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<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial>Bryce,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial>We'll make sure to note it with a warning notice. There
are also workarounds for lower versions of postgreSQL which aren't too
bad. </FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial>Like example we show here:</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial><A
href="http://www.postgis.org/documentation/manual-svn/ST_MakeLine.html">http://www.postgis.org/documentation/manual-svn/ST_MakeLine.html</A></FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial>We can document that too. As it stands 8.4 is the only
PostgreSQL in PostGIS 2.0 we are supporting where an ordered aggregate would be
an issue. I don't think we should enforce too much constraint until
possibly 2.1 if we see alot of people are shooting themselves in the
foot.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial>I think for PostGIS 2.0 we want to get out something useful
and relatively easy to use which won't be perfect (time is running out
since December is just around the corner and feature freeze time)
</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial>I think we've got a lot of stuff already that people can use
and are already using and that's fantastic. We can use 2.0 release to learn from
people how they are using it to see what needs to be changed / reworked what
they find awkward to write etc.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial>Thanks,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial>Regina</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=659030700-22112011><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV><FONT color=#0000ff size=2
face=Arial></FONT><FONT color=#0000ff size=2 face=Arial></FONT><BR>
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<FONT size=2 face=Tahoma><B>From:</B>
postgis-devel-bounces@postgis.refractions.net
[mailto:postgis-devel-bounces@postgis.refractions.net] <B>On Behalf Of
</B>Bryce L Nordgren<BR><B>Sent:</B> Monday, November 21, 2011 6:47
PM<BR><B>To:</B> PostGIS Development Discussion<BR><B>Subject:</B> Re:
[postgis-devel] ST_Union specification questions<BR></FONT><BR></DIV>
<DIV></DIV>On Mon, Nov 21, 2011 at 10:56 PM, Pierre Racine <SPAN
dir=ltr><<A
href="mailto:Pierre.Racine@sbf.ulaval.ca">Pierre.Racine@sbf.ulaval.ca</A>></SPAN>
wrote:<BR>
<DIV class=gmail_quote><BR>
<BLOCKQUOTE
style="BORDER-LEFT: rgb(204,204,204) 1px solid; MARGIN: 0pt 0pt 0pt 0.8ex; PADDING-LEFT: 1ex"
class=gmail_quote>I would suggest you write a prototype of your own view of
what should be ST_MapAlgebra using your raster iterator. That would be more
useful. More constructive.<BR></BLOCKQUOTE>
<DIV><BR>A] I was asking about ST_Union.<BR>B] I wasn't talking about the
raster iterator at all.<BR>C] More useful and constructive than what? Pointing
out something that I see might cause problems which are potentially very
difficult to debug? <BR><BR>Regina's response was constructive, for which I am
eternally grateful. In this case, I learned that postgresql 9+ has a notion of
ordered aggregates. This modifies the question into: Is there any way to
require that expressions which depend on order occur only within an ordered
aggregate? Conversely, how do we disable (and should we attempt to disable)
these expressions on platforms (postgres < 9) which do not support ordered
aggregates, or in contexts where the aggregate ordering is not specified?
<BR><BR>At the very least, I think I'd suggest that the documentation for
ST_Union contain a fairly heavyhanded warning about the dangers of using
expressions where the order matters in a non-ordered-aggregate
context....<BR><BR>Bryce <BR></DIV></DIV></BLOCKQUOTE></BODY></HTML>