[BUG]

[alazovik147]

Component

Full Dashboard

Performance Monitor Version

2.4.1

SQL Server Version

Microsoft SQL Server 2022 (RTM-CU23) (KB5078297) - 16.0.4236.2 (X64) Jan 22 2026 17:50:56 Copyright (C) 2022 Microsoft Corporation Developer Edition (64-bit) on Windows Server 2022 Standard 10.0 (Build 20348: ) (Hypervisor)

Windows Version

Windows Server 2022

Describe the Bug

MCP service returns error:

What are the most expensive queries by CPU?

● sql-monitor - get_top_queries_by_cpu (MCP)(server_name: "DEV 1.36")
⎿  Error during get_top_queries_by_cpu: Argument data type nvarchar(max) is invalid for argument 1 of Decompress function.

Steps to Reproduce

1. run claude
2. What are the most expensive queries by CPU?

Expected Behavior

some result

Actual Behavior

Error during get_top_queries_by_cpu: Argument data type nvarchar(max) is invalid for argument 1 of Decompress function.

Error Messages / Log Output

Error during get_top_queries_by_cpu: Argument data type nvarchar(max) is invalid for argument 1 of Decompress function.

Screenshots

No response

Additional Context

No response

[erikdarlingdata]

@alazovik147 Thanks for reporting. The DECOMPRESS error suggests the query_text column in collect.query_stats may be nvarchar(max) instead of varbinary(max). This would happen if the database was created with an older version that predated compression.

Could you check:

1. Did you run the installer (CLI or GUI) to upgrade the database to 2.4.1, or just replace the Dashboard exe?
2. What does this return on your monitored server?

SELECT 
    c.name AS column_name,
    t.name AS data_type
FROM PerformanceMonitor.sys.columns AS c
JOIN PerformanceMonitor.sys.types AS t
    ON c.system_type_id = t.system_type_id
    AND c.user_type_id = t.user_type_id
WHERE c.object_id = OBJECT_ID(N'PerformanceMonitor.collect.query_stats')
AND   c.name IN (N'query_text', N'query_plan_text');

If the data types come back as nvarchar instead of varbinary, running the installer against the server should fix it via the upgrade scripts.