SQL Server / Hierarchy ID Performance -


take following scenario...

create table #parentitems ( itemid uniqueidentifier, hid hierarchyid, treeid uniqueidentifier, hidlevel hid.getlevel() )  create table #childitems ( itemid uniqueidentifier, hid hierarchyid, treeid uniqueidentifier, hidlevel hid.getlevel() )     create unique nonclustered index pind on #parentitems(treeid, hidlevel, hid) create unique nonclustered index cind on #childitems(treeid, hidlevel, hid)

so 2 tables, parent table has bunch of ids/hids know ancestors of items in child tables. there multiple different tree structures in each, hence treeid (all hids same tree, share same treeid).

assume #parentitems , #childitems have 20,000+ rows in each.

the following query reasonable fast (for it's doing...) takes around second complete.

select distinct liparent.itemid parentid               , lichild.itemid childid  #parentitems liparent inner join #childitems lichild  on lichild.hid.isdescendantof(liparent.hid)=1

however, ignores treeid relationship well. second add "where liparent.treeid = lichild.treeid" query (or add join) whole query jumps around 30 second execution time. seems simple change, , believe index in place... slows down massively.

anyone have ideas? in advance!


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