# Plugin causing errors during rebuild

**URL:** https://meta.discourse.org/t/plugin-causing-errors-during-rebuild/241110
**Category:** Self-hosting
**Created:** [October 6, 2022, 9:35am UTC](https://meta.discourse.org/t/plugin-causing-errors-during-rebuild/241110 "2022-10-06T09:35:29Z")
**Posts on this page:** 1
**Showing post:** 23

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### Author: ![angus](https://sea3.discourse-cdn.com/meta/user_avatar/meta.discourse.org/angus/32/341715_2.png) [@angus](https://meta.discourse.org/u/angus)
#### Post date: [October 6, 2022, 1:14pm UTC](https://meta.discourse.org/t/plugin-causing-errors-during-rebuild/241110/23 "2022-10-06T13:14:39Z")

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@Jaap-Jan_Swijnenburg I’m sorry you’ve experienced an issue.

> [@pfaffman](#):
>
> The issue isn’t the migration itself

I’ll respectfully disagree with you there 🙂

The old QnA plugin used [standard Discourse custom field type casting](https://github.com/paviliondev/discourse-question-answer/blob/master/plugin.rb#L85), which is meant to handle casting that field to JSON. But that just doesn’t work in some cases (like this one), which is why you (ideally) need to build in format checks when you’re working with Discourse custom fields (particularly if you’re working with quite old code and data like this). I would suggest that that is what the Upvotes Plugin needs to do here, which indeed is where the immediate error is coming from.

> [@Jaap-Jan\_Swijnenburg](#):
>
> How would I be able to connect to the Discourse DB myself, to verify what’s in the post\_custom\_fields table?

You can use the [data explorer](https://meta.discourse.org/t/32566?silent=true) plugin to check what you’ve got there.

> [@Discourse Data Explorer](https://meta.discourse.org/t/discourse-data-explorer/32566):
>
> discourse2Summary Discourse [Data Explorer](https://meta.discourse.org/t/32566?silent=true) allows you to make SQL queries against your live database, allowing for up-to-the-minute stats reporting.open_bookInstall Guide This plugin is bundled with Discourse core. There is no need to install the plugin separately.information_source If you’re looking for examples or support for any custom queries, you can find lots of topics in our #Data & reporting category under the #sql-query tag. If there’s not one to suit your pa…

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