
// Any addtional filtering here
;

FOR idx=0 to NoOfRows('VariableDescription')-1
 LET vVarname = Peek('Name',$(idx),'VariableDescription');
 LET [$(vVarname)] = Peek('RawValue',$(idx),'VariableDescription');
NEXT idx

SET idx=;
SET vVarname=;
DROP Table VariableDescription;

Happy Scripting!

-Rob

 

 

Share

Expanding the Qlik Sense Editor Pane

Summary: In this post I present a non-intrusive bookmarklet to hide the Sections pane in the Qlik Sense Script Editor to provide more real estate for typing script. 

EditNote in the comments below that hiding the pane can be done out of the box using keyboard shortcuts such as Alt-F11.   That reminds me to read the doc! Nevertheless the concept of bookmarklets is useful and this post is bringing in some interesting contributions. 

I sometimes wish for a larger window in the Qlik Sense Script Editor where we type  statements.  This is especially true when I am projecting and I’ve zoomed my browser to make the text legible to the audience, or I’m saddled with a very low resolution.

The UI allows me to hide the Data Connections pane which provides  more space, but I’m still left with the Sections pane consuming 250 pixels on the left which may not serve me at the moment.

Wouldn’t it be great if I could hide/show the Sections pane on demand, like I can do with  Data Connections? Here’s a simple non-intrusive hack that will allow you to do just that.

Paste the following code in a bookmarklet. If you’re not familiar with bookmarklets, they are small bits of javascript code that can be executed from the bookmarks menu.  If you are using Chrome as I do, it’s as simple as pasting the javascript code in the URL property of a bookmark.  Google to learn more about bookmarklets.  If you are using a browser other than Chrome google to see how to create (if possible) bookmarklets in your browser.   Here’s the javascript:

javascript: (function () {
 var size = ($('.scripteditor-left').css("width") == "0px") ? "250px": "0px";
 $('.scripteditor-left').css("width", size);
 $('.scripteditor-stage').css("left", size);
 }());

Apply the bookmark and here is what the editor looks like now:

Apply the bookmark again and the Sections pane reappears.

 

This is an unsupported hack of Qlik Sense.  If something else does not work in the editor, you should refresh the browser — which will completely remove any effects of the bookmark — before suspecting or reporting that Qlik Sense has a defect.

This is  a very clean technique to add behavior because we have not modified any Qlik Sense files.

I file my QS bookmarklets in a Bookmarks Bar folder named “QS” which gives me easy access in a dropdown to mods I’ve created for Sense.

Here’s another bookmarklet I find useful.  This one opens the Qlik Sense script log folder for QS Desktop.  My userid in the path is hardcoded, you would of course update to the correct folder name for your machine.

file:///C:/Users/rob/Documents/Qlik/Sense/Log

Please share if you develop additional useful bookmarklets for Qlik Sense.

-Rob

 

Share

AutoNumber vs AutoNumberHash128

Summary:  AutoNumberHash128(A, B) runs about 30% faster than AutoNumber(A &’-‘ & B).

It’s a common practice to use the script AutoNumber() function to reduce the storage required for large compound keys in a Qlik data model. For example:

AutoNumber(A & '-' & B) as %KeyField

As a standard practice, we generally include a separator like ‘-‘ to ensure ‘1’ & ’11’ does not get confused with ’11’ & ‘1’.

The AutoNumber process can add significant run time to a script with many rows.

I’ve always wondered what the AutoNumberHash128() function was good for.

AutoNumberHash128(A,B) as %KeyField

This function first hashes A & B and then autonumbers the result. The end result is the same as the first example given using AutoNumber().  I find the AutoNumberHash128 syntax a bit simpler as a separator is not required.

What surprised me is that the AutoNumberHash128() function runs faster.  Typically about 30% faster than a plain AutoNumber with a concatenated string parameter.

Why is it faster?  The difference is in the function used to create the single value to be autonumbered.  Hash128 is considerably faster than string concatenation (&).

AutoNumberHash128() can take any number of fields, but it does not have an “AutoId” parameter.  The “AutoId” (second parameter) in AutoNumber() is recommended to ensure we get sequential integers when autonumbering more than one key field.  Sequential integers are the most memory efficient storage for keys.

Don’t despair.  AutoNumberHash128() will use the “default” AutoId.  That is fine if you are autonumbering only one key.  If you are doing more than one key, use AutoNumberHash128() for your largest — most rows — key and use AutoNumber() with AutoId for the rest.  You will improve the script run time of one key.

Another possible tradeoff when you have many large keys is to use AutoNumberHash128 for all keys and forgo the sequential integer optimization.  You will use only 8 bytes per key value which could be significantly less than the original string keys.

-Rob

 

Share

LET, SET, Quotes

Summary: In Qlik script SET is often a better choice than LET, even when the value contains quotes. 

I sometimes see the LET script statement used when SET would be syntactically  easier and more readable.

A brief review:  SET assigns the given parameter as-is to the variable,  LET treats the parameter as an expression and assigns the evaluated result to the variable.

SET x = 1+3;  // x is "1+3"

LET x = 1+3; // x is "4"

I frequently see a variable assignment like this:

LET eSales='sum(Sales)';

eSales stores an expression that will be used later in charts.  It could also be written (simpler in my estimation) as:

SET eSales=sum(Sales);

So far just a matter of style, but the difference becomes clear when we have quotes as part of the string, for example, “Region={‘US’}”.   As LET requires a quoted string,  embedded quotes require some sort of escaping.  In QV10 and earlier, a common way to write this with LET would be:

LET x = 'Region={' & chr(39) & 'US' & '}';

Not real pretty. Many people carry over this style even though QV11 introduced two single quotes to represent an embedded single quote.

LET x = 'Region={''US''}';

Easier to read for sure.  But I think it’s even easier with SET.

SET x = Region={'US'};

That’s it. No special escaping required, just type it as it should be.  What about those quotes? Shouldn’t SET strings be enclosed in quotes?

I find the documentation on SET to be thin, but here is the rule as I understand it.

Single or Double quotes in a SET statement require no special treatment as long as they are balanced (even number of quotes).

SET x = Region={'US'},Product={'Shoe'};  // Valid

SET x = Region={"U*"},Product={'Shoe'}; // Valid

SET x = I won't go;   // Invalid

If the quotes are unbalanced (odd number), then the entire string needs to be enclosed in quotes or brackets.  Use double quotes if we are enclosing single quotes.

SET x = "I won't go";

SET x = [I won't go];

I always favor SET over LET unless I truly want an evaluation.  An exception to this is the string “$(” which will trigger an Dollar Sign Expansion, even in SET.

-Rob

For more on character escaping in Qlik from HIC see https://community.qlik.com/blogs/qlikviewdesignblog/2015/06/08/escape-sequences

Share

QV12 REM Logging Change

Summary: QV12 no longer prints the REM statement to the Document Log.

In QV11 “//” and “/*” comments do not appear in the Document Log, but “REM” comments do appear in the log.  I found REM useful to provide some documentation in my logfile or record which branch was taken in an IF-THEN-ELSE.

QV12 has changed the logging of REM.  The REM statement will now appear in the log obfuscated as a series of asterisks  For example, the statement

REM  Beginning of weekly load;

will appear in the log as

2017-05-18 14:24:34 0005 *** *** ******

My understanding is that the change was made to support security standards, as someone could REM a CONNECT string or other sensitive data thereby exposing it in the log.

To provide log documentation, use the TRACE statement instead.  I don’t find TRACE as pretty as REM because TRACE generates double lines, but it will do the job.

I maintain a collection of upgrade notes for QV12 that you can download here to assist in your planning.  Please do read all the Qlik doc — release notes and help site — as well.

-Rob

 

Share