我有一个表 upload_temp 如下:
CREATE TABLE upload_temp (
codigo serial PRIMARY KEY NOT NULL,
codigo_upload_temp_pai INTEGER,
nome TEXT NOT NULL,
codigo_extensao INTEGER,
data_inclusao TIMESTAMP NOT NULL DEFAULT NOW(),
codigo_usuario_inclusao INTEGER NOT NULL,
CONSTRAINT fk_upload_upload_pai FOREIGN KEY (codigo_upload_temp_pai) REFERENCES upload_temp (codigo) MATCH SIMPLE ON UPDATE CASCADE ON DELETE CASCADE,
CONSTRAINT fk_extensao_upload FOREIGN KEY (codigo_extensao) REFERENCES extensao (codigo) MATCH SIMPLE ON UPDATE CASCADE ON DELETE NO ACTION,
CONSTRAINT fk_usuario_upload FOREIGN KEY (codigo_usuario_inclusao) REFERENCES usuario (chave) MATCH SIMPLE ON UPDATE CASCADE ON DELETE CASCADE,
CONSTRAINT uq_upload UNIQUE('nome', COALESCE('codigo_extensao', -1), COALESCE('codigo_upload_temp_pai', -1), 'codigo_usuario_inclusao', DATE(data_inclusao))
);
这个表存储了我系统所有的临时上传,这些上传可以是文件夹和文件。表上的自引用功能可以解决这个问题。但问题是:当某些文件注册到系统时,它变成了官方数字文件并且 upload_temp 被删除。删除时,只有当它变成空文件夹时,才必须删除它的父文件夹。通过这种方式,我需要从这棵树中删除所有文件夹,只要它们因失去唯一的 child 而变空。下图包含更多细节:
文件5.jpg属于文件夹5,属于文件夹4,依此类推。如果我选择文件5.jpg注册到系统,它会从upload_temp中删除,这会清空文件夹5。因此,文件夹 5 为空,因此也必须删除,在这种情况下,所有父文件夹也会发生同样的情况。
虽然我使用的是 PHP,但我需要一个针对性能的 PostgreSQL 解决方案。我试图了解 WITH RECURSIVE
的工作原理,但我遇到了困难。我编写了以下代码,应该从文件 5.jpg 开始递归删除所有父项,忽略空特征:
WITH RECURSIVE all_uploads (codigo, parent, ext, main) AS (
SELECT ut1.codigo, ut1.codigo_upload_temp_pai AS parent, ut1.codigo_extensao AS ext, ut1.codigo AS main
FROM upload_temp ut1
UNION ALL
SELECT ut2.codigo, ut2.codigo_upload_temp_pai AS parent, ut2.codigo_extensao AS ext, au.main
FROM upload_temp ut2
JOIN all_uploads au ON au.parent = ut2.codigo
)
DELETE FROM upload_temp WHERE codigo IN (SELECT codigo FROM all_uploads WHERE codigo = 486);
下图显示了 SELECT * FROM upload_temp ORDER BY codigo
的结果:
嗯,它不工作。它只是删除一个文件。我能做些什么来解决这个问题?谢谢!
最佳答案
WITH RECURSIVE all_uploads (codigo, parent, ext, main) AS (
SELECT ut1.codigo, ut1.codigo_upload_temp_pai AS parent,
ut1.codigo_extensao AS ext, ut1.codigo AS main
FROM upload_temp ut1
WHERE ut1.codigo = 486
UNION ALL
SELECT ut2.codigo, ut2.codigo_upload_temp_pai AS parent,
ut2.codigo_extensao AS ext, au.main
FROM upload_temp ut2
JOIN all_uploads au ON au.parent = ut2.codigo
)
DELETE FROM upload_temp WHERE codigo IN (SELECT codigo FROM all_uploads);
您必须将起点放在初始选择中(在 with 内),或者您必须以某种方式制作一个代表“树”顶部的伪列,这对于整棵树中的每一行都是相同的。将初始选择中的“顶部位置”放在 with 内是更简单的解决方案。
关于php - 删除递归 PostgreSQL,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/41363443/