>>What is the fastest way to search through a file to find a substring within a field? I know you can
>>

>>set filter to 'xyz" $ yourfield
>>go top
>>

>>or an SQL Select equivalent, but in a file where there are thousands of records, it takes a long time, specially on a network...
>>Is there a quicker way?
>
>If you have a limited set of sub-strings to search for, you can
>

>index on 'xyz" $ yourfield tag xyz_ binary
>

>
>Then any search will get optimized

I'd either use binary as you did for faster execution, less memory overall or

index on at('xyz", yourfield) tag xyz

on the chance of position becoming relevant at some future point in in time and query for at()>0 if going the index way ;-)