PostgreSQL更新查询问题 [英] Problems with a PostgreSQL upsert query

问题描述

我正在尝试通过将新记录更新或插入到 vote_user_table 中来更新数据库。该表的定义如下：

I'm trying to update the database by either updating or inserting a new record into the vote_user_table. The table is defined as follows:

  Column   |  Type   |                          Modifiers                           
-----------+---------+--------------------------------------------------------------
 id        | integer | not null default nextval('vote_user_table_id_seq'::regclass)
 review_id | integer | not null
 user_id   | integer | not null
 positive  | boolean | default false
 negative  | boolean | default false
Indexes:
    "vote_user_table_pkey" PRIMARY KEY, btree (id)

这是我正在使用的查询。我实际上对所有值都使用了参数，但出于测试目的，我将其替换为我确定应该可以使用的值。用户名 [e-mail] 存在。

Here's the query I'm using. I'm actually using parameters for all of the values, but for testing purposes I replaced them with values that I'm sure should work. The username [e-mail] exists.

WITH updated AS (
    UPDATE vote_user_table
    SET
        positive = 'true',
        negative = 'false'
    FROM usuario
    WHERE
        review_id = 6           AND
        user_id = usuario.id    AND
        usuario.username ILIKE '[e-mail]'
    RETURNING vote_user_table.id
)
INSERT INTO vote_user_table
    (review_id, user_id, positive, negative)
SELECT 6, usuario.id, 'true', 'false'
FROM usuario, updated
WHERE
    updated.id IS NULL AND
    usuario.username ILIKE '[e-mail]'

运行查询后得到的输出是：

The output I obtain after running the query is:

INSERT 0 0

尽管应该插入新值，因为该行在数据库上尚不存在。当我仅使用insert子句手动插入一行，然后执行上面显示的upsert查询时，它正确地更新了该行。

我使用的是PostgreSQL版本9.2.4。

Although it is supposed to insert the new value, because the row doesn't exist on the database yet. When I inserted a row manually, using only the insert clause, and then performed the upsert query shown above, it updated the row correctly.
I'm using PostgreSQL version 9.2.4.

我想到了从另一个问题编写此查询的想法：

插入PostgreSQL中的重复更新吗？

I got the idea of writing this query from this other question:
Insert, on duplicate update in PostgreSQL?

关于我可能做错什么的任何想法？

关于如何实现自己的目标的任何建议？

Any ideas on what could I be doing wrong?
Any suggestion on how can I achieve what I want to do?

为 vote_user_table创建语句：

CREATE TABLE vote_user_table (
    id integer NOT NULL,
    review_id integer NOT NULL,
    user_id integer NOT NULL,
    positive boolean DEFAULT false,
    negative boolean DEFAULT false
);

CREATE SEQUENCE vote_user_table_id_seq
    START WITH 1
    INCREMENT BY 1
    NO MINVALUE
    NO MAXVALUE
    CACHE 1;

ALTER SEQUENCE vote_user_table_id_seq OWNED BY vote_user_table.id;

推荐答案

UPDATE 已更新中的c $ c>产生无行。这意味着，对于 updated.id ，您也不会获得 NULL 值。加入已更新时，您什么都不会得到，因此也不会发生 INSERT 的情况。

The UPDATE in the first CTE updated produces no row. That means, you don't get a NULL value for updated.id either. When joining to updated, you get nothing, so no INSERT happens either.

应该与不存在一起工作：

WITH updated AS (
   UPDATE vote_user_table v
   SET    positive = TRUE       -- use booleann values ..
         ,negative = FALSE      -- .. instead of quoted string literals
   FROM   usuario u
   WHERE  v.review_id = 6       -- guessing origin
   AND    v.user_id = u.id
   AND    u.username ILIKE '[e-mail]'
   RETURNING v.id
   )
INSERT INTO vote_user_table (review_id, user_id, positive, negative)
SELECT 6, u.id, TRUE, FALSE
FROM   usuario u
WHERE NOT EXISTS (SELECT 1 FROM updated)
AND    u.username ILIKE '[e-mail]';

请注意，在繁重的并行负载下，竞争条件的可能性仍然很小。此相关问题下的详细信息：

通过事务进行更新

Be aware that there is still a very tiny chance for a race condition under heavy concurrent load. Details under this related question:
Upsert with a transaction

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