I have an application which sends queries like the following to the database:
x like '%abc%'
I can't modify these queries, but I can index the underlying tables. Is there any way to put a full text index on a table such that double open-ended like queries can be performed without a full scan?
No, there is no way to make LIKE predicates with wildcards avoid a table-scan so they perform well for full-text search. You must use Oracle Text features and modify your queries to use text-searching predicates.