Re: Faster data type for one-length values

Tom Lane escreveu: <blockquote cite="mid20197.1179929832@sss.pgh.pa.us" type="cite"><pre wrap="">André Volpato <a
class="moz-txt-link-rfc2396E"
href="mailto:andre.volpato@ecomtecnologia.com.br"><andre.volpato@ecomtecnologia.com.br></a>writes:
</pre><blockquotetype="cite"><pre wrap="">I need to store one-length values like '1', '2', '3' or '4' .
</pre></blockquote><prewrap=""> </pre><blockquote type="cite"><pre wrap="">Today, this field is indexed with btree and
isof type smallint (int2).  
How much performance will be improved if I change it to "char" (1 byte
length) ?   </pre></blockquote><pre wrap="">
The improvement will be zero.  Because of alignment restrictions, you
don't save any space from making an index entry smaller than 4 bytes.

If you have several such fields adjacent in a table row, making them all
narrower can save space, but it doesn't help for standalone index
entries.
        regards, tom lane </pre></blockquote><br /> Tom,<br /><br /> The ammount of space saved seems pretty clear to
me.<br /><br /> What are you saying is that the index behaviour is the same, for all types smaller than 4 bytes ?  For
queryperformance, in a search is based on that standalone indexed field, would be any difference using :<br /> a.
char(1);  b. int2;  c. "char"<br /><br /> Thanks again !<br /><br /><pre class="moz-signature" cols="72">--  
[]´s,

André Volpato
ECOM Tecnologia Ltda
<a class="moz-txt-link-abbreviated"
href="mailto:andre.volpato@ecomtecnologia.com.br">andre.volpato@ecomtecnologia.com.br</a>
(41) 3014 2322</pre>