Optimising Searching of a 2-dimensional Array with LINQ

Question

I have a 2-dimensional array of objects (predominantly, but not exclusively strings) that I want to filter by a string ( sSearch ) using LINQ. The following query works, but isn't as fast as I would like.

I have changed Count to Any , which led to a significant increase in speed and replaced Contains by a regular expression that ignores case, thereby elimiating the call to ToLower . Combined this has more than halved the execution time.

What is now very noticeable is that increasing the length of the search term from 1 to 2 letters triples the execution time and there is another jump from 3 to 4 letters (~50% increase in execution time). While this is obviously not surprising I wonder whether there is anything else that could be done to optimise the matching of strings?

Regex rSearch = new Regex(sSearch, RegexOptions.IgnoreCase);
rawData.Where(row => row.Any(column => rSearch.IsMatch(column.ToString())));

In this case the dataset has about 10k rows and 50 columns, but the size could vary fairly significantly.

Any suggestions on how to optimise this would be greatly appreciated.

Answer 1

One optimisation is to use Any instead of Count - that way as soon as one matching column has been found, the row can be returned.

rawData.Where(row => row.Any(column => column.ToString()
                                             .ToLower().Contains(sSearch)))

You should also be aware that ToLower is culture-sensitive. If may not be a problem in your case, but it's worth being aware of. ToLowerInvariant may be a better option for you. It's a shame there isn't an overload for Contains which lets you specify that you want a case-insensitive match...

EDIT: You're using a regular expression now - have you tried RegexOptions.Compiled ? It may or may not help...