在红移中查找具有多个UUID标识符的唯一实体

Question

为每个用户创建一个包含多种UUID类型的事件表，我们希望能够将所有这些UUID拼接在一起，以获得单个用户的最高可能定义。

例如：

UUID1 | UUID2 
    1  a 
    1  a 
    2  a 
    2  b 
    3  c 
    4  c 

有2个用户在这里，第一个与UUID1 = {1,2}和UUID2 = {A，B}，第二个与UUID1 = {3,4- }和uuid2 = {c}。这些连锁店可能会很长。没有交集（即1c不存在），所有行都是时间戳排序的。

有没有办法在redshift中生成这些唯一的“访客”标识符而不用创建一个包含许多连接的庞大查询？

在此先感谢！

Answer 1

创建测试数据表

-- DROP TABLE uuid_test; 
CREATE TEMP TABLE uuid_test AS 
      SELECT 1 row_id, 1::int uuid1, 'a'::char(1) uuid2 
UNION ALL SELECT 2 row_id, 1::int uuid1, 'a'::char(1) uuid2 
UNION ALL SELECT 3 row_id, 2::int uuid1, 'a'::char(1) uuid2 
UNION ALL SELECT 4 row_id, 2::int uuid1, 'b'::char(1) uuid2 
UNION ALL SELECT 5 row_id, 3::int uuid1, 'c'::char(1) uuid2 
UNION ALL SELECT 6 row_id, 4::int uuid1, 'c'::char(1) uuid2 
UNION ALL SELECT 7 row_id, 4::int uuid1, 'd'::char(1) uuid2 
UNION ALL SELECT 8 row_id, 5::int uuid1, 'e'::char(1) uuid2 
UNION ALL SELECT 9 row_id, 6::int uuid1, 'e'::char(1) uuid2 
UNION ALL SELECT 10 row_id, 6::int uuid1, 'f'::char(1) uuid2 
UNION ALL SELECT 11 row_id, 7::int uuid1, 'f'::char(1) uuid2 
UNION ALL SELECT 12 row_id, 8::int uuid1, 'g'::char(1) uuid2 
UNION ALL SELECT 13 row_id, 8::int uuid1, 'h'::char(1) uuid2 
; 

的实际问题通过使用严格的排序，以找到每一个地方，独特的用户变化，捕捉，作为一个查找表，然后将其应用到原始数据解决。

-- Create lookup table with a from-to range of IDs for each unique user 
WITH unique_user AS (

-- Calculate the end of the id range using LEAD() to look ahead 
-- Use an inline MAX() to find the ending ID for the last entry 

SELECT row_id AS from_id 
    , NVL(LEAD(row_id,1) OVER (ORDER BY row_id)-1, (SELECT MAX(row_id) FROM uuid_test)) AS to_id 
    , unique_uuid 

-- Mark unique user change when there is discontinuity in either UUID 
FROM (SELECT row_id 
      ,CASE WHEN NVL(LAG(uuid1,1) OVER (ORDER BY row_id), 0) <> uuid1 
        AND NVL(LAG(uuid2,1) OVER (ORDER BY row_id), '') <> uuid2 
      THEN MD5(uuid1||uuid2) 
      ELSE NULL END unique_uuid 
     FROM uuid_test) t 
WHERE unique_uuid IS NOT NULL 
ORDER BY row_id 
) 

-- Apply the unique user value to each row using a range join to the lookup table 
SELECT a.row_id, a.uuid1, a.uuid2, b.unique_uuid 
FROM uuid_test AS a 
JOIN unique_user AS b 
    ON a.row_id BETWEEN b.from_id AND b.to_id 
ORDER BY a.row_id 
; 

下面是输出

row_id | uuid1 | uuid2 |   unique_uuid 
--------+-------+-------+---------------------------------- 
     1 |  1 | a  | efaa153b0f682ae5170a3184fa0df28c 
     2 |  1 | a  | efaa153b0f682ae5170a3184fa0df28c 
     3 |  2 | a  | efaa153b0f682ae5170a3184fa0df28c 
     4 |  2 | b  | efaa153b0f682ae5170a3184fa0df28c 
     5 |  3 | c  | 5fcfcb7df376059d0075cb892b2cc37f 
     6 |  4 | c  | 5fcfcb7df376059d0075cb892b2cc37f 
     7 |  4 | d  | 5fcfcb7df376059d0075cb892b2cc37f 
     8 |  5 | e  | 18a368e1052b5aa0388ef020dd9a1e20 
     9 |  6 | e  | 18a368e1052b5aa0388ef020dd9a1e20 
    10 |  6 | f  | 18a368e1052b5aa0388ef020dd9a1e20 
    11 |  7 | f  | 18a368e1052b5aa0388ef020dd9a1e20 
    12 |  8 | g  | 321fcc2447163a81d470b9353e394121 
    13 |  8 | h  | 321fcc2447163a81d470b9353e394121