Question

过了一段时间后，我想到了非常快速的一次通过合并声明来历史缓慢变化的维度类型2.

它在没有唯一约束的表上完美运行。

大多数情况下它也适用于具有唯一约束的表。但有时（通常当历史记录的变化较大时）我得到错误ORA-00001，唯一约束违规。当然，我知道有两种方法可行，但速度较慢。

我唯一的猜测是Oracle有时会在UPDATE之前执行INSERT，它会暂时复制TH_Valid_To_Date。

任何想法如何避免它（在保持主键的同时）？

来源表：

public Items(IEnumerable<Item> items) {
    _items = items.ToList();
}

历史表：

CREATE TABLE TESTS 
  (
     T_Key_1                        NUMBER(38,0)    DEFAULT -1 NOT NULL ENABLE /*  */
    ,T_Key_2                        NUMBER(38,0)    DEFAULT -1 NOT NULL ENABLE /*  */
    ,Text_Value                     VARCHAR2(100)    /*  */
    ,Number_Value                   NUMBER(38,0)    DEFAULT -1 NOT NULL ENABLE /*  */
    ,Amount                         NUMBER           /*  */

    ,CONSTRAINT T_PK PRIMARY KEY (T_Key_1, T_Key_2)  /* Primární klíč */    
  )
;

合并：

CREATE TABLE TEST_HISTORY 
  (
     T_Key_1                        NUMBER(38,0)    DEFAULT -1 NOT NULL
    ,T_Key_2                        NUMBER(38,0)    DEFAULT -1 NOT NULL
    ,Text_Value                     VARCHAR2(100)    
    ,Number_Value                   NUMBER(38,0)    DEFAULT -1 NOT NULL
    ,Amount                         NUMBER          
    ,TH_Valid_From_Date             DATE            DEFAULT to_date('1000-01-01','yyyy-mm-dd') NOT NULL /* SCD2 - Start of validity of record. */
    ,TH_Valid_To_Date               DATE            DEFAULT to_date('3000-01-01','yyyy-mm-dd') NOT NULL /* SCD2 - End of validity of record. */

    ,CONSTRAINT TH_PK PRIMARY KEY (T_Key_1, T_Key_2, TH_Valid_To_Date) using index local 
  )
/** Physical Options **************************************************************************************************/
partition by range (TH_Valid_To_Date) interval (NUMTOYMINTERVAL (1, 'MONTH'))
(partition P_10000000 values less than (TO_DATE ('01-01-1000', 'DD-MM-YYYY')))
ENABLE ROW MOVEMENT 
;

Answer 1

我自己遇到了同样的问题：你不能同时插入和更新记录。 Oracle确定在首次执行连接时是插入还是更新记录。这是一个简化的测试用例，说明了这一点：

-- This is the table into which we will be merging data

CREATE TABLE merge_table
(
    mt_col1   INTEGER NOT NULL
  , mt_col2   INTEGER
);

-- Make mt_col1 unique
ALTER TABLE merge_table ADD (
  UNIQUE (mt_col1)
  USING INDEX);

-- This is the table from which we will be drawing the data

CREATE TABLE datasource_table
(
    ds_col1   INTEGER
  , ds_col2   INTEGER
);

-- Load up the data source with 10 rows (1-10)

INSERT INTO datasource_table (
           ds_col1, ds_col2
            )
    SELECT ROWNUM r, ROWNUM r
      FROM all_objects
     WHERE ROWNUM < 11;

-- Create a duplicate record

INSERT INTO datasource_table (
           ds_col1, ds_col2
            )
     VALUES (1, 1);

-- Create a record to be updated

INSERT INTO merge_table (
           mt_col1, mt_col2
            )
     VALUES (2, 2);

COMMIT;

-- This merge will fail with a unique constraint violation because
-- an mt_col1 value of 1 does not exist. The datasource table contains
-- two entries for 1, so the merge will try to insert two mt_col1=1 records,
-- violating the unique constraint.

MERGE INTO merge_table dt
     USING (SELECT ds_col1, ds_col2
              FROM datasource_table) a
        ON (a.ds_col1 = dt.mt_col1)
WHEN MATCHED
THEN
    UPDATE SET mt_col2   = a.ds_col2 + 10
WHEN NOT MATCHED
THEN
    INSERT     (
               mt_col1, mt_col2
               )
        VALUES (ds_col1, ds_col2);

-- ORA-00001: unique constraint (SYS_C0013990) violated

-- Delete one of the duplicate records and the merge succeeds

DELETE FROM datasource_table
      WHERE ds_col1 = 1
        AND ROWNUM < 2;

-- Merge is now successful

MERGE INTO merge_table dt
     USING (SELECT ds_col1, ds_col2
              FROM datasource_table) a
        ON (a.ds_col1 = dt.mt_col1)
WHEN MATCHED
THEN
    UPDATE SET mt_col2   = a.ds_col2 + 10
WHEN NOT MATCHED
THEN
    INSERT     (
               mt_col1, mt_col2
               )
        VALUES (ds_col1, ds_col2);

-- 10 rows updated

SCD2一次通过合并违反了Oracle 12中的主键

1 个答案: