无法在 Postgres 函数中删除温度 table："being used by active queries in this session"

Question

现在预计将接收一个名为 waypoints 的 table 并跟随函数体。

drop function if exists everything(waypoints);
create function everything(waypoints) RETURNS TABLE(node int, xy text[]) as $$
BEGIN
    drop table if exists bbox;
    create temporary table bbox(...);
    insert into bbox
        select ... from waypoints;

    drop table if exists b_spaces;
    create temporary table b_spaces(
        ...
    );
    insert into b_spaces
        select ...

    drop table if exists b_graph; -- Line the error flags.
    create temporary table b_graph(
       ...
    );
    insert into b_graph
        select ...

    drop table if exists local_green;
    create temporary table local_green(
        ...
    );
    insert into local_green 
        ...

    with aug_temp as (
        select ...
    )
    insert into b_graph(source, target, cost) (
        (select ... from aug_temp) 
        UNION 
        (select ... from aug_temp)
    );

    return query
        with 
        results as (
            select id1, ... from b_graph -- The relation being complained about.
        ),
        pkg as (
            select loc, ...
        )
        select id1, array_agg(loc) 
        from pkg
        group by id1;
    return;
END;
$$ LANGUAGE plpgsql;

这个returnscannot DROP TABLE b_graph because it is being used by active queries in this session

我该如何解决这个问题？

Answer 1

错误信息很明显，你不能删除正在使用的临时文件table。

您可以通过添加 ON COMMIT DROP:

来避免该问题

Temporary table and loops in a function

但是，这可能更简单。如果您 不需要 所有这些温度 table 开始（我怀疑），您可以将它们全部替换为 CTE（或者其中大部分可能甚至更便宜子查询）并简化为一个大查询。可以是 plpgsql 或只是 SQL:

CREATE FUNCTION everything(waypoints)
  RETURNS TABLE(node int, xy text[]) AS
$func$
   WITH bbox      AS (SELECT ... FROM waypoints)  -- not the fct. parameter!
    , b_spaces    AS (SELECT ... )
    , b_graph     AS (SELECT ... )
    , local_green AS (SELECT ... )
    , aug_temp    AS (SELECT ... )
    , b_graph2(source, target, cost) AS (
        SELECT ... FROM b_graph
        UNION ALL  -- guessing you really want UNION ALL
        SELECT ... FROM aug_temp
        UNION ALL 
        SELECT ... FROM aug_temp
       )
    , results     AS (SELECT id1, ... FROM b_graph2)
    , pkg         AS (SELECT loc, ... )
   SELECT id1, array_agg(loc) 
   FROM   pkg
   GROUP  BY id1
$func$ LANGUAGE sql;

视图仅存储查询 ("the recipe")，而不是实际结果值 ("the soup")。

通常使用 CTE 比创建临时 tables 更便宜。
在查询 中派生了 table，按它们的典型整体性能排序（涉及索引的特殊情况除外）。从慢到快：

CREATE TABLE
CREATE UNLOGGED TABLE
CREATE TEMP TABLE
CTE
subquery

UNION 会尝试折叠重复的行。通常，人们真的想要 UNION ALL，它只是附加行。更快，并且不会尝试删除重复项。

无法在 Postgres 函数中删除温度 table："being used by active queries in this session"

Can't drop temp table in Postgres function: "being used by active queries in this session"

postgresql

plpgsql

common-table-expression