I've having the same hassle, using FB 1.5 takes < 0.08 seconds on FB
2.0 13+ minutes.

SELECT *
FROM "Inventory" i
WHERE i.id NOT IN (SELECT "InventoryID" FROM "InventoryGroupsTL")

Inventory has 50 000 records, InventoryGroupsTL has 49000. How would
an EXIST sort this out?

When I try force the plan I get an error
"Token unknown - line 5, column 1.
PLAN."

SELECT *
FROM "Inventory" I
WHERE I.id NOT IN (SELECT "InventoryID" FROM "InventoryGroupsTL")
PLAN ("InventoryGroupsTL" INDEX ("PK_InventoryGroupsTL"))
PLAN (I NATURAL)


Thanks
Roy