Fetching datasubset from view based on filters

sparshs over 8 years ago

General Interest: Hi i am fetching datasubset from a view on the basis of specific filters and showing in a read only grid(but in this grid i can select rows). My view does not have a unique field and batch size of my grid is 10. When i am selecting a row on grid page 1, all the rows which corresponds to page1 row are getting selected in rest of my grid pages. If i do not have a unique field to identify then how to solve this issue. I want each row of grid to be selected uniquely. Please provide your inputs on this.

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0 sikhivahans over 8 years ago

@sparshs Though I haven't come across this issue till date, I am aware of this via forum posts. I have seen @philb suggesting a function to obtain a unique value for each row. I would like to suggest to try it once and let us know if you are happy with it. Might be @philb or any other practitioners can suggest you a solution in-case if you haven't achieved the desired functionality. The post at https://forum.appian.com/suite/tempo/entry/e-172933 can be taken as a reference and please refer @philb's comments over there. Hope that gives you leads.
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0 sparshs over 8 years ago

@sikhi : thanks for the help . It is helpful.
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0 PhilB
Certified Lead Developer
over 8 years ago

As Sikhi says, just add a column that is something along the lines of SELECT UUID() AS 'id' and add that column as the unique ID in the CDT. It will produce a different value for each row each time you select - even for the same row - so can't be used to write, but that's fine as you shouldn't write to a view. The UUID function should also perform slightly better than alternatives such as concatenating column values.
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0 PhilB
Certified Lead Developer
over 8 years ago

Just to add, you'll need to do this in conjunction with a local variable - that is, you'll have to read all possible data into a local variable, and then use todatasubset() on the local variable to implement paging. This is because the UUID() function will generate a new set of keys each time a select is performed on the view. Saving the data in a local variable means the select is not performed again and so the IDs remain static.
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0 sparshs over 8 years ago

Thanks philb. Your inputs are valuable. Thanks both of you .
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0 sparshs over 8 years ago

Philb: If i had to generate unique values for my grid through appian. How should i achieve that because i already had my datasubset and according to the count of that data subset i generate my unique integer values. But i am not able to get these values a column name in the final datasubset which i generate by merging two data arrays i.e one data array which is fetched from database and another data array in which i have generated unique integer value on the basis of count of my datasubset returned from database. Please provide your pointers on this.
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0 sparshs over 8 years ago

to add to above statement, i should have some unique column in my datasubset , but here i am able to generate unique values but i am not able to put those values under a column in my final datasubset.
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0 PhilB
Certified Lead Developer
over 8 years ago

You'll have to add a field to the CDT to contain the generated IDs, then either use a plugin like updatecdt to add the values to that CDT element, or an apply of your type across your data, adding in the identifier with each iteration.

It's much easier to have the database generate those IDs as we've previously mentioned, and then map them to a column in the CDT.
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0 PhilB
Certified Lead Developer
over 8 years ago

Also, another option is to build the a!dataSubset manually and assign the identifiers as part of that function.
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0 sparshs over 8 years ago

@philb: I used UUID function in one of the fields of my view but while retrieving it through query entity , it is throwing error like Expression evaluation error at function a!queryEntity: An error occurred while retrieving the data.. I am not able to understand this error. If i remove ID column from my query entity then it is working fine.Please help me with this.
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