Bad query performance with more conditions? - Mailing list pgsql-general

From kaifeng.zhu
Subject Bad query performance with more conditions?
Date
Msg-id AANLkTimfZAklVjQ5bQMXjyFEY6EWE3SutaD1Qkww-lar@mail.gmail.com
Whole thread Raw
Responses Re: Bad query performance with more conditions?  (Thom Brown <thombrown@gmail.com>)
Re: Bad query performance with more conditions?  (Alban Hertroys <dalroi@solfertje.student.utwente.nl>)
List pgsql-general
Hi All,

I have a table named emails which created by following script:
create table emails (
    email_id bigserial primary key,
    email_msg_id char(36) not null,
    email_sender text not null)

The table has more than 10 million of records and I have already
created indexes on email_msg_id and email_sender

Following script finished very quickly (less than 1 seconds):
    select * from emails where email_msg_id =
'4dba381b-f55e-02d3-4b4a-95e2e98178e2' limit 1
But a similar script cost more than ten seconds:
    select * from emails where email_msg_id =
'4dba381b-f55e-02d3-4b4a-95e2e98178e2' and email_sender_text =
'sender@domain.com' limit 1

Both those scripts returns 0 rows of records indeed.

Any comment are highly appreciated.

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