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<!DOCTYPE html>
<html>
<head>
<title>Basic Example</title>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<meta name="viewport" content="width=device-width, target-densitydpi=160dpi, initial-scale=1.0; maximum-scale=1.0; user-scalable=0;">
<link rel="stylesheet" media="all" href="docco.css" />
</head>
<body>
<div id="container">
<div id="background"></div>
<ul class="sections">
<li id="section-1">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-1">¶</a>
</div>
<h1 id="basic-example">Basic Example</h1>
<p>This example covers the basic functionalities of
tantivy.</p>
<p>We will :</p>
<ul>
<li>define our schema
= create an index in a directory</li>
<li>index few documents in our index</li>
<li>search for the best document matchings “sea whale”</li>
<li>retrieve the best document original content.</li>
</ul>
</div>
</li>
<li id="section-2">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-2">¶</a>
</div>
<hr>
</div>
</li>
<li id="section-3">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-3">¶</a>
</div>
<p>Importing tantivy…</p>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-meta">#[macro_use]</span>
<span class="hljs-keyword">extern</span> <span class="hljs-keyword">crate</span> tantivy;
<span class="hljs-keyword">use</span> tantivy::collector::TopDocs;
<span class="hljs-keyword">use</span> tantivy::query::QueryParser;
<span class="hljs-keyword">use</span> tantivy::schema::*;
<span class="hljs-keyword">use</span> tantivy::Index;
<span class="hljs-keyword">use</span> tantivy::ReloadPolicy;
<span class="hljs-keyword">use</span> tempfile::TempDir;
<span class="hljs-function"><span class="hljs-keyword">fn</span> <span class="hljs-title">main</span></span>() -> tantivy::<span class="hljs-built_in">Result</span><()> {</pre></div></div>
</li>
<li id="section-4">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-4">¶</a>
</div>
<p>Let’s create a temporary directory for the
sake of this example</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">let</span> index_path = TempDir::new()?;</pre></div></div>
</li>
<li id="section-5">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-5">¶</a>
</div>
<h1 id="defining-the-schema">Defining the schema</h1>
<p>The Tantivy index requires a very strict schema.
The schema declares which fields are in the index,
and for each field, its type and “the way it should
be indexed”.</p>
</div>
</li>
<li id="section-6">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-6">¶</a>
</div>
<p>first we need to define a schema …</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">let</span> <span class="hljs-keyword">mut</span> schema_builder = Schema::builder();</pre></div></div>
</li>
<li id="section-7">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-7">¶</a>
</div>
<p>Our first field is title.
We want full-text search for it, and we also want
to be able to retrieve the document after the search.</p>
<p><code>TEXT | STORED</code> is some syntactic sugar to describe
that.</p>
<p><code>TEXT</code> means the field should be tokenized and indexed,
along with its term frequency and term positions.</p>
<p><code>STORED</code> means that the field will also be saved
in a compressed, row-oriented key-value store.
This store is useful to reconstruct the
documents that were selected during the search phase.</p>
</div>
<div class="content"><div class='highlight'><pre> schema_builder.add_text_field(<span class="hljs-string">"title"</span>, TEXT | STORED);</pre></div></div>
</li>
<li id="section-8">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-8">¶</a>
</div>
<p>Our second field is body.
We want full-text search for it, but we do not
need to be able to retrieve it
for our application.</p>
<p>We can make our index lighter and
by omitting <code>STORED</code> flag.</p>
</div>
<div class="content"><div class='highlight'><pre> schema_builder.add_text_field(<span class="hljs-string">"body"</span>, TEXT);
<span class="hljs-keyword">let</span> schema = schema_builder.build();</pre></div></div>
</li>
<li id="section-9">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-9">¶</a>
</div>
<h1 id="indexing-documents">Indexing documents</h1>
<p>Let’s create a brand new index.</p>
<p>This will actually just save a meta.json
with our schema in the directory.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">let</span> index = Index::create_in_dir(&index_path, schema.clone())?;</pre></div></div>
</li>
<li id="section-10">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-10">¶</a>
</div>
<p>To insert document we need an index writer.
There must be only one writer at a time.
This single <code>IndexWriter</code> is already
multithreaded.</p>
<p>Here we give tantivy a budget of <code>50MB</code>.
Using a bigger heap for the indexer may increase
throughput, but 50 MB is already plenty.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">let</span> <span class="hljs-keyword">mut</span> index_writer = index.writer(<span class="hljs-number">50_000_000</span>)?;</pre></div></div>
</li>
<li id="section-11">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-11">¶</a>
</div>
<p>Let’s index our documents!
We first need a handle on the title and the body field.</p>
</div>
</li>
<li id="section-12">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-12">¶</a>
</div>
<h3 id="adding-documents">Adding documents</h3>
<p>We can create a document manually, by setting the fields
one by one in a Document object.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">let</span> title = schema.get_field(<span class="hljs-string">"title"</span>).unwrap();
<span class="hljs-keyword">let</span> body = schema.get_field(<span class="hljs-string">"body"</span>).unwrap();
<span class="hljs-keyword">let</span> <span class="hljs-keyword">mut</span> old_man_doc = Document::<span class="hljs-keyword">default</span>();
old_man_doc.add_text(title, <span class="hljs-string">"The Old Man and the Sea"</span>);
old_man_doc.add_text(
body,
<span class="hljs-string">"He was an old man who fished alone in a skiff in the Gulf Stream and \
he had gone eighty-four days now without taking a fish."</span>,
);</pre></div></div>
</li>
<li id="section-13">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-13">¶</a>
</div>
<p>… and add it to the <code>IndexWriter</code>.</p>
</div>
<div class="content"><div class='highlight'><pre> index_writer.add_document(old_man_doc);</pre></div></div>
</li>
<li id="section-14">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-14">¶</a>
</div>
<p>For convenience, tantivy also comes with a macro to
reduce the boilerplate above.</p>
</div>
<div class="content"><div class='highlight'><pre> index_writer.add_document(doc!(
title => <span class="hljs-string">"Of Mice and Men"</span>,
body => <span class="hljs-string">"A few miles south of Soledad, the Salinas River drops in close to the hillside \
bank and runs deep and green. The water is warm too, for it has slipped twinkling \
over the yellow sands in the sunlight before reaching the narrow pool. On one \
side of the river the golden foothill slopes curve up to the strong and rocky \
Gabilan Mountains, but on the valley side the water is lined with trees—willows \
fresh and green with every spring, carrying in their lower leaf junctures the \
debris of the winter’s flooding; and sycamores with mottled, white, recumbent \
limbs and branches that arch over the pool"</span>
));
index_writer.add_document(doc!(
title => <span class="hljs-string">"Of Mice and Men"</span>,
body => <span class="hljs-string">"A few miles south of Soledad, the Salinas River drops in close to the hillside \
bank and runs deep and green. The water is warm too, for it has slipped twinkling \
over the yellow sands in the sunlight before reaching the narrow pool. On one \
side of the river the golden foothill slopes curve up to the strong and rocky \
Gabilan Mountains, but on the valley side the water is lined with trees—willows \
fresh and green with every spring, carrying in their lower leaf junctures the \
debris of the winter’s flooding; and sycamores with mottled, white, recumbent \
limbs and branches that arch over the pool"</span>
));</pre></div></div>
</li>
<li id="section-15">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-15">¶</a>
</div>
<p>Multivalued field just need to be repeated.</p>
</div>
<div class="content"><div class='highlight'><pre> index_writer.add_document(doc!(
title => <span class="hljs-string">"Frankenstein"</span>,
title => <span class="hljs-string">"The Modern Prometheus"</span>,
body => <span class="hljs-string">"You will rejoice to hear that no disaster has accompanied the commencement of an \
enterprise which you have regarded with such evil forebodings. I arrived here \
yesterday, and my first task is to assure my dear sister of my welfare and \
increasing confidence in the success of my undertaking."</span>
));</pre></div></div>
</li>
<li id="section-16">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-16">¶</a>
</div>
<p>This is an example, so we will only index 3 documents
here. You can check out tantivy’s tutorial to index
the English wikipedia. Tantivy’s indexing is rather fast.
Indexing 5 million articles of the English wikipedia takes
around 3 minutes on my computer!</p>
</div>
</li>
<li id="section-17">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-17">¶</a>
</div>
<h3 id="committing">Committing</h3>
<p>At this point our documents are not searchable.</p>
<p>We need to call .commit() explicitly to force the
index_writer to finish processing the documents in the queue,
flush the current index to the disk, and advertise
the existence of new documents.</p>
<p>This call is blocking.</p>
</div>
<div class="content"><div class='highlight'><pre> index_writer.commit()?;</pre></div></div>
</li>
<li id="section-18">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-18">¶</a>
</div>
<p>If <code>.commit()</code> returns correctly, then all of the
documents that have been added are guaranteed to be
persistently indexed.</p>
<p>In the scenario of a crash or a power failure,
tantivy behaves as if has rolled back to its last
commit.</p>
</div>
</li>
<li id="section-19">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-19">¶</a>
</div>
<h1 id="searching">Searching</h1>
<h3 id="searcher">Searcher</h3>
<p>A reader is required to get search the index.
It acts as a <code>Searcher</code> pool that reloads itself,
depending on a <code>ReloadPolicy</code>.</p>
<p>For a search server you will typically create one reader for the entire lifetime of your
program, and acquire a new searcher for every single request.</p>
<p>In the code below, we rely on the ‘ON_COMMIT’ policy: the reader
will reload the index automatically after each commit.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">let</span> reader = index
.reader_builder()
.reload_policy(ReloadPolicy::OnCommit)
.try_into()?;</pre></div></div>
</li>
<li id="section-20">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-20">¶</a>
</div>
<p>We now need to acquire a searcher.</p>
<p>A searcher points to snapshotted, immutable version of the index.</p>
<p>Some search experience might require more than
one query. Using the same searcher ensures that all of these queries will run on the
same version of the index.</p>
<p>Acquiring a <code>searcher</code> is very cheap.</p>
<p>You should acquire a searcher every time you start processing a request and
and release it right after your query is finished.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">let</span> searcher = reader.searcher();</pre></div></div>
</li>
<li id="section-21">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-21">¶</a>
</div>
<h3 id="query">Query</h3>
</div>
</li>
<li id="section-22">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-22">¶</a>
</div>
<p>The query parser can interpret human queries.
Here, if the user does not specify which
field they want to search, tantivy will search
in both title and body.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">let</span> query_parser = QueryParser::for_index(&index, <span class="hljs-built_in">vec!</span>[title, body]);</pre></div></div>
</li>
<li id="section-23">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-23">¶</a>
</div>
<p>QueryParser may fail if the query is not in the right
format. For user facing applications, this can be a problem.
A ticket has been opened regarding this problem.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">let</span> query = query_parser.parse_query(<span class="hljs-string">"sea whale"</span>)?;</pre></div></div>
</li>
<li id="section-24">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-24">¶</a>
</div>
<p>A query defines a set of documents, as
well as the way they should be scored.</p>
<p>A query created by the query parser is scored according
to a metric called Tf-Idf, and will consider
any document matching at least one of our terms.</p>
</div>
</li>
<li id="section-25">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-25">¶</a>
</div>
<h3 id="collectors">Collectors</h3>
<p>We are not interested in all of the documents but
only in the top 10. Keeping track of our top 10 best documents
is the role of the TopDocs.</p>
</div>
</li>
<li id="section-26">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-26">¶</a>
</div>
<p>We can now perform our query.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">let</span> top_docs = searcher.search(&query, &TopDocs::with_limit(<span class="hljs-number">10</span>))?;</pre></div></div>
</li>
<li id="section-27">
<div class="annotation">
<div class="pilwrap ">
<a class="pilcrow" href="#section-27">¶</a>
</div>
<p>The actual documents still need to be
retrieved from Tantivy’s store.</p>
<p>Since the body field was not configured as stored,
the document returned will only contain
a title.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">for</span> (_score, doc_address) <span class="hljs-keyword">in</span> top_docs {
<span class="hljs-keyword">let</span> retrieved_doc = searcher.doc(doc_address)?;
<span class="hljs-built_in">println!</span>(<span class="hljs-string">"{}"</span>, schema.to_json(&retrieved_doc));
}
<span class="hljs-literal">Ok</span>(())
}</pre></div></div>
</li>
</ul>
</div>
</body>
</html>