For any column that has no index defined, or whenever it is the most effective, query results are produced using the default index. This structure is fastest for projections, but generally is slower than any of the three column index types you define for anything other than a projection. Performance is still faster than most RDBMSs since one column of data is fetched, while other RDBMSs need to fetch all columns which results in more disk I/O operations.
Sybase IQ supports the lookup of default indexes on fixed-width columns that are one or two bytes wide.
The sp_iqindexmetadata stored procedure generates a report describing a specified index or indexes belonging to a specified owner or table. For example, the output allows easy checking of whether a given index is a 1-byte or 2-byte default index.
Sybase recommends that if users see “Old One Byte FP” (or “Old Two Byte FP”), they rebuild the default index to leverage the newer, faster index structure. After the rebuild, users see the typical “One Byte FP”.
For details, see “sp_iqindexmetadata procedure” in the Sybase IQ Reference Manual.
