SemVer2 - Missing db index on Packages table #498

[xavierdecoster]

Noticed an increase in DTU consumption on the gallery db after deploying semver2, and it's caused by a missing index on the Packages table.

The Query Processor estimates that implementing the following index could improve the query cost by 99.5235%.

Affected EF query:

(@p__linq__0 int, @p__linq__4 int,@p__linq__5 int)

SELECT	[GroupBy1].[A1] AS [C1]
FROM 
( 
	SELECT	COUNT(1) AS [A1]
    FROM	[dbo].[Packages] AS [Extent1]
    WHERE	([Extent1].[Deleted] <> 1) 
		AND (([Extent1].[SemVerLevelKey] = @p__linq__0) 
			OR (([Extent1].[SemVerLevelKey] IS NULL) AND (@p__linq__0 IS NULL))
			) 
		AND ((
			CASE 
			WHEN (@p__linq__4 = @p__linq__5) 
			THEN [Extent1].[IsLatestSemVer2] 
			ELSE [Extent1].[IsLatest] 
			END) = 1)
)  AS [GroupBy1]

[joelverhagen]

What are the parameters in this case? What code path does this primarily affect?

[xavierdecoster]

@joelverhagen https://github.com/NuGet/NuGetGallery/blob/master/src/NuGetGallery/Controllers/ODataV2FeedController.cs#L86

[scottbommarito]

Any reason for these not to be in a single migration?

[xavierdecoster]

Yes, they were separate PRs, and have been evaluated separately to find out whether the change was for the better or not.

[xavierdecoster]

Want to point out these indices have already been applied (see offline discussion), and monitoring has clearly shown they had a positive effect on gallery db DTU consumption.