SQL search for a pattern in the middle of a string (infix search) without full table scan

With SQL, I need to select rows which have a pattern like %hello% (i.e. hello) in a column, with potentially 100 millions of rows or more. In the answer [Infix search in MySQL with an index](https://stackoverflow.com/questions/76121624/infix-search-in-mysql-search-with-pattern-in-the-middle-with-an-index/76121736#76121736) , it is said that: * an index won't help * even an *FTS index* won't help either Question: **are there RDBMS (e.g. PostgreSQL) that have features that can speed up queries like** select * from t where key like "%hello%" **and avoid a full table scan?** With specific data structures (tries, etc.), or bigrams, trigrams, etc. TL;DR: I have a MySQL InnoDB like this: create table t (id int primary key auto_increment, key varchar(200), value varchar(200)); create index key_index on t(key) using BTREE; create index value_index on t(value) using BTREE; and I would like to do this without a full table scan: select * from t where key like "%hello%" Notes: * the strings are not words separated by spaces. Columns key and value have typically 10 to 50 characters, with no spaces. They can be abcdefhelloworldblablabla. * see also https://dba.stackexchange.com/questions/187658/what-is-it-called-when-you-search-the-middle-of-a-string-instead-of-the-beginnin