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<div class="section" id="sub-filter">
<h1>8.11.10. sub_filter<a class="headerlink" href="#sub-filter" title="Permalink to this headline">¶</a></h1>
<div class="section" id="summary">
<h2>8.11.10.1. Summary<a class="headerlink" href="#summary" title="Permalink to this headline">¶</a></h2>
<p><tt class="docutils literal"><span class="pre">sub_filter</span></tt> evaluates <tt class="docutils literal"><span class="pre">filter_string</span></tt> in <tt class="docutils literal"><span class="pre">scope</span></tt> context.</p>
<p><tt class="docutils literal"><span class="pre">sub_filter</span></tt> can be used in only <tt class="docutils literal"><span class="pre">--filter</span></tt> in
<a class="reference internal" href="../commands/select.html"><em>select</em></a>.</p>
</div>
<div class="section" id="syntax">
<h2>8.11.10.2. Syntax<a class="headerlink" href="#syntax" title="Permalink to this headline">¶</a></h2>
<p><tt class="docutils literal"><span class="pre">sub_filter</span></tt> requires two arguments. They are <tt class="docutils literal"><span class="pre">scope</span></tt> and
<tt class="docutils literal"><span class="pre">filter_string</span></tt>.</p>
<div class="highlight-none"><div class="highlight"><pre>sub_filter(scope, filter_string)
</pre></div>
</div>
</div>
<div class="section" id="usage">
<h2>8.11.10.3. 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>Sample schema:</p>
<p>Execution example:</p>
<div class="highlight-none"><div class="highlight"><pre>table_create Comment TABLE_PAT_KEY UInt32
# [[0, 1337566253.89858, 0.000355720520019531], true]
column_create Comment name COLUMN_SCALAR ShortText
# [[0, 1337566253.89858, 0.000355720520019531], true]
column_create Comment content COLUMN_SCALAR ShortText
# [[0, 1337566253.89858, 0.000355720520019531], true]
table_create Blog TABLE_PAT_KEY ShortText
# [[0, 1337566253.89858, 0.000355720520019531], true]
column_create Blog title COLUMN_SCALAR ShortText
# [[0, 1337566253.89858, 0.000355720520019531], true]
column_create Blog content COLUMN_SCALAR ShortText
# [[0, 1337566253.89858, 0.000355720520019531], true]
column_create Blog comments COLUMN_VECTOR Comment
# [[0, 1337566253.89858, 0.000355720520019531], true]
column_create Comment blog_comment_index COLUMN_INDEX Blog comments
# [[0, 1337566253.89858, 0.000355720520019531], true]
table_create Lexicon TABLE_PAT_KEY ShortText --default_tokenizer TokenBigram
# [[0, 1337566253.89858, 0.000355720520019531], true]
column_create Lexicon comment_content COLUMN_INDEX|WITH_POSITION Comment content
# [[0, 1337566253.89858, 0.000355720520019531], true]
column_create Lexicon comment_name COLUMN_INDEX|WITH_POSITION Comment name
# [[0, 1337566253.89858, 0.000355720520019531], true]
column_create Lexicon blog_content COLUMN_INDEX|WITH_POSITION Blog content
# [[0, 1337566253.89858, 0.000355720520019531], true]
</pre></div>
</div>
<p>Sample data:</p>
<p>Execution example:</p>
<div class="highlight-none"><div class="highlight"><pre>load --table Comment
[
{"_key": 1, "name": "A", "content": "groonga"},
{"_key": 2, "name": "B", "content": "groonga"},
{"_key": 3, "name": "C", "content": "rroonga"},
{"_key": 4, "name": "A", "content": "mroonga"},
]
# [[0, 1337566253.89858, 0.000355720520019531], 4]
load --table Blog
[
{"_key": "groonga's blog", "content": "content of groonga's blog", comments: [1, 2, 3]},
{"_key": "mroonga's blog", "content": "content of mroonga's blog", comments: [2, 3, 4]},
{"_key": "rroonga's blog", "content": "content of rroonga's blog", comments: [3]},
]
# [[0, 1337566253.89858, 0.000355720520019531], 3]
</pre></div>
</div>
<dl class="docutils">
<dt>Here is the simple usage of <tt class="docutils literal"><span class="pre">sub_filter</span></tt> function which extracts the blog entry</dt>
<dd>user 'A' commented out.</dd>
</dl>
<p>Execution example:</p>
<div class="highlight-none"><div class="highlight"><pre>select Blog --output_columns _key --filter "comments.name @ \"A\" && comments.content @ \"groonga\""
# [
# [
# 0,
# 1337566253.89858,
# 0.000355720520019531
# ],
# [
# [
# [
# 2
# ],
# [
# [
# "_key",
# "ShortText"
# ]
# ],
# [
# "groonga's blog"
# ],
# [
# "mroonga's blog"
# ]
# ]
# ]
# ]
</pre></div>
</div>
<p>When executing the above query, not only "groonga's blog", but also "mroonga's blog".
This is not what you want because user "A" does not mention "groonga" to "mroonga's blog".</p>
<p>Without sub_filter, it means that following conditions are met.</p>
<ul class="simple">
<li>There is at least one record that user "A" commented out.</li>
<li>There is at least one record that mentioned about "groonga".</li>
</ul>
<p>Execution example:</p>
<div class="highlight-none"><div class="highlight"><pre>select Blog --output_columns _key --filter 'sub_filter(comments, "name @ \\"A\\" && content @ \\"groonga\\"")'
# [
# [
# 0,
# 1337566253.89858,
# 0.000355720520019531
# ],
# [
# [
# [
# 1
# ],
# [
# [
# "_key",
# "ShortText"
# ]
# ],
# [
# "groonga's blog"
# ]
# ]
# ]
# ]
</pre></div>
</div>
<p>On the other hand, executing the above query returns the intended result.
Because the arguments of sub_filter is evaluated in comments column's context.</p>
<p>It means that sub_filter requires the following condition is met.</p>
<ul class="simple">
<li>There are the records that user "A" mentions about "groonga".</li>
</ul>
</div>
<div class="section" id="parameters">
<h2>8.11.10.4. Parameters<a class="headerlink" href="#parameters" title="Permalink to this headline">¶</a></h2>
<p>There are two required parameter, <tt class="docutils literal"><span class="pre">scope</span></tt> and <tt class="docutils literal"><span class="pre">filter_string</span></tt>.</p>
<div class="section" id="scope">
<h3>8.11.10.4.1. <tt class="docutils literal"><span class="pre">scope</span></tt><a class="headerlink" href="#scope" title="Permalink to this headline">¶</a></h3>
<p>It specifies a column of the table that is specified by <tt class="docutils literal"><span class="pre">table</span></tt>
parameter in <tt class="docutils literal"><span class="pre">select</span></tt>. <tt class="docutils literal"><span class="pre">filter_string</span></tt> is evaluated in the column
context. It means that <tt class="docutils literal"><span class="pre">filter_string</span></tt> is evaluated like
<tt class="docutils literal"><span class="pre">select</span> <span class="pre">--table</span> <span class="pre">TYPE_OF_THE_COLUMN</span> <span class="pre">--filter</span> <span class="pre">FILTER_STRING</span></tt>.</p>
<p>The specified column type must be a table. In other words, the column
type must be reference type.</p>
<p>See <em class="xref std std-ref">select-table</em> about <tt class="docutils literal"><span class="pre">table</span></tt> parameter in <tt class="docutils literal"><span class="pre">select</span></tt>.</p>
</div>
<div class="section" id="filter-string">
<h3>8.11.10.4.2. <tt class="docutils literal"><span class="pre">filter_string</span></tt><a class="headerlink" href="#filter-string" title="Permalink to this headline">¶</a></h3>
<p>It specifies a search condition in
<a class="reference internal" href="../grn_expr/script_syntax.html"><em>Script syntax</em></a>. It is evaluated in <tt class="docutils literal"><span class="pre">scope</span></tt>
context.</p>
</div>
</div>
<div class="section" id="return-value">
<h2>8.11.10.5. Return value<a class="headerlink" href="#return-value" title="Permalink to this headline">¶</a></h2>
<p><tt class="docutils literal"><span class="pre">sub_filter</span></tt> returns whether any record is matched or not. If one or
more records are matched, it returns <tt class="docutils literal"><span class="pre">true</span></tt>. Otherwise, it returns
<tt class="docutils literal"><span class="pre">false</span></tt>.</p>
</div>
<div class="section" id="see-also">
<h2>8.11.10.6. 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>
<li><a class="reference internal" href="../grn_expr/script_syntax.html"><em>Script syntax</em></a></li>
</ul>
</div>
</div>
</div>
</div>
</div>
<div class="sphinxsidebar">
<div class="sphinxsidebarwrapper">
<h3><a href="../../index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">8.11.10. sub_filter</a><ul>
<li><a class="reference internal" href="#summary">8.11.10.1. Summary</a></li>
<li><a class="reference internal" href="#syntax">8.11.10.2. Syntax</a></li>
<li><a class="reference internal" href="#usage">8.11.10.3. Usage</a></li>
<li><a class="reference internal" href="#parameters">8.11.10.4. Parameters</a><ul>
<li><a class="reference internal" href="#scope">8.11.10.4.1. <tt class="docutils literal"><span class="pre">scope</span></tt></a></li>
<li><a class="reference internal" href="#filter-string">8.11.10.4.2. <tt class="docutils literal"><span class="pre">filter_string</span></tt></a></li>
</ul>
</li>
<li><a class="reference internal" href="#return-value">8.11.10.5. Return value</a></li>
<li><a class="reference internal" href="#see-also">8.11.10.6. See also</a></li>
</ul>
</li>
</ul>
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