CM93VectorDataSet.IndexPath Property
Gets or sets the directory where the dataset index files are saved.
Syntax
public System.String IndexPath { get; set; }Property Value
Default: ""
The directory where the dataset index files are saved.
This property can only be modified before the dataset has been initialized. Attempting to modify it after initialization will cause an exception to be thrown.
Remarks
This property specifies a directory where the dataset will save one or more index files. Three different types of index files may be written: a spatial file index, a text search index, and a raster cache. The name of the files will be <dataset type>_<hash>.<extension>, where <dataset type> is the type of dataset (e.g. "ShapefileDataSet"), hash is a string that is calculated from the properties of the dataset, and the extension is one of .carmentafileindex, .carmentasearchindex or .carmentarastercache. The generated name can be overridden by using the IndexFileName property, see for instance MultiFileDataSet.IndexFileName. Most Carmenta Engine datasets typically only support one or two of these index types.
The file index is always created when the dataset is first initialized, and will always be kept in memory. It contains the names of all files the dataset will read, and their bounds stored in a spatial index for efficient lookup. If this property is specified, the dataset will save the file index to the index file. When the dataset is loaded again at a later time, it can read the index file instead of recreating the index from the data file, which can reduce dataset load time significantly.
Some datasets can create a text search index, allowing the application to perform quick searches, for instance for features with certain city or street names. The search index is also stored in the directory specified by this property. See for instance ShapefileDataSet.SearchableAttributes for information.
Some raster datasets can create a raster cache, to speed up access to the raster data. This raster cache is also stored in a file in the directory specified by this property. See for instance ImageDataSet.RasterCachePolicy for information.
If a dataset has a path property indicating the data directory, it will try to determine the relative path from the data directory to the index file when generating the hash for the file name. This will make it possible to move both data and pre-generated index files to a different location, perhaps to a different machine; the index files will be used from the new location. This will however not work on Windows if the data files and index files are located on different drives; the index will be regenerated after a move. The same thing will also happen if the path is left empty, but setting it to "." will work.
If you specify a search index or a raster cache, you must also specify this property, or you will get an exception.
In addition to creating an index of all the files in a dataset, some datasets also create a per-file index of all the features in the file. This is specified with a different property, see for instance ShapefileDataSet.FeatureIndexPath.
Platforms
Windows