Question

I have this query in Oracle 10g:

 DELETE FROM "BMAN_TP1"."CELLS_ITEM" TABLE1
 WHERE EXISTS (
     SELECT "CELLS_ITEM".*
     FROM "BMAN_TP1"."CELLS_ITEM"
     INNER JOIN "BMAN_TP1"."CELLS" ON ("CELLS_ITEM"."SET_ID"="CELLS"."SET_ID") AND ("CELLS_ITEM"."META_CELL_ID"="CELLS"."META_CELL_ID")
     INNER JOIN "BMAN_TP1"."META_CELLS" ON ("CELLS"."META_CELL_ID"="META_CELLS"."META_CELL_ID")
     WHERE ("META_CELLS"."UDA_ID" = variable)
     AND (TABLE1."SET_ID" = "CELLS_ITEM"."SET_ID")
     AND (TABLE1."META_CELL_ID" = "CELLS_ITEM"."META_CELL_ID")
)

which currently takes about 10 sec for 50K records to delete (and about 100K records in the table)

I know that it repeats 100K times the select query, that slows it down a lot.
Also TABLE1 has a two-fields PK, which makes the things more complicated.

Any ideas to make it faster?

EDIT:

Tried this one but it takes almost the same:

DELETE FROM "BMAN_TP1"."CELLS_ITEM" TABLE1
WHERE EXISTS (
    SELECT "META_CELL_ID"
    FROM "BMAN_TP1"."META_CELLS"
    WHERE ("META_CELLS"."UDA_ID"=55823)
    AND (TABLE1."META_CELL_ID" = "META_CELLS"."META_CELL_ID")
)

Answer 1

Without knowing your schema, it is hard to tell, but using the table you want to delete from in the subquery seems useless. I would write instead:

DELETE FROM BMAN_TP1.CELLS_ITEM TABLE1
WHERE EXISTS (
    SELECT CELLS.META_CELL_ID
    FROM BMAN_TP1.CELLS 
    INNER JOIN BMAN_TP1.META_CELLS ON (CELLS.META_CELL_ID=META_CELLS.META_CELL_ID)
    WHERE (META_CELLS.UDA_ID = variable)
        AND (TABLE1.SET_ID = CELLS_ITEM.SET_ID)
        AND (TABLE1.META_CELL_ID = CELLS_ITEM.META_CELL_ID)
)

EDIT: the above is dated now, since you modified your DELETE statement. Please ignore it.

But another idea: if there are triggers defined on CELLS_ITEM, you can try disabling them. They can chew on bigger deletes for quite long, I know it first-hand.