Re: Alter column to type serial

<div class="gmail_quote">On 4 November 2010 14:04, Tom Lane <span dir="ltr"><<a
href="mailto:tgl@sss.pgh.pa.us">tgl@sss.pgh.pa.us</a>></span>wrote:<br /><blockquote class="gmail_quote"
style="margin:0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div class="im">Thom
Brown<<a href="mailto:thom@linux.com">thom@linux.com</a>> writes:<br /> > Would it be possible (or reasonable)
toadd support for changing the type of<br /> > a column to serial or bigserial (yes, yes, I know they're not
actual<br/> > types)?<br /><br /></div>We've looked at that in the past and decided there were enough corner<br />
casesthat it wasn't clearly a good idea.  In particular, what do you do<br /> with the existing data in the column?
 Whatdo you do if there's already<br /> a DEFAULT expression for the column, throw it away?  In particular, what<br />
ofthe special case that the column is in fact already a serial, so the<br /> default is pointing at an existing
sequence?<br/><br /> It is possible to accomplish everything that such a command would do<br /> manually, so the
argumentfor having it boils down to wanting it to<br /> be a bit easier.  But unless the command can always do the
rightthing<br /> automatically, I'm not sure "easy" is a good argument.<br /><br /> There's also the objection that
suchan operation would actually have<br /> very little to do with ALTER COLUMN TYPE --- most of the things it would<br
/>do are not that.  The fact that serial was bolted on as a fake type is a<br /> wart that maybe we shouldn't extend in
thisparticular fashion.<br /><br /></blockquote></div><br />I suspected this may have been discussed previously, I just
failedto find it.  And yes, it's purely for simplification, and to auto-clean sequences when tables are dropped.  I
didn'tthink it would be straightforward, but clearly there are show-stoppers abound.<br /><br />Thanks for the reply
though.:)<br clear="all" /><br />-- <br />Thom Brown<br />Twitter: @darkixion<br />IRC (freenode): dark_ixion<br
/>RegisteredLinux user: #516935<br />