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><H1
><A
NAME="SQL-ALTERSEQUENCE"
></A
>ALTER SEQUENCE</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN64575"
></A
><H2
>Name</H2
>ALTER SEQUENCE -- change the definition of a sequence generator
</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN64580"
></A
><H2
>Synopsis</H2
><PRE
CLASS="SYNOPSIS"
>ALTER SEQUENCE [ IF EXISTS ] <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> [ INCREMENT [ BY ] <TT
CLASS="REPLACEABLE"
><I
>increment</I
></TT
> ]
[ MINVALUE <TT
CLASS="REPLACEABLE"
><I
>minvalue</I
></TT
> | NO MINVALUE ] [ MAXVALUE <TT
CLASS="REPLACEABLE"
><I
>maxvalue</I
></TT
> | NO MAXVALUE ]
[ START [ WITH ] <TT
CLASS="REPLACEABLE"
><I
>start</I
></TT
> ]
[ RESTART [ [ WITH ] <TT
CLASS="REPLACEABLE"
><I
>restart</I
></TT
> ] ]
[ CACHE <TT
CLASS="REPLACEABLE"
><I
>cache</I
></TT
> ] [ [ NO ] CYCLE ]
[ OWNED BY { <TT
CLASS="REPLACEABLE"
><I
>table_name</I
></TT
>.<TT
CLASS="REPLACEABLE"
><I
>column_name</I
></TT
> | NONE } ]
ALTER SEQUENCE [ IF EXISTS ] <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> OWNER TO <TT
CLASS="REPLACEABLE"
><I
>new_owner</I
></TT
>
ALTER SEQUENCE [ IF EXISTS ] <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> RENAME TO <TT
CLASS="REPLACEABLE"
><I
>new_name</I
></TT
>
ALTER SEQUENCE [ IF EXISTS ] <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> SET SCHEMA <TT
CLASS="REPLACEABLE"
><I
>new_schema</I
></TT
></PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN64597"
></A
><H2
>Description</H2
><P
> <TT
CLASS="COMMAND"
>ALTER SEQUENCE</TT
> changes the parameters of an existing
sequence generator. Any parameters not specifically set in the
<TT
CLASS="COMMAND"
>ALTER SEQUENCE</TT
> command retain their prior settings.
</P
><P
> You must own the sequence to use <TT
CLASS="COMMAND"
>ALTER SEQUENCE</TT
>.
To change a sequence's schema, you must also have <TT
CLASS="LITERAL"
>CREATE</TT
>
privilege on the new schema.
To alter the owner, you must also be a direct or indirect member of the new
owning role, and that role must have <TT
CLASS="LITERAL"
>CREATE</TT
> privilege on
the sequence's schema. (These restrictions enforce that altering the owner
doesn't do anything you couldn't do by dropping and recreating the sequence.
However, a superuser can alter ownership of any sequence anyway.)
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN64606"
></A
><H2
>Parameters</H2
><P
> <P
></P
></P><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
></DT
><DD
><P
> The name (optionally schema-qualified) of a sequence to be altered.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>IF EXISTS</TT
></DT
><DD
><P
> Do not throw an error if the sequence does not exist. A notice is issued
in this case.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>increment</I
></TT
></DT
><DD
><P
> The clause <TT
CLASS="LITERAL"
>INCREMENT BY <TT
CLASS="REPLACEABLE"
><I
>increment</I
></TT
></TT
> is
optional. A positive value will make an ascending sequence, a
negative one a descending sequence. If unspecified, the old
increment value will be maintained.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>minvalue</I
></TT
><BR><TT
CLASS="LITERAL"
>NO MINVALUE</TT
></DT
><DD
><P
> The optional clause <TT
CLASS="LITERAL"
>MINVALUE <TT
CLASS="REPLACEABLE"
><I
>minvalue</I
></TT
></TT
> determines
the minimum value a sequence can generate. If <TT
CLASS="LITERAL"
>NO
MINVALUE</TT
> is specified, the defaults of 1 and
-2<SUP
>63</SUP
>-1 for ascending and descending sequences,
respectively, will be used. If neither option is specified,
the current minimum value will be maintained.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>maxvalue</I
></TT
><BR><TT
CLASS="LITERAL"
>NO MAXVALUE</TT
></DT
><DD
><P
> The optional clause <TT
CLASS="LITERAL"
>MAXVALUE <TT
CLASS="REPLACEABLE"
><I
>maxvalue</I
></TT
></TT
> determines
the maximum value for the sequence. If <TT
CLASS="LITERAL"
>NO
MAXVALUE</TT
> is specified, the defaults are
2<SUP
>63</SUP
>-1 and -1 for ascending and descending
sequences, respectively, will be used. If neither option is
specified, the current maximum value will be maintained.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>start</I
></TT
></DT
><DD
><P
> The optional clause <TT
CLASS="LITERAL"
>START WITH <TT
CLASS="REPLACEABLE"
><I
>start</I
></TT
></TT
> changes the
recorded start value of the sequence. This has no effect on the
<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>current</I
></SPAN
> sequence value; it simply sets the value
that future <TT
CLASS="COMMAND"
>ALTER SEQUENCE RESTART</TT
> commands will use.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>restart</I
></TT
></DT
><DD
><P
> The optional clause <TT
CLASS="LITERAL"
>RESTART [ WITH <TT
CLASS="REPLACEABLE"
><I
>restart</I
></TT
> ]</TT
> changes the
current value of the sequence. This is equivalent to calling the
<CODE
CLASS="FUNCTION"
>setval</CODE
> function with <TT
CLASS="LITERAL"
>is_called</TT
> =
<TT
CLASS="LITERAL"
>false</TT
>: the specified value will be returned by the
<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>next</I
></SPAN
> call of <CODE
CLASS="FUNCTION"
>nextval</CODE
>.
Writing <TT
CLASS="LITERAL"
>RESTART</TT
> with no <TT
CLASS="REPLACEABLE"
><I
>restart</I
></TT
> value is equivalent to supplying
the start value that was recorded by <TT
CLASS="COMMAND"
>CREATE SEQUENCE</TT
>
or last set by <TT
CLASS="COMMAND"
>ALTER SEQUENCE START WITH</TT
>.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>cache</I
></TT
></DT
><DD
><P
> The clause <TT
CLASS="LITERAL"
>CACHE <TT
CLASS="REPLACEABLE"
><I
>cache</I
></TT
></TT
> enables
sequence numbers to be preallocated and stored in memory for
faster access. The minimum value is 1 (only one value can be
generated at a time, i.e., no cache). If unspecified, the old
cache value will be maintained.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>CYCLE</TT
></DT
><DD
><P
> The optional <TT
CLASS="LITERAL"
>CYCLE</TT
> key word can be used to enable
the sequence to wrap around when the
<TT
CLASS="REPLACEABLE"
><I
>maxvalue</I
></TT
> or
<TT
CLASS="REPLACEABLE"
><I
>minvalue</I
></TT
> has been
reached by
an ascending or descending sequence respectively. If the limit is
reached, the next number generated will be the
<TT
CLASS="REPLACEABLE"
><I
>minvalue</I
></TT
> or
<TT
CLASS="REPLACEABLE"
><I
>maxvalue</I
></TT
>,
respectively.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>NO CYCLE</TT
></DT
><DD
><P
> If the optional <TT
CLASS="LITERAL"
>NO CYCLE</TT
> key word is
specified, any calls to <CODE
CLASS="FUNCTION"
>nextval</CODE
> after the
sequence has reached its maximum value will return an error.
If neither <TT
CLASS="LITERAL"
>CYCLE</TT
> or <TT
CLASS="LITERAL"
>NO
CYCLE</TT
> are specified, the old cycle behavior will be
maintained.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>OWNED BY</TT
> <TT
CLASS="REPLACEABLE"
><I
>table_name</I
></TT
>.<TT
CLASS="REPLACEABLE"
><I
>column_name</I
></TT
><BR><TT
CLASS="LITERAL"
>OWNED BY NONE</TT
></DT
><DD
><P
> The <TT
CLASS="LITERAL"
>OWNED BY</TT
> option causes the sequence to be
associated with a specific table column, such that if that column
(or its whole table) is dropped, the sequence will be automatically
dropped as well. If specified, this association replaces any
previously specified association for the sequence. The specified
table must have the same owner and be in the same schema as the
sequence.
Specifying <TT
CLASS="LITERAL"
>OWNED BY NONE</TT
> removes any existing
association, making the sequence <SPAN
CLASS="QUOTE"
>"free-standing"</SPAN
>.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>new_owner</I
></TT
></DT
><DD
><P
> The user name of the new owner of the sequence.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>new_name</I
></TT
></DT
><DD
><P
> The new name for the sequence.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>new_schema</I
></TT
></DT
><DD
><P
> The new schema for the sequence.
</P
></DD
></DL
></DIV
><P>
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN64727"
></A
><H2
>Notes</H2
><P
> To avoid blocking of concurrent transactions that obtain numbers from the
same sequence, <TT
CLASS="COMMAND"
>ALTER SEQUENCE</TT
>'s effects on the sequence
generation parameters are never rolled back; those changes take effect
immediately and are not reversible. However, the <TT
CLASS="LITERAL"
>OWNED BY</TT
>,
<TT
CLASS="LITERAL"
>OWNER TO</TT
>, <TT
CLASS="LITERAL"
>RENAME TO</TT
>, and <TT
CLASS="LITERAL"
>SET SCHEMA</TT
>
clauses cause ordinary catalog updates that can be rolled back.
</P
><P
> <TT
CLASS="COMMAND"
>ALTER SEQUENCE</TT
> will not immediately affect
<CODE
CLASS="FUNCTION"
>nextval</CODE
> results in backends,
other than the current one, that have preallocated (cached) sequence
values. They will use up all cached values prior to noticing the changed
sequence generation parameters. The current backend will be affected
immediately.
</P
><P
> <TT
CLASS="COMMAND"
>ALTER SEQUENCE</TT
> does not affect the <CODE
CLASS="FUNCTION"
>currval</CODE
>
status for the sequence. (Before <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>
8.3, it sometimes did.)
</P
><P
> For historical reasons, <TT
CLASS="COMMAND"
>ALTER TABLE</TT
> can be used with
sequences too; but the only variants of <TT
CLASS="COMMAND"
>ALTER TABLE</TT
>
that are allowed with sequences are equivalent to the forms shown above.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN64745"
></A
><H2
>Examples</H2
><P
> Restart a sequence called <TT
CLASS="LITERAL"
>serial</TT
>, at 105:
</P><PRE
CLASS="PROGRAMLISTING"
>ALTER SEQUENCE serial RESTART WITH 105;</PRE
><P></P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN64750"
></A
><H2
>Compatibility</H2
><P
> <TT
CLASS="COMMAND"
>ALTER SEQUENCE</TT
> conforms to the <ACRONYM
CLASS="ACRONYM"
>SQL</ACRONYM
>
standard, except for the <TT
CLASS="LITERAL"
>START WITH</TT
>,
<TT
CLASS="LITERAL"
>OWNED BY</TT
>, <TT
CLASS="LITERAL"
>OWNER TO</TT
>, <TT
CLASS="LITERAL"
>RENAME TO</TT
>, and
<TT
CLASS="LITERAL"
>SET SCHEMA</TT
> clauses, which are
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> extensions.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN64761"
></A
><H2
>See Also</H2
><A
HREF="sql-createsequence.html"
>CREATE SEQUENCE</A
>, <A
HREF="sql-dropsequence.html"
>DROP SEQUENCE</A
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