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首頁 云數(shù)據(jù)庫 RDS RDS PostgreSQL數(shù)據(jù)庫 時空引擎（GanosBase） Trajectory SQL參考 SQL參考手冊 時空關系判斷 ST_{2D|2DT|3D|3DT}DWithin_IndexLeft

ST_{2D|2DT|3D|3DT}DWithin_IndexLeft

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ST_ndDwithin_IndexLeft函數(shù)，判斷指定的兩個對象在指定的坐標軸上是否距離小于等于某一給定值，并指定使用第一個參數(shù)所在的列的索引。

語法

bool ST_{2D|2DT|3D|3DT}DWithin_IndexLeft(trajectory traj1, trajectory traj2, float8 dist);
bool ST_{2D|2DT|3D|3DT}DWithin_IndexLeft(trajectory traj1, trajectory traj2, timestamp ts, timestamp te, float8 dist);

參數(shù)

參數(shù)名稱

描述

traj1

需要判斷的軌跡對象，或者產(chǎn)生子軌跡的原始軌跡。

traj2

需要判斷的軌跡對象，或者產(chǎn)生子軌跡的原始軌跡。

ts

如存在，表示按此時間作為開始時間截取子軌跡。

te

如存在，表示按此時間作為結束時間截取子軌跡。

dist

距離的臨界值。

描述

當ST_ndDWithin(...)操作涉及兩個軌跡列時（即調用ST_{2D|2DT|3D|3DT}DWithin(trajectory traj1, trajectory traj2, float8 dist)或ST_{2D|2DT|3D|3DT}DWithin(trajectory traj1, trajectory traj2, timestamp ts, timestamp te, float8 dist)函數(shù)時），數(shù)據(jù)庫無法判斷應當使用哪個列的索引，因此會帶來額外的計算開銷。

我們可以使用ST_ndDwithin_IndexLeft函數(shù)手工指定使用第一個參數(shù)所對應的列上的索引，以降低計算開銷。

示例

EXPLAIN SELECT count(*) FROM sqltr_test_trajs WHERE ST_3DTDWithin_IndexLeft(traj, ST_makeTrajectory('STPOINT', 'LINESTRING(-70 -30, -72 -34, -73 -35)'::geometry, '[2000-01-01 00:01:30, 2000-01-01 00:15:00)'::tsrange,
  '{"leafcount":3,"attributes":{"velocity": {"type": "integer", "length": 2,"nullable" : true,"value": [120,130,140]}, "accuracy": {"type": "float", "length": 4, "nullable" : false,"value": [120,130,140]}, "bearing": {"type": "float", "length": 8, "nullable" : false,"value": [120,130,140]}, "acceleration": {"type": "string", "length": 20, "nullable" : true,"value": ["120","130","140"]}, "active": {"type": "timestamp", "nullable" : false,"value": ["Fri Jan 01 11:35:00 2010", "Fri Jan 01 12:35:00 2010", "Fri Jan 01 13:30:00 2010"]}}, "events": [{"2" : "Fri Jan 02 15:00:00 2010"}, {"3" : "Fri Jan 02 15:30:00 2010"}]}'), 2);

QUERY PLAN
--------------
Aggregate  (cost=4341.89..4341.90 rows=1 width=8)
   ->  Bitmap Heap Scan on sqltr_test_trajs  (cost=103.31..4340.56 rows=529 width=0)
         Recheck Cond: ('BOX2DT(-75 -37 2000-01-01 00:01:29.999994,-68 -28 2000-01-01 00:15:00)'::boxndf &/#& traj)
         Filter: _st_3dtdwithin(traj, '{"trajectory":{"version":1,"type":"STPOINT","leafcount":3,"start_time":"2000-01-01 00:01:30","end_time":"2000-01-01 00:15:00","spatial":"LINESTRING(-70 -30,-72 -34,-73 -35)","timeline":["2000-01-01 00:01:30","2000-01-01 00:08:15","2000-01-01 00:15:00"],"attributes":{"leafcount":3,"velocity":{"type":"integer","length":2,"nullable":true,"value":[120,130,140]},"accuracy":{"type":"float","length":4,"nullable":false,"value":[120.0,130.0,140.0]},"bearing":{"type":"float","length":8,"nullable":false,"value":[120.0,130.0,140.0]},"acceleration":{"type":"string","length":20,"nullable":true,"value":["120","130","140"]},"active":{"type":"timestamp","length":8,"nullable":false,"value":["2010-01-01 11:35:00","2010-01-01 12:35:00","2010-01-01 13:30:00"]}},"events":[{"2":"2010-01-02 15:00:00"},{"3":"2010-01-02 15:30:00"}]}}'::trajectory, '2'::double precision)
         ->  Bitmap Index Scan on sqltr_test_traj_gist_2dt  (cost=0.00..103.18 rows=1586 width=0)
               Index Cond: (traj &/#& 'BOX2DT(-75 -37 2000-01-01 00:01:29.999994,-68 -28 2000-01-01 00:15:00)'::boxndf)