Explodera

Returnerar en ny rad för varje element i den angivna matrisen eller kartan. Använder standardkolumnnamnet col för element i matrisen och keyvalue för element på kartan om inget annat anges.

Syntax

from pyspark.sql import functions as sf

sf.explode(col)

Parameterar

Retur

pyspark.sql.Column: En rad per matrisobjekt eller mappningsnyckelvärde.

Examples

Exempel 1: Explodera en matriskolumn

from pyspark.sql import functions as sf
df = spark.sql('SELECT * FROM VALUES (1,ARRAY(1,2,3,NULL)), (2,ARRAY()), (3,NULL) AS t(i,a)')
df.show()

+---+---------------+
|  i|              a|
+---+---------------+
|  1|[1, 2, 3, NULL]|
|  2|             []|
|  3|           NULL|
+---+---------------+

df.select('*', sf.explode('a')).show()

+---+---------------+----+
|  i|              a| col|
+---+---------------+----+
|  1|[1, 2, 3, NULL]|   1|
|  1|[1, 2, 3, NULL]|   2|
|  1|[1, 2, 3, NULL]|   3|
|  1|[1, 2, 3, NULL]|NULL|
+---+---------------+----+

Exempel 2: Explodera en kartkolumn

from pyspark.sql import functions as sf
df = spark.sql('SELECT * FROM VALUES (1,MAP(1,2,3,4,5,NULL)), (2,MAP()), (3,NULL) AS t(i,m)')
df.show(truncate=False)

+---+---------------------------+
|i  |m                          |
+---+---------------------------+
|1  |{1 -> 2, 3 -> 4, 5 -> NULL}|
|2  |{}                         |
|3  |NULL                       |
+---+---------------------------+

df.select('*', sf.explode('m')).show(truncate=False)

+---+---------------------------+---+-----+
|i  |m                          |key|value|
+---+---------------------------+---+-----+
|1  |{1 -> 2, 3 -> 4, 5 -> NULL}|1  |2    |
|1  |{1 -> 2, 3 -> 4, 5 -> NULL}|3  |4    |
|1  |{1 -> 2, 3 -> 4, 5 -> NULL}|5  |NULL |
+---+---------------------------+---+-----+

Exempel 3: Exploderar flera matriskolumner

import pyspark.sql.functions as sf
df = spark.sql('SELECT ARRAY(1,2) AS a1, ARRAY(3,4,5) AS a2')
df.select(
    '*', sf.explode('a1').alias('v1')
).select('*', sf.explode('a2').alias('v2')).show()

+------+---------+---+---+
|    a1|       a2| v1| v2|
+------+---------+---+---+
|[1, 2]|[3, 4, 5]|  1|  3|
|[1, 2]|[3, 4, 5]|  1|  4|
|[1, 2]|[3, 4, 5]|  1|  5|
|[1, 2]|[3, 4, 5]|  2|  3|
|[1, 2]|[3, 4, 5]|  2|  4|
|[1, 2]|[3, 4, 5]|  2|  5|
+------+---------+---+---+

Exempel 4: Explodera en matris med structkolumn

import pyspark.sql.functions as sf
df = spark.sql('SELECT ARRAY(NAMED_STRUCT("a",1,"b",2), NAMED_STRUCT("a",3,"b",4)) AS a')
df.select(sf.explode('a').alias("s")).select("s.*").show()

+---+---+
|  a|  b|
+---+---+
|  1|  2|
|  3|  4|
+---+---+