Archives of the TeradataForum
Message Posted: Tue, 07 Aug 2012 @ 19:07:40 GMT
| Subj: || || Re: Concept of Index Only Scans in Teradata? |
| From: || || Dieter Noeth |
| ||Some DBMSs will recognize when a query can be resolved by retrieving data only by scanning a secondary index without having to retrieve
data from the base table.|| |
| ||Does Teradata apply a similar concept?|| |
Of course, you'll see it in Explain: ... by way of index #n without accesing the base table ...
| ||With a PI on ColA and a NUSI on ColC,ColD, if a query selected only ColC and ColD would the query do a single AMP query against the
index or would it still use the base table?|| |
It will use the index but NUSI access is All-AMPs not single AMP.