Session14

# Session14 - CSCI585 CSCI585 Spatial Index Structures...

This preview shows pages 1–10. Sign up to view the full content.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: CSCI585 CSCI585 Spatial Index Structures Instructor: Cyrus Shahabi CSCI585 CSCI585 Outline • Grid File • Z-ordering • Hilbert Curve • Quad Tree – PM – PR • R Tree (next session) – R* Tree – R+ Tree CSCI585 CSCI585 Grid File • Hashing methods for multidimensional points (extension of Extensible hashing) • Idea: Use a grid to partition the space b each cell is associated with one page • Two disk access principle (exact match) CSCI585 CSCI585 Grid File • Start with one bucket for the whole space. • Select dividers along each dimension. Partition space into cells • Dividers cut all the way. CSCI585 CSCI585 Grid File • Each cell corresponds to 1 disk page. • Many cells can point to the same page. • Cell directory potentially exponential in the number of dimensions CSCI585 CSCI585 Grid File Implementation • Dynamic structure using a grid directory – Grid array: a 2 dimensional array with pointers to buckets (this array can be large, disk resident) G(0,…, nx-1, 0, …, ny-1) – Linear scales: Two 1 dimensional arrays that used to access the grid array (main memory) X(0, …, nx-1), Y(0, …, ny-1) CSCI585 CSCI585 Example Linear scale X Linear scale Y Grid Directory Buckets/Disk Blocks CSCI585 CSCI585 The scales do not need to be uniform X 1 X 2 X 3 X 4 Y 1 Y 2 Y 3 Scales Grid-file buckets CSCI585 CSCI585 Grid File Search • Exact Match Search: at most 2 I/Os assuming linear scales fit in memory. – First use liner scales to determine the index into the cell directory – access the cell directory to retrieve the bucket address (may cause 1 I/O if cell directory does not fit in memory) – access the appropriate bucket (1 I/O) • Range Queries: – use linear scales to determine the index into the cell directory.directory....
View Full Document

{[ snackBarMessage ]}

### Page1 / 26

Session14 - CSCI585 CSCI585 Spatial Index Structures...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online