ST_MD5Sum-AnalyticDB(AnalyticDB)-阿里云帮助中心

Returns the MD5 hash of a raster object.

Syntax

text ST_MD5Sum(raster raster_obj)

Parameters

Parameter	Description
`raster_obj`	The name of the raster object.

How it works

ST_MD5Sum first looks up the MD5 hash in the raster object's metadata. If no hash is found there, it calculates the MD5 hash from the Object Storage Service (OSS) path where the raster object is stored.

Note ST_MD5Sum returns NULL for raster objects stored internally (not in OSS) if no MD5 hash exists in metadata.

Two Grand Unified Configuration (GUC) parameters control this behavior:

ganos.raster.calculate_md5 — Specifies whether to calculate and store the MD5 hash in metadata when a raster object is written. Default: false. See ganos.raster.calculate_md5.
ganos.raster.md5sum_chunk_size — The amount of data, in MB, buffered per read when calculating the MD5 hash. Default: 10. See ganos.raster.md5sum_chunk_size.

Examples

Query the MD5 hash of a single raster object

SELECT ST_MD5SUM(rast)
FROM raster_table
WHERE id = 1;

Result:

              st_md5sum
-----------------------------------
 21f41fd983d3139c75b04bff2b7bf5c9