Changes between Version 7 and Version 8 of UsersWikiExamplesNetworkTopology
- Timestamp:
- 06/14/09 20:51:37 (15 years ago)
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UsersWikiExamplesNetworkTopology
v7 v8 29 29 }}} 30 30 31 The above query creates a node table from a roads table by selecting all the start and end points from the road segments while maintaining the link between the node geometry and the line segment id. Then nodes are grouped into a single topologically distinct set where every POINT references an array of line segment ids as integer[].31 The above query creates a node table from a roads table by selecting all the start and end points from the road segments while maintaining the link between the node geometry and the line segment id. Then, nodes are grouped into a single topologically distinct set where every POINT references an array of line segment ids as integer[]. 32 32 33 33 {{{ … … 72 72 }}} 73 73 74 Unfortunately, PostgreSQL does not seem to use any btree indexes we might have placed on the id arrays, road_leaving and road_entering. Such queries estimated to take many hours to execute on a small table of 50000 roads. Subsequently, the following approach can be taken:74 Unfortunately, PostgreSQL does not seem to make use any btree indexes we might have placed on the id arrays, road_leaving and road_entering. Such queries estimated to take many hours to execute on a small table of 50000 roads. Subsequently, the following approach can be taken: 75 75 76 76 {{{