ST_attrNullFilter-AnalyticDB(AnalyticDB)-阿里云帮助中心

Filters trajectory points where the specified attribute field has a null value, and returns a new trajectory object composed of those points.

Syntax

trajectory ST_attrNullFilter(trajectory traj, cstring attr_field_name);

Parameters

Parameter	Description
`traj`	The trajectory object.
`attr_field_name`	The name of the attribute field to filter on.

Usage notes

This function works with all attribute field types.

Examples

The following example creates a 16-point trajectory with a heading attribute, then extracts the points where heading is null. Four of the 16 points have null values, so the result is a new trajectory with four points.

SELECT st_attrNullFilter(
  ST_makeTrajectory(
    'STPOINT'::leaftype,
    'LINESTRING(-179.48077 51.72814,-179.46731 51.74634,-179.46502 51.74934,-179.46183 51.75378,-179.45943 51.75736,-179.45560 51.76273,-179.44845 51.77186,-179.43419 51.78977,-179.41259 51.81643,-179.41001 51.81941,-179.40751 51.82223,-179.40497 51.82505,-179.40242 51.82796,-179.39981 51.83095,-179.39734 51.83398,-179.39499 51.83709)'::geometry,
    ARRAY[
      '2017-01-15 09:06:39'::timestamp,
      '2017-01-15 09:13:39',
      '2017-01-15 09:14:48',
      '2017-01-15 09:16:28',
      '2017-01-15 09:17:48',
      '2017-01-15 09:19:48',
      '2017-01-15 09:23:19',
      '2017-01-15 09:30:28',
      '2017-01-15 09:34:40',
      '2017-01-15 09:36:59',
      '2017-01-15 09:38:09',
      '2017-01-15 09:39:18',
      '2017-01-15 09:40:40',
      '2017-01-15 09:47:38',
      '2017-01-15 09:48:49',
      '2017-01-15 21:18:30'
    ],
    '{"leafcount": 16, "attributes": {"heading": {"type": "float", "length": 4, "nullable": true, "value": [23.0,23.0,23.0,null,21.0,21.0,null,72.0,72.0,null,73.0,74.0,73.0,73.0,null,73.0]}}}'
  ),
  'heading'
);

Output:

                                  st_attrnullfilter
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 {"trajectory":{"version":1,"type":"STPOINT","leafcount":4,"start_time":"2017-01-15 09:16:28","end_time":"2017-01-15 09:48:49","spatial":"LINESTRING(-179.46183 51.75378,-179.44845 51.77186,-179.41001 51.81941,-179.39734 51.83398)","timeline":["2017-01-15 09:16:28","2017-01-15 09:23:19","2017-01-15 09:36:59","2017-01-15 09:48:49"],"attributes":{"leafcount":4,"heading":{"type":"float","length":4,"nullable":true,"value":[null,null,null,null]}}}}
(1 row)