SSAS 2019 Tabular processing returns “Success” with 0 rows when using Snowflake via ODBC (MSDASQL)

I’m migrating an on‑prem SSAS 2019 Tabular model from SQL Server (local) to Snowflake. The model is deployed, and I’ve added a new legacy data source via 64‑bit ODBC. Processing a table in SSMS completes with “Success,” but 0 rows are processed. The same query returns rows in Snowflake (Snowsight and SnowSQL), so the data is available and connectivity is established.

Environment

• SSAS 2019 Tabular, on‑prem
• SSMS for processing
• Snowflake accessed via 64‑bit
• ODBC Provider: MSDASQL (legacy datasource)
• Driver:SnowflakeDSIIDriver
• Authentication: Key‑pair (Authenticator = SNOWFLAKE_JWT), private key on local filesystem
• Impersonation mode:ImpersonateServiceAccount
• SSAS service account has read access to the private key directory

Connection string (simplified)

Provider=MSDASQL;Driver=SnowflakeDSIIDriver;Server=<account/host>;
Database=<db>;Schema=<schema>;
User=<user>;Role=<role>;Warehouse=<warehouse>;
Authenticator=SNOWFLAKE_JWT;
JWT_private_key_file=<path-to-private-key>;
Password=<private-key-passphrase>

What I’ve verified

• The Snowflake SQL query returns rows in Snowsight.
• The same query runs successfully via SnowSQL on the SSAS host.
• The SSAS service account has read permissions on the private key file and directory.
• The ODBC DSN and connection string resolve (no connection errors reported).
• The model deploys; changing the table’s data source to the Snowflake source applies without errors.

Symptoms

• Processing a single table in SSMS ends with “Success” but shows 0 rows processed.
• No obvious errors in SSAS logs tied to the processing event.
• Query works outside SSAS, but SSAS appears to neither push the query nor ingest rows.

Questions

1. Why does SSAS processing report “Success” with 0 rows when querying Snowflake via ODBC (MSDASQL) with JWT key‑pair auth?
2. Are there known limitations or required settings when using MSDASQL + Snowflake ODBC for SSAS Tabular?
3. What diagnostics or logging (SSAS flight recorder, OLE DB/ODBC tracing) would reveal whether SSAS is issuing the query and receiving rows?
4. Is there a recommended alternative provider/driver path (e.g., an OLE DB provider for Snowflake, ADO.NET via gateway, or different auth) that works reliably for SSAS Tabular?

Additional details and hypotheses

• Column type mapping: Could SSAS be silently discarding rows due to unsupported types or nullability mismatches? Any known mappings for VARIANT, TIMESTAMP_NTZ/LTZ/TZ, or large VARCHARs that break Tabular processing?
• Rowset vs query mode: Does SSAS require specific ODBC settings (e.g., “Use Query Result Format” or “NoDescribeParam”) to return a rowset it can consume?
• Role/warehouse: The Snowflake role and warehouse are set in the connection string. Is SSAS ignoring them or overriding via session parameters?
• JWT integration: MSDASQL + SnowflakeDSIIDriver with SNOWFLAKE_JWT works in SnowSQL; does SSAS need the key in a specific format (PKCS#8 vs PKCS#12, encrypted vs unencrypted)?
• Isolation/transactions: Any SSAS differences with ODBC cursors or fetch sizes that cause an empty result?

What would help diagnose

• A sample working SSAS Tabular connection string to Snowflake (including any critical ODBC parameters).
• Guidance on enabling detailed SSAS processing logs and ODBC driver tracing for Snowflake to confirm query execution and row retrieval.
• Known compatibility notes for SSAS 2019 + Snowflake ODBC via MSDASQL.

Expected vs Actual

• Expected: Processing runs the query against Snowflake and loads N rows into the table partition.
• Actual: Processing reports “Success,” but 0 rows are loaded. Query works elsewhere.