Improve query performance when joining on a linked server table

Question

Unfortunately as a temporary measure whilst we fix our datacentre I need to run the following cross server query, can anyone suggest how I can get the performance to increase...

as have to run this statement at the start of a cursor

SELECT t.SearchId, t.VisitSourceId, t.SiteDomainId, t.trpUTMid, t.FlightPlus, t.StartDate,
t.CountryId, t.ProvinceId, t.Locationid, t.PlaceId, t.EstabId, t.CheckInDate, 
t.CheckOutDate, t.Rooms, t.Room1Adults, t.Room1Children, t.Room2Adults, t.Room2Children, 
t.Room3Adults, t.Room3Children, tc.OutcomeDate, tc.OutcomeId, tc.HotelsFound, tc.Notes

FROM [MLT_VisitTracking].[dbo].TrackingAcomSearches_tbl t
INNER JOIN TrackingAcomSearchesOutcome_tbl tc
ON t.trpUTMid = tc.trpUTMid
LEFT JOIN [YAZOO].[MLT_VisitTracking].[dbo].TrackingAcomSearches_tbl tid
ON t.trpUTMid = tid.trpUTMid
WHERE tid.trpUTMid IS NULL

Answer 1

One possible option would be to get the remote table replicated to the local server. This would put all tables on the same server, enabling the optimizer to use statistics to generate the best plan. Since you are only using trpUTMid, you could just replicate that column.

Another option would be to use temp tables. Same idea, get all tables on the same server:

SELECT trpUTMid
INTO #Yazoo_TrackingAcomSearches_tbl
FROM [YAZOO].[MLT_VisitTracking].[dbo].TrackingAcomSearches_tbl


SELECT t.SearchId, t.VisitSourceId, t.SiteDomainId, t.trpUTMid, t.FlightPlus, t.StartDate,
t.CountryId, t.ProvinceId, t.Locationid, t.PlaceId, t.EstabId, t.CheckInDate, 
t.CheckOutDate, t.Rooms, t.Room1Adults, t.Room1Children, t.Room2Adults, t.Room2Children, 
t.Room3Adults, t.Room3Children, tc.OutcomeDate, tc.OutcomeId, tc.HotelsFound, tc.Notes

FROM [MLT_VisitTracking].[dbo].TrackingAcomSearches_tbl t
INNER JOIN TrackingAcomSearchesOutcome_tbl tc
ON t.trpUTMid = tc.trpUTMid
LEFT JOIN #Yazoo_TrackingAcomSearches_tbl tid
ON t.trpUTMid = tid.trpUTMid
WHERE tid.trpUTMid IS NULL

You could also create an index on the temp table to improve performance.

I'd also recommend checking for lack of existence rather than the old left join where null ( read this for more info ):

SELECT trpUTMid
INTO #Yazoo_TrackingAcomSearches_tbl
FROM [YAZOO].[MLT_VisitTracking].[dbo].TrackingAcomSearches_tbl


SELECT t.SearchId, t.VisitSourceId, t.SiteDomainId, t.trpUTMid, t.FlightPlus, t.StartDate,
t.CountryId, t.ProvinceId, t.Locationid, t.PlaceId, t.EstabId, t.CheckInDate, 
t.CheckOutDate, t.Rooms, t.Room1Adults, t.Room1Children, t.Room2Adults, t.Room2Children, 
t.Room3Adults, t.Room3Children, tc.OutcomeDate, tc.OutcomeId, tc.HotelsFound, tc.Notes

FROM [MLT_VisitTracking].[dbo].TrackingAcomSearches_tbl t
INNER JOIN TrackingAcomSearchesOutcome_tbl tc
ON t.trpUTMid = tc.trpUTMid
WHERE NOT EXISTS (
    SELECT NULL 
    FROM #Yazoo_TrackingAcomSearches_tbl
    WHERE trpUTMid = t.trpUTMid
)