Slow query with cfqueryparam searching on indexed column containing hashes

Question

I have the following query that runs in 16ms - 30ms.

    SELECT hash FROM jobs WHERE hash in(
           


        

Answer 1

Your issue may be related to VARCHAR vs NVARCHAR. These 2 links may help Querying MS SQL Server G/UUIDs from ColdFusion and nvarchar vs. varchar in SQL Server, BEWARE

What might be happening is there is a setting in ColdFusion administrator if cfqueryparam sends varchars as unicode or not. If that setting does not match the column setting (in your case, if that setting is enabled) then MS SQL will not use that index.

Answer 2

I don't think cfqueryparam causing issue. As you have mention big hike in execution it may be index not going to use for your query when trying with cfqueryparam. I have created same scenario on my development computer but I got same execution time with and without cfqueryparam. There may be some overhead using list as in first query you are passing it directly as test and in second coldfusion need to create from query parameter from provided list but again this should not that much. I will suggest to start "SQL Server Profiler" and monitor query executed on server, this will give you better who costing another 500 ms.

Answer 3

As Mark points out it is is probably got a bad execution plan in the cache. One of the advantages of cfqueryparam is that when you pass in different values it can reuse the cached plan it has for that statement. This is why when you try it with a smaller list you see no improvement. When you do not use cfqueryparam SQL Server has to work out the Execution Plan each time. This normally a bad thing unless it has a sub optimal plan in the cache. Try clearing the cache as explained here http://www.devx.com/tips/Tip/14401 this hopefully will mean that the next time you run your statement with cfqueryparam in it'll cache the better plan.

Make sense?