Troubleshooting Guide: SQL Server Error 1982 — Non-Deterministic CLR Member Function Reference in Indexed View

Why This Error Happens

This error occurs when you attempt to create an index on a view that references a CLR (Common Language Runtime) user-defined type’s member function, but SQL Server cannot verify that the function is deterministic and precise. Since indexed views require all referenced expressions to return consistent, repeatable results for the same input, SQL Server’s query optimizer rejects any CLR method lacking the IsDeterministic and IsPrecise attributes set to true. This typically stems from the CLR assembly being authored without proper attribute decoration, or from using built-in system CLR types (like geography or hierarchyid) whose specific methods are inherently non-deterministic by design.

Step-by-Step Resolution Guide

Step 1: Identify the Offending Function and View

• Capture the full error text, which specifies the exact view name and the CLR function/type causing the conflict.
• Run the following query to inspect view definitions referencing CLR types:

  SELECT definition FROM sys.sql_modules WHERE object_id = OBJECT_ID('YourViewName');

• Cross-reference the flagged method against Microsoft documentation to confirm its determinism status (e.g., many geography/geometry methods like STDistance are non-deterministic).

Step 2: Modify or Remove the Non-Deterministic Reference

• If the function belongs to a custom CLR assembly, open the source project (typically a .cs or .vb file) and locate the method definition.
• Decorate the method with the required attribute in the SqlMethod declaration:

  [SqlMethod(IsDeterministic = true, IsPrecise = true)]
  public SqlDouble CalculateValue() { ... }

• Recompile the assembly into a .dll and redeploy it using ALTER ASSEMBLY or CREATE ASSEMBLY in SQL Server Management Studio (SSMS).
• If the function is a built-in system type method (not user-editable), rewrite the view’s SELECT statement to exclude that specific call and instead compute the value in a separate deterministic scalar function or persisted computed column.

Step 3: Redeploy the Assembly and Rebuild the View

• Drop and recreate the view without the problematic reference, or replace it with a precomputed/persisted column:

  ALTER TABLE YourTable ADD ComputedCol AS dbo.YourDeterministicFunction(Col1) PERSISTED;

• Re-run the CREATE UNIQUE CLUSTERED INDEX statement on the view to confirm SQL Server now accepts the definition.
• Check sys.assemblies and sys.assembly_modules to confirm the updated assembly version is correctly registered:

  SELECT * FROM sys.assembly_modules WHERE assembly_id = (SELECT assembly_id FROM sys.assemblies WHERE name = 'YourAssemblyName');

Step 4: Validate Database Compatibility Level

• Confirm the database is running at a compatibility level supported by SQL Server 2025 (160 or higher) using:

  SELECT compatibility_level FROM sys.databases WHERE name = 'YourDatabaseName';

• Older compatibility levels may enforce stricter or differently-validated determinism checks on CLR types, so update if necessary with ALTER DATABASE YourDatabaseName SET COMPATIBILITY_LEVEL = 160;.

Alternative or Verification Steps

• Verify the fix by re-executing the CREATE INDEX statement on the view — successful completion without Error 1982 confirms resolution.
• As an alternative, if altering the CLR assembly isn’t feasible, remove the indexed view requirement entirely and use a standard (non-indexed) view, or materialize the data into a physical table via a scheduled ETL/trigger process instead.