index not used with inherited tables - Mailing list pgsql-novice

From Verena Ruff
Subject index not used with inherited tables
Date
Msg-id 4461E4D4.30708@triosolutions.at
Whole thread Raw
Responses Re: index not used with inherited tables
List pgsql-novice
Hi,

there is a table person, which has some child tables. the definition
(part of):

CREATE TABLE person
(
  pers_id serial NOT NULL,
  -- some other fields --
  CONSTRAINT person_pk PRIMARY KEY (pers_id)
)

one of these child tables is mitarbeiter:
CREATE TABLE mitarbeiter
(
  -- some fields --
  CONSTRAINT pers_id_pk_mitarbeiter PRIMARY KEY (pers_id)
) INHERITS (person)

as you see the inherited column pers_id is used as primary key in the
child table as well. if I do
EXPLAIN SELECT * FROM mitarbeiter WHERE pers_id=7; I see that PostgreSQL
does a seq scan on mitarbeiter instead of an index scan. There are some
other child tables and it seems like in some cases the index is used, in
others not, but I have no idea why.

Any hints?

Regards,
Verena

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