Xamin and batch queries

Over the next couple of weeks we plan for Xamin to take over responsibility for batch queries sent to the HEASARC. In our initial tests the Xamin queries ran about 4 times faster.  While we’ve made some efforts to minimize the differences between Xamin and the current Browse-based results there are still a few.

The differences include:

  • The name of the column giving the offset between the target position and the row in the table is _offset, not Search_offset
  • The value of the offset column does not include the central position.  E.g., if you have asked for rows near the position 00 40 24, 40 32 , the current offset column might contain 0.235 (00 40 24, 40 32) but it will just be 0.235 in the new version.
  • Class codes will be returned for the HEASARC classifications, not the string value corresponding to the class code.
  • The mission name is not given when the list of available tables is shown.  In Xamin not all tables are associated with missions (some are associated with regimes or object types).  We added a ‘archive’ column to keep the format similar.
  • Error messages are very different.  E.g., If a user requests a VOTable output, Browse still gives an HTML error message when there is an error retrieving data, but Xamin returns an VOTable with the error status.  If there are errors when the user is making a FITS or Excel format request, then there may be no output where Browse might have returned an HTML error message.
  • There are numerous detailed format differences in the Excel and FITS outputs.  E.g., Xamin uses a binary table format while Browse uses ASCII tables.

There are some new features.  Since we are limited to the interface that the Xamin batch script provides only a few of the new capabilities of Xamin are available, but a few do leak though e.g.,

  • The fields displayed can contain expressions of fields, not just one or more column names: fields=’SomeText’, ra+dec,cos(ra/57)
  • Results can be sorted by multiple columns (sortvar=col1,col2) and in both ascending and descending order (sortvar=col1:+,col2:-).

Please let us know if you have any problems with the new format.  If you would like to test this out before we release it change the URL the batch script points to from http://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl to http://heasarc.gsfc.nasa.gov/xamin/BrowseBatch.

 

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