应用功能和查询百万/十亿行表中值的最有效方法

问题描述

我有包含百万/十亿行的镶木地板文件，我试图找到一个更快的过程来应用函数并查询这些大表上的值。 1M行表的ipynb代码示例：

from pyarrow import parquet as pq
from ttictoc import TicToc #Preferred time tracker
t = TicToc() 

#Function to be applied
def val_calc(x,n_cols): 
    import random
    import string

    #Mapping process
    abc_vals = string.ascii_uppercase[:n_cols] #N-alphabets in the df
    x_map = {i:random.randint(j,n_cols+10) for i,j in zip(abc_vals,range(n_cols))} #map-dict

    #Calculations... Formula: Σ(Xi*Yi)/ΣY 
    y_vals = {i:j**2 for i,j in x_map.items()} #Y's set of values to use 

    weights = [x_val*y_val for x_val,y_val in zip(x_map.values(),y_vals.values())] #(Xi*Yi)

    result = sum(weights)/sum(y_vals.values()) #Σ(X*Y)/ΣY 

    return result

#Getting the parquet file
file_path = 'C:/XYZ/project/'
file_name = 'gx6c'

#pyarrow parquet -> pandas
large_pq = pq.read_table(file_path+file_name+'.pq').to_pandas()

#Number of columns - column per alphabet in a row: 
n_columns = int(file_name.split('x')[-1].replace('c',''))

#-------------------------------------------------------Results and time taken
t.tic() #start time
                              #Function applied
large_pq['values'] = large_pq.apply(lambda x: val_calc(x,n_columns),axis=1) 

t.toc() #end time

print(f'Time passed for applying function: {round(t.elapsed,5)} seconds')
display(large_pq)


#Querying part
t.tic()
queried = large_pq[large_pq['values'].between(12,13)]
t.toc()

print(f'Time passed for query: {round(t.elapsed,5)} seconds')
display(queried)

输出：

Time passed for applying function: 17.60126 seconds
    
    abc     values
0   AAAAAA  13.258228
1   AAAAAB  10.227642
2   AAAABA  11.264317
3   AAABAA  12.422303
4   AABAAA  13.537634
... ... ...
999995  JJIJJJ  12.620214
999996  JJJIJJ  11.323636
999997  JJJJIJ  10.756757
999998  JJJJJI  10.358811
999999  JJJJJJ  10.896328
1000000 rows × 2 columns

Time passed for query: 0.04801 seconds
    
    abc     values
3   AAABAA  12.422303
5   ABAAAA  12.062818
13  AAAAAD  12.762040
16  AADAAA  12.925373
25  AAAAAF  12.661267
... ... ...
999967  IJJJII  12.936667
999972  JIJIJI  12.331742
999986  JIJJJI  12.133333
999993  IJJJJJ  12.179487
999995  JJIJJJ  12.620214
284129 rows × 2 columns

对于每行17个字母（或17个“列”）的13M行表重复相同的操作大约需要10分钟，查询步骤为0.22524秒。对于较大的文件，我会遇到内存错误，因此无法达到十亿行的标记。是否有任何变通办法可以在更短的时间范围内执行这些过程，例如对于一个13M行的表来说，是10秒而不是几分钟？

解决方法

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