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| <h1 id="Lucene_Net_Spatial_Prefix" data-uid="Lucene.Net.Spatial.Prefix" class="text-break">Namespace Lucene.Net.Spatial.Prefix |
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| <p>Prefix Tree Strategy</p> |
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| <div class="markdown level0 conceptual"></div> |
| <div class="markdown level0 remarks"></div> |
| <h3 id="classes">Classes |
| </h3> |
| <h4><a class="xref" href="Lucene.Net.Spatial.Prefix.AbstractPrefixTreeFilter.html">AbstractPrefixTreeFilter</a></h4> |
| <section><p>Base class for Lucene Filters on SpatialPrefixTree fields.</p> |
| <div class="lucene-block lucene-experimental">This is a Lucene.NET EXPERIMENTAL API, use at your own risk</div></section> |
| <h4><a class="xref" href="Lucene.Net.Spatial.Prefix.AbstractPrefixTreeFilter.BaseTermsEnumTraverser.html">AbstractPrefixTreeFilter.BaseTermsEnumTraverser</a></h4> |
| <section><p>Holds transient state and docid collecting utility methods as part of |
| traversing a <span class="xref">Lucene.Net.Index.TermsEnum</span>.</p> |
| </section> |
| <h4><a class="xref" href="Lucene.Net.Spatial.Prefix.AbstractVisitingPrefixTreeFilter.html">AbstractVisitingPrefixTreeFilter</a></h4> |
| <section><p>Traverses a <a class="xref" href="Lucene.Net.Spatial.Prefix.Tree.SpatialPrefixTree.html">SpatialPrefixTree</a> indexed field, using the template & |
| visitor design patterns for subclasses to guide the traversal and collect |
| matching documents. |
| <p> |
| Subclasses implement <span class="xref">Lucene.Net.Search.Filter.GetDocIdSet(Lucene.Net.Index.AtomicReaderContext, Lucene.Net.Util.IBits)</span> |
| by instantiating a custom <a class="xref" href="Lucene.Net.Spatial.Prefix.AbstractVisitingPrefixTreeFilter.VisitorTemplate.html">AbstractVisitingPrefixTreeFilter.VisitorTemplate</a> subclass (i.e. an anonymous inner class) and implement the |
| required methods.</p> |
| <div class="lucene-block lucene-internal">This is a Lucene.NET INTERNAL API, use at your own risk</div></section> |
| <h4><a class="xref" href="Lucene.Net.Spatial.Prefix.AbstractVisitingPrefixTreeFilter.VisitorTemplate.html">AbstractVisitingPrefixTreeFilter.VisitorTemplate</a></h4> |
| <section><p>An abstract class designed to make it easy to implement predicates or |
| other operations on a <a class="xref" href="Lucene.Net.Spatial.Prefix.Tree.SpatialPrefixTree.html">SpatialPrefixTree</a> indexed field. An instance |
| of this class is not designed to be re-used across AtomicReaderContext |
| instances so simply create a new one for each call to, say a |
| <span class="xref">Lucene.Net.Search.Filter.GetDocIdSet(Lucene.Net.Index.AtomicReaderContext, Lucene.Net.Util.IBits)</span>. |
| The <a class="xref" href="Lucene.Net.Spatial.Prefix.AbstractVisitingPrefixTreeFilter.VisitorTemplate.html#Lucene_Net_Spatial_Prefix_AbstractVisitingPrefixTreeFilter_VisitorTemplate_GetDocIdSet">GetDocIdSet()</a> method here starts the work. It first checks |
| that there are indexed terms; if not it quickly returns null. Then it calls |
| <a class="xref" href="Lucene.Net.Spatial.Prefix.AbstractVisitingPrefixTreeFilter.VisitorTemplate.html#Lucene_Net_Spatial_Prefix_AbstractVisitingPrefixTreeFilter_VisitorTemplate_Start">Start()</a> so a subclass can set up a return value, like an |
| <span class="xref">Lucene.Net.Util.FixedBitSet</span>. Then it starts the traversal |
| process, calling <a class="xref" href="Lucene.Net.Spatial.Prefix.AbstractVisitingPrefixTreeFilter.VisitorTemplate.html#Lucene_Net_Spatial_Prefix_AbstractVisitingPrefixTreeFilter_VisitorTemplate_FindSubCellsToVisit_Lucene_Net_Spatial_Prefix_Tree_Cell_">FindSubCellsToVisit(Cell)</a> |
| which by default finds the top cells that intersect <code>queryShape</code>. If |
| there isn't an indexed cell for a corresponding cell returned for this |
| method then it's short-circuited until it finds one, at which point |
| <a class="xref" href="Lucene.Net.Spatial.Prefix.AbstractVisitingPrefixTreeFilter.VisitorTemplate.html#Lucene_Net_Spatial_Prefix_AbstractVisitingPrefixTreeFilter_VisitorTemplate_Visit_Lucene_Net_Spatial_Prefix_Tree_Cell_">Visit(Cell)</a> is called. At |
| some depths, of the tree, the algorithm switches to a scanning mode that |
| calls <a class="xref" href="Lucene.Net.Spatial.Prefix.AbstractVisitingPrefixTreeFilter.VisitorTemplate.html#Lucene_Net_Spatial_Prefix_AbstractVisitingPrefixTreeFilter_VisitorTemplate_VisitScanned_Lucene_Net_Spatial_Prefix_Tree_Cell_">VisitScanned(Cell)</a> |
| for each leaf cell found.</p> |
| <div class="lucene-block lucene-internal">This is a Lucene.NET INTERNAL API, use at your own risk</div></section> |
| <h4><a class="xref" href="Lucene.Net.Spatial.Prefix.AbstractVisitingPrefixTreeFilter.VNode.html">AbstractVisitingPrefixTreeFilter.VNode</a></h4> |
| <section><p>A Visitor node/cell found via the query shape for <a class="xref" href="Lucene.Net.Spatial.Prefix.AbstractVisitingPrefixTreeFilter.VisitorTemplate.html">AbstractVisitingPrefixTreeFilter.VisitorTemplate</a>. |
| Sometimes these are reset(cell). It's like a LinkedList node but forms a |
| tree.</p> |
| <div class="lucene-block lucene-internal">This is a Lucene.NET INTERNAL API, use at your own risk</div></section> |
| <h4><a class="xref" href="Lucene.Net.Spatial.Prefix.ContainsPrefixTreeFilter.html">ContainsPrefixTreeFilter</a></h4> |
| <section><p>Finds docs where its indexed shape <a class="xref" href="Lucene.Net.Spatial.Queries.SpatialOperation.html#Lucene_Net_Spatial_Queries_SpatialOperation_Contains">Contains</a> |
| the query shape. For use on <a class="xref" href="Lucene.Net.Spatial.Prefix.RecursivePrefixTreeStrategy.html">RecursivePrefixTreeStrategy</a>.</p> |
| <div class="lucene-block lucene-experimental">This is a Lucene.NET EXPERIMENTAL API, use at your own risk</div></section> |
| <h4><a class="xref" href="Lucene.Net.Spatial.Prefix.IntersectsPrefixTreeFilter.html">IntersectsPrefixTreeFilter</a></h4> |
| <section><p>A Filter matching documents that have an <span class="xref">Spatial4n.Core.Shapes.SpatialRelation.INTERSECTS</span> |
| (i.e. not DISTINCT) relationship with a provided query shape.</p> |
| <div class="lucene-block lucene-internal">This is a Lucene.NET INTERNAL API, use at your own risk</div></section> |
| <h4><a class="xref" href="Lucene.Net.Spatial.Prefix.PointPrefixTreeFieldCacheProvider.html">PointPrefixTreeFieldCacheProvider</a></h4> |
| <section><p>Implementation of <a class="xref" href="Lucene.Net.Spatial.Util.ShapeFieldCacheProvider-1.html">ShapeFieldCacheProvider<T></a> |
| designed for <a class="xref" href="Lucene.Net.Spatial.Prefix.PrefixTreeStrategy.html">PrefixTreeStrategy</a>s.</p> |
| <p>Note, due to the fragmented representation of Shapes in these Strategies, this implementation |
| can only retrieve the central <span class="xref">Spatial4n.Core.Shapes.IPoint</span> of the original Shapes.</p> |
| <div class="lucene-block lucene-internal">This is a Lucene.NET INTERNAL API, use at your own risk</div></section> |
| <h4><a class="xref" href="Lucene.Net.Spatial.Prefix.PrefixTreeStrategy.html">PrefixTreeStrategy</a></h4> |
| <section><p>An abstract SpatialStrategy based on <a class="xref" href="Lucene.Net.Spatial.Prefix.Tree.SpatialPrefixTree.html">SpatialPrefixTree</a>. The two |
| subclasses are <a class="xref" href="Lucene.Net.Spatial.Prefix.RecursivePrefixTreeStrategy.html">RecursivePrefixTreeStrategy</a> and |
| <a class="xref" href="Lucene.Net.Spatial.Prefix.TermQueryPrefixTreeStrategy.html">TermQueryPrefixTreeStrategy</a>. This strategy is most effective as a fast |
| approximate spatial search filter.</p> |
| <p><h4>Characteristics:</h4> |
| <ul><li>Can index any shape; however only |
| <a class="xref" href="Lucene.Net.Spatial.Prefix.RecursivePrefixTreeStrategy.html">RecursivePrefixTreeStrategy</a> |
| can effectively search non-point shapes.</li><li>Can index a variable number of shapes per field value. This strategy |
| can do it via multiple calls to <a class="xref" href="Lucene.Net.Spatial.Prefix.PrefixTreeStrategy.html#Lucene_Net_Spatial_Prefix_PrefixTreeStrategy_CreateIndexableFields_Spatial4n_Core_Shapes_IShape_">CreateIndexableFields(IShape)</a> |
| for a document or by giving it some sort of Shape aggregate (e.g. NTS |
| WKT MultiPoint). The shape's boundary is approximated to a grid precision. |
| </li><li>Can query with any shape. The shape's boundary is approximated to a grid |
| precision.</li><li>Only <a class="xref" href="Lucene.Net.Spatial.Queries.SpatialOperation.html#Lucene_Net_Spatial_Queries_SpatialOperation_Intersects">Intersects</a> |
| is supported. If only points are indexed then this is effectively equivalent |
| to IsWithin.</li><li>The strategy supports <a class="xref" href="Lucene.Net.Spatial.Prefix.PrefixTreeStrategy.html#Lucene_Net_Spatial_Prefix_PrefixTreeStrategy_MakeDistanceValueSource_Spatial4n_Core_Shapes_IPoint_System_Double_">MakeDistanceValueSource(IPoint, Double)</a> |
| even for multi-valued data, so long as the indexed data is all points; the |
| behavior is undefined otherwise. However, <code>it will likely be removed in |
| the future</code> in lieu of using another strategy with a more scalable |
| implementation. Use of this call is the only |
| circumstance in which a cache is used. The cache is simple but as such |
| it doesn't scale to large numbers of points nor is it real-time-search |
| friendly.</li></ul></p> |
| <p><h4>Implementation:</h4> |
| The <a class="xref" href="Lucene.Net.Spatial.Prefix.Tree.SpatialPrefixTree.html">SpatialPrefixTree</a> |
| does most of the work, for example returning |
| a list of terms representing grids of various sizes for a supplied shape. |
| An important |
| configuration item is <a class="xref" href="Lucene.Net.Spatial.Prefix.PrefixTreeStrategy.html#Lucene_Net_Spatial_Prefix_PrefixTreeStrategy_DistErrPct">DistErrPct</a> which balances |
| shape precision against scalability. See those docs.</p> |
| <div class="lucene-block lucene-internal">This is a Lucene.NET INTERNAL API, use at your own risk</div></section> |
| <h4><a class="xref" href="Lucene.Net.Spatial.Prefix.RecursivePrefixTreeStrategy.html">RecursivePrefixTreeStrategy</a></h4> |
| <section><p>A <a class="xref" href="Lucene.Net.Spatial.Prefix.PrefixTreeStrategy.html">PrefixTreeStrategy</a> which uses <a class="xref" href="Lucene.Net.Spatial.Prefix.AbstractVisitingPrefixTreeFilter.html">AbstractVisitingPrefixTreeFilter</a>. |
| This strategy has support for searching non-point shapes (note: not tested). |
| Even a query shape with distErrPct=0 (fully precise to the grid) should have |
| good performance for typical data, unless there is a lot of indexed data |
| coincident with the shape's edge.</p> |
| <div class="lucene-block lucene-experimental">This is a Lucene.NET EXPERIMENTAL API, use at your own risk</div></section> |
| <h4><a class="xref" href="Lucene.Net.Spatial.Prefix.TermQueryPrefixTreeStrategy.html">TermQueryPrefixTreeStrategy</a></h4> |
| <section><p>A basic implementation of <a class="xref" href="Lucene.Net.Spatial.Prefix.PrefixTreeStrategy.html">PrefixTreeStrategy</a> using a large |
| <span class="xref">Lucene.Net.Queries.TermsFilter</span> of all the cells from |
| <a class="xref" href="Lucene.Net.Spatial.Prefix.Tree.SpatialPrefixTree.html#Lucene_Net_Spatial_Prefix_Tree_SpatialPrefixTree_GetCells_Spatial4n_Core_Shapes_IShape_System_Int32_System_Boolean_System_Boolean_">GetCells(IShape, Int32, Boolean, Boolean)</a>. |
| It only supports the search of indexed Point shapes. |
| <p> |
| The precision of query shapes (DistErrPct) is an important factor in using |
| this Strategy. If the precision is too precise then it will result in many |
| terms which will amount to a slower query.</p> |
| <div class="lucene-block lucene-experimental">This is a Lucene.NET EXPERIMENTAL API, use at your own risk</div></section> |
| <h4><a class="xref" href="Lucene.Net.Spatial.Prefix.WithinPrefixTreeFilter.html">WithinPrefixTreeFilter</a></h4> |
| <section><p>Finds docs where its indexed shape is |
| <a class="xref" href="Lucene.Net.Spatial.Queries.SpatialOperation.html#Lucene_Net_Spatial_Queries_SpatialOperation_IsWithin">IsWithin</a> |
| the query shape. It works by looking at cells outside of the query |
| shape to ensure documents there are excluded. By default, it will |
| examine all cells, and it's fairly slow. If you know that the indexed shapes |
| are never comprised of multiple disjoint parts (which also means it is not multi-valued), |
| then you can pass <code>SpatialPrefixTree.GetDistanceForLevel(maxLevels)</code> as |
| the <code>queryBuffer</code> constructor parameter to minimally look this distance |
| beyond the query shape's edge. Even if the indexed shapes are sometimes |
| comprised of multiple disjoint parts, you might want to use this option with |
| a large buffer as a faster approximation with minimal false-positives.</p> |
| <div class="lucene-block lucene-experimental">This is a Lucene.NET EXPERIMENTAL API, use at your own risk</div></section> |
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