Why are post metas are stored as an array instead of sperarate keys

[joehoyle]

I noticed for some reason, all meta for a single key is stored as a single meta key (serialized array) in the revision meta, this makes calling get_post_meta on a revision return an array-encapsulated data rather than the data you would get from calling get_post_meta on the parent post. I just wondered why that was?

[adamsilverstein]

Hmm, I need to look at this more closely, I am seeing this as well.

[adamsilverstein]

@joehoyle I pushed a proposed fix for this issue in #27 - if you have a chance can you give it a test? Thanks

[roborourke]

Hey @adamsilverstein, I'm not sure #27 is the solution as meta data can be stored in any of the following ways:

1. Single string value
2. Serialised array / object value
3. Multiple entries of either of the above with the same key

Using get_post_meta() with $single set to true you'll lose data in scenario 3.

I think at some point some assumptions would have to be made about the data if it's an array so if the response from get_post_meta( $id, $key ) is:

1. A numbered array with one entry
   1. Store the array value eg add_metadata( 'post', $id, $key, $meta[0] )
   2. When retrieved using get_post_meta( $id, $key ) should be an array with one entry
2. A numbered array with multiple entries
3. Loop over the array and call add_metadata( 'post', $id, $key, $item )
4. When retrieving the metadata you should get an array of the items back

It should be enough to change it in the following way:

$meta_values = get_post_meta( $post_id, $meta_key );

/*
 * Use the underlying add_metadata() function vs add_post_meta()
 * to ensure metadata is added to the revision post and not its parent.
 */
foreach ( $meta_values as $meta_value ) {
    add_metadata( 'post', $revision_id, $meta_key, $meta_value );
}

There are then going to need to be updates to the way revision is restored and also compared I think.

[danielbachhuber]

Hi @joehoyle

[adamsilverstein]

Note: Planning to implement #56 as soon as we can get to expanding tests for it.