滑动窗口分析

Python 中的 Spark SQL 入门

Mark Plutowski

Data Scientist

原始文本

ADVENTURE  I.  A SCANDAL IN BOHEMIA

I.


To Sherlock Holmes she is always the woman. I have seldom heard him mention 
her under any other name. In his eyes she eclipses and predominates the whole 
of her sex. It was not that he felt any emotion akin to love for Irene Adler. 
All emotions, and that one particularly, were abhorrent to his cold, precise 
but admirably balanced mind. He was, I take it, the most perfect reasoning 
and observing machine that the world has seen, but as a lover he would have 
placed himself in a false position. He never spoke of the softer passions, 
save with a gibe and a sneer. They were admirable things for the observer--
excellent for drawing the veil from men's motives and actions. But for the 
trained reasoner to admit such intrusions into his own delicate and finely 
adjusted temperament was to introduce a distracting factor which might throw 
a doubt upon all his mental results. Grit in a sensitive instrument, or a 
crack in one of his own high-power lenses, would not be more disturbing than 
a strong emotion in a nature such as his. And yet there was but one woman to 
him, and that woman was the late Irene Adler, of dubious and questionable 
memory.
Python 中的 Spark SQL 入门

处理后的文本

+--------+---+----+
|    word| id|part|
+--------+---+----+
| scandal|305|   1|
|      in|306|   1|
| bohemia|307|   1|
|       i|308|   1|
|      to|309|   1|
|sherlock|310|   1|
|  holmes|311|   1|
|     she|312|   1|
|      is|313|   1|
|  always|314|   1|
|     the|315|   1|
|   woman|316|   1|
|       i|317|   1|
|    have|318|   1|
|  seldom|319|   1|
|   heard|320|   1|
|     him|321|   1|
| mention|322|   1|
|     her|323|   1|
|   under|324|   1|
+--------+---+----+
Python 中的 Spark SQL 入门

分区

df.select('part', 'title').distinct().sort('part').show(truncate=False)
+----+---------------------+
|part|title                |
+----+---------------------+
|1   |Sherlock Chapter I   |
|2   |Sherlock Chapter II  |
|3   |Sherlock Chapter III |
|4   |Sherlock Chapter IV  |
|5   |Sherlock Chapter V   |
|6   |Sherlock Chapter VI  |
|7   |Sherlock Chapter VII |
|8   |Sherlock Chapter VIII|
|9   |Sherlock Chapter IX  |
|10  |Sherlock Chapter X   |
|11  |Sherlock Chapter XI  |
|12  |Sherlock Chapter XII |
+----+---------------------+
Python 中的 Spark SQL 入门

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Python 中的 Spark SQL 入门

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Python 中的 Spark SQL 入门

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Python 中的 Spark SQL 入门

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Python 中的 Spark SQL 入门

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Python 中的 Spark SQL 入门

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Python 中的 Spark SQL 入门

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Python 中的 Spark SQL 入门

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Python 中的 Spark SQL 入门

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Python 中的 Spark SQL 入门

单词已建立索引

+---+----------+
| id|      word|
+---+----------+
|  0|       the|
|  1|   project|
|  2| gutenberg|
|  3|     ebook|
|  4|        of|
|  5|       the|
|  6|adventures|
|  7|        of|
|  8|  sherlock|
|  9|    holmes|
| 10|        by|
| 11|       sir|
| 12|    arthur|
| 13|     conan|
| 14|     doyle|
| 15|       #15|
| 16|        in|
| 17|       our|
| 18|    series|
| 19|        by|
+---+----------+
Python 中的 Spark SQL 入门

滑动窗口查询

query = """
   SELECT id, word AS w1,
   LEAD(word,1) OVER(PARTITION BY part ORDER BY id ) AS w2,
   LEAD(word,2) OVER(PARTITION BY part ORDER BY id ) AS w3
   FROM df
""" 
spark.sql(query).sort('id').show()
+---+----------+----------+----------+
| id|        w1|        w2|        w3|
+---+----------+----------+----------+
|  0|       the|   project| gutenberg|
|  1|   project| gutenberg|     ebook|
|  2| gutenberg|     ebook|        of|
|  3|     ebook|        of|       the|
|  4|        of|       the|adventures|
|...|..........|..........|..........|
Python 中的 Spark SQL 入门

滑动窗口输出

+---+----------+----------+----------+
| id|        w1|        w2|        w3|
+---+----------+----------+----------+
|  0|       the|   project| gutenberg|
|  1|   project| gutenberg|     ebook|
|  2| gutenberg|     ebook|        of|
|  3|     ebook|        of|       the|
|  4|        of|       the|adventures|
|  5|       the|adventures|        of|
|  6|adventures|        of|  sherlock|
|  7|        of|  sherlock|    holmes|
|  8|  sherlock|    holmes|        by|
|  9|    holmes|        by|       sir|
| 10|        by|       sir|    arthur|
| 11|       sir|    arthur|     conan|
| 12|    arthur|     conan|     doyle|
+---+----------+----------+----------+
Python 中的 Spark SQL 入门

LAG 窗口函数

lag_query = """
   SELECT 
   id,
   LAG(word,2) OVER(PARTITION BY part ORDER BY id ) AS w1,
   LAG(word,1) OVER(PARTITION BY part ORDER BY id ) AS w2,
   word AS w3
   FROM df
   ORDER BY id
"""

spark.sql(lag_query).show()
Python 中的 Spark SQL 入门

LAG 窗口函数——输出

+---+----------+----------+----------+
| id|        w1|        w2|        w3|
+---+----------+----------+----------+
|  0|      null|      null|       the|
|  1|      null|       the|   project|
|  2|       the|   project| gutenberg|
|  3|   project| gutenberg|     ebook|
|  4| gutenberg|     ebook|        of|
|  5|     ebook|        of|       the|
|  6|        of|       the|adventures|
|  7|       the|adventures|        of|
|  8|adventures|        of|  sherlock|
|  9|        of|  sherlock|    holmes|
| 10|  sherlock|    holmes|        by|
| 11|    holmes|        by|       sir|
| 12|       ...|       ...|       ...|
+---+----------+----------+----------+
Python 中的 Spark SQL 入门

窗口限定在分区内

lag_query = """
   SELECT 
   id,
   LAG(word,2) OVER(PARTITION BY part ORDER BY id ) AS w1,
   LAG(word,1) OVER(PARTITION BY part ORDER BY id ) AS w2,
   word AS w3
   FROM df
   WHERE part=2
"""

spark.sql(lag_query).show()
Python 中的 Spark SQL 入门

窗口限定在分区内——输出

+----+----------+----------+----------+
|  id|        w1|        w2|        w3|
+----+----------+----------+----------+
|8859|      null|      null|     part2|
|8860|      null|     part2| adventure|
|8861|     part2| adventure|        ii|
|8862| adventure|        ii|       the|
|8863|        ii|       the|red-headed|
|8864|       the|red-headed|    league|
|....|..........|..........|..........|
Python 中的 Spark SQL 入门

重新分区

  • PARTITION BY
  • repartition()
Python 中的 Spark SQL 入门

Passons à la pratique !

Python 中的 Spark SQL 入门

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