I had 328 posts that I needed to add a meta field value to. Thankfully they all had the same value at the moment, so what I really needed was to tell WP “For all posts in the custom post type of ‘show’ add the post_meta key of ‘tvtype’ with a value of ‘tvshow’.”
That sounded simple. It wasn’t.
Googling “Updating multiple posts” or “Bulk Update Multiple Posts” (with WordPress in there) was frustratingly vague and told me to do things like the bulk edit from the post lists page. Well. Sure. If I added my post meta to the bulk editor (which I do know how to do) and felt like updating them 20 shows at a time, I could do that. Heck, I could make my page list 50 and not 20, and do it in 5 ‘cycles.’
But that wasn’t what I wanted to do. No, I wanted to figure out how to do it faster forever, so that if I had to update 32,800 posts, I could do it in the least CPU intensive way.
PHP
If I was to do this in PHP, it would look like this:
$ids = array(
'post_type' => 'post_type_shows',
'numberposts' => -1,
'post_status' => array('publish', 'pending', 'draft', 'future'),
);
foreach ($ids as $id){
add_post_meta( $id, 'tvtype', 'tvshow' );
}
I picked add_post_meta instead of update_ because while the update will add the meta if it’s not found, I didn’t want to update any of the shows I’d manually fiddled with already. And to run this, I’d have to put it in an MU plugin and delete it when I was done.
Which… Yes. That could work. I’d want to wrap it around a user capability check to make sure it didn’t run indefinitely, but it would work.
WP-CLI
Doesn’t a nice command line call sound better, though? Spoiler alert: It’s not.
I knew I could get a list of the IDs with this:
$ wp post list --post_type=post_type_shows --fields=ID --format=ids
That gave me a space-separated list
And I knew I could add the meta like this for each show:
$ wp post meta add 123 tvtype tvshow
But who wants to do that 328 times?
The documentation for wp post meta update said “Update a meta field.” A. Singular. Now it was possible that this could be for multiple posts, since the information on wp post update said “Update one or more posts” and “one or more” means one or more. But the example only had this:
$ wp post update 123 --post_name=something --post_status=draft
Notice how there’s no mention of how one might handle multiple posts? In light of clear documentation, I checked what the code was doing. For the update function, I found this:
public function update( $args, $assoc_args ) {
foreach( $args as $key => $arg ) {
if ( is_numeric( $arg ) ) {
continue;
}
The check for if ( is_numeric( $arg ) ) is the magic there. It says “If this is an ID, keep going.” And no spaces. So the answer to “How do I update multiple posts?” is this:
$ wp post update 123 124 125 --post_name=something --post_status=draft
Great! So can I do that with post meta? Would this work?
$ wp post meta add 123 124 125 tvtype tvshow
Answer: No.
So I took that list, used search/replace to turn it into 328 separate commands, and pasted them in (in 50 line chunks) to my terminal to update everything.
Yaaaay.
