Hi, I've got a table, DOCUMENTS, with lots of columns (and lots of rows). DOC_ID is the PK, and DOC_HOLD_STATUS is another column in the table, which is NOT NULL and will always have 'Y' or 'N'. Now, I've got a query where, given the DOC_ID, I want to determine if a particular document is on hold. Note that DOCUMENTS contains on the order of 170M rows, of which approximately 200k rows are flagged as DOC_HOLD_STATUS=3D'Y', or, docs that are on hold. So, given the large disparity in the number of docs on hold vs. not on hold, I created a function-based index defined as: Create DOC_ON_HOLD on DOCUMENTS(DECODE(DOC_HOLD_STATUS,'Y',DOC_ID,NULL)); Now, that gives me a convenient index of just the docs that are on hold. (And with only around 200k DOC_IDs, it's *much* smaller than if I just had an index on DOC_HOLD_STATUS, which makes it a lot more cache friendly.) So, finally, I get to the problem. When I execute this query: SELECT /*+ index(doc doc_on_hold) */ DOC_ID=20 FROM DOCUMENTS doc=20 WHERE DECODE(DOC_HOLD_STATUS,'Y',DOC_ID,NULL) =3D :B1; I get this execution plan: Execution Plan ---------------------------------------------------------- 0 SELECT STATEMENT Optimizer=3DCHOOSE (Cost=3D1 Card=3D1430947 Bytes=3D10016629) 1 0 TABLE ACCESS (BY INDEX ROWID) OF 'DOCUMENTS' (Cost=3D1 Card=3D1430947 Bytes=3D10016629) 2 1 INDEX (RANGE SCAN) OF 'DOC_ON_HOLD' (NON-UNIQUE) (Cost=3D3 Card=3D1430947) So, the index is recognized, and that's great. My question is, why is the TABLE ACCESS BY ROWID required? Since only the DOC_ID is in the select list, why the table access? Thanks, -Mark PS Granted, this is an efficient query, and the elimination of the table access amounts to one less consistent get. However, this is a VERY heavily hit query, and reducing 4 or 5 consistent gets to 3 or 4 could potentially be a big savings on a query that gets executed as much as this one does. Mark J. Bobak Oracle DBA ProQuest Company Ann Arbor, MI "Post Hoc Ergo Propter Hoc" ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx put 'unsubscribe' in the subject line. -- Archives are at //www.freelists.org/archives/oracle-l/ FAQ is at //www.freelists.org/help/fom-serve/cache/1.html -----------------------------------------------------------------