The following 2 explain plans show the same query, but the top one uses a new index (IDX_SRX_TRX_MAPID, line 9) that was not available in the bottom explain plan. The bottom plan uses a table (SRX_TRANSACTIONS, line 9) and an index scan on its index (line 10).
Can someone please offer an opinion as to whether of not the index used in the top plan represents a performance improvement over the bottom plan, just based on looking at the two plans. I know what an index range scan is, but I'm not familiar with the relative efficiency of a single "index range scan" vs a combination of a "table access by global index rowid" followed by an "index unique scan".
With new index:
Without new index:
However, if the new index is larger, there may be more "get" operations in order to do the index scans.