cloudera impala中的多个查询执行

Question

是否可以在impala中同时执行多个查询？如果是，那么黑斑羚如何处理呢？

Answer 1

Impala可以同时执行多个查询，只要它没有达到内存上限即可。

Answer 2

你可以发出像impala-shell -f <<file_name>>这样的命令，其中文件有多个查询，每个查询用分号分隔（;）

Answer 3

如果你是一个python极客，你甚至可以尝试impyla包来创建多个连接并立即运行所有查询。

pip install impyla

Answer 4

我当然会自己做一些测试，但我无法执行多个查询：我使用的是Impala连接，并从.sql文件中读取查询。这适用于单个命令。

from impala.dbapi import connect
# actual server and port changed for this post for security
conn=connect(host='impala server', port=11111,auth_mechanism="GSSAPI")
cursor = conn.cursor()
cursor.execute((open("sandbox/z_temp.sql").read()))

这是我收到的错误。

 HiveServer2Error: AnalysisException: Syntax error in line 2:

这就是SQL在.sql文件中的样子。

Select * FROM database1.table1;
Select * FROM database1.table2;

我能够在单独的.sql文件中使用SQL命令运行多个命令，迭代指定文件夹中的所有.sql文件。

#Create list of file names for recon .sql files this will be sorted
#Numbers at begining of filename are important to sort so that files will be executed in correct order

file_names = glob.glob('folder/.sql')

asc_names = sorted(file_names, reverse = False)
filename = ""
for file_name in asc_names:
  str_filename = str(file_name)
  print(filename)
  query = (open(str_filename).read())

  cursor = conn.cursor()

# creates an error log dataframe to print, or write to file at end of job.

  try:
# Each SQL command must be executed seperately
    cursor.execute(query)
    df_id= pd.DataFrame([{'test_name': str_filename[-40:], 'test_status': 'PASS'}])
    df_log = df_log.append(df_id, ignore_index=True)

  except:
    df_id= pd.DataFrame([{'test_name': str_filename[-40:], 'test_status': 'FAIL'}])
    df_log = df_log.append(df_id, ignore_index=True)
    continue

另一种方法是将一个.sql文件中的所有SQL语句分隔开;然后循环通过.sql文件拆分语句;一次运行一个。

from impala.dbapi import connect
from impala.util import as_pandas

conn=connect(host='impalaserver', port=11111, auth_mechanism='GSSAPI')
cursor = conn.cursor()

# split SQL statements from one file seperated by ';', Note: last command will not have semicolon at end.

sql_file = open("sandbox/temp.sql").read()
sql = sql_file.split(';')
for cmd in sql:
# This gets rid of the non printing characters you may have
      cmd = cmd.replace('/r','')
      cmd = cmd.replace('/n','')
# This runs your SQL commands one at a time.
      cursor.execute(cmd)
  print(cmd)