使用COPY ON CONFLICT覆蓋匯入資料 -

AnalyticDB PostgreSQL版支援COPY ON CONFLICT覆蓋匯入資料。目前COPY ON CONFLICT僅支援全資料表條件約束檢查及全列覆蓋寫入。

在AnalyticDB PostgreSQL版中，您可以通過COPY快速匯入資料，但是在COPY匯入資料的過程中，如果資料與表的約束衝突，COPY任務會報錯並終止。AnalyticDB PostgreSQL提供了COPY ON CONFLICT功能，支援在約束衝突時進行覆蓋寫入或忽略寫入，避免COPY任務因為約束衝突而失敗。

說明

僅核心編譯日期為20210528及以後的AnalyticDB PostgreSQL 6.0版執行個體支援COPY ON CONFLICT功能。為了更好地使用該功能，建議您升級至最新的核心版本，升級核心小版本，請參見版本升級。

使用約束

目標表需為堆表，不支援AO表（AO表不支援唯一索引，所以不支援AO表）。
僅V6.3.6.1及以上核心版本支援目標表為分區表。如何升級核心版本，請參見版本升級。
目標表不支援Updatable View（可更新視圖）。
COPY ON CONFLICT僅支援COPY FROM，不支援COPY TO。
不支援指定約束索引列，COPY ON CONFLICT預設判斷所有約束列。若指定約束索引列，則COPY執行失敗，報錯資訊如下：
```
COPY NATION FROM stdin DO ON CONFLICT(n_nationkey) DO UPDATE;
ERROR:  COPY ON CONFLICT does NOT support CONFLICT index params
```

不支援指定更新列，COPY ON CONFLICT預設更新所有列。若指定更新列，則COPY執行失敗，報錯資訊如下：

COPY NATION FROM stdin DO ON CONFLICT DO UPDATE SET n_nationkey = excluded.n_nationkey;
ERROR:  COPY ON CONFLICT does NOT support UPDATE SET targets

文法

COPY table [(column [, ...])] FROM {'file' | STDIN}
     [ [WITH] 
       [BINARY]
       [OIDS]
       [HEADER]
       [DELIMITER [ AS ] 'delimiter']
       [NULL [ AS ] 'null string']
       [ESCAPE [ AS ] 'escape' | 'OFF']
       [NEWLINE [ AS ] 'LF' | 'CR' | 'CRLF']
       [CSV [QUOTE [ AS ] 'quote'] 
            [FORCE NOT NULL column [, ...]]
       [FILL MISSING FIELDS]
       [[LOG ERRORS]  
       SEGMENT REJECT LIMIT count [ROWS | PERCENT] ]
    [DO ON CONFLICT DO UPDATE | NOTHING]

COPY ON CONFLICT提供了DO ON CONFLICT DO UPDATE和DO ON CONFLICT DO NOTHING兩個子句：

DO ON CONFLICT DO UPDATE表示資料表條件約束衝突時全列更新。
DO ON CONFLICT DO NOTHING表示資料表條件約束衝突時忽略輸入內容。

樣本

建立一個表NATION，表中包含4列，其中N_NATIONKEY為主鍵列，具有主鍵約束，建表語句如下：

CREATE TABLE NATION (
    N_NATIONKEY  INTEGER,
    N_NAME       CHAR(25),
    N_REGIONKEY  INTEGER,
    N_COMMENT    VARCHAR(152),
    PRIMARY KEY (N_NATIONKEY)
);

通過COPY匯入部分資料，COPY語句如下：

COPY NATION FROM stdin;

出現>>標誌後逐條輸入如下內容：

0 'ALGERIA' 0 'haggle. carefully final deposits detect slyly agai'
1 'ARGENTINA' 1 'al foxes promise slyly according to the regular accounts. bold requests alon'
2 'BRAZIL' 1 'y alongside of the pending deposits. carefully special packages are about the ironic forges. slyly speci'
3 'CANADA' 1 'eas hang ironic, silent packages. slyly regular packages are furiously over the tithes. fluffily bold'
\.

說明

複製以上資料時，請將兩列值之間的空格替換為Tab。

查詢NATION表，查看已經匯入的資料，查詢語句如下：

SELECT * from NATION;

返回資訊如下：

 n_nationkey |          n_name           | n_regionkey |                                                 n_comment                                                
  
-------------+---------------------------+-------------+------------------------------------------------------------------------------------------------------------
           2 | 'BRAZIL'                  |           1 | 'y alongside of the pending deposits. carefully special packages are about the ironic forges. slyly speci'
           3 | 'CANADA'                  |           1 | 'eas hang ironic, silent packages. slyly regular packages are furiously over the tithes. fluffily bold'
           0 | 'ALGERIA'                 |           0 | ' haggle. carefully final deposits detect slyly agai'
           1 | 'ARGENTINA'               |           1 | 'al foxes promise slyly according to the regular accounts. bold requests alon'
(4 rows)

使用COPY語句匯入一行主鍵衝突的資料，COPY語句如下：

COPY NATION FROM stdin;

出現>>標誌後逐條輸入如下內容：

0 'GERMANY' 3 'l platelets. regular accounts x-ray: unusual, regular acco'
\.

說明

複製以上資料時，請將兩列值之間的空格替換為Tab。

此時執行會產生報錯，報錯內容如下：

ERROR:  duplicate key value violates unique constraint "nation_pkey"
DETAIL:  Key (n_nationkey)=(0) already exists.
CONTEXT:  COPY nation, line 1

使用COPY ON CONFLICT語句，在主鍵衝突的情況下更新資料，COPY ON CONFLICT語句如下：

COPY NATION FROM stdin DO  ON CONFLICT DO UPDATE;

出現>>標誌後逐條輸入如下內容：

0 'GERMANY' 3 'l platelets. regular accounts x-ray: unusual, regular acco'
\.

說明

複製以上資料時，請將兩列值之間的空格替換為Tab。

此時COPY語句不會產生報錯資訊，查詢NATION表可以看到主鍵為0的行資料已更新，查詢語句如下：

SELECT * FROM NATION;

返回資訊如下：

 n_nationkey |          n_name           | n_regionkey |                                                 n_comment                                                
  
-------------+---------------------------+-------------+------------------------------------------------------------------------------------------------------------
           2 | 'BRAZIL'                  |           1 | 'y alongside of the pending deposits. carefully special packages are about the ironic forges. slyly speci'
           3 | 'CANADA'                  |           1 | 'eas hang ironic, silent packages. slyly regular packages are furiously over the tithes. fluffily bold'
           1 | 'ARGENTINA'               |           1 | 'al foxes promise slyly according to the regular accounts. bold requests alon'
           0 | 'GERMANY'                 |           3 | 'l platelets. regular accounts x-ray: unusual, regular acco'
(4 rows)

使用COPY ON CONFLICT功能，在主鍵衝突的情況下，忽略輸入：

COPY NATION FROM stdin DO ON CONFLICT DO NOTHING;

出現>>標誌後逐條輸入如下內容：

1 'GERMANY' 3 'l platelets. regular accounts x-ray: unusual, regular acco'
\.

說明

複製以上資料時，請將兩列值之間的空格替換為Tab。

此時COPY語句不會產生報錯資訊，查詢NATION表可以看到主鍵為1的行資料沒有更新，查詢語句如下：

SELECT * FROM NATION;

返回資訊如下：

 n_nationkey |          n_name           | n_regionkey |                                                 n_comment                                                
  
-------------+---------------------------+-------------+------------------------------------------------------------------------------------------------------------
           2 | 'BRAZIL'                  |           1 | 'y alongside of the pending deposits. carefully special packages are about the ironic forges. slyly speci'
           3 | 'CANADA'                  |           1 | 'eas hang ironic, silent packages. slyly regular packages are furiously over the tithes. fluffily bold'
           1 | 'ARGENTINA'               |           1 | 'al foxes promise slyly according to the regular accounts. bold requests alon'
           0 | 'GERMANY'                 |           3 | 'l platelets. regular accounts x-ray: unusual, regular acco'
(4 rows)