h3_kring function

Applies to: check marked yes Databricks SQL check marked yes Databricks Runtime 11.3 LTS and above

Returns the H3 cells that are within (grid) distance k of the origin cell. The set of these H3 cells is called the k-ring of the origin cell.

Syntax 

h3_kring ( h3CellIdExpr, kExpr )

Arguments

  • h3CellIdExpr: A BIGINT expression, or a hexadecimal STRING expression representing an H3 cell ID.

  • kExpr: An INTEGER expression representing the grid distance. kExpr must be non-negative.

Returns

An ARRAY of values of the same type as the type of the h3CellIdExpr expression, corresponding to the H3 cell IDs that have the same resolution as the input H3 cell and are within grid distance k of the input H3 cell, where k is the value of the kExpr.

The function returns NULL if any one of the input expressions is NULL. The function does partial validation regarding whether the input argument is a valid H3 cell ID. A necessary, but not sufficient condition for a valid H3 ID is that its value is between 0x08001fffffffffff and 0x08ff3b6db6db6db6. The behavior of the function is undefined if the input cell ID is not a valid cell ID. If the value of the grid distance is zero, the returned array contains a single value equal to the input H3 cell ID.

Error conditions

  • If h3CellIdExpr is a STRING that cannot be converted to a BIGINT or corresponds to a BIGINT value that is smaller than 0x08001fffffffffff or larger than 0x08ff3b6db6db6db6, the function returns H3_INVALID_CELL_ID.

  • If kExpr is negative, the function returns H3_INVALID_GRID_DISTANCE_VALUE.

Examples 

-- Simple example where the first argument is a BIGINT.
> SELECT h3_kring(599686042433355775, 1)
  [599686042433355775,599686030622195711,599686044580839423,599686038138388479,599686043507097599,599686015589810175,599686014516068351]

-- Simple example where the first argument is a STRING.
> SELECT h3_kring('85283473fffffff', 1)
  [85283473fffffff,85283447fffffff,8528347bfffffff,85283463fffffff,85283477fffffff,8528340ffffffff,8528340bfffffff]

-- First input is an invalid H3 cell ID.
> SELECT h3_kring(0, 0)
  [H3_INVALID_CELL_ID] 0 is not a valid H3 cell ID

-- Second input is an invalid grid distance value.
> SELECT h3_kring('85283473fffffff', -1)
  [H3_INVALID_GRID_DISTANCE_VALUE] H3 grid distance -1 must be non-negative