High-Concurrency Locking in R-Trees
Marcel Kornacker, Douglas Banks · 1995
In this paper we present a solution to the problem of concurrent operations in the R-tree, a dynamic access structure capable of storing multidimensional and spatial data. We describe the R-link tree, a variant of the R-tree that adds sibling pointers to nodes, a technique first deployed in B-link trees, to compensatefor concurrent structure modifications. The main obstacle to the use of sibling pointers is the lack of linear ordering among the keys in an R-tree; we overcome this by assigning sequence numbers to nodes that let us reconstruct the "lineage" of a node at any point in time. The search, insert and delete algorithms for R-link trees are designed to completely avoid holding locks during I/O operations and to allow concurrent modifications of the tree structure. In addition, we further describe how to achieve degree 3 consistency with an inexpensive predicate locking mechanism and demonstrate how to make R-link trees recoverable in a write-ahead logging environment. Experiment...