Improving Performance for Distance-Based Operations

A PGD index file is a supplemental file to the TAB file set that can make performance for native, native extended (NativeX), and seamless TABs comparable to that of GSB files. The PGD Builder, a command-line utility, is available to generate these specialized index files to improve performance of certain distance-based operations for native datasets containing lines and polygons. An index built using the PGD Builder is helpful when the data you are searching is based on lines and regions and you are using:
  • the Point in Polygon stage, when you are including distance
  • the Find Nearest stage, when the input is a point (whether or not you are including distance)
  • SearchNearest operations in the Feature Service, with an input point and a line or polygon search table
The PGD Builder utility can be downloaded from the Spectrum Spatial section of the Welcome Page, under PGD Builder on the Utilities tab. A link to the is also available on the Welcome Page next to the download link for the utility.
Note: A PGD file is 5-6 times larger than the .MAP file for the TAB. One PGD file is generated per TAB file, except in the case of a seamless TAB which will have PGD files created for each sub-TAB.

Also, a PGD file will no longer be used by the system if you change the data in the TAB (that is, if rows have been added or deleted or a geometry has been changed in the MAP portion of the TAB). If warnings are enabled (see Spatial Logging), a message about the out-of-date PGD file will appear in the wrapper.log or if applicable, in the log file that has been configured for Spatial logging. You must then regenerate the PGD for the updated TAB file.