How to text search in BLOB field - sql

Question

We have created a BLOB type column to store 6000 to 7000 ASCII characters of payload.
I am inserting the payload using following code.
PreparedStatement stmt=conn.prepareStatement(insertQuery);
String record="My ASCII Payload";
stmt.setBytes(1, record.getBytes());
stmt.execute();
When i run below query i can see the length of chars in the output.
select dbms_lob.getLength(MY_PAYLOAD)
from RAW_DATA;
6085
I wanted to perform text search in this BLOB column , i tried following options nothing works. What is the correct way to perform text search in a BLOB column ?
SELECT * FROM RAW_DATA t
WHERE dbms_lob.instr(t.MY_PAYLOAD,utl_raw.cast_to_raw(‘1234’))>0
select *
from RAW_DATA
where dbms_lob.instr (MY_PAYLOAD, -- the blob
utl_raw.cast_to_raw ('1234'),
1, -- where to start. i.e. offset
1 -- Which occurrance i.e. 1=first
) > 0

Answer 1

You can create text indexes on blobs as long as they contain text (naturally)
SQL> create table t ( x int, b blob);
Table created.
SQL>
SQL> insert into t values ( 1, utl_raw.cast_to_Raw('Hello there'));
1 row created.
SQL> insert into t values ( 2, utl_raw.cast_to_Raw('Goodbye tomorrow'));
1 row created.
SQL>
SQL> create index t_ix on t ( b )
2 indextype is ctxsys.context;
Index created.
SQL>
SQL> select x
2 from t where contains(b,'Hello') > 0;
X
----------
1
SQL>
SQL> select utl_raw.cast_to_varchar2(b)
2 from t
3 where contains(b,'Hello') > 0;
UTL_RAW.CAST_TO_VARCHAR2(B)
---------------------------------------------------------------------------------
Hello there