ST_attrType

Syntax

text ST_attrType(trajectory traj, integer index);
text ST_attrType(trajectory traj, text name);

Parameters

Description

ST_attrType returns a string identifying the data type of the specified attribute field. The possible return values are: integer, float, string, timestamp, and bool.

Use the index-based overload when iterating over all fields; use the name-based overload when the field name is known.

Examples

Both examples query the same trajectory object — a two-point STPOINT trajectory with five typed attribute fields: velocity (integer), speed (float), angle (string), tngel2 (timestamp), and bearing (bool).

Query by index

Pass 0 to get the data type of the first attribute field (velocity).

With traj AS (
  select '{"trajectory":{"version":1,"type":"STPOINT","leafcount":2,"start_time":"2010-01-01 11:30:00","end_time":"2010-01-01 12:30:00","spatial":"SRID=4326;LINESTRING(1 1,3 5)","timeline":["2010-01-01 11:30:00","2010-01-01 12:30:00"],"attributes":{"leafcount":2,"velocity":{"type":"integer","length":4,"nullable":true,"value":[1,null]},"speed":{"type":"float","length":8,"nullable":true,"value":[null,1.0]},"angle":{"type":"string","length":64,"nullable":true,"value":["test",null]}, "tngel2":{"type":"timestamp","length":8,"nullable":true,"value":["2010-01-01 12:30:00",null]},"bearing":{"type":"bool","length":1,"nullable":true,"value":[null,true]}}}}'::trajectory a)
Select st_attrType(a, 0) from traj;

Output:

 st_attrtype
-------------
 integer
(1 row)

Query by name

Pass the field name 'velocity' to get its data type directly.

With traj AS (
  select '{"trajectory":{"version":1,"type":"STPOINT","leafcount":2,"start_time":"2010-01-01 11:30:00","end_time":"2010-01-01 12:30:00","spatial":"SRID=4326;LINESTRING(1 1,3 5)","timeline":["2010-01-01 11:30:00","2010-01-01 12:30:00"],"attributes":{"leafcount":2,"velocity":{"type":"integer","length":4,"nullable":true,"value":[1,null]},"speed":{"type":"float","length":8,"nullable":true,"value":[null,1.0]},"angle":{"type":"string","length":64,"nullable":true,"value":["test",null]}, "tngel2":{"type":"timestamp","length":8,"nullable":true,"value":["2010-01-01 12:30:00",null]},"bearing":{"type":"bool","length":1,"nullable":true,"value":[null,true]}}}}'::trajectory a)
Select st_attrType(a, 'velocity') from traj;

Output:

 st_attrtype
-------------
 integer
(1 row)

What's next

• ST_attrCount — get the total number of attribute fields in a trajectory

• ST_attrName — get the name of an attribute field by index

• ST_attrValue — get the value of an attribute field