ST_SetHistogram syntax, parameters, and examples-ApsaraDB RDS(RDS)-阿里云帮助中心

Sets the histogram for a specified band of a raster object using a JSON-formatted histogram definition.

Syntax

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

Parameters

Parameter	Type	Description
rast	raster	The raster object.
band	integer	The band index, starting from 0.
histogram	cstring	The histogram definition in JSON format. For the JSON structure, see Histogram JSON format.

Histogram JSON format

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 array. Each element represents the number of values in the corresponding bin.
`binFunction`	object	Defines the binning strategy. See binFunction fields.

binFunction fields

Field	Type	Description
`type`	STRING	The binning method. Valid values: `linear`, `logarithm`, `explicit`.
`binTable`	object	The explicit bin table. Applies only when `type` is `explicit`.
`binTable.binValues`	NUMBER[]	The bin boundary values. Applies only when `type` is `explicit`.
`binRange`	object	The bin range definition. Applies only when `type` is `logarithm` or `linear`.
`binRange.minValue`	NUMBER	The minimum value of the bin range. Applies only when `type` is `logarithm` or `linear`.
`binRange.maxValue`	NUMBER	The maximum value of the bin range. Applies only when `type` is `logarithm` or `linear`.
`binRange.outRange`	NUMBER	The value assigned to data points outside the bin range. Applies only when `type` is `logarithm` or `linear`.
`binRange.binValues`	NUMBER[]	The bin boundary values within the range. Applies only when `type` is `logarithm` or `linear`.

Examples

Example 1: Histogram with a bin range

This example uses a binRange-based histogram with 179 bins spanning values 29.0 to 207.0.

{
  "approximate": false,
  "histsCounts": [2,1,1,0,8,17,47,101,193,345,443,640,877,1189,1560,1847,2087,2560,2816,3193,3567,3840,4101,4415,4498,3876,3235,2458,1800,1598,1087,731,638,426,264,198,147,126,104,104,80,84,86,71,80,62,74,85,72,80,70,88,69,68,62,58,63,51,53,55,54,56,55,63,47,39,49,59,66,62,64,73,66,72,67,84,86,79,91,92,117,138,136,142,157,225,287,285,382,449,567,628,750,855,1021,1142,1242,1410,1504,1590,1786,1870,2044,2099,2277,2373,2451,2585,2646,2882,2878,3091,3396,3620,3911,4124,4304,4700,4893,5314,5446,5657,5765,5649,5749,5753,5601,5335,5161,4943,4592,4445,4207,4083,4090,4270,4465,4514,4844,5204,5331,5597,5777,5838,6004,6316,6095,5762,5567,5465,4923,4677,4220,3843,3401,3041,2571,2345,1972,1725,1376,1140,1008,841,716,548,442,373,308,212,133,78,68,31,24,12,2,2,1],
  "binFunction": {
    "type": "unknown",
    "binRange": {
      "minValue": 29.0,
      "maxValue": 208.0,
      "outRange": "include",
      "binValues": [29.0,30.0,31.0,32.0,33.0,34.0,35.0,36.0,37.0,38.0,39.0,40.0,41.0,42.0,43.0,44.0,45.0,46.0,47.0,48.0,49.0,50.0,51.0,52.0,53.0,54.0,55.0,56.0,57.0,58.0,59.0,60.0,61.0,62.0,63.0,64.0,65.0,66.0,67.0,68.0,69.0,70.0,71.0,72.0,73.0,74.0,75.0,76.0,77.0,78.0,79.0,80.0,81.0,82.0,83.0,84.0,85.0,86.0,87.0,88.0,89.0,90.0,91.0,92.0,93.0,94.0,95.0,96.0,97.0,98.0,99.0,100.0,101.0,102.0,103.0,104.0,105.0,106.0,107.0,108.0,109.0,110.0,111.0,112.0,113.0,114.0,115.0,116.0,117.0,118.0,119.0,120.0,121.0,122.0,123.0,124.0,125.0,126.0,127.0,128.0,129.0,130.0,131.0,132.0,133.0,134.0,135.0,136.0,137.0,138.0,139.0,140.0,141.0,142.0,143.0,144.0,145.0,146.0,147.0,148.0,149.0,150.0,151.0,152.0,153.0,154.0,155.0,156.0,157.0,158.0,159.0,160.0,161.0,162.0,163.0,164.0,165.0,166.0,167.0,168.0,169.0,170.0,171.0,172.0,173.0,174.0,175.0,176.0,177.0,178.0,179.0,180.0,181.0,182.0,183.0,184.0,185.0,186.0,187.0,188.0,189.0,190.0,191.0,192.0,193.0,194.0,195.0,196.0,197.0,198.0,199.0,200.0,201.0,202.0,203.0,204.0,205.0,206.0,207.0]
    }
  }
}

Example 2: Histogram with explicit bins

This example uses an explicit bin table with five bins.

{
  "approximate": true,
  "histsCounts": [1,2,3,4,5],
  "binFunction": {
    "type": "explicit",
    "binTable": {
      "binValues": [1.0,2.0,3.0,4.0,5.0]
    }
  }
}

Example 3: Set a histogram on a raster band

The following SQL statement sets the histogram on band 0 of the raster column in the rat table using an explicit bin table.

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;

Expected output:

--------------------------------
(1 row)