mysql: efficient way for postfix-search (like '%text' aka. prefix wildcard)?

Question

Is there any build-in functionality in MySQL to do the above without scanning the entire table?

Only solution I found is to store a mirrored version of the column I want to compare and do a like 'txet%'.

I also don't see a way of getting around the postfix-search. It is for a German dictionary. Many words have a version with prefix, e.g. the user searches for "Gericht" (Engl. curt), but it is also valuable to know that there is a word "Amtsgericht" (Engl. district curt). Unfortunately often there is no space separating the two parts of the word in German language. Approx 15% of queries actually use the prefix-search.

Answer 1

A index over reverse field will be the solution, some think like:

create index idx_reverse on table ( reverse( field ) );
select * from table where reverse(field) like 'txet%';

but MySQL don't alow index over expressions, only over columns:

this is MySQL create index syntax:

CREATE [UNIQUE|FULLTEXT|SPATIAL] INDEX index_name
    [index_type]
    ON tbl_name (index_col_name,...)
    [index_option] ...

This is postgres create index syntax:

CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] name ON table [ USING method ]
    ( { column | ( expression ) } [ opclass ] [, ...] )
    ...

A work around may be create indexed second field (field -> dleif) and a mysql trigger to keep reversed field:

alter table my_table add column dleif ...;
create index idx_reverse on my_table ( dleif );
Create Trigger `reverse_field` Before Update on `my_table` for each row BEGIN
    set new.dleif = reverse( new.field );
END;
select * from table where dleif like reverse('%text');

Answer 2

MySQL won't use an index when your value starts with a wildcard character.

Storing a second column in reverse order is a defensible approach. It will fail on a suffix, though.

If you know the compounded words, you can pre-compute "valuable to know" matches and store them in another table. I think that's unlikely to work well for a German dictionary, but you might know something I don't.