Reusable interface in record field, duplicate validation check

In the Record->Data Model you can configure common validations for a field. Refer related Document here and here  which uses a!applyValidation for reusable validations for reusable interfaces for record field. Generally for checks like '@' in email or phone number formatting this validation configuration will be helpful. 

For Duplication check in your usecase I suggest you to create validation logic and configure them in the reusable interface for each field. You can use 'additionalValidations '  attribute of the a!applyValidation() to check duplicates and show validation as configuring/testing them in the Data Model field's Validation can be tricky. Below is an example where date validation is added on the reusable interface for the endDate field. Similarly you can check for duplicate using an expression and show user's validation message. Hope it helps!

a!applyValidations(
 recordField: recordType!Case.field.endDate,
 context: ri!record,
 additionalValidations: {
    if(
     ri!record[recordType!Case.fields.endDate] > today(),
     "",
     "Enter Valid Date"
    )
    }
)

Configure validation directly on the record field: Record Type -> Field -> Validations with a!queryRecordType() duplicate check expression.
This automatically applies to all reusable interfaces via a!applyValidations() function without modifying individual interface code

https://docs.appian.com/suite/help/25.3/fnc_system_a_applyValidations.html

This documentation will solve your all questions.
https://docs.appian.com/suite/help/25.3/build-best-data-fabric.html#reusable-record-field-validations

To do the duplicate check, i have to query the record to get existing values. So Appian will have to query the record for each field.

To do the duplicate check, i have to query the record to get existing values. So Appian will have to query the record for each field.

Did you consider to add a form or section level validation?

You can also do this in field-level validation as mentioned above.
Check the syntax below and replace it with your record type appropriately.

if(
  a!queryRecordType(
    recordType: cons!YOUR_RECORD_TYPE,
    filters: {
      a!queryFilter(
        field: 'recordType!YourRecordType.fields.username',
        operator: "=", 
        value: rv!record['recordType!YourRecordType.fields.username'] 
      ),
      a!queryFilter(
        field: 'recordType!YourRecordType.fields.id', 
        operator: "<>", 
        value: rv!record['recordType!YourRecordType.fields.id']
      )
    },
    pagingInfo: a!pagingInfo(1, 1) 
  ).totalCount > 0, 
  "Username already exists",
  null
)

Yes within the textField->Validations of the field's interface you can query the record type. Pass the value in the queryfilter to checks of duplicates instead of gettting all existing values from record. 

vamsiKrishna said:

So Appian will have to query the record for each field.

Even when we dont use reusable interface, the validations need to have queryRecord for each field which you need to check, so its similar! Appian will query the record by passing in the value of the field and check if duplicate exists - This remains the same with or without reusable interface. 

Thanks, 

Yeah i can check for specific user entered value, that should help.

but if we don't use reusable interface, we can query once for all in a normal UI, and use that data to check duplicates right?

I need field level validations.

interesting approach 

Thanks Shubham Aware 

I think this should help

even if i need to do for every field, this won't impact performance much right?

it will query for each field and each time user enters a value right?