an empty tablea /( + full table the expected number of probes to retrieve or insert randomly chosen key is listed in table as function of the load factor table expected number of probes as function of the load factor the numerical results are indeed surprisingand they explain the exceptionally good performance of the key transformation method even if table is fullon the average only probes are necessary to either locate the key or to find an empty location note in particular that this figure does not depend on the absolute number of keys presentbut only on the load factor the above analysis was based on the use of collision handling method that spreads the keys uniformly over the remaining locations methods used in practice yield slightly worse performance detailed analysis for linear probing yields an expected number of probes as ( / ( asome numerical values for (aare listed in table [ table expected number of probes for linear probing the results obtained even for the poorest method of collision handling are so good that there is temptation to regard key transformation (hashingas the panacea for everything this is particularly so because its performance is superior even to the most sophisticated tree organization discussedat least on the basis of comparison steps needed for retrieval and insertion it is therefore important to point out explicitly some of the drawbacks of hashingeven if they are obvious upon unbiased consideration certainly the major disadvantage over techniques using dynamic allocation is that the size of the table is fixed and cannot be adjusted to actual demand fairly good priori estimate of the number of data items to be classified is therefore mandatory if either poor storage utilization or poor performance (or even table overflowis to be avoided even if the number of items is exactly known -an extremely rare case -the desire for good performance dictates to dimension the table slightly (say %too large the second major deficiency of scatter storage techniques becomes evident if keys are not only to be inserted and retrievedbut if they are also to be deleted deletion of entries in hash table is extremely cumbersome unless direct chaining in separate overflow area is used it is thus fair to say that tree organizations are still attractiveand actually to be preferredif the volume of data is largely unknownis strongly variableand at times even decreases