Question

在我的表 plin_korisnik 中，我有字段活动，它被定义为布尔类型。

我正在尝试执行此查询以从该表和另外两个表中获取数据：

SELECT
    pk.omm AS omm,
    pk.br_plin AS br_plin,
    pk.naziv AS naziv,
    pk.ulica||' '||pk.kbr AS adresa,
    pk.pu||' - '||pk.naziv_pu AS mjesto,
    po.datum AS datum,
    CASE WHEN po.stanje >= 999999 THEN NULL ELSE po.stanje END AS stanje,
    po.napomena AS napomena,
    po.plin_postar AS laus,
    pp.ime||' '||pp.prezime AS postar
FROM plin_korisnik pk
INNER JOIN
    plin_ocitanje po ON pk.omm = po.omm
INNER JOIN plin_postar pp ON pp.laus = po.plin_postar
WHERE po.datum>='2017-01-26'
    AND po.datum<='2017-01-26'
    AND pk.tip='p'
    AND pk.active = TRUE
ORDER BY po.datum, pk.naziv

但是查询需要很长时间（就像永远;我在半小时后中断了它），但是当我从WHERE子句中删除 pk.active = TRUE 测试时，查询以预期的速度执行。我曾尝试将布尔类型转换为整数，但问题仍然存在。

如果有人能解释如何在此查询和类似查询中使用布尔字段，我将不胜感激。有效字段未编入索引，也许应该是，请帮助。

编辑：经过几个小时的思考后，我推出了使用WITH子句的解决方案：

WITH pk AS (
    SELECT * FROM plin_korisnik WHERE active AND tip='p' 
)
SELECT
   pk.omm AS omm,
   pk.br_plin AS br_plin,
   pk.naziv AS naziv,
   pk.ulica||' '||pk.kbr AS adresa,
   pk.pu||' - '||pk.naziv_pu AS mjesto,
   po.datum AS datum,
   CASE WHEN po.stanje >= 999999 THEN NULL ELSE po.stanje END AS stanje,
   po.napomena AS napomena,
   po.plin_postar AS laus,
   pp.ime||' '||pp.prezime AS postar
FROM pk
INNER JOIN
   plin_ocitanje po ON pk.omm = po.omm
INNER JOIN plin_postar pp ON pp.laus = po.plin_postar
WHERE po.datum>='2017-01-26'
   AND po.datum<='2017-01-26'
ORDER BY po.datum, pk.naziv;

Answer 1

我认为如果你改变where子句中的顺序，从初始表开始，你可以加快速度。关于pk.active和po.datum的索引绝对会有所帮助。您可能需要考虑将po.datum放在内连接中，而不是放在哪里。

po.datum>='2017-01-26'
AND po.datum<='2017-01-26'
AND pk.tip='p'
AND pk.active = TRUE

将是：

pk.active = TRUE
AND pk.tip='p'
AND po.datum>='2017-01-26'
AND po.datum<='2017-01-26'

Postgres SQL - 布尔字段的性能问题

1 个答案: