terraformer

<!doctype html> <html> <head> <meta charset="utf-8"> <meta content="IE=edge,chrome=1" http-equiv="X-UA-Compatible"> <title>Terraformer</title> <link href="/assets/css/terraformer-02847305.css" media="screen" rel="stylesheet" type="text/css" /> </head> <body class="geostore geostore_alternate-indexes geostore_alternate-indexes_index" id="wrap"> <nav> <ul> <li> <a href="/" class="">Terraformer</a> </li> <li> <a href="https://github.com/search?q=%40Esri+terraformer" class="">GitHub</a> </li> <li> <a href="/install" class="">Install</a> </li> <li> <a href="/" data-direction="active-top" class="toggle" id="close-drawer">Docs</a> </li> </ul> </nav> <div class="drawer" id="drawer"> <div class="doctoc drawer-nav drawer-top"> <div class="container"> <ul> <h3>Terraformer Documentation</h3> <li><a href="/getting-started/">Getting Started</a></li> <li><a href="/core/">Terraformer Core</a></li> <li class="indent"><a href="/core/#terraformerprimitive">Primitives</a></li> <li class="indent"><a href="/core/#terraformertools">Tools</a></li> <li><a href="/geostore/">GeoStores</a></li> <li class="indent"><a href="/geostore/data-stores/">DataStores</a></li> <li class="indent"><a href="/geostore/spatial-indexes/">Spatial Indexes</a></li> <li><a href="/arcgis-parser/">ArcGIS Parser</a></li> <li><a href="/wkt-parser/">WKT Parser</a></li> <li><a href="/glossary/">Glossary</a></li> </ul> </div> </div> </div> <main class="docs main-content" id="main-content"> <h1>GeoStore Alternate Indexes</h1> Alternate Indexes are a very powerful way to apply additional filters to your searches on <code>properties</code> of a <code>Feature</code>. <h2> <a id='using-alternate-indexes' class='section-link'></a> <a href='#using-alternate-indexes' class='header-link'>Link</a> Using Alternate Indexes <a href='#' class='back-to-top-link'>Back to Top</a> </h2> Alternate Indexes can be added to an existing GeoStore very easily: <pre class="highlight javascript"><code>// create an index on the properties.street value gs.addIndex({ property: "street", index: new BTree() }); // create an index on the properties.crime value gs.addIndex({ property: "crime", index: new BTree() }); </code></pre> Queries against Alternate Indexes are very specific to the index, but the basic syntax of a query is straightforward: <pre class="highlight javascript"><code>gs.within( geojson, { "name": { "equals": "Main" }, "crime": { "equals": "Arson" } }, function (err, res) { // node.js style callback } ); </code></pre> In this example, first every <code>Feature</code> that is within the GeoJSON is found in the Spatial Index, then each of those entries are searched for in the B-Tree indexes. Only those entries that have a <code>properties.street</code> of “Main” and a <code>properties.crime</code> of “Arson” are returned. <h3> <a id='indexable-data' class='section-link'></a> <a href='#indexable-data' class='header-link'>Link</a> Indexable Data <a href='#' class='back-to-top-link'>Back to Top</a> </h3> Only data that is available in <code>properties</code> is indexable. When a <code>Feature</code> is added to the GeoStore, the list of Alternate Indexes is scanned, and any property that is found is added to that Alternate Index. Alternate Indexes are asyncronous and use Node.js style callbacks. <h3> <a id='existing-alternate-indexes' class='section-link'></a> <a href='#existing-alternate-indexes' class='header-link'>Link</a> Existing Alternate Indexes <a href='#' class='back-to-top-link'>Back to Top</a> </h3> Terraformer currently ships with a single alternate index, with more coming soon. <ul> <li><a href="https://github.com/JerrySievert/terraformer-geostore-index-btree">B-Tree</a> - A B-Tree index </li> </ul> <h2> <a id='writing-an-alternate-index' class='section-link'></a> <a href='#writing-an-alternate-index' class='header-link'>Link</a> Writing an Alternate Index <a href='#' class='back-to-top-link'>Back to Top</a> </h2> Alternate Indexes rely on two methods to be exposed to the GeoStore to add and remove data. Additional methods can be added for querying and are introspected for searching. For instance, when a <code>equals</code> query is made against an Alternate Index, if the <code>equals</code> method is on the index, then it is called with all arguments from the <code>contains</code> or <code>within</code>. <h3> <a id='indexadd' class='section-link'></a> <a href='#indexadd' class='header-link'>Link</a> Index.add(value, id, callback) <a href='#' class='back-to-top-link'>Back to Top</a> </h3> Add a value to the Alternate Index by <code>id</code>. <table><thead> <tr> <th>Option</th> <th>Value</th> <th>Description</th> </tr> </thead><tbody> <tr> <td>value</td> <td><code>String</code> or <code>Number</code></td> <td>The value to add to the index</td> </tr> <tr> <td>id</td> <td><code>String</code> or <code>Number</code></td> <td>The <code>id</code> of the <code>Feature</code> to be added</td> </tr> <tr> <td>callback</td> <td><code>function</code></td> <td>Callback to be fired when the <code>add</code> has been completed</td> </tr> </tbody></table> Example: <pre class="highlight javascript"><code>idx.add(value, id, function (err, res) { // Node.js style callback }); </code></pre> <h3> <a id='indexremove' class='section-link'></a> <a href='#indexremove' class='header-link'>Link</a> Index.remove(value, id, callback) <a href='#' class='back-to-top-link'>Back to Top</a> </h3> Add a value to the Alternate Index by <code>id</code>. <table><thead> <tr> <th>Option</th> <th>Value</th> <th>Description</th> </tr> </thead><tbody> <tr> <td>value</td> <td><code>String</code> or <code>Number</code></td> <td>The value to remove from the index</td> </tr> <tr> <td>id</td> <td><code>String</code> or <code>Number</code></td> <td>The <code>id</code> of the <code>Feature</code> to be removed</td> </tr> <tr> <td>callback</td> <td><code>function</code></td> <td>Callback to be fired when the <code>remove</code> has been completed</td> </tr> </tbody></table> Example: <pre class="highlight javascript"><code>idx.add(value, id, function (err, res) { // Node.js style callback }); </code></pre> </main> <footer> Terraformer is an open source project from the <a href="http://pdx.esri.com/">Esri Portland R&D Center</a> </footer> <script src="/assets/javascripts/modernizr.custom-cadc78a2.js" type="text/javascript"></script> <script src="/assets/javascripts/classie-b6db1f70.js" type="text/javascript"></script> <script src="/assets/javascripts/drawer-3a1490eb.js" type="text/javascript"></script> </body> </html>