Re: Adding nextval() to a select caused hang/very slow execution

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Subject: Re: Adding nextval() to a select caused hang/very slow execution
From: Tom Lane <tgl@xxxxxxxxxxxxx>
Date: Wed, 04 Nov 2020 14:35:44 -0500
Cc: pgsql-performance@xxxxxxxxxxxxxxxxxxxx
Comments: In-reply-to Eric Raskin <eraskin@xxxxxxxxxxxx> message dated "Wed, 04 Nov 2020 14:25:00 -0500"
In-reply-to: <CAF9L-R5Ff5ouhKCzrk6sjF=JCQBzDmkxBpedci3J3HC-jAvinQ@mail.gmail.com>
References: <CAF9L-R7G_ge=v21mnfH=sbfCt9LF7LhaDbUzqso+LsFhgeKbyQ@mail.gmail.com> <1234726.1604513058@sss.pgh.pa.us> <CAF9L-R4oiksGgY8AWVfpYqCnMpyPDPk8-Sct05buKmkbVM03_w@mail.gmail.com> <CAF9L-R4ve0h0xHO9S6EHX7tK6wpZPuy44d1O8=SqqyCxHW7z2A@mail.gmail.com> <1237035.1604516511@sss.pgh.pa.us> <CAF9L-R42+L101Pg63bUFFtXWzRqGcHLkL6DFibfqUprNccTEZw@mail.gmail.com> <1237916.1604517808@sss.pgh.pa.us> <CAF9L-R5Ff5ouhKCzrk6sjF=JCQBzDmkxBpedci3J3HC-jAvinQ@mail.gmail.com>

... btw, it occurs to me that at least as a stopgap,
"set enable_nestloop = off" would be worth trying.
The killer problem with rowcount-1 estimates is that they
encourage the planner to use nestloops when it shouldn't.

			regards, tom lane

References:
- Adding nextval() to a select caused hang/very slow execution
  - From: Eric Raskin
- Re: Adding nextval() to a select caused hang/very slow execution
  - From: Tom Lane
- Re: Adding nextval() to a select caused hang/very slow execution
  - From: Eric Raskin
- Re: Adding nextval() to a select caused hang/very slow execution
  - From: Eric Raskin
- Re: Adding nextval() to a select caused hang/very slow execution
  - From: Tom Lane
- Re: Adding nextval() to a select caused hang/very slow execution
  - From: Eric Raskin
- Re: Adding nextval() to a select caused hang/very slow execution
  - From: Tom Lane
- Re: Adding nextval() to a select caused hang/very slow execution
  - From: Eric Raskin

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