Frequently Asked Questions (FAQ)
Tables are corrupted and show “[ERROR] TABLE IS CORRUPTED”

While seeing this error is (understandably) scary, please remain calm—in almost all cases it’s possible to restore the table data. This page tries to provide some guidance for that.

Background

Internally, TablePress stores tables as two-dimensional fields or arrays. To be able to store these in the database, these arrays are encoded to text strings in the JSON format. In this widely used and open data format, certain characters like quotation marks ", backslashes \, and square brackets [] serve as control characters and have special meanings. Therefore, when these characters are used in the actual content, precautions have to be taken to not mix them up with their control character function when it comes to reading (decoding to its original representation) the JSON text string again. This is done by escaping these characters with a prepended backslash \. For example, a quotation mark " is actually stored as \" internally.

All this is completely irrelevant when working with tables in TablePress, as everything regarding loading (decoding) and storing (encoding) the data happens automatically behind the scenes. The escaping however is one reason why JSON text strings are fragile when it comes to direct data manipulation—that is when working with the stored JSON data as plain text outside of TablePress—in contrast to first decoding it to its original data structure.

For example, a process that works with a raw JSON text string must never add extra quotation marks " to it, but it needs to appropriately escape them as \" first. It is also not directly allowed to just append or add extra content or data to the end of a JSON string that represents an array internally. If such a wrong data manipulation is done, the JSON text string will not have the correct format for it to be decoded to its original represenation again—the JSON data is corrupted.

Causes for table data corruption

Possible causes for such corruption of TablePress tables mainly are the wrong or careless handling of JSON content in the database, by other plugins, themes, or even WordPress itself, or security breaches and hacks of websites, databases, or servers. From a more technical perspective, this can for example mean that something on your site or server

  • removed the escaping backslashes \, e.g. by wrongly using the PHP stripslashes() function,
  • inserted content that includes quotation marks " into the JSON string, but without the mandatory escaping backslashes \,
  • or appended extra text or code to the end of the JSON string.

While the first of these possibilities does not happen often anymore, the problem of text or code being automatically appended to the JSON strings can still be observed at a small but constant rate. Very often, this is done by automated scripts that append malicious HTML and JavaScript code to all posts, pages, and tables of a site, with the intent to possibly infect the visitors’ computers with malware or to display ads on your site. One indicator that your site or database might have been hacked and modified in this way is that all TablePress tables show the corrupted data error.

The second mentioned possibility became a problem for some time with the release of WordPress 5.1 at the end of February of 2019, due to a bug in it. In most cases, only a few but not all tables on the site would be affected here, and only if they contained certain HTML code for a clickable link.

Fixing and restoring corrupted table data

You most likely were directed to this page by a notice on the TablePress screens of your site, telling you that the internal data of a table is corrupted. This means that the JSON text string that was read from the database could not be decoded into a two-dimensional array properly. To fix the JSON text string, the wrong parts in it have to be identified and either be corrected or be removed. To stick with the possible causes from the previous section, content that was added without the escaping backslash \ probably just needs that inserted, while extra HTML <script> tags from a hacking script need to be removed from the end of the JSON code.

For most cases that I have seen in the past, this process can be automated. I therefore developed a WordPress plugin, the “TablePress Extension: Fix corrupted tables”, that will do this for you.

  1. To restore your corrupted tables, please download the “TablePress Extension: Fix corrupted tables” plugin as a ZIP archive to your computer.
  2. In your WordPress admin dashboard, go to “Plugins” -> “Add New”, and click the “Upload Plugin” button near the top.
  3. Choose the ZIP file that you downloaded in step 1 and upload it. (Alternatively, you could extract the ZIP archive and upload the contained folder to your site’s /wp-content/plugins/ folder via your FTP program.)
  4. On the next screen, click the “Activate Plugin” button.
  5. The Extension will then try to fix the internal JSON data format of the TablePress tables by performing simple search/replace operations in your database.
  6. After this, you will see a notice text at the top of the screen about the process, including some success statistics, and a suggestion to create a backup.
  7. Finally, you may go to the “Plugins” screen and “Deactivate” and then “Delete” the “TablePress Extension: Fix corrupted tables” plugin again.
  8. In addition, on the “Plugins” screen, please make sure that you have updated TablePress to the latest version!

Please be assured that I’m very sorry that you experienced corrupted TablePress tables on your site! I’m doing everything I can to prevent this in TablePress, but unfortunately, I can’t protect your table data from external influences on the database, like other plugins or scripts with malicious intent. It is therefore always recommended to keep a backup of your site as a whole, and your tables in particular, e.g. by exporting them to files.

If you find that the Extension did not restore all your TablePress tables, it is possible that they are corrupted in other ways. Most likely, we’ll still be able to restore the data. For help with that, please contact me directly via email (wordpressno-spam@mailtobias.baethge.com) with the details to a temporary admin account to your site. I’ll then gladly take a direct look and assist with restoring your table data!

If TablePress or this Extension is helpful for you, please consider supporting further TablePress development with a donation. Thank you!

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