Apparatus and method for resolving geospatial queries
A method implemented by a computer with a processor and a memory storing instructions executed by the processor includes receiving a query with a search region and a predicate. The search region is mapped to a set of blocks. For each block in the set of blocks, ellipsoidal geographic coordinates of the search region are transformed to flat coordinates. Results are retrieved from a primary index when the block does not contain a boundary of the search region. Results are retrieved from a secondary index when the block does contain a boundary of the search region. Retrieving results from the secondary index includes processing the boundary and the predicate against the secondary index.
1. A method implemented by a computer with a processor and a memory storing instructions executed by the processor, comprising:
receiving a query with a search region and a predicate, wherein the search region is characterized by ellipsoidal geographic coordinates;
mapping the search region to a set of blocks;
for each block in the set of blocks,
transforming the ellipsoidal geographic coordinates of the search region to flat coordinates,
retrieving results from a primary index when the block does not contain a boundary of the search region, wherein the primary index stores non-boundary entries with associated flat coordinates, wherein retrieving results from the primary index includes retrieving results based upon qeohash prefix substrings derived from a qeohash prefix string,
retrieving results from a secondary index when the block does contain a boundary of the search region, wherein the retrieving results from the secondary index includes processing the boundary and the predicate against the secondary index to obtain a list of interactions between the boundary and regions within the secondary index, wherein the interactions are characterized as hit, miss or unresolved, and wherein the secondary index stores boundary entries with associated flat coordinates.
2. The method of claim 1 wherein the predicate is a space relation between the boundary and regions within the secondary index.
3. The method of claim 1 wherein the predicate is selected from equals, disjoint, touches, contains, intersects, inside and covered by.
4. The method of claim 1 wherein processing the boundary and the predicate against the secondary index includes utilizing the Dimensionally Extended Nine-Intersection Model (DE-9IM) to characterize special relations between the boundary and regions within the secondary index.