“TRUNCATE”处或附近的语法错误 - Aurora Postgres 10.12

Question

我正在尝试重构查询并删除一组窗口函数，以按原样捕获所有记录。当我去粘贴查询以替换我的函数时，pgAdmin 在“截断”语句附近指示语法错误。我只是无法弄清楚它是什么，并且可能是一些非常明显的东西，但我会欣赏另一（或许多）眼睛。

我在 Postgres 10.12 上。

这是我要插入的代码（最后包含了“之前”代码。任何建议将不胜感激。尝试了括号、逗号和分号闭包的所有类型和组合，并在斗智斗勇……

我正在尝试插入的代码

预期结果：从暂存中取出行并插入到目标中。完成后截断暂存

  WITH ins_agent AS (
     INSERT INTO agents (
        currentagentsnapshot,
        previousagentsnapshot,
        agentarn,
        eventid,
        eventtimestamp,
        eventtype,
        instancearn)
     SELECT 
        agent_stg.currentagentsnapshot::jsonb AS currentagentsnapshot,
        agent_stg.previousagentsnapshot::jsonb AS previousagentsnapshot,
        agent_stg.agentarn::text AS agentarn,
        agent_stg.eventid::text AS eventid,
        agent_stg.eventtimestamp::timestamptz AS eventtimestamp,
        agent_stg.eventtype::text AS eventtype,
        agent_stg.instancearn::text AS instancearn
    FROM agents_staging AS agent_stg
    WHERE agent_stg.agentarn IS NOT NULL)
    TRUNCATE agents_staging;

我正在尝试更改的代码

预期结果：选择不同的代理并捕获他们最近的快照。将 agent_id 插入另一个表。考虑 upserts。

更改原因：除了需要对数百万条记录进行查询之外，它几乎没有任何价值，因为它会丢弃所有代理快照，因为它们是不同的，除了它们的最新快照。不是我们想要的。

WITH ins_agent AS (INSERT INTO agents (currentagentsnapshot,
                                       previousagentsnapshot,
                                       agentarn,
                                       eventid,
                                       eventtimestamp,
                                       eventtype,
                                       instancearn)
    SELECT DISTINCT LAST_VALUE(currentagentsnapshot::jsonb)
                    OVER (PARTITION BY agentarn ORDER BY lat.eventtimestamp DESC ) AS previousagentsnapshot,
                    LAST_VALUE(previousagentsnapshot::jsonb)
                    OVER (PARTITION BY agentarn ORDER BY lat.eventtimestamp DESC ) AS previousagentsnapshot,
                    agentarn,
                    LAST_VALUE(eventid)
                    OVER (PARTITION BY agentarn ORDER BY lat.eventtimestamp DESC)  AS eventid,
                    LAST_VALUE(lat.eventtimestamp)
                    OVER (PARTITION BY agentarn ORDER BY lat.eventtimestamp DESC)  AS eventtimestamp,
                    LAST_VALUE(eventtype)
                    OVER (PARTITION BY agentarn ORDER BY lat.eventtimestamp DESC)  AS eventtype,
                    LAST_VALUE(instancearn)
                    OVER (PARTITION BY agentarn ORDER BY lat.eventtimestamp DESC)  AS instancearn
    FROM agents_staging AS agent
             CROSS JOIN LATERAL (SELECT agent.eventtimestamp::timestamp AS eventtimestamp) AS lat
    WHERE NOT (
            agent.agentarn IS NULL
            OR agent.currentagentsnapshot IS NULL
            OR agent.currentagentsnapshot = '{}')
    ON CONFLICT (agentarn)
        DO NOTHING
    RETURNING agentarn, agent_id)
UPDATE contact_trace_records
SET agent_id=ins_agent.agent_id
FROM ins_agent
WHERE contact_trace_records.agent_id IS NULL
  AND ins_agent.agentarn = contact_trace_records.agent ->> 'ARN';

TRUNCATE agents_staging;

Answer 1

语法错误是 CTE 不能附加到 TRUNCATE 命令。仅限 INSERT、UPDATE、DELETE 或 SELECT。 （嗯，技术上也是TABLE，但这只是SELECT * FROM 的简短语法。）

删除WITH 子句，并运行两个单独的命令。

INSERT INTO agents (
    currentagentsnapshot,
    previousagentsnapshot,
    agentarn,
    eventid,
    eventtimestamp,
    eventtype,
    instancearn)
SELECT 
    agent_stg.currentagentsnapshot::jsonb AS currentagentsnapshot,
    agent_stg.previousagentsnapshot::jsonb AS previousagentsnapshot,
    agent_stg.agentarn::text AS agentarn,
    agent_stg.eventid::text AS eventid,
    agent_stg.eventtimestamp::timestamptz AS eventtimestamp,
    agent_stg.eventtype::text AS eventtype,
    agent_stg.instancearn::text AS instancearn
FROM agents_staging AS agent_stg
WHERE agent_stg.agentarn IS NOT NULL;

TRUNCATE agents_staging;

如果您需要防御竞争条件，请将整个操作包装在一个事务中，并首先对表进行写锁定：

BEGIN;
LOCK TABLE agents_staging;
INSERT ...;
TRUNCATE agents_staging;
COMMIT;

除此之外：外部SELECT 中的表别名在INSERT 命令中什么都不做。这些充其量只是文档。但是由于所有列都已经有了最终的名称，所以这实际上只是噪音。

如果源列具有兼容的数据类型（隐式或赋值转换为目标类型，而不是显式转换），您可能也不需要表限定或显式转换。看起来两个表都具有相同的数据类型？然后您可以在很大程度上简化为：

INSERT INTO agents
      (currentagentsnapshot, previousagentsnapshot, agentarn, eventid, eventtimestamp, eventtype, instancearn)
SELECT currentagentsnapshot, previousagentsnapshot, agentarn, eventid, eventtimestamp, eventtype, instancearn
FROM   agents_staging
WHERE  agentarn IS NOT NULL;