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<div class="section" id="indexing">
<h1><span class="section-number">7.21. </span>Indexing<a class="headerlink" href="#indexing" title="Permalink to this headline">¶</a></h1>
<p>Groonga supports both online index construction and offline
index construction since 2.0.0.</p>
<div class="section" id="online-index-construction">
<span id="id1"></span><h2><span class="section-number">7.21.1. </span>Online index construction<a class="headerlink" href="#online-index-construction" title="Permalink to this headline">¶</a></h2>
<p>In online index construction, registered documents can be
searchable quickly while indexing. But indexing requires
more cost rather than indexing by offline index
construction.</p>
<p>Online index construction is suitable for a search system
that values freshness. For example, a search system for
tweets, news, blog posts and so on will value
freshness. Online index construction can make fresh
documents searchable and keep searchable while indexing.</p>
</div>
<div class="section" id="offline-index-construction">
<span id="id2"></span><h2><span class="section-number">7.21.2. </span>Offline index construction<a class="headerlink" href="#offline-index-construction" title="Permalink to this headline">¶</a></h2>
<p>In offline index construction, indexing cost is less than
indexing cost by online index construction. Indexing time
will be shorter. Index will be smaller. Resources required
for indexing will be smaller. But a registering document
cannot be searchable until all registered documents are
indexed.</p>
<p>Offline index construction is suitable for a search system
that values less required resources. If a search system
doesn’t value freshness, offline index construction will be
suitable. For example, a reference manual search system
doesn’t value freshness because a reference manual will be
updated only at a release.</p>
</div>
<div class="section" id="how-to-use">
<h2><span class="section-number">7.21.3. </span>How to use<a class="headerlink" href="#how-to-use" title="Permalink to this headline">¶</a></h2>
<p>Groonga uses online index construction by default. We
register a document, we can search it quickly.</p>
<p>Groonga uses offline index construction by adding an index
to a column that already has data.</p>
<p>We define a schema:</p>
<p>Execution example:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>table_create Tweets TABLE_NO_KEY
# [[0, 1337566253.89858, 0.000355720520019531], true]
column_create Tweets content COLUMN_SCALAR ShortText
# [[0, 1337566253.89858, 0.000355720520019531], true]
table_create Lexicon TABLE_HASH_KEY ShortText --default_tokenizer TokenBigram --normalizer NormalizerAuto
# [[0, 1337566253.89858, 0.000355720520019531], true]
</pre></div>
</div>
<p>We register data:</p>
<p>Execution example:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>load --table Tweets
[
{"content":"Hello!"},
{"content":"I just start it!"},
{"content":"I'm sleepy... Have a nice day... Good night..."}
]
# [[0, 1337566253.89858, 0.000355720520019531], 3]
</pre></div>
</div>
<p>We can search with sequential search when we don’t have index:</p>
<p>Execution example:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>select Tweets --match_columns content --query 'good nice'
# [
# [
# 0,
# 1337566253.89858,
# 0.000355720520019531
# ],
# [
# [
# [
# 1
# ],
# [
# [
# "_id",
# "UInt32"
# ],
# [
# "content",
# "ShortText"
# ]
# ],
# [
# 3,
# "I'm sleepy... Have a nice day... Good night..."
# ]
# ]
# ]
# ]
</pre></div>
</div>
<p>We create index for <code class="docutils literal notranslate"><span class="pre">Tweets.content</span></code>. Already registered
data in <code class="docutils literal notranslate"><span class="pre">Tweets.content</span></code> are indexed by offline index
construction:</p>
<p>Execution example:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>column_create Lexicon tweet COLUMN_INDEX|WITH_POSITION Tweets content
# [[0, 1337566253.89858, 0.000355720520019531], true]
</pre></div>
</div>
<p>We search with index. We get a matched record:</p>
<p>Execution example:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>select Tweets --match_columns content --query 'good nice'
# [
# [
# 0,
# 1337566253.89858,
# 0.000355720520019531
# ],
# [
# [
# [
# 1
# ],
# [
# [
# "_id",
# "UInt32"
# ],
# [
# "content",
# "ShortText"
# ]
# ],
# [
# 3,
# "I'm sleepy... Have a nice day... Good night..."
# ]
# ]
# ]
# ]
</pre></div>
</div>
<p>We register data again. They are indexed by online index
construction:</p>
<p>Execution example:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>load --table Tweets
[
{"content":"Good morning! Nice day."},
{"content":"Let's go shopping."}
]
# [[0, 1337566253.89858, 0.000355720520019531], 2]
</pre></div>
</div>
<p>We can also get newly registered records by searching:</p>
<p>Execution example:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>select Tweets --match_columns content --query 'good nice'
# [
# [
# 0,
# 1337566253.89858,
# 0.000355720520019531
# ],
# [
# [
# [
# 2
# ],
# [
# [
# "_id",
# "UInt32"
# ],
# [
# "content",
# "ShortText"
# ]
# ],
# [
# 3,
# "I'm sleepy... Have a nice day... Good night..."
# ],
# [
# 4,
# "Good morning! Nice day."
# ]
# ]
# ]
# ]
</pre></div>
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<h3><a href="../index.html">Table of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">7.21. Indexing</a><ul>
<li><a class="reference internal" href="#online-index-construction">7.21.1. Online index construction</a></li>
<li><a class="reference internal" href="#offline-index-construction">7.21.2. Offline index construction</a></li>
<li><a class="reference internal" href="#how-to-use">7.21.3. How to use</a></li>
</ul>
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