Question

现在需要一个名为waypoints的表格，并按照功能正文进行操作。

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;

这会返回cannot DROP TABLE b_graph because it is being used by active queries in this session

如何解决此问题？

Answer 1

错误信息非常明显，您无法在使用临时表时删除它。

您可以通过添加ON COMMIT DROP：

来避免此问题

Temporary table and loops in a function

然而，这可能更简单。如果你不需要所有那些临时表（我怀疑），你可以用CTE替换它们（或者大多数可能用更便宜的子查询替换它们）并简化为一个大问题。可以是plpgsql，也可以只是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;

视图只是存储查询（＆＃34;食谱＆＃34;），而不是实际结果值（＆＃34;汤＆＃34;）。

使用CTE而不是创建临时表通常更便宜 查询中的派生表，按其典型整体性能排序（涉及索引的特殊情况的例外情况）。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，它只是追加行。更快，不会试图删除欺骗。

无法在Postgres函数中删除临时表：“在此会话中被活动查询使用”

1 个答案: