Expressions with pipelines

Question

we have a need here in which we want to upload expressions to pipeline dynamically.
Is there any API out there which can upload expressions file dynamically on pipelines ?
Can expressions files be loaded from file system ? currently, it cant support expression while we upload expression files.
Answers will be much appreciated here…
Thanks…
Rishi

ryagnik · Answer

any response here ? awaiting for input here.

nganapathiraju · Answer

Please state your use case for using dynamic expression files and what it contains.
Currently you cannot refer expression files from external file systems.
The situation you will run into is while developing the pipeline, the expression functions/variables you are referring to need to be validated and unless they are available in SLDB, it will not be successful.
You can make the expression library file reference an expression but it still has to exist within SLDB.
You can try uploading as a first step before the pipeline using the expr library; to upload to SLDB from an external file system.
Hope you got it.

Write expr library file to SLDB after reading from an external file system based on whatever logic
use the expression on the pipeline edit properties to derive it based on some logic.

Try it out and let us know.

ryagnik · Answer

nganapathiraju:

to upload to SLDB from an external file system.

It wont help here if we are changing the expression on pipeline edit properties however our use case as follows -
We expect files from 200 financial entities, every one has its own rule to parse the file and it can be changed dynamically.A business user can manage the rules and change the rules, at the same time we can leverage the same set of rules when we add the new payer.
In our design, we are building the rules in the expression files but here we need some capability to add expressions dynamically on pipeline whenever business user changes the rules.
Hope it helps here…
Thanks…
Rishi

tstack · Answer

ryagnik:

Can expressions files be loaded from file system ? currently, it cant support expression while we upload expression files.

The Expression Libraries feature might be useful in this case.  Libraries are files that are loaded into a pipeline at startup and made available to all expression properties through the ‘lib’ variable.  So, you can create an object with a bunch of arrow functions containing the expressions you need access to.  For example, if you created a file named ‘demo.expr’, with the following content and imported it into a pipeline.  You could square numbers by calling ‘lib.demo.square(2)’ in an expression property.
{
    square: x =&gt; x * x
}
If that doesn’t quite work for you, there is also the eval function, which you can use to evaluate an expression string that was created dynamically.  You could imagine using it in a similar fashion where the content was loaded into a string, eval’d, and then the resulting functions would be available for use.  The downside being that the functions would not be available in every expression property.

ryagnik · Answer

I am well verse with expression library features,please refer to my use case mentioned in previous answer.

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Expressions with pipelines

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