Postgres SQL - performance issue with boolean field - sql

Question

In my table plin_korisnik, I have field active which is defined as boolean type.
I'm trying to execute this query to fetch data from that table and two other tables:
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
but query takes to much time (like forever; I interrupted it after half an hour), but when I remove pk.active = TRUE test from WHERE clause, then query executes with expected speed. I had try to cast boolean type to integer, but problem remains.
I'd appreciate it if someone could explain how to use a boolean field in this and similar queries. active field is not indexed, maybe it should be, please help.
EDIT:
After few hours of thinking I came out with this solution which use WITH clause:
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

I think you may make it faster if you change the order in the where clause, start with the initial table.
An index on pk.active and on po.datum will absolutely help.
You may want to consider putting the po.datum in the inner join, instead of the where.
po.datum>='2017-01-26'
AND po.datum<='2017-01-26'
AND pk.tip='p'
AND pk.active = TRUE
Will be:
pk.active = TRUE
AND pk.tip='p'
AND po.datum>='2017-01-26'
AND po.datum<='2017-01-26'