CODEWITHSUNDEEP
sqlpostgresql
sergzach
sergzach

Reputation: 6754

Sequence ALTER RESTART does not affect on the current value of a sequence

Why the next ALTER does not define currval of the sequence comments_comment_id_seq?

db=# alter sequence comments_comment_id_seq restart with 65545;
ALTER SEQUENCE
db=# SELECT currval('comments_comment_id_seq');
ERROR:  currval of sequence "comments_comment_id_seq" is not yet defined in this session
db=#

Additional detail

The table which owns the sequence is a child of another table:

   Column   |            Type             |                             Modifiers              
------------+-----------------------------+--------------------------------------------------------------------
 comment_id | bigint                      | not null default nextval('comments_base_comment_id_seq'::regclass)
 auser_id   | bigint                      | not null
 dt         | timestamp without time zone | not null
 text       | text                        | not null
 is_deleted | smallint                    | default 0
 parent     | bigint                      | default 0
 post_id    | bigint                      | not null
Indexes:
    "comments_pkey" PRIMARY KEY, btree (comment_id)
Inherits: comments_base

Upvotes: 2

Views: 380

Answers (1)

Uwe Allner
Uwe Allner

Reputation: 3467

When you restart the sequence you set it into a state like it was just created. And in this case you don't have a currval before you first selected a nextval.

Upvotes: 3

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