Most efficient way to search for values from CPT in Post content

I have a Glossary CPT. Title, editor, slug and featured image.

I would like to add a filter to Post content (and content of my other CPT “species”) which looks through all of the content in each post and replaces any words found in the Glossary with a link to the glossary entry.

For example…

Glossary entry: test

Post content: <p>This is a test post to explain what I mean.</p>

Outcome after filter: <p>This is a <a href="/glossary/t/test/">test</a> post to explain what I mean.</p>.

There may be up to 2000 glossary entries at any given time however, so I’m worried about efficiency.

EDIT: THIS CODE NEEDS SOME REWORKING!

I’ve started to use code as suggested by Matthew Boynes.

I have adapted it somewhat, as I was receiving an error with my $wordlist variable.

More information on said error is available here.

function add_glossary_links($content) {
    global $wpdb, $wordlist;
    if ( !$wordlist && !$wordlist = get_option('wordlist') ) {
        mysql_query('SET SESSION group_concat_max_len = 100000');
        $wordlist = $wpdb->get_var('SELECT GROUP_CONCAT(DISTINCT post_title SEPARATOR "|") AS list FROM '.$wpdb->posts.' WHERE post_status="publish" AND post_type="glossary" AND post_parent>0');
        add_option('wordlist', $wordlist);
    }

    $wordlist = str_replace(array(" ", "'", ".", "/"), array("s", "'", ".", "/"), $wordlist);

    $content = preg_replace_callback(
        '/b('.$wordlist.')b/i',
        create_function(
            '$matches',
            'return "<a href="/glossary/" . strtolower(substr($matches[0],0,1) . "/" . $matches[0]) . "/">" . $matches[0] . "</a>";'
        ),
        $content
    );

    return preg_replace('/(<[^<]+)<as.*?>(.*?)</a>/si','$1$2', $content);
}

add_filter( 'the_content', 'add_glossary_links' );

The function above works, to an extent. I now have two issues:

1. The function is linking everything:

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2. This may be a pushing my luck, but would it be possible to make this code case-sensitive, i.e. content only matches wordlist if case is the same, unless it’s the first word of a sentence?

Thanks in advance,