Method getChangedBaseRow

memstore/backfill.go:599–630

getChangedBaseRow get changed row from base batch if there are any changes to sort columns or array columns. It will fetch the whole row in base batch and apply patch value to it. for array columns, only when array size change will trigger the base batch change, value change while size not change wi

(baseRecordID memCom.RecordID, changedPatchRow []*memCom.DataValue)

// for array columns, only when array size change will trigger the base batch change, value change while size not change will be covered in
// the unsorted column change
func (ctx *backfillContext) getChangedBaseRow(baseRecordID memCom.RecordID, changedPatchRow []*memCom.DataValue) []*memCom.DataValue {
	var changedBaseRow []*memCom.DataValue
	for columnID, patchValue := range changedPatchRow {
		// loop through sorted columns and array columns
		if patchValue != nil && (utils.IndexOfInt(ctx.sortColumns, columnID) >= 0 || ctx.new.Columns[columnID].IsList()) {
			baseDataValue := ctx.new.Columns[columnID].GetDataValueByRow(int(baseRecordID.Index))
			// there's change in sorted column or size change in array column
			if (ctx.new.Columns[columnID].IsList() && memCom.ArrayLengthCompare(&baseDataValue, patchValue) != 0) ||
				(!ctx.new.Columns[columnID].IsList() && baseDataValue.Compare(*patchValue) != 0) {
				changedBaseRow = make([]*memCom.DataValue, len(ctx.new.Columns))
				// Mark deletion for this row.
				ctx.baseRowDeleted = append(ctx.baseRowDeleted, int(baseRecordID.Index))
				// Copy the whole row in base batch to changed row and apply the change.
				for newColumnID := 0; newColumnID < len(ctx.new.Columns); newColumnID++ {
					if ctx.columnDeletions[newColumnID] {
						continue
					}
					if changedPatchRow[newColumnID] != nil {
						// column changed, get from patch
						changedBaseRow[newColumnID] = changedPatchRow[newColumnID]
					} else {
						// column unchanged, get from base
						existingValue := ctx.new.Columns[newColumnID].GetDataValueByRow(int(baseRecordID.Index))
						changedBaseRow[newColumnID] = &existingValue
					}
				}
				break
			}
		}
	}
	return changedBaseRow
}

// writePatchValueForUnsortColumn writes the patch value to forked columns if value changes.
// this function return false if no column update happens