I'm a c# developer, however I'm quite experienced with SQL. I have had a bit of experience with optimising queries but I've come up across one that has me stumped.
The query takes about 3 minutes to run for approximately 20,000 rows. The rows start streaming immediately but for the 3 minute period, the SQL server cpu is pegged at 100%.
In this particular case, my queries performed well until the client requested I test them with 20k rows. These 20k rows (Clients) were distributed amongst 20 Practitioners (so roughly 1000 each)
Here's my database schema for the relevant tables:
The query uses a Recursive CTE to gather, given a source practitioner, the (n-level) tree of clients below them. It then joins to some FK type tables to collect additional information.
It appears the slow-down is coming from the join to the authority table, which represents which practitioners manage which clients.
pooling.PractitionerAccountFirstContact are all views which all come back with sub-second selects for the full data set.
Right, now for the actual query (sorry, it's a bit of a monster):
with h (distance, id, name, parentid, [path]) as ( select 0, pa.id, pa.name, null, convert(varchar(80), ltrim(str(pa.id))) as node_seq from pooling.practitioneraccount pa left outer join pooling.practitioneraccountrelation as par on pa.id = par.childid where pa.id = @PractitionerAccountId or (@PractitionerAccountId is null and par.parentid is null) union all select 1, -1, 'Unmanaged Clients', -1, '-1' where @practitioneraccountid is null union all select distance + 1, pa.id, pa.name, par.parentid, convert(varchar(80), h.path + ',' + ltrim(str(pa.id))) from pooling.practitioneraccount pa inner join pooling.practitioneraccountrelation as par on pa.id = par.childid inner join h on par.parentid = h.id ) select distance as Depth, h.id as PractitionerAccountId, h.name as PractitionerAccountName, pafc.FullName as PractitionerAccountContactName, h.parentid as PractitionerAccountParentId, path as PractitionerAccountPath, ca.id as ClientAccountId, ca.name as ClientAccountName, ca.irdnumber as ClientAccountIrdNumber, bd.id as ClientAccountBalanceDateId, bd.day as ClientAccountBalanceDateDay, bd.month as ClientAccountBalanceDateMonth, cafc.FirstName as ClientAccountContactFirstName, cafc.LastName as ClientAccountContactLastName, cafc.PhoneNumber as ClientAccountContactPhoneNumber, cafc.MobileNumber as ClientAccountContactMobileNumber, ca.TownOrCity as ClientAccountLocation, rr.Rate as ClientAccountRwtRate, rr.Id as ClientAccountRwtRateId, cairg.RateGroupId as ClientAccountInheritedRateGroupId, cairg.RateGroupName as ClientAccountInheritedRateGroupName, ag.id as ClientAccountAssociatedGroupId, ag.name as ClientAccountAssociatedGroupName, agca.uniqueid as ClientAccountAssociatedGroupUniqueId, agca.approved as ClientAccountAssociatedGroupApproved from h left outer join security.practitioneraccountauthority as paa on (h.id = paa.practitioneraccountid) left outer join pooling.clientaccount as ca on ( paa.clientaccountid = ca.id or (h.id = -1 and ca.id not in ( select clientaccountid from security.practitioneraccountauthority ) ) ) left outer join config.RwtRate as rr on ca.RwtRateId = rr.Id left outer join config.balancedate as bd on (ca.balancedateid = bd.id) left outer join pooling.ClientAccountInheritedRateGroup as cairg on (ca.id = cairg.ClientAccountId) left outer join security.associatedgroupclientaccount as agca on (ca.id = agca.clientaccountid) left outer join security.associatedgroup as ag on (agca.associatedgroupid = ag.id) left outer join pooling.ClientAccountFirstContact as cafc on (cafc.ClientAccountId = ca.Id) left outer join pooling.PractitionerAccountFirstContact as pafc on (pafc.PractitionerAccountId = paa.PractitionerAccountId)
The CTE in the query gives us the full tree of practitioners, which is then joined via the authority table to the clients under them. The CTE portion of the query returns almost instantly, only when we start joining to the clients does the performance issue appear.
I've added an index (and statistics) onto the ClientAccountId column of the authority table
CREATE NONCLUSTERED INDEX [IX_PractitionerAccountAuthority_ClientAccountId] ON [security].[PractitionerAccountAuthority] ( [ClientAccountId] ASC )
Please ask if you need additional information such as the definition of the views mentioned above.