Phrase prefix identifies documents containing a phrase followed by a term prefix. 
SELECT description, rating, category
FROM mock_items
WHERE description @@@ pdb.phrase_prefix(ARRAY['running', 'sh']);
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phrases
required
An ARRAY of tokens that the search is looking to match, followed by a term prefix rather than a complete term.
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max_expansions
default:50
Limits the number of term variations that the prefix can expand to during the search. This helps in controlling the breadth of the search by setting a cap on how many different terms the prefix can match.

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Performance Considerations

Expanding a prefix might lead to thousands of matching terms, which impacts search times. With max_expansions, the prefix term is expanded to at most max_expansions terms in lexicographic order. For instance, if sh matches shall, share, shoe, and shore but max_expansions is set to 3, sh will only be expanded to shall, share, and shoe.