There are many find-like methods which are able to employ indexes to speed up the searching (FindLike, FindRegEx, FindContains, and so on). Of course, the field must be indexed and search preference is set to kPreferIndexed.
But currently there are two issues when index search may bring a wrong result:
1.Index keeps only first 256 symbols of the value – so rest of the symbols are just ignored in such a search.
2. Index-By-Words index and multi-word searching pattern.
Some of the methods like FindRegEx don’t use an index-search but scan the table instead if any of the above occurred. The rest of the methods are less strict choosing the searching algorithm. Now you will get the warning in such cases and you can switch algorithm to not-index search (kPreferNotIndexed) if it is relevant (less speedy but more accurate). Also you should consider to change index type of such a lengthly fields to the index-by-words.
“Index search in the first 256 symbols only : FindContains t1:f1”
“Index-By-Words search : FindContains t1:f1”