Some SQL Access Path Improvements

(Originally posted 2006-03-30.)

Just briefly, here are some Access Path fixes I’ve been meaning to talk about:

PK14923 QUERY COST ESTIMATE IS TOO HIGH IN SOME CASES

PK16521 ONE FETCH INDEX ACCESS (I1) NOT USED WITH DUPLICATE PREDICATES

PK15143 POOR QUERY PERFORMANCE WHEN SORT MERGE JOIN IS CHOSEN AND MULTIPLE JOIN COLUMNS ARE POSSIBLE OR COL=LIT EXISTS ON SMJ KEY

PK20229 POOR QUERY PERFORMANCE WHEN FETCH FIRST 1 ROW AND INDEX EXISTS WHERE ALL COLUMNS HAVE MATCHING PREDICATES BUT IS NOT CHOSEN

PK19398 POOR PERFORMANCE MAY OCCUR IF REVERSE INDEX SCAN COULD BE USED BUT IS NOT CHOSEN FOR A 1-FETCH PLAN

Published by Martin Packer

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