check whether a Guid is an RT.Comb one about rt.comb HOT 2 CLOSED

Hi Pál,

I'm glad to hear it!

To test, you can look for GUIDs outside your expected date range:

SELECT * FROM myTable WHERE 
guid < SELECT CAST(
    CAST(DATEDIFF_BIG(MILLISECOND, '1970-1-1', '2015-01-22') AS BINARY(16))
    AS UNIQUEIDENTIFIER)
OR guid > SET @startGuid = SELECT CAST(
    CAST(DATEDIFF_BIG(MILLISECOND, '1970-1-1', GETUTCDATE()) AS BINARY(16))
    AS UNIQUEIDENTIFIER);

The above code assumes that you started using COMBs on 2015-01-22 and that you are using the UnixTimeStampStrategy with SqlCombProvider on MSSQL 2016+ or Azure DB. The same approach can be used with the other strategies or database platforms.

This is not foolproof -- there is a small but real chance that a random non-COMB GUID may have a "valid" COMB date/time. If you have other data you can compare to -- for example, an audit log of when the record was inserted -- you could look for a smaller valid date range.

I'm looking at doing the same thing with some legacy data. In my case, the GUIDs were created using the original SqlDateTimeStrategy and I've now standardized my code to use the UnixTimeStampStrategy. So in my case I'll be looking for GUIDs outside the acceptable Unix date range but within the SQL DateTime range, extracting the timestamp, and re-creating the equivalent Unix timestamp GUID. I haven't written the code for that yet, but it'll be similar to the above. Fortunately, none of the GUIDs in my case are used as foreign keys, so this should be a fairly simple process.

from rt.comb.

Hi Richard,
thanks for the check code, info!

from rt.comb.