Deleting many records with child tables

Question

Situation:

• Table TBL has ~10k entries for deletion,
• Table TBL has 14 child tables with delete rule "no action",
• I want to delete 10k entries and referenced entries in child tables.

Procedure:

• Delete records in child tables,
• Disable constraints (if constraints are not disabled deletion in next step takes forever),
• Delete records in TBL table,
• Enable constraints.

Is there more elegant way for doing this?

The problem is that third step takes too long because it is checking 14 big tables for existence of non existent records. My procedure has good execution time but I think that there is more elegant way.

Answer 1

It sounds like you need to index your foreign keys on your child tables. Every time you delete a parent record without an index on the child table it must do a full table scan of the child to check if the foreign key constraint was broken.

With the index, it is at worst case an index range scan.

Edit: More info, and a script to determine if this is your problem can be found here. http://asktom.oracle.com/tkyte/unindex/index.html