Selections Using Indices Index scan-search algorithms that use an index selection condition must be on search-key of index. A2(clustering index,equality on key).Retrieve a single record that satisfies the corresponding equality condition ·Cost=(h+1)*(tr+ts) A3(clustering index,equality on nonkey)Retrieve multiple records. Records will be on consecutive blocks Let b number of blocks containing matching records Cost=hi *(tr+ts)ts +tr*b Database System Concepts-7th Edition 15.11 ©Silberscha乜，Korth and SudarshanDatabase System Concepts - 7 15.11 ©Silberschatz, Korth and Sudarshan th Edition Selections Using Indices ▪ Index scan – search algorithms that use an index • selection condition must be on search-key of index. ▪ A2 (clustering index, equality on key). Retrieve a single record that satisfies the corresponding equality condition • Cost = (hi + 1) * (tT + tS) ▪ A3 (clustering index, equality on nonkey) Retrieve multiple records. • Records will be on consecutive blocks ▪ Let b = number of blocks containing matching records • Cost = hi * (tT + tS) + tS + tT * b