Question

SELECT MAX(verification_id)
  FROM VERIFICATION_TABLE
 WHERE head = 687422
   AND mbr = 23102
   AND RTRIM(LTRIM(lname)) = '.iq bzw'
   AND  TO_CHAR(dob,'MM/DD/YYYY')= '08/10/2004'
   AND system_code = 'M';

This query is taking 153 seconds to run. there are millions of rows in VERIFICATION_TABLE.

I think query is taking long because of the functions in where clause. However, I need to do ltrim rtrim on the columns and also date has to be matched in MM/DD/YYYY format. How can I optimize this query?

Explain plan:

SELECT STATEMENT, GOAL = ALL_ROWS           80604   1   59
 SORT AGGREGATE                                   1   59
  TABLE ACCESS FULL P181    VERIFICATION_TABLE  80604   1   59

Primary key:

VRFTN_PK    Primary VERIFICATION_ID 

Indexes:

N_VRFTN_IDX2    head, mbr, dob, lname, verification_id
N_VRFTN_IDX3    last_update_date
N_VRFTN_IDX4    mbr, lname, dob, verification_id
N_VRFTN_IDX4    verification_id

Though, in the explain plan I dont see indexes/primary key being used. is that the problem?

Answer 1

Try this:

SELECT MAX(verification_id)
  FROM VERIFICATION_TABLE
 WHERE head = 687422
   AND mbr = 23102
   AND TRIM(lname) = '.iq bzw'
   AND TRUNCATE(dob) = TO_DATE('08/10/2004')
   AND system_code = 'M';

Remove that TRUNCATE() if dob doesn’t have time on it already, from the looks of it (Date of Birth?) it may not. Past that, you need some indexing work. If you’re querying that much in this style, I’d index mbr and head in a 2 column index, if you said what the columns mean it’d help determine the best indexing here.