Select ID from TableA where not exists ( Select ID from Table B where ID
= TableA.ID)
might give you index scan. Of course, that is only useful is TableA is
very small table.
Not appropriate for 250k rows
on 2/1/2006 12:12 PM Ralph Mason said the following:
Hi,
I have 2 tables both have an index on ID (both ID columns are an oid).
I want to find only only rows in one and not the other.
Select ID from TableA where ID not IN ( Select ID from Table B)
This always generates sequential scans.
Table A has about 250,000 rows. Table B has about 250,000 Rows.
We should get a Scan on Table B and a Index Lookup on Table A.
Is there any way to force this? enable_seqscan off doesn't help at all.
The Plan is
Seq Scan on tablea(cost=100000000.00..23883423070450.96 rows=119414
width=4)
Filter: (NOT (subplan))"
SubPlan -> Seq Scan on tableb (cost=100000000.00..100004611.17
rows=242617 width=4)
Thanks
Ralph
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