Use ST_InsertAttr to insert an attribute to a trajectory - PolarDB

Inserts a new attribute into a trajectory at a specified position.

Syntax

trajectory ST_InsertAttr(trajectory traj, anyarray arr, text name, integer loc default -1);

Parameters

Parameter	Type	Default	Description
`traj`	trajectory	—	The original trajectory.
`arr`	anyarray	—	An array that contains the value of the new attribute.
`name`	text	—	The name of the new attribute.
`loc`	integer	-1	The position at which to insert the new attribute. Valid values: [-n, n], where n is the number of existing attributes.

loc parameter

The loc parameter controls where the new attribute appears relative to existing attributes:

Positive values (0 to n): Count from the left. 0 inserts before the first attribute; n inserts after the nth attribute counted from the left.
Negative values (-n to -1): Count from the right. -1 (default) appends after the last attribute; -n inserts after the leftmost attribute.

Return value

Returns the updated trajectory with the new attribute inserted at the specified position.

Example

The following example creates a trajectory with five attributes (velocity, accuracy, bearing, acceleration, active) and inserts a new integer attribute named add at position 3 — after bearing and before acceleration.

With traj as (select ST_MakeTrajectory('STPOINT'::leaftype,
                                       st_geomfromtext('LINESTRING (114 35, 115 36, 116 37)', 4326),
                                       '[2010-01-01 14:30, 2010-01-01 15:30)'::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 14:30:00 2010", "Fri Jan 01 15:00:00 2010", "Fri Jan 01 15:30:00 2010"]}}}') as tj)
SELECT ST_InsertAttr(tj, ARRAY[1, 4, 6], 'add', 3) from traj;

Result:

{"trajectory":{"version":1,"type":"STPOINT","leafcount":3,"start_time":"2010-01-01 14:30:00","end_time":"2010-01-01 15:30:00","spatial":"SRID=4326;LINESTRING(114 35,115 36,116 37)","timeline":["2010-01-01 14:30:00","2010-01-01 15:00:00","2010-01-01 15:30:00"],"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]},"add":{"type":"integer","length":4,"nullable":true,"value":[1,4,6]},"acceleration":{"type":"string","length":20,"nullable":true,"value":["120","130","140"]},"active":{"type":"timestamp","length":8,"nullable":false,"value":["2010-01-01 14:30:00","2010-01-01 15:00:00","2010-01-01 15:30:00"]}}}}

The add attribute (type: integer, values: [1, 4, 6]) is inserted between bearing and acceleration, preserving all original attributes and their values.