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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 or pdb.snippets 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. pdb.snippet returns the single best snippet, sorted by relevance score. 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 snippet. A snippet may contain multiple matches if they are close to each other.
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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Multiple Snippets

pdb.snippets(<column>) returns an array of snippets, allowing you to retrieve multiple highlighted matches from a document. This is particularly useful when a document has several relevant matches spread throughout its content. 
SELECT id, pdb.snippets(description, max_num_chars => 15)
FROM mock_items
WHERE description ||| 'artistic vase'
LIMIT 5;

 id |                snippets
----+-----------------------------------------
 19 | {<b>Artistic</b>,"ceramic <b>vase</b>"}
(1 row)

Time: 10.614 ms
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start_tag
default:"<b>"
The leading indicator around the highlighted region.
​
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 snippet. When max_num_chars is small, multiple snippets may be generated for a single document.
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limit
default:5
The maximum number of snippets to return per document.
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offset
default:0
The number of snippets to skip before returning results. Use with limit for pagination.
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sort_by
default:"score"
The order in which to sort the snippets. Can be 'score' (default, sorts by relevance) or 'position' (sorts by appearance in the document).

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Limiting and Offsetting Snippets

You can control the number and order of snippets returned using the limit, offset, and sort_by parameters. For example, to get only the first snippet: 
SELECT id, pdb.snippets(description, max_num_chars => 15, "limit" => 1)
FROM mock_items
WHERE description ||| 'running'
LIMIT 5;
To get the second snippet (by skipping the first one): 
SELECT id, pdb.snippets(description, max_num_chars => 15, "limit" => 1, "offset" => 1)
FROM mock_items
WHERE description ||| 'running'
LIMIT 5;

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Sorting Snippets

Snippets can be sorted either by their relevance score ('score') or their position within the document ('position'). To sort snippets by their appearance in the document: 
SELECT id, pdb.snippets(description, max_num_chars => 15, sort_by => 'position')
FROM mock_items
WHERE description ||| 'artistic vase'
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)