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Atomic Operation-Based Split-Supporting Index Algorithm

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The algorithm is based on atomic operations and versioning of items, with minimal latching during node splitting. It allows local updates during splits and merges, and handles non-local updates using a priority queue. Sibling nodes are managed efficiently to prevent overflow.

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Atomic Operation-Based Split-Supporting Index Algorithm

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  1. Split-supporting Index • Algorithm is based on atomic operations and versioning of the items • Latching is minimal

  2. Node Split - exclusive latch between non-local updates - marks logically deleted items p14 p14 p3 p4 p5 p14

  3. Node Split - exclusive latch between non-local updates - marks logically deleted items R3 R4 R5 p1 p2 p6 p7 p14 R9 p3 p4 p5 p14

  4. Node Split - exclusive latch between non-local updates - marks logically deleted items R10 p14 R3 R4 R5 R9 p2 p3 p4 p5 p14 p1 p6 p7

  5. Local Updates • Are allowed during splits and merges R3 Secondary index N2 N3 N1 p1 p2 N1 N1’ Nil Nil 0 N1 N1’ Nil Nil 1 N2’ N2 0 R4 N2’ N1’ N3’ p3 p4 p6 p7

  6. Non-Local Updates • Are not allowed to make changes for items which are involved into split • Updates are put into a priority queue and retried later

  7. Merge of the node Merge underflow node with one of the sibling nodes • Sibling node have space for all entries • Sibling node would become overflow after insertion

  8. Sibling node have space for all entries • Sibling and underflow nodes are latched • New empty node is created • Entries form sibling and underflow nodes are copied into the new node • New node is introduced into structure by atomic swap of the pointers

  9. Sibling node would become overflow • Split of the sibling node is performed • Split function accepts all entries from the underflow node instead of one entry • Entries are distributed between two new nodes • Two new nodes are introduced into structure in two atomic operations

  10. Summary of the algorithm Advantages Disadvantages • Local updates are permitted during node splits and merges • Queries can execute concurrently • High complexity due to avoidance of locks • Creation of artificial updates

  11. Related Work • Logical and Physical Versioning in Main Memory Databases [Rastogi et al. 1997] • An Enhanced Concurrency Control Scheme for Multi-dimensional Index Structures [Song et al. 2004] • Main-memory indexing [Šidlauskas et al. 2009] • …

  12. Status of the Project • A paper on presented algorithms • Theoretical foundation of the two ideas

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