Re: Maybe a bug found with nextval() function

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Alexander Troppmann <talex(at)cocktaildreams(dot)de>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: Maybe a bug found with nextval() function
Date: 2004-02-20 20:37:39
Message-ID: 200402202037.i1KKbdi24175@candle.pha.pa.us
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Look at this:

test=> CREATE SEQUENCE x;
CREATE SEQUENCE
test=> \d x
Sequence "public.x"
Column | Type
---------------+---------
sequence_name | name
last_value | bigint
increment_by | bigint
max_value | bigint
min_value | bigint
cache_value | bigint
log_cnt | bigint
is_cycled | boolean
is_called | boolean

test=> SELECT * FROM x;
sequence_name | last_value | increment_by | max_value |
min_value | cache_value | log_cnt | is_cycled | is_called
---------------+------------+--------------+---------------------+-----------+-------------+---------+-----------+-----------

x | 1 | 1 | 9223372036854775807 |
1 | 1 | 1 | f | f
(1 row)

I suspect you have a very high increment_by value for the sequence:

CREATE [ TEMPORARY | TEMP ] SEQUENCE name [ INCREMENT [ BY ] increment ]
[ MINVALUE minvalue | NO MINVALUE ] [ MAXVALUE maxvalue | NO MAXVALUE ]
[ START [ WITH ] start ] [ CACHE cache ] [ [ NO ] CYCLE ]

I wish we had a better way to show sequence information. \ds+ doesn't
see to show much detail. I have added a TODO:

* Have psql show more information about sequences

---------------------------------------------------------------------------

Alexander Troppmann wrote:
> ============================================================================
> POSTGRESQL BUG REPORT TEMPLATE
> ============================================================================
>
> Your name : Alexander Troppmann
> Your email address : talex(at)cocktaildreams(dot)de
>
>
> System Configuration
> --------------------
> Architecture : AMD Duron
> Operating System : Fedora Core 1.A (Linux 2.4.22-1.2174.nptl)
> PostgreSQL version : PostgreSQL-7.3.4
> Compiler used : gcc-3.3.2
>
>
> Please enter a FULL description of your problem:
> ------------------------------------------------
>
>
> The nextval() function returns instead of the next valid integer value in the
> corresponding SEQUENCE a whole range of exactly 435 values with each function
> call... The sequence and tables have been migrated from a previous PostgreSQL
> version - newer created tables and sequences work fine!
>
>
>
>
> Please describe a way to repeat the problem. Please try to provide a
> concise reproducible example, if at all possible:
> ----------------------------------------------------------------------
>
>
> My database has been migrated from previous versions of PostgreSQL. One table
> is called "recipe" and has a column "id" of type SERIAL as primary key:
>
> Column | Type | Modifiers
> ---------+-----------+----------------------------------------------------
> id | integer | not null default nextval('"recipe_id_seq"'::text)
>
> I din't use the features from a SERIAL type on this table before but at the
> moment I'm working on a complete new database frontend.... So first I tried
> to update the value of the "recipe_id_seq" SEQUENCE appropriate to the
> latest recipe.id value:
>
> SELECT SETVAL('recipe_id_seq', max(id)) FROM recipe;
>
> returns the following output:
>
> setval
> --------
> 455
> (1 row)
>
> Now I tried to fetch the next free primary key id for my "recipe" table:
>
> SELECT NEXTVAL('recipe_id_seq') FROM receipt;
>
> I just wonder because the NEXTVAL query returns after every call exactly
> 435 rows of increasing integer values...?! Also I tested some other tables
> with a SERIAL primary key and the same result - instead of the next valid
> integer value I get a whole range of values, 435 times...
>
> A table created with a PostgreSQL 7.3.x version works fine - the SEQUENCE
> returns exactly (the next valid) integer value - so maybe the migrated table
> structures/data from my previous PostgreSQL installations cause the troubles?
>
> I already tried to fix the problem by dropping the "recipe_id_seq" and
> creating a new one - with any success... :-(
>
>
>
> best regards,
> Alex Troppmann
>
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 8: explain analyze is your friend
>

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073

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