Cone Searching & HTM
Many of the queries we want to do are related to the position of objects in the sky. We use HTM - Hierarchical Triangular Mesh - to index the sky and utilise the API to augment our SQL queries. In this document I will attempt to use HTM with Cassandra. This may of course be a bad match of technologies (see issues below), and there may be other spatial indexing technologies that tie in better with Cassandra.
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Decimal | Binary | Base4 | |
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HTM16 | 54680902005 | 110010111011001111000101100101110101 | N02323033011211311 |
HTM13 | 854389093 | 110010111011001111000101100101 | N02323033011211 |
HTM10 | 13349829 | 110010111011001111000101 | N02323033011 |
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Code Block |
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select * from tcs_cat_gaia_dr2 where htm10 IN ('S23023222101','S23023222132') AND (htm13) IN ('000','001','002','003'); |
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