Rushmore Query Optimization technology is a data access technique that uses standard Visual FoxPro indexes to optimize access to data. You can use Rushmore with any Visual FoxPro index, including FoxPro 1.x (.idx) indexes, compact (.idx) indexes, and compound (.cdx) indexes.
Both .cdx and compact .idx indexes use a compression technique that produces indexes as small as one-sixth the size of uncompressed old-format indexes. Visual FoxPro can process a compressed index faster because it requires less disk access, and because more of the index can be buffered in memory. Although Rushmore Query Optimization, like other file access techniques, benefits from the smaller size of compact indexes, it also functions very well with indexes in older formats.
When Visual FoxPro processes very large tables on computers with only the minimum amount of RAM, Rushmore might not find sufficient memory to operate. In that case, Visual FoxPro might display a warning message ("Not enough memory for optimization"). Although your program will function correctly and not lose any data, the query will not benefit from Rushmore optimization.
In its simplest form, Rushmore speeds the performance of single-table commands using FOR clauses that specify sets of records in terms of existing indexes. Also, Rushmore can speed the operation of certain commands such as LOCATE and INDEX. For a complete list of optimizable commands, see the next section, "Using Rushmore Query Optimization with Tables."
Visual FoxPro SQL commands use Rushmore as a basic tool in multi-table query optimization, using existing indexes and even creating new ad-hoc indexes to speed queries.
[ 本帖最后由 TonyDeng 于 2014-3-17 20:13 编辑 ]
Both .cdx and compact .idx indexes use a compression technique that produces indexes as small as one-sixth the size of uncompressed old-format indexes. Visual FoxPro can process a compressed index faster because it requires less disk access, and because more of the index can be buffered in memory. Although Rushmore Query Optimization, like other file access techniques, benefits from the smaller size of compact indexes, it also functions very well with indexes in older formats.
When Visual FoxPro processes very large tables on computers with only the minimum amount of RAM, Rushmore might not find sufficient memory to operate. In that case, Visual FoxPro might display a warning message ("Not enough memory for optimization"). Although your program will function correctly and not lose any data, the query will not benefit from Rushmore optimization.
In its simplest form, Rushmore speeds the performance of single-table commands using FOR clauses that specify sets of records in terms of existing indexes. Also, Rushmore can speed the operation of certain commands such as LOCATE and INDEX. For a complete list of optimizable commands, see the next section, "Using Rushmore Query Optimization with Tables."
Visual FoxPro SQL commands use Rushmore as a basic tool in multi-table query optimization, using existing indexes and even creating new ad-hoc indexes to speed queries.
[ 本帖最后由 TonyDeng 于 2014-3-17 20:13 编辑 ]
授人以渔，不授人以鱼。
