<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >ALTER SEQUENCE</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 8.0.11 Documentation" HREF="index.html"><LINK REL="UP" TITLE="SQL Commands" HREF="sql-commands.html"><LINK REL="PREVIOUS" TITLE="ALTER SCHEMA" HREF="sql-alterschema.html"><LINK REL="NEXT" TITLE="ALTER TABLE" HREF="sql-altertable.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2007-02-02T03:57:22"></HEAD ><BODY CLASS="REFENTRY" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="5" ALIGN="center" VALIGN="bottom" >PostgreSQL 8.0.11 Documentation</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="sql-alterschema.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="sql-alterschema.html" >Fast Backward</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="top" ><A HREF="sql-altertable.html" >Fast Forward</A ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="top" ><A HREF="sql-altertable.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="SQL-ALTERSEQUENCE" ></A >ALTER SEQUENCE</H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN37013" ></A ><H2 >Name</H2 > ALTER SEQUENCE -- change the definition of a sequence generator </DIV ><A NAME="AEN37016" ></A ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN37018" ></A ><H2 >Synopsis</H2 ><PRE CLASS="SYNOPSIS" >ALTER SEQUENCE <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 ] [ RESTART [ WITH ] <TT CLASS="REPLACEABLE" ><I >start</I ></TT > ] [ CACHE <TT CLASS="REPLACEABLE" ><I >cache</I ></TT > ] [ [ NO ] CYCLE ] </PRE ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN37026" ></A ><H2 >Description</H2 ><P > <TT CLASS="COMMAND" >ALTER SEQUENCE</TT > changes the parameters of an existing sequence generator. Any parameter not specifically set in the <TT CLASS="COMMAND" >ALTER SEQUENCE</TT > command retains its prior setting. </P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN37031" ></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="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" >RESTART WITH <TT CLASS="REPLACEABLE" ><I >start</I ></TT ></TT > changes the current value of the sequence. </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 >CYCLE</DT ><DD ><P > The optional <TT CLASS="LITERAL" >CYCLE</TT > key word may 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 >NO CYCLE</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 behaviour will be maintained. </P ></DD ></DL ></DIV ><P> </P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN37100" ></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="AEN37105" ></A ><H2 >Notes</H2 ><P > To avoid blocking of concurrent transactions that obtain numbers from the same sequence, <TT CLASS="COMMAND" >ALTER SEQUENCE</TT > is never rolled back; the changes take effect immediately and are not reversible. </P ><P > <TT CLASS="COMMAND" >ALTER SEQUENCE</TT > will not immediately affect <TT CLASS="LITERAL" >nextval</TT > 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 parameters. The current backend will be affected immediately. </P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN37112" ></A ><H2 >Compatibility</H2 ><P > <TT CLASS="COMMAND" >ALTER SEQUENCE</TT > conforms with <ACRONYM CLASS="ACRONYM" >SQL:2003</ACRONYM >. </P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="sql-alterschema.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="sql-altertable.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >ALTER SCHEMA</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="sql-commands.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >ALTER TABLE</TD ></TR ></TABLE ></DIV ></BODY ></HTML >