Question

I was inspired by the good answers from my previous question about SQL.
Now this SQL is run on a DB with Interbase 2009. It is about 21 GB in size.

SELECT DistanceAsMeters, AddrDistance.Bold_Id, AddrDistance.Created, AddressFrom.CityName_CO as FromCity, AddressTo.CityName_CO as ToCity
FROM AddrDistance
LEFT JOIN Address AddressFrom ON AddrDistance.FromAddress = AddressFrom.Bold_Id
LEFT JOIN Address AddressTo ON AddrDistance.ToAddress = AddressTo.Bold_Id
Where  DistanceAsMeters = 0 and PseudoDistanceAsCostKm = 0
       and not AddrDistance.bold_id in (select bold_id from DistanceQueryTask)
Order By Created Desc

There are 840000 rows with AddrDistance
190000 rows with Address and 4 with DistanceQueryTask.

The question is, can this be done faster? I guess, the same query is run many times select bold_id from DistanceQueryTask. Note that I’m not interested in stored procedures, just plain SQL 🙂

EDIT1 Here is the current execution plan:

Statement: SELECT DistanceAsMeters, AddrDistance.Bold_Id, AddrDistance.Created, AddressFrom.CityName_CO as FromCity, AddressTo.CityName_CO as ToCity
FROM AddrDistance
LEFT JOIN Address AddressFrom ON AddrDistance.FromAddress = AddressFrom.Bold_Id
LEFT JOIN Address AddressTo ON AddrDistance.ToAddress = AddressTo.Bold_Id
Where  DistanceAsMeters = 0 and PseudoDistanceAsCostKm = 0
       and not AddrDistance.bold_id in (select bold_id from DistanceQueryTask)
Order By Created Desc

PLAN (DISTANCEQUERYTASK INDEX (RDB$PRIMARY218))
PLAN SORT (JOIN (JOIN (ADDRDISTANCE NATURAL,ADDRESSFROM INDEX (RDB$PRIMARY234)),ADDRESSTO INDEX (RDB$PRIMARY234)))

And yes, DistanceQueryTask is meant to have a low number if rows in the database.

Answer 1

Using Left Join and subqueries will slow down any query.

You can get some improvements with the correct indexes (on Bold_id, DistanceMeters, PseudoDistanceAsCostKm ) remember that more indexes increase the size of the database