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Sybase IQ 12.6 included performance enhancements for delete batch processing. The HG_DELETE_METHOD option lets you specify which of three algorithms to apply to the delete. If no algorithm is specified, the 12.6 cost model considers many factors, including I/O costs, CPU costs, available resources, index metadata, parallelism, and predicates available from the query. See the Sybase IQ Reference Manual for details about HG_DELETE_METHOD.
Costing currently does not consider the effects of range
predicates on the large delete. This can cause mid delete to be
chosen in cases where large delete would be faster. You can use HG_DELETE_METHOD to
force the use of the large delete algorithm.
