Обсуждение: Create Type with typmod_in

<div class="WordSection1"><p class="MsoNormal">I’m trying to create a custom type (PostgreSQL 9.0) which will
essentiallyauto truncate a string to a certain length.<p class="MsoNormal"> <p class="MsoNormal">The type
(auto_trunc_char)will be used as follows:<p class="MsoNormal"> <p class="MsoNormal">Create table blah (<p
class="MsoNormal">               Some_name auto_trunc_char(40)<p class="MsoNormal">)<p class="MsoNormal"> <p
class="MsoNormal">Canthis be done purely in plpgsql?<p class="MsoNormal">If so, how?<p class="MsoNormal"> <p
class="MsoNormal">Iknow I have to declare the following (at least) but I’m not sure how to flesh out the functions:<p
class="MsoNormal"> <pclass="MsoNormal">create type auto_trunc_char (<p class="MsoNormal">                INTERNALLENGTH
=VARIABLE,<p class="MsoNormal">                INPUT = auto_trunc_char_in_function,<p class="MsoNormal">               
OUTPUT= auto_trunc_char_out_function,<p class="MsoNormal">                TYPMOD_IN = auto_trunc_char_modifier_in<p
class="MsoNormal">);<pclass="MsoNormal"> <p class="MsoNormal"> <p class="MsoNormal"><span
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I’m trying to create a custom type (PostgreSQL 9.0) which will essentially auto truncate a string to a certain length.

 

Can this be done purely in plpgsql?

If so, how?

 

An explicit cast of a value to varchar(n) causes the value to be truncated to n characters.