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<p>It might have something to do with implicit transactional
behaviour, ( START TRANSACTION;<i> commands</i>; COMMIT).</p>
<p>Anyway, another little tidbit to remember <br>
</p>
<pre class="moz-signature" cols="72">Med venlig hilsen / Kind regards
Bo Victor Thomsen</pre>
<div class="moz-cite-prefix">Den 21-04-2022 kl. 17:32 skrev Paul
Ramsey:<br>
</div>
<blockquote type="cite"
cite="mid:3DA049FF-B46E-41E4-8553-13EC0DE7CD65@cleverelephant.ca">
<pre class="moz-quote-pre" wrap="">Well now that you mention it, it does seem funky, and I have no idea what the expected behavour is...
create table foo (old text, new text);
insert into foo (old) values ('1234');
update foo set old = left(old, 2), new = old
where old = '1234';
select * from foo;
I'm going to go out on a limb and suggest that maybe the values on the right-hand side of the assignment are actually always implicitly from the original record, so in trigger terms, the assignments look like NEW.colname = OLD.colname.
P
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On Apr 21, 2022, at 2:12 AM, Bo Victor Thomsen <a class="moz-txt-link-rfc2396E" href="mailto:bo.victor.thomsen@gmail.com"><bo.victor.thomsen@gmail.com></a> wrote:
Am I the only one that get "semantic itch" looking at the UPDATE expression? I would prefer it like this:
UPDATE nyc_neighborhoods
SET geom_invalid = geom,
geom = ST_MakeValid(geom)
WHERE NOT ST_IsValid(geom);
where you save the original "geom" value into another column "geom_invalid" before rectifying it and saving it into the original column.
Disclaimer: I have no clue about the internal methods of the SQL interpreter and how and in which order it assigns values.
Med venlig hilsen / Kind regards
Bo Victor Thomsen
Den 20-04-2022 kl. 16:59 skrev Regina Obe:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">Thanks for the errata. Corrected now.
From: postgis-users [<a class="moz-txt-link-freetext" href="mailto:postgis-users-bounces@lists.osgeo.org">mailto:postgis-users-bounces@lists.osgeo.org</a>] On Behalf Of Jian He
Sent: Wednesday, April 20, 2022 5:12 AM
To: PostGIS Users Discussion <a class="moz-txt-link-rfc2396E" href="mailto:postgis-users@lists.osgeo.org"><postgis-users@lists.osgeo.org></a>
Subject: [postgis-users] PostGis introduction doc code block seems wrong....
23. Validity — Introduction to PostGIS
last code block,
-- Fix invalid and save the original
UPDATE nyc_neighborhoods
SET geom = ST_MakeValid(geom),
invalid_geom = geom
WHERE NOT ST_IsValid(geom);
I think it should be:
-- Fix invalid and save the original
UPDATE nyc_neighborhoods
SET geom = ST_MakeValid(geom),
geom_invalid = geom
WHERE NOT ST_IsValid(geom);
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