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

Sets the histogram for a specified band of a raster object. Pass the histogram as a JSON string.

Syntax

raster ST_SetHistogram(raster rast, integer band, cstring histogram);

Parameters

Parameter	Type	Description
`rast`	raster	The raster object to update.
`band`	integer	The band index, starting from 0.
`histogram`	cstring	The histogram definition in JSON format. See Histogram JSON schema.

Histogram JSON schema

The histogram parameter accepts a JSON object with the following fields.

Top-level fields

Field	Type	Description
`approximate`	BOOLEAN	Specifies whether to use data sampling when computing the histogram.
`histsCounts`	INTEGER[]	The bin counts. Each element is the number of pixel values that fall into the corresponding bin.
`binFunction`	object	Defines how bins are calculated. See binFunction fields.

binFunction fields

Field	Type	Applies when	Description
`binFunction/type`	STRING	Always	The binning strategy: `linear`, `logarithm`, or `explicit`.
`binFunction/binTable/binValues`	NUMBER[]	`type` is `explicit`	The explicit list of bin boundary values.
`binFunction/binRange/minValue`	NUMBER	`type` is `linear` or `logarithm`	The lower bound of the bin range.
`binFunction/binRange/maxValue`	NUMBER	`type` is `linear` or `logarithm`	The upper bound of the bin range.
`binFunction/binRange/outRange`	STRING	`type` is `linear` or `logarithm`	How pixel values outside [minValue, maxValue] are handled. Use `"include"` to count them in the nearest edge bin, or `"exclude"` to discard them.
`binFunction/binRange/binValues`	NUMBER[]	`type` is `linear` or `logarithm`	The computed bin boundary values within the range.

Choosing a bin function type

Type	When to use
`linear`	Bins are evenly spaced across a numeric range. Use for uniformly distributed data.
`logarithm`	Bins are spaced on a logarithmic scale. Use for data with a wide dynamic range.
`explicit`	Bin boundaries are specified directly. Use when you need irregular or custom intervals.

Examples

Example 1: Set a histogram with explicit bin boundaries

UPDATE rat
SET raster = ST_SetHistogram(
    raster,
    0,
    '{"approximate":true,"histsCounts":[1,2,3,4,5],"binFunction":{"type":"explicit","binTable":{"binValues":[1.0,2.0,3.0,4.0,5.0]}}}'
)
WHERE id = 1;

This sets the histogram for band 0 using five explicit bin boundaries. approximate is true, so data sampling is used when the histogram is computed.