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<div class="section" id="snippet-html">
<h1>8.11.9. snippet_html<a class="headerlink" href="#snippet-html" title="Permalink to this headline">¶</a></h1>
<div class="admonition caution">
<p class="first admonition-title">Caution</p>
<p class="last">This feature is experimental. API will be changed.</p>
</div>
<div class="section" id="summary">
<h2>8.11.9.1. Summary<a class="headerlink" href="#summary" title="Permalink to this headline">¶</a></h2>
<p><tt class="docutils literal"><span class="pre">snippet_html</span></tt> extracts snippets of target text around search
keywords (<tt class="docutils literal"><span class="pre">KWIC</span></tt>. <tt class="docutils literal"><span class="pre">KeyWord</span> <span class="pre">In</span> <span class="pre">Context</span></tt>). The snippets are prepared
for embedding HTML. Special characters such as <tt class="docutils literal"><span class="pre"><</span></tt> and <tt class="docutils literal"><span class="pre">></span></tt> are
escapsed as <tt class="docutils literal"><span class="pre">&lt;</span></tt> and <tt class="docutils literal"><span class="pre">&gt;</span></tt>. Keyword is surrounded with <tt class="docutils literal"><span class="pre"><span</span>
<span class="pre">class="keyword"></span></tt> and <tt class="docutils literal"><span class="pre"></span></span></tt>. For example, a snippet of <tt class="docutils literal"><span class="pre">I</span> <span class="pre">am</span> <span class="pre">a</span>
<span class="pre">groonga</span> <span class="pre">user.</span> <span class="pre"><3</span></tt> for keyword <tt class="docutils literal"><span class="pre">groonga</span></tt> is <tt class="docutils literal"><span class="pre">I</span> <span class="pre">am</span> <span class="pre">a</span> <span class="pre"><span</span>
<span class="pre">class="keyword">groonga</span></span> <span class="pre">user.</span> <span class="pre">&lt;3</span></tt>.</p>
</div>
<div class="section" id="syntax">
<h2>8.11.9.2. Syntax<a class="headerlink" href="#syntax" title="Permalink to this headline">¶</a></h2>
<p><tt class="docutils literal"><span class="pre">snippet_html</span></tt> has only one parameter:</p>
<div class="highlight-none"><div class="highlight"><pre>snippet_html(column)
</pre></div>
</div>
<p><tt class="docutils literal"><span class="pre">snippet_html</span></tt> has many parameters internally but they can't be
specified for now. You will be able to custom those parameters soon.</p>
</div>
<div class="section" id="usage">
<h2>8.11.9.3. Usage<a class="headerlink" href="#usage" title="Permalink to this headline">¶</a></h2>
<p>Here are a schema definition and sample data to show usage.</p>
<p>Execution example:</p>
<div class="highlight-none"><div class="highlight"><pre>table_create Documents TABLE_NO_KEY
# [[0, 1337566253.89858, 0.000355720520019531], true]
column_create Documents content COLUMN_SCALAR Text
# [[0, 1337566253.89858, 0.000355720520019531], true]
table_create Terms TABLE_PAT_KEY|KEY_NORMALIZE ShortText --default_tokenizer TokenBigram
# [[0, 1337566253.89858, 0.000355720520019531], true]
column_create Terms documents_content_index COLUMN_INDEX|WITH_POSITION Documents content
# [[0, 1337566253.89858, 0.000355720520019531], true]
load --table Documents
[
["content"],
["Groonga is a fast and accurate full text search engine based on inverted index. One of the characteristics of groonga is that a newly registered document instantly appears in search results. Also, groonga allows updates without read locks. These characteristics result in superior performance on real-time applications."],
["Groonga is also a column-oriented database management system (DBMS). Compared with well-known row-oriented systems, such as MySQL and PostgreSQL, column-oriented systems are more suited for aggregate queries. Due to this advantage, groonga can cover weakness of row-oriented systems."]
]
# [[0, 1337566253.89858, 0.000355720520019531], 2]
</pre></div>
</div>
<p><tt class="docutils literal"><span class="pre">snippet_html</span></tt> can be used in only <tt class="docutils literal"><span class="pre">--output_columns</span></tt> in
<a class="reference internal" href="../commands/select.html"><em>select</em></a>.</p>
<p>You need to specify <tt class="docutils literal"><span class="pre">--command_version</span> <span class="pre">2</span></tt> argument explicitly
because function call in <tt class="docutils literal"><span class="pre">--output_columns</span></tt> is experimental feature
in groonga 2.0.9. It will be enabled by default soon.</p>
<p>You also need to specify <tt class="docutils literal"><span class="pre">--query</span></tt> and/or <tt class="docutils literal"><span class="pre">--filter</span></tt>. Keywords are
extracted from <tt class="docutils literal"><span class="pre">--query</span></tt> and <tt class="docutils literal"><span class="pre">--filter</span></tt> arguments.</p>
<p>The following example uses <tt class="docutils literal"><span class="pre">--query</span> <span class="pre">"fast</span> <span class="pre">performance"</span></tt>. In this
case, <tt class="docutils literal"><span class="pre">fast</span></tt> and <tt class="docutils literal"><span class="pre">performance</span></tt> are used as keywords.</p>
<p>Execution example:</p>
<div class="highlight-none"><div class="highlight"><pre>select Documents --output_columns "snippet_html(content)" --command_version 2 --match_columns content --query "fast performance"
# [
# [
# 0,
# 1337566253.89858,
# 0.000355720520019531
# ],
# [
# [
# [
# 1
# ],
# [
# [
# "snippet_html",
# "null"
# ]
# ],
# [
# [
# "Groonga is a <span class=\"keyword\">fast</span> and accurate full text search engine based on inverted index. One of the characteristics of groonga is that a newly registered document instantly appears in search results. Also, gro",
# "onga allows updates without read locks. These characteristics result in superior <span class=\"keyword\">performance</span> on real-time applications."
# ]
# ]
# ]
# ]
# ]
</pre></div>
</div>
<p><tt class="docutils literal"><span class="pre">--query</span> <span class="pre">"fast</span> <span class="pre">performance"</span></tt> matches to only the first record's
content. <tt class="docutils literal"><span class="pre">snippet_html(content)</span></tt> extracts two text parts that
include the keywords <tt class="docutils literal"><span class="pre">fast</span></tt> or <tt class="docutils literal"><span class="pre">performance</span></tt> and surronds the
keywords with <tt class="docutils literal"><span class="pre"><span</span> <span class="pre">class="keyword"></span></tt> and <tt class="docutils literal"><span class="pre"></span></span></tt>.</p>
<p>The max number of text parts is 3. If there are 4 or more text parts
that include the keywords, only the leading 3 parts are only used.</p>
<p>The max size of a text part is 200byte. The unit is bytes not
chracters. The size doesn't include inserted <tt class="docutils literal"><span class="pre"><span</span> <span class="pre">keyword="keyword"></span></tt>
and <tt class="docutils literal"><span class="pre"></span></span></tt>.</p>
<p>Both the max number of text parts and the max size of a text part
aren't customizable.</p>
<p>You can specify string literal instead of column.</p>
<p>Execution example:</p>
<div class="highlight-none"><div class="highlight"><pre>select Documents --output_columns 'snippet_html("Groonga is very fast fulltext search engine.")' --command_version 2 --match_columns content --query "fast performance"
# [
# [
# 0,
# 1337566253.89858,
# 0.000355720520019531
# ],
# [
# [
# [
# 1
# ],
# [
# [
# "snippet_html",
# "null"
# ]
# ],
# [
# [
# "Groonga is very <span class=\"keyword\">fast</span> fulltext search engine."
# ]
# ]
# ]
# ]
# ]
</pre></div>
</div>
</div>
<div class="section" id="return-value">
<h2>8.11.9.4. Return value<a class="headerlink" href="#return-value" title="Permalink to this headline">¶</a></h2>
<p><tt class="docutils literal"><span class="pre">snippet_html</span></tt> returns an array of string. An element of array is a
snippet:</p>
<div class="highlight-none"><div class="highlight"><pre>[SNIPPET1, SNIPPET2, SNIPPET3]
</pre></div>
</div>
<p>A snippet includes one or more keywords. The max byte size of a
snippet except <tt class="docutils literal"><span class="pre"><span</span> <span class="pre">keyword="keyword"></span></tt> and <tt class="docutils literal"><span class="pre"></span></span></tt> is
200byte. The unit isn't the number of chracters.</p>
<p>The array size is larger than or equal to 0 and less than or equal
to 3. The max size 3 will be customizable soon.</p>
</div>
<div class="section" id="todo">
<h2>8.11.9.5. TODO<a class="headerlink" href="#todo" title="Permalink to this headline">¶</a></h2>
<ul class="simple">
<li>Make the max number of text parts customizable.</li>
<li>Make the max size of a text part customizable.</li>
<li>Make keywords customizable.</li>
<li>Make tag that surrounds a keyword customizable.</li>
<li>Make normalization customizable.</li>
<li>Support options by object literal.</li>
</ul>
</div>
<div class="section" id="see-also">
<h2>8.11.9.6. See also<a class="headerlink" href="#see-also" title="Permalink to this headline">¶</a></h2>
<ul class="simple">
<li><a class="reference internal" href="../commands/select.html"><em>select</em></a></li>
</ul>
</div>
</div>
</div>
</div>
</div>
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<h3><a href="../../index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">8.11.9. snippet_html</a><ul>
<li><a class="reference internal" href="#summary">8.11.9.1. Summary</a></li>
<li><a class="reference internal" href="#syntax">8.11.9.2. Syntax</a></li>
<li><a class="reference internal" href="#usage">8.11.9.3. Usage</a></li>
<li><a class="reference internal" href="#return-value">8.11.9.4. Return value</a></li>
<li><a class="reference internal" href="#todo">8.11.9.5. TODO</a></li>
<li><a class="reference internal" href="#see-also">8.11.9.6. See also</a></li>
</ul>
</li>
</ul>
<h4>Previous topic</h4>
<p class="topless"><a href="rand.html"
title="previous chapter">8.11.8. rand</a></p>
<h4>Next topic</h4>
<p class="topless"><a href="sub_filter.html"
title="next chapter">8.11.10. sub_filter</a></p>
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