如何识别Hive中字符串列的重复出现? [英] How to identify repeated occurrences of a string column in Hive?

问题描述

我在Hive中有这样的看法:

I have a view like this in Hive:

id        sequencenumber          appname
242539622              1          A
242539622              2          A
242539622              3          A
242539622              4          B
242539622              5          B
242539622              6          C
242539622              7          D
242539622              8          D
242539622              9          D
242539622             10          B
242539622             11          B
242539622             12          D
242539622             13          D
242539622             14          F 

我希望每个ID具有以下视图:

I'd like to have, per each id, the following view:

id        sequencenumber          appname    appname_c
242539622              1          A             A
242539622              2          A             A
242539622              3          A             A
242539622              4          B             B_1
242539622              5          B             B_1
242539622              6          C             C
242539622              7          D             D_1
242539622              8          D             D_1
242539622              9          D             D_1
242539622             10          B             B_2
242539622             11          B             B_2
242539622             12          D             D_2
242539622             13          D             D_2
242539622             14          F             F 

或者与此类似的任何事物，可以识别序列中给定事件的再次发生.

Or anything close to this, that can identify re-occurrence of a given event in the sequence.

我的最终目标是计算每组事件(或状态，如果您希望在Markov建模环境中使用)所花费的时间，并考虑是否存在任何环回.例如，可以将上面示例中在B_1中花费的时间与B_2进行比较.

My ultimate goal is to calculate time spent in each group of events (or state if you wish in the context of Markov modeling) taking into account if there is any loop-back. For example, time spent in B_1 in the above example can be very compared to B_2.

已经在Hive中搜索了窗口函数(链接)，但是我认为他们无法像R/Python那样进行逐行比较.

Have searched window functions in Hive (link) but I think they cannot to conduct row-wise comparisons like R/Python does.

推荐答案

使用Hive窗口函数的解决方案.我用您的数据对其进行了测试，删除了your_table CTE并使用了您的表.结果符合预期.

Solution using Hive window functions. I used your data to test it, remove your_table CTE and use your table instead. The result is as expected.

with your_table as (--remove this CTE, use your table instead
select stack(14,
'242539622', 1,'A',
'242539622', 2,'A',
'242539622', 3,'A',
'242539622', 4,'B',
'242539622', 5,'B',
'242539622', 6,'C',
'242539622', 7,'D',
'242539622', 8,'D',
'242539622', 9,'D',
'242539622',10,'B',
'242539622',11,'B',
'242539622',12,'D',
'242539622',13,'D',
'242539622',14,'F'
) as (id,sequencenumber,appname)
) --remove this CTE, use your table instead

select id,sequencenumber,appname, 
       case when sum(new_grp_flag) over(partition by id, group_name) = 1 then appname --only one group of consequent runs exists (like A)
            else        
            nvl(concat(group_name, '_', 
                       sum(new_grp_flag) over(partition by id, group_name order by sequencenumber) --rolling sum of new_group_flag
                       ),appname) 
        end appname_c       
from
(       

select id,sequencenumber,appname,
       case when appname=prev_appname or appname=next_appname then appname end group_name, --identify group of the same app
       case when appname<>prev_appname or prev_appname is null then 1 end new_grp_flag     --one 1 per each group
from       
(
select id,sequencenumber,appname,
       lag(appname)  over(partition by id order by sequencenumber) prev_appname, --need these columns
       lead(appname) over(partition by id order by sequencenumber) next_appname  --to identify groups of records w same app
from your_table --replace with your table
)s
)s
order by id,sequencenumber
;

结果:

OK
id        sequencenumber     appname    appname_c
242539622       1       A       A
242539622       2       A       A
242539622       3       A       A
242539622       4       B       B_1
242539622       5       B       B_1
242539622       6       C       C
242539622       7       D       D_1
242539622       8       D       D_1
242539622       9       D       D_1
242539622       10      B       B_2
242539622       11      B       B_2
242539622       12      D       D_2
242539622       13      D       D_2
242539622       14      F       F
Time taken: 232.319 seconds, Fetched: 14 row(s)

这篇关于如何识别Hive中字符串列的重复出现?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！