spark TempView和GlobalTempView的区别

TempView和GlobalTempView在spark的Dataframe中经常使用，两者的区别和应用场景有什么不同。

我们以下面的例子比较下两者的不同。

from pyspark.sql import SparkSession
import numpy as np
import pandas as pd

spark = SparkSession.builder.getOrCreate()

d = np.random.randint(1,100, 5*5).reshape(5,-1)
data = pd.DataFrame(d, columns=list("abcde"))
df = spark.createDataFrame(data)
df.show()

+---+---+---+---+---+
|  a|  b|  c|  d|  e|
+---+---+---+---+---+
| 17| 30| 61| 61| 33|
| 32| 23| 24|  7|  7|
| 47|  6|  4| 95| 34|
| 50| 69| 83| 21| 46|
| 52| 12| 83| 49| 85|
+---+---+---+---+---+

从tempview中取数据

temp = df.createTempView("temp")
temp_sql = "select * from temp where a=50"
res = spark.sql(temp_sql)
res.show()

+---+---+---+---+---+
|  a|  b|  c|  d|  e|
+---+---+---+---+---+
| 50| 69| 83| 21| 46|
+---+---+---+---+---+

从globaltempview中取数据

glob = df.createGlobalTempView("glob")
glob_sql = "select * from global_temp.glob where a = 17"
res2 = spark.sql(glob_sql)
res2.show()

+---+---+---+---+---+
|  a|  b|  c|  d|  e|
+---+---+---+---+---+
| 17| 30| 61| 61| 33|
+---+---+---+---+---+

Globaltempview 数据可以在多个sparkSession中共享

# 创建新的sparkSession
spark2 = spark.newSession()
spark2 == spark

False

# 新的sparkSession可以获取globaltempview中的数据
new_sql = "select * from global_temp.glob where a = 47"
temp = spark2.sql(new_sql)
temp.show()

+---+---+---+---+---+
|  a|  b|  c|  d|  e|
+---+---+---+---+---+
| 47|  6|  4| 95| 34|
+---+---+---+---+---+

# 新的sparkSession无法获取tempview中的数据
# 会提示找不到temp表

new_sql2 = "select * from temp where a = 47"
temp = spark2.sql(new_sql2)
temp.show()

# 使用global_temp前缀也不行
new_sql2 = "select * from global_temp.temp where a = 47"
temp = spark2.sql(new_sql2)
temp.show()

---------------------------------------------------------------------------
Py4JJavaError                             Traceback (most recent call last)
# 此处多行删除异常信息
AnalysisException: "Table or view not found: `global_temp`.`temp`; line 1 pos 14;
"Project [*]
+- "Filter ("a = 47)
   +- "UnresolvedRelation `global_temp`.`temp`
"

tempview删除后无法使用

spark.catalog.dropTempView("temp")
spark.catalog.dropGlobalTempView("glob")

# 报错，找不到table temp
temp_sql2 = "select * from temp where a = 47"
temp = spark.sql(temp_sql2)

# 报错，找不到global_temp.glob，spark和spark2中均报错
glob_sql2 = "select * from global_temp.glob where a = 47"
temp = spark.sql(glob_sql2)
temp = spark2.sql(glob_sql2)

总结

spark中有四个tempview方法

• df.createGlobalTempView
• df.createOrReplaceGlobalTempView
• df.createOrReplaceTempView
• df.createTempView

replace方法：不存在则直接创建，存在则替换

tempview删除后无法使用

两个删除方法
spark.catalog.dropTempView("temp")
spark.catalog.dropGlobalTempView("glob")

TempView和GlobalTempView的异同

1. tempview只能在一个sparkSession中使用
2. GlobaltempView可以在多个sparkSession中共享使用
3. 但是他们都不能跨Application使用