lecture08BTree - B+ Trees External Storage and Indices...

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1 B+ Trees External Storage and Indices Another balanced tree approach B+ tree: Balance comes from allowing an m -ary structure rather than binary m is large so that the tree is shallow Each tree node is a disk block Each leaf has up to L data items Do not let the nodes to be too empty
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2 External Storage Welcome to the world of database! What are we storing? Data records clustered index <indexing_field, record_id> dense index
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3 Key issue in external storage Data comes in “blocks” This is related to the size of physical units of storage on the disk Nearly always a power of 2 Ranges from 2K to 64K Oracle default is 8K Everything needs to fit in blocks
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4 B+ Trees Most common “external” index structure Data in the leaf nodes Non-leaf nodes are of the form: Every node holds m entries d m 2d (in initial examples) d is the order of the tree Exception: root node 1 m 2d k m k n k o k p
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This note was uploaded on 07/25/2008 for the course CSE 331 taught by Professor M.mccullen during the Spring '08 term at Michigan State University.

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lecture08BTree - B+ Trees External Storage and Indices...

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