diff options
Diffstat (limited to 'doc/src/sgml/func.sgml')
| -rw-r--r-- | doc/src/sgml/func.sgml | 48 |
1 files changed, 28 insertions, 20 deletions
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index 4eb91311e6b..fcad177b7d2 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -9741,6 +9741,27 @@ nextval('foo'::text) <lineannotation><literal>foo</literal> is looked up at execute <function>nextval</function> concurrently, each will safely receive a distinct sequence value. </para> + + <para> + If a sequence object has been created with default parameters, + successive <function>nextval</function> calls will return successive + values beginning with 1. Other behaviors can be obtained by using + special parameters in the <xref linkend="sql-createsequence"> command; + see its command reference page for more information. + </para> + + <important> + <para> + To avoid blocking concurrent transactions that obtain numbers from the + same sequence, a <function>nextval</function> operation is never + rolled back; that is, once a value has been fetched it is considered + used, even if the transaction that did the + <function>nextval</function> later aborts. This means that aborted + transactions might leave unused <quote>holes</quote> in the sequence + of assigned values. + </para> + </important> + </listitem> </varlistentry> @@ -9804,31 +9825,18 @@ SELECT setval('foo', 42, false); <lineannotation>Next <function>nextval</> wi The result returned by <function>setval</function> is just the value of its second argument. </para> + <important> + <para> + Because sequences are non-transactional, changes made by + <function>setval</function> are not undone if the transaction rolls + back. + </para> + </important> </listitem> </varlistentry> </variablelist> </para> - <para> - If a sequence object has been created with default parameters, - successive <function>nextval</function> calls will return successive values - beginning with 1. Other behaviors can be obtained by using - special parameters in the <xref linkend="sql-createsequence"> command; - see its command reference page for more information. - </para> - - <important> - <para> - To avoid blocking concurrent transactions that obtain numbers from the - same sequence, a <function>nextval</function> operation is never rolled back; - that is, once a value has been fetched it is considered used, even if the - transaction that did the <function>nextval</function> later aborts. This means - that aborted transactions might leave unused <quote>holes</quote> in the - sequence of assigned values. <function>setval</function> operations are never - rolled back, either. - </para> - </important> - </sect1> |