SQL Query running slow on the DB server - sql-server

Question

Execution plan is attached
SELECT a.*, k.UserPrivileges, k.Type
FROM NotifyInterests2 a, KUAF k
WHERE a.UserID = k.ID
AND EXISTS (SELECT ID FROM KUAF WHERE a.UserID = ID AND NOT Type IN (1, 2, 4))
AND (a.NodeID IN ( SELECT 0 UNION ALL ( SELECT DISTINCT( -1 * ID )
FROM KUAF WHERE Type = 5 ) UNION ALL ( SELECT DISTINCT AncestorID
FROM DTreeAncestors
WHERE Exists ( SELECT EventInt2 FROM LLEventQueue
WHERE EventHandlerID = 9001 AND EventSeqNo <=45075882 AND EventInt2 = DataID
UNION ALL SELECT EventInt2 * -1 FROM LLEventQueue
WHERE EventHandlerID = 9001
AND EventSeqNo <=45075882 AND EventInt2 = DataID ))))

Answer 1

that's quite the query =) Tip: try to 'group' the parts of your code for readability; it will make your life a 100 times easier; now while you're writing this and even more in the future when you're maintaining this =)
Some questions remain:
What do you call 'slow'?
How many records are present in each table?
How many records are returned by the query?
What are the indexes on the tables? (sp_helpindex)
Also, it probably would have been helpful to see the entire query plan, but one thing that stands out immediately is that KEAF doesn't seem to have clustered index. I presume it's thus also missing a Primary Key? As you have a field ID there I'd expect that this uniquely identifies each record? If so, add a PK to the table and check what effect this has on the entire query.
I've tried to re-arrange things a bit for readability and I ended up with below. I've gambled on some of the aliases as they are missing in the original query.
SELECT a.*, k.UserPrivileges, k.Type
FROM NotifyInterests2 a
JOIN KUAF k
ON k.ID = a.UserID
WHERE EXISTS ( SELECT kx.ID
FROM KUAF kx
WHERE kx.ID = a.UserID
AND NOT kx.Type IN (1, 2, 4) )
AND a.NodeID IN ( SELECT 0
UNION ALL
SELECT DISTINCT( -1 * k5.ID )
FROM KUAF k5
WHERE k5.Type = 5
UNION ALL
SELECT DISTINCT da.AncestorID
FROM DTreeAncestors da
WHERE EXISTS ( SELECT l1.EventInt2
FROM LLEventQueue l1
WHERE l1.EventHandlerID = 9001
AND l1.EventSeqNo <= 45075882
AND l1.EventInt2 = da.DataID
UNION ALL
SELECT l2.EventInt2 * -1
FROM LLEventQueue l2
WHERE l2.EventHandlerID = 9001
AND l2.EventSeqNo <= 45075882
AND l2.EventInt2 = da.DataID )
)
Some parts can be simplified I think.
This doesn't really make sense:
SELECT DISTINCT da.AncestorID
FROM DTreeAncestors da
WHERE EXISTS ( SELECT l1.EventInt2
FROM LLEventQueue l1
WHERE l1.EventHandlerID = 9001
AND l1.EventSeqNo <= 45075882
AND l1.EventInt2 = da.DataID
UNION ALL
SELECT l2.EventInt2 * -1
FROM LLEventQueue l2
WHERE l2.EventHandlerID = 9001
AND l2.EventSeqNo <= 45075882
AND l2.EventInt2 = da.DataID )
You're simply doing the same query twice in the WHERE EXISTS() part.
Also, as this part belongs to a WHERE IN (...) construction there's no real need for the DISTINCT. In fact, it's probably easier to convert it to a WHERE EXISTS() construction. Something like this:
AND ( a.NodeID = 0
OR EXISTS (SELECT *
FROM KUAF k5
WHERE k5.Type = 5
AND ( -1 * k5.ID ) = a.node_id)
OR EXISTS ( SELECT *
FROM DTreeAncestors da
WHERE da.AncestorID = a.NodeID
AND EXISTS ( SELECT *
FROM LLEventQueue l1
WHERE l1.EventHandlerID = 9001
AND l1.EventSeqNo <= 45075882
AND l1.EventInt2 = da.DataID )
)
Normally I'm no fan of OR but I think that in this case it might work.
So I end up with:
SELECT a.*, k.UserPrivileges, k.Type
FROM NotifyInterests2 a
JOIN KUAF k
ON k.ID = a.UserID
WHERE EXISTS ( SELECT kx.ID
FROM KUAF kx
WHERE a.UserID = kx.ID
AND NOT kx.Type IN (1, 2, 4) )
AND ( a.NodeID = 0
OR EXISTS (SELECT *
FROM KUAF k5
WHERE k5.Type = 5
AND ( -1 * k5.ID ) = a.node_id)
OR EXISTS ( SELECT *
FROM DTreeAncestors da
WHERE da.AncestorID = a.NodeID
AND EXISTS ( SELECT *
FROM LLEventQueue l
WHERE l.EventHandlerID = 9001
AND l.EventSeqNo <= 45075882
AND l.EventInt2 = da.DataID )
)
)
Give this a try and check the query plan. If it still is too slow we'll need to look at the indexes that are on the bespoken tables to see where we can optimize those.

Answer 2

You didn't mention if and which indexes exist in the table.
I would try creating the following indexes and see if there is any performance gain:
CREATE INDEX kuaf_idx_id_type ON KUAF (ID,Type);
CREATE INDEX kuaf_idx_type ON KUAF (Type);
CREATE INDEX lleventqueue_idx_eventha_eventin_dataid_eventse ON LLEventQueue (EventHandlerID,EventInt2,DataID,EventSeqNo);