This plugin, when installed, finds related posts based on the contents of a post rather than just its title.

By default Similar Posts scans a post each time it needs to find words to match. For long posts this can add an unwanted overhead. The plugin can speed up the process by caching the search terms as a custom field (named similarterms). When a post is published for the first time or subsequently edited the custom field gets updated. Since you probably have a lot of posts you wont want to edit each one manually to cache the terms. Instead, the Admin|Options|Similar Posts page lets you process all your posts in one go. It wont overwrite any terms that are already cached so there is also a button to clear all terms.

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