Parsa

This plugin optimizes WordPress meta data storage by saving all meta data for each post, comment, user, or term in a single row with separate columns for each meta key. This reduces the number of rows and improves the query performance and data export. The plugin works seamlessly with WordPress core functions and hooks, and supports any plugins that use them. Some of the features of this plugin are:
<ul>
<li>Custom database tables for each type of meta data (post, comment, user, term)</li>
<li>Compatibility with WordPress queries</li>
<li>Faster queries and easy data export</li>
<li>Data migration from default WordPress meta tables</li>
<li>Option to exclude specific fields from core meta tables</li>
<li>Support for popular plugins and themes such as Advanced Custom Fields, Meta Box, CMB2, and more.</li>
</ul>

Meta Optimizer

Meta Optimizer is a WordPress plugin that helps you speed up your website by using meta data. It lets you optimize the meta tables for your posts, com …

Tran Ngoc Tuan Anh

Meta Box

<a href="https://metabox.io/plugins/mb-comment-meta/" rel="nofollow ugc">MB Comment Meta</a> is an extension for <a href="https://metabox.io" rel="nofollow ugc">Meta Box</a> plugin, which adds custom fields to comments in WordPress.
<blockquote>
Meta Box Lite 
 We recommend using <a href="https://metabox.io/lite/" rel="nofollow ugc">Meta Box Lite</a>, a feature-rich free UI version of Meta Box that provides UI and all free features for managing custom fields and dynamic content on WordPress, including post types, taxonomies, custom fields, and relationships.
</blockquote>
The plugin supports all field types from Meta Box: text, select, color, media, date time, etc. and all the field options.
<h3>Plugin Links</h3>
<ul>
<li><a href="https://metabox.io/plugins/mb-comment-meta/" rel="nofollow ugc">Project Page</a></li>
<li><a href="https://github.com/rilwis/mb-comment-meta/" rel="nofollow ugc">Github Repo</a></li>
</ul>
See more <a href="https://metabox.io/plugins/" rel="nofollow ugc">Meta Box extensions</a>.

MB Comment Meta

Add custom fields for comments. Support 40+ field types with easy config.

Meta Optimizer vs MB Comment Meta