How does postgres remain the unique index unique?

<pre><pre></pre></pre><pre><pre>Hello,<br />everyone,<br />    I want to know how postgres remain its unique index
uniqueafter i have change it,For<br />example:<br />    CREATE TABLE human(age INT,name CHAR(30));<br />then in
pg_attributecatalog the unique index pg_attribute_relid_attnum_index will use the relid of<br />'human' and attnum of
ageto create a index tuple for attribute:age,which is a unique index tuple describing<br />age ,then i do：<br />
ALTERTABLE human RENAME　age TO birthdate;<br />in the unique index pg_attribute_relid_attnum_index will appear two
indextuple which keys are relid of 'human'<br />and attnum:1 to describe age(In my mind,when insert or update a heap
tuple,postgresonly inserts a new index <br />tuple for it in its index relation if it has not delete or tag the old
indextuple),but there is no error<br />happening!!!!So i am interested in the method of remianing the dynamic index
uniquevery much.<br />    would you please tell me how postgres completes it and the src of this?<br />thank:)<br />
                   庄继锋 <br />                        ２００４－４－３０</pre></pre> ========================== 263电子邮件－信赖邮自专业
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