AsTopo JSON — 返回拓扑几何的TopOJSON表示。
text
AsTopoJSON
(
topogeometry
tg
, regclass
edgeMapTable
)
;
返回拓扑几何的TopOJSON表示。如果
edgeMapTable
不为空,则它将用作边标识符到弧形索引的查找/存储映射。这将允许在最终文档中使用紧凑的“圆弧”数组。
如果给定该表,则应该有一个类型为“Serial”的“arcid”字段和一个类型为INTEGER的“edge_id”;代码将在该表中查询“edge_id”,因此建议在该字段上添加一个索引。
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Topo JSON输出中的圆弧索引是从0开始的,但在“edgeMapTable”表中是从1开始的。 |
除了此函数返回的代码片段外,完整的TopOJSON文档还需要包含实际弧线和一些头文件。请参阅 Topo JSON规范 。
可用性:2.1.0
增强:2.2.1增加了对拼音输入的支持
CREATE TEMP TABLE edgemap(arc_id serial, edge_id int unique);
-- header
SELECT '{ "type": "Topology", "transform": { "scale": [1,1], "translate": [0,0] }, "objects": {'
-- objects
UNION ALL SELECT '"' || feature_name || '": ' || AsTopoJSON(feature, 'edgemap')
FROM features.big_parcels WHERE feature_name = 'P3P4';
-- arcs
WITH edges AS (
SELECT m.arc_id, e.geom FROM edgemap m, city_data.edge e
WHERE e.edge_id = m.edge_id
), points AS (
SELECT arc_id, (st_dumppoints(geom)).* FROM edges
), compare AS (
SELECT p2.arc_id,
CASE WHEN p1.path IS NULL THEN p2.geom
ELSE ST_Translate(p2.geom, -ST_X(p1.geom), -ST_Y(p1.geom))
END AS geom
FROM points p2 LEFT OUTER JOIN points p1
ON ( p1.arc_id = p2.arc_id AND p2.path[1] = p1.path[1]+1 )
ORDER BY arc_id, p2.path
), arcsdump AS (
SELECT arc_id, (regexp_matches( ST_AsGeoJSON(geom), '\[.*\]'))[1] as t
FROM compare
), arcs AS (
SELECT arc_id, '[' || array_to_string(array_agg(t), ',') || ']' as a FROM arcsdump
GROUP BY arc_id
ORDER BY arc_id
)
SELECT '}, "arcs": [' UNION ALL
SELECT array_to_string(array_agg(a), E',\n') from arcs
-- footer
UNION ALL SELECT ']}'::text as t;
-- Result:
{ "type": "Topology", "transform": { "scale": [1,1], "translate": [0,0] }, "objects": {
"P3P4": { "type": "MultiPolygon", "arcs": [[[-1]],[[6,5,-5,-4,-3,1]]]}
}, "arcs": [
[[25,30],[6,0],[0,10],[-14,0],[0,-10],[8,0]],
[[35,6],[0,8]],
[[35,6],[12,0]],
[[47,6],[0,8]],
[[47,14],[0,8]],
[[35,22],[12,0]],
[[35,14],[0,8]]
]}