Skip to content

G
Gpdb

Greenplum / Gpdb

通知 7
Star 1
Fork 0
G
Gpdb

体验新版 GitCode，发现更多精彩内容 >>

提交 64a5d99b 编写于 作者: A Andreas Scherbaum 提交者： Andreas Scherbaum
浏览文件
操作

Add sequence overflow documentation and example. (#2793) 

* Add sequence overflow documentation and example.
上级 da41d2e1
隐藏空白更改
内联 并排
Showing with 19 addition and 2 deletion
gpdb-doc/dita/admin_guide/ddl/ddl-sequence.xml
浏览文件 @ 64a5d99b
......@@ -83,13 +83,30 @@
<codeph>SERIAL</codeph> or <codeph>BIGSERIAL</codeph> type):</p>
<p>
<codeblock>CREATE TABLE ... (
id INT4 DEFAULT nextval('id_seq')
id INT4 DEFAULT nextval('myserial')
);
</codeblock>
</p>
<p>Alternatively, a column can be altered and a sequence can be added as default value:</p>
<codeblock>ALTER TABLE ... ALTER COLUMN id SET DEFAULT nextval('id_seq');
<codeblock>ALTER TABLE ... ALTER COLUMN id SET DEFAULT nextval('myserial');
</codeblock>
</body>
</topic>
<topic id="topic92" xml:lang="en">
<title>Sequence Wraparound</title>
<body>
<p>By default, a sequence does not wrap around. That is, when the sequence reaches the max value
(<codeph>+32767</codeph> for <codeph>SMALLSERIAL</codeph>, <codeph>+2147483647</codeph>
for <codeph>SERIAL</codeph>, <codeph>+9223372036854775807</codeph> for
<codeph>BIGSERIAL</codeph>), every <codeph>nextval()</codeph> call produces an error.
Alter the sequence to make it cycle around and start at <codeph>1</codeph> again:</p>
<p>
<codeblock>ALTER SEQUENCE myserial CYCLE;</codeblock>
</p>
<p>The wraparound behaviour can also specified when a sequence is created manually:</p>
<p>
<codeblock>CREATE SEQUENCE myserial CYCLE;</codeblock>
</p>
</body>
</topic>
</topic>
Markdown is supported
0% 或 .
You are about to add 0 people to the discussion. Proceed with caution.
先完成此消息的编辑！
想要评论请 注册 或