[wp-hackers] Duplicate key=value pairs in wp_postmeta

[scribu]

I'm not talking about multiple values for the same key on the same post, i'm
talking about something like this:

*meta_id*  *post_id*  *meta_key * *meta_value*
 001          001         foo             bar
 002          001         foo             bar

On Thu, Feb 26, 2009 at 4:27 PM, Will Anderson <wp-hackers at itsananderson.com
> wrote:

> When you store multiple key/value pairs for a post, that key is turned into
> an array.
>
> I think it's pretty obvious from the function signature (with the $single
> argument) that this is intentional.
>
> One way I've used multiple values for one key before was for a portfolio. I
> used a key called "featured" to indicate which clients I wanted in my
> featured clients list. The value of that meta field indicated what service
> they were featured for. Having duplicate key/value pairs allowed me to
> indicate that a client was to be featured in multiple service categories.
>
> Now I know this sounds like something that should be done with tags, but I
> was already tagging ALL client posts with the services they had used, so I
> needed a way to differentiate the featured clients. I also couldn't use
> Cagetories for this because I was using the category name in the permalink
> structure and placing a post in the "Portfolio" and the "Featured" category
> would cause problems.
>
> Another way to use multiple values for a key is to support pseudo
> categories
> for pages (which can then be used in page lists).
>
> So anyway, that was a long winded way of saying that allowing multiple
> values for one key is important. It doesn't break the "unique list"
> relational algebra paradigms used by the database manager because WordPress
> assigns each {postid, key, value} a unique metaid.
>
> On Thu, Feb 26, 2009 at 7:11 AM, scribu <scribu at gmail.com> wrote:
>
> > I was trying to delete duplicate custom fields from postmeta. A duplica
> > custom field means that for the same post you have:
> >
> > key = value
> > key = value
> >
> > I think a unique(post_id, meta_key,meta_value) constraint would a good
> way
> > to avoid this problem in the future, as I can't see any practical use for
> > having the same custom field and value more than once for the same post.
> >
> > --
> > http://scribu.net
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>
>
>
> --
> Will Anderson
> http://www.itsananderson.com/
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