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Highlighting is an expensive process and can slow down query times. We recommend passing a LIMIT to any query where pdb.snippet is called to restrict the number of snippets that need to be generated.
Highlighting is not supported for fuzzy search.
Highlighting refers to the practice of visually emphasizing the portions of a document that match a user’s search query.

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Basic Usage

pdb.snippet(<column>) can be added to any query where an @@@ operator is present. The following query generates highlighted snippets against the description field. 
SELECT id, pdb.snippet(description)
FROM mock_items
WHERE description ||| 'shoes'
LIMIT 5;
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start_tag
default:"<b>"
The leading indicator around the highlighted region.
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end_tag
default:"</b>"
The trailing indicator around the highlighted region.
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max_num_chars
default:150
Max number of characters for a highlighted fragment.
By default, <b></b> encloses the snippet. This can be configured with start_tag and end_tag: 
SELECT id, pdb.snippet(description, start_tag => '<i>', end_tag => '</i>')
FROM mock_items
WHERE description ||| 'shoes'
LIMIT 5;

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Byte Offsets

pdb.snippet_positions(<column>) returns the byte offsets in the original text where the snippets would appear. It returns an array of tuples, where the the first element of the tuple is the byte index of the first byte of the highlighted region, and the second element is the byte index after the last byte of the region. 
SELECT id, pdb.snippet(description), pdb.snippet_positions(description)
FROM mock_items
WHERE description ||| 'shoes'
LIMIT 5;

 id |          snippet           | snippet_positions
----+----------------------------+-------------------
  3 | Sleek running <b>shoes</b> | {"{14,19}"}
  4 | White jogging <b>shoes</b> | {"{14,19}"}
  5 | Generic <b>shoes</b>       | {"{8,13}"}
(3 rows)
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