Return metadata of a raster object using ST_MetaData - PolarDB

Returns the metadata of a raster object as a JSON string.

Syntax

Three overloads are available:

-- Variant 1: Return all metadata of a raster object
text ST_MetaData(raster raster_obj);

-- Variant 2: Return a specific metadata item, or all metadata items
text ST_MetaData(raster raster_obj,
                text key);

-- Variant 3: Return a specific metadata item, or all metadata items, for a band
text ST_MetaData(raster raster_obj,
                integer band,
                text key);

Parameters

Parameter	Description
`raster_obj`	The raster object.
`band`	The band index, starting from 0.
`key`	The name of the metadata item to retrieve. Set this parameter to `'all'` to return all metadata items as a JSON object.

Examples

Variant 1: Return all metadata of a raster object

SELECT ST_MetaData(raster_obj)
FROM raster_table;

Variant 2: Query by key name or retrieve all metadata

Query a single metadata item by key name:

SELECT ST_MetaData(raster_obj, 'swh#scale_factor')
FROM raster_table;

Result:

      st_metadata
-----------------------
 0.0001488117874873806

Retrieve all metadata items:

SELECT ST_MetaData(raster_obj, 'all')
FROM raster_table;

Result:

      st_metadata
-----------------------
{"AREA_OR_POINT":"Area"}

The result may contain multiple metadata fields. For example:

{"add_offset":"4.907141431495487","long_name":"Significant height of combined wind waves and swell","missing_value":"-32767","NETCDF_DIM_time":"1043112","NETCDF_VARNAME":"swh","scale_factor":"0.0001488117874873806","units":"m","_FillValue":"-32767"}

Variant 3: Query band metadata by key name

Query a single metadata item for band 0:

SELECT ST_MetaData(raster_obj, 0, 'NETCDF_DIM_time')
FROM raster_table;

Result:

 st_metadata
-------------
 1043112

PolarDB:ST_MetaData

Syntax

Parameters

Examples

Variant 1: Return all metadata of a raster object

Variant 2: Query by key name or retrieve all metadata

Variant 3: Query band metadata by key name

See also