This doesn't seem either buggy or strange...
An index on the ordering of that column is not helpful in handling a
leading wildcard, and so the query optimizer will, in such cases, revert,
correctly, to using a sequential scan and filtering the results.
If you have cases where this sort of wildcard needs to be fast, a
functional index could help.
Create index foo on tbl (reverse(col));
And reverse the wildcard so the index is usable:
Select * from tbl where reverse(col) like 'esrever%';
That query can harness the reversed index.
Unfortunately, no ordered index helps with
Select * from too where col like '%something%';
For that, a full text search index can help, but that is a longer story.
At any rate, what you are observing is no surprise, and consistent with
what many database systems do.
