int32_tscanFlag;// table scan flag to denote if it is a repeat/reverse/main scan
int32_tscanFlag;// table scan flag to denote if it is a repeat/reverse/main scan
int32_tdataBlockLoadFlag;
doublesampleRatio;// data block sample ratio
SIntervalinterval;// if the upstream is an interval operator, the interval info is also kept here to get the time window to check if current data block needs to be loaded.