2014-10-03 6:06 GMT+02:00 David G Johnston <david.g.johns...@gmail.com>:
> Jim Nasby-5 wrote
> > On 10/2/14, 6:51 AM, Pavel Stehule wrote:
> >> EXECUTE format('UPDATE tbl SET %I = newvalue WHERE key = %L',
> >> colname, keyvalue)
> >> or
> > -1, because of quoting issues
> >> EXECUTE format('UPDATE tbl SET %I = newvalue WHERE key = $1',
> >> colname)
> >> USING keyvalue;
> > Better, but I think it should really be quote_ident( colname )
>
>
> http://www.postgresql.org/docs/9.4/static/plpgsql-statements.html#PLPGSQL-QUOTE-LITERAL-EXAMPLE
>
> The use of %I and %L solve all quoting issues when using format(); they
> likely call the relevant quote_ function on the user's behalf.
>
>
> >> A old examples are very instructive, but little bit less readable and
> >> maybe too complex for beginners.
> >>
> >> Opinions?
> > Honestly, I'm not to fond of either. format() is a heck of a lot nicer
> > than a forest of ||'s, but I think it still falls short of what we'd
> > really want here which is some kind of variable substitution or even a
> > templating language. IE:
> >
> > EXECUTE 'UDPATE tbl SET $colname = newvalue WHERE key = $keyvalue';
>
> Putting that example into the docs isn't a good idea...it isn't valid in
> PostgreSQL ;)
>
>
> My complaint with the topic is that it is not specific enough. There are
> quite a few locations with dynamic queries. My take is that the
> concatenation form be shown only in "possible ways to accomplish this" type
> sections but that all actual examples or recommendations make use of the
> format function.
>
> The link above (40.5.4 in 9.4) is one such section where both forms need to
> be showed but I would suggest reversing the order so that we first
> introduce
> - prominently - the format function and then show the old-school way. That
> said there is some merit to emphasizing the wrong and hard way so as to
> help
> the reader conclude that the less painful format function really is their
> best friend...but that would be my fallback position here.
>
It is a good idea.
Regards
Pavel
>
> David J.
>
>
>
>
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