pyspark pivot具有更好的性能

ffx8fchx  于 2021-05-17  发布在  Spark
关注(0)|答案(0)|浏览(540)

下面是我的输入数据集:

df = spark.createDataFrame([ \
    ("0","CattyCat","B2K","B"), \
    ("0","CattyCat","B3L","I"), \
    ("0","CattyCat","B3U","I"), \
    ("0","CattyCat","D3J","C"), \
    ("0","CattyCat","J1N","H"), \
    ("0","CattyCat","K7A","I"), \
    ("0","CattyCat","L1B","D"), \
    ("0","CattyCat","U3F","B"), \
    ("1","CattyCat","B2K","I"), \
    ("1","CattyCat","B3L","I"), \
    ("1","CattyCat","B3U","I"), \
    ("1","CattyCat","D3J","C"), \
    ("1","CattyCat","J1N","H"), \
    ("1","CattyCat","K7A","I"), \
    ("1","CattyCat","L1B","D"), \
    ("1","CattyCat","U3F","B"), \
    ("2","CattyCat","B2K","B"), \
    ("2","CattyCat","B3L","B"), \
    ("2","CattyCat","B3U","I"), \
    ("2","CattyCat","D3J","C"), \
    ("2","CattyCat","J1N","H"), \
    ("2","CattyCat","K7A","I"), \
    ("2","CattyCat","L1B","D"), \
    ("2","CattyCat","U3F","B"), \
], ["RowCount","CatName","Name","Value"])

df.show(30)

+--------+--------+----+-----+
|RowCount| CatName|Name|Value|
+--------+--------+----+-----+
|       0|CattyCat| B2K|    B|
|       0|CattyCat| B3L|    I|
|       0|CattyCat| B3U|    I|
|       0|CattyCat| D3J|    C|
|       0|CattyCat| J1N|    H|
|       0|CattyCat| K7A|    I|
|       0|CattyCat| L1B|    D|
|       0|CattyCat| U3F|    B|
|       1|CattyCat| B2K|    I|
|       1|CattyCat| B3L|    I|
|       1|CattyCat| B3U|    I|
|       1|CattyCat| D3J|    C|
|       1|CattyCat| J1N|    H|
|       1|CattyCat| K7A|    I|
|       1|CattyCat| L1B|    D|
|       1|CattyCat| U3F|    B|
|       2|CattyCat| B2K|    B|
|       2|CattyCat| B3L|    B|
|       2|CattyCat| B3U|    I|
|       2|CattyCat| D3J|    C|
|       2|CattyCat| J1N|    H|
|       2|CattyCat| K7A|    I|
|       2|CattyCat| L1B|    D|
|       2|CattyCat| U3F|    B|
+--------+--------+----+-----+

我的目标是对这些数据进行透视/交叉制表。我使用groupby.pivot.agg实现了这一点,如下所示:

import pyspark.sql.functions as F
display(df.groupBy("RowCount","CatName").pivot("Name").agg(F.first("value")))

+----------+----------+-----+-----+-----+-----+-----+-----+-----+-----+
| RowCount | CatName  | B2K | B3L | B3U | D3J | J1N | K7A | L1B | U3F |
+----------+----------+-----+-----+-----+-----+-----+-----+-----+-----+
| 0        | CattyCat | B   | I   | I   | C   | H   | I   | D   | B   |
+----------+----------+-----+-----+-----+-----+-----+-----+-----+-----+
| 1        | CattyCat | I   | I   | I   | C   | H   | I   | D   | B   |
+----------+----------+-----+-----+-----+-----+-----+-----+-----+-----+
| 2        | CattyCat | B   | B   | I   | C   | H   | I   | D   | B   |
+----------+----------+-----+-----+-----+-----+-----+-----+-----+-----+

但我面临的问题是,当数据集很大(1亿)时,性能非常差(单个执行者的最后阶段的单个任务,停留了几个小时)p.s:我还发现pivot还可以采用第二个参数,即一系列可能提供更好性能的列名。但不幸的是我不能提前知道这些列名。
有没有一种方法可以更好地完成这个“交叉表”?

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