st_nrings
Applies to: 
Databricks Runtime 18.1 and above
Preview
Support for GEOGRAPHY values is in Public Preview. Support for GEOMETRY values is generally available.
Returns the total number of rings of the input polygon or multipolygon, including exterior and interior rings. For a multipolygon, returns the sum of all rings across all polygons.
For the corresponding Databricks SQL function, see st_nrings function.
Syntax
Python
from pyspark.databricks.sql import functions as dbf
dbf.st_nrings(col=<col>)
Parameters
Examples
Empty 2D polygon GEOMETRY:
Python
from pyspark.databricks.sql import functions as dbf
df = spark.createDataFrame([('POLYGON EMPTY',)], ['wkt'])
df.select(dbf.st_nrings(dbf.st_geomfromtext('wkt')).alias('result')).collect()
Output
[Row(result=0)]
4D polygon GEOGRAPHY with two rings (one exterior, one interior):
Python
from pyspark.databricks.sql import functions as dbf
df = spark.createDataFrame([('POLYGON ZM ((0 0 111 -11,10 0 222 -22,0 10 333 -33,0 0 444 -44),(1 1 555 -55,4 1 666 -66,1 4 777 -77,1 1 888 -88))',)], ['wkt'])
df.select(dbf.st_nrings(dbf.st_geogfromtext('wkt')).alias('result')).collect()
Output
[Row(result=2)]
Empty 3DZ multipolygon GEOMETRY:
Python
from pyspark.databricks.sql import functions as dbf
df = spark.createDataFrame([('MULTIPOLYGON Z EMPTY',)], ['wkt'])
df.select(dbf.st_nrings(dbf.st_geomfromtext('wkt', 4326)).alias('result')).collect()
Output
[Row(result=0)]
Multipolygon GEOGRAPHY with four rings across two polygons:
Python
from pyspark.databricks.sql import functions as dbf
df = spark.createDataFrame([('MULTIPOLYGON (((0 0,10 0,10 10,0 10,0 0),(1 1,4 1,4 4,1 4,1 1),(5 5,6 5,6 6,5 6,5 5)),((20 20,30 20,30 30,20 30,20 20)))',)], ['wkt'])
df.select(dbf.st_nrings(dbf.st_geogfromtext('wkt')).alias('result')).collect()
Output
[Row(result=4)]