Question

I have 2 delete statements that are taking a long time to complete. There are several indexes on the columns in where clause.

What is a duplicate?
If 2 or more records have same values in columns id,cid,type,trefid,ordrefid,amount and paydt then there are duplicates.

The DELETEs delete about 1 million record.

Can they be re-written in any way to make it quicker.

DELETE FROM TABLE1 A WHERE loaddt < (
    SELECT max(loaddt) FROM TABLE1 B
    WHERE 
    a.id=b.id and
    a.cid=b.cid and
    NVL(a.type,'-99999') = NVL(b.type,'-99999') and
    NVL(a.trefid,'-99999')=NVL(b.trefid,'-99999') and
    NVL(a.ordrefid,'-99999')= NVL(b.ordrefid,'-99999') and
    NVL(a.amount,'-99999')=NVL(b.amount,'-99999') and
    NVL(a.paydt,TO_DATE('9999-12-31','YYYY-MM-DD'))=NVL(b.paydt,TO_DATE('9999-12-31','YYYY-MM-DD'))
);

    COMMIT;

DELETE FROM TABLE1 a where rowid > (
    Select min(rowid) from TABLE1 b
    WHERE 
    a.id=b.id and
    a.cid=b.cid and
    NVL(a.type,'-99999') = NVL(b.type,'-99999') and
    NVL(a.trefid,'-99999')=NVL(b.trefid,'-99999') and
    NVL(a.ordrefid,'-99999')= NVL(b.ordrefid,'-99999') and
    NVL(a.amount,'-99999')=NVL(b.amount,'-99999') and
    NVL(a.paydt,TO_DATE('9999-12-31','YYYY-MM-DD'))=NVL(b.paydt,TO_DATE('9999-12-31','YYYY-MM-DD'))
);

commit;

Explain Plan:

DELETE  TABLE1         

    HASH JOIN 1296491 
    Access Predicates 

        AND 
        A.ID=ITEM_1 
        A.CID=ITEM_2 
        ITEM_3=NVL(TYPE,'-99999') 
        ITEM_4=NVL(TREFID,'-99999') 
        ITEM_5=NVL(ORDREFID,'-99999') 
        ITEM_6=NVL(AMOUNT,(-99999)) 
        ITEM_7=NVL(PAYDT,TO_DATE(' 9999-12-31 00:00:00', 'syyyy-mm-dd hh24:mi:ss')) 

    Filter Predicates 
        LOADDT<MAX(LOADDT)

    TABLE ACCESS  TABLE1     FULL    267904 
    VIEW VW_SQ_1         690385 
    SORT GROUP BY    690385 
        TABLE ACCESS TABLE1      FULL    267904 

Answer 1

How large is the table? If count of deleted rows is up to 12% then you may think about index.
Could you somehow partition your table – like week by week and then scan only actual week?

Maybe this could be more effecient. When you’re using aggregate function, then oracle must walk through all relevant rows (in your case fullscan), but when you use exists it stops when the first occurence is found. (and of course the query would be much faster, when there was one function-based(because of NVL) index on all columns in where clause)

DELETE FROM TABLE1 A 
WHERE exists (
SELECT 1 
FROM TABLE1 B
WHERE 
A.loaddt != b.loaddt
a.id=b.id and
a.cid=b.cid and
NVL(a.type,'-99999') = NVL(b.type,'-99999') and
NVL(a.trefid,'-99999')=NVL(b.trefid,'-99999') and
NVL(a.ordrefid,'-99999')= NVL(b.ordrefid,'-99999') and
NVL(a.amount,'-99999')=NVL(b.amount,'-99999') and
NVL(a.paydt,TO_DATE('9999-12-31','YYYY-MM-DD'))=NVL(b.paydt,TO_DATE('9999-12-31','YYYY-MM-DD'))
);