| | Input: transaction database D. |
| | Output: frequent item set L of D |
| (1) | Start |
| (2) | Scan D |
| (3) | For each transaction T ∈ D { |
| (4) | Find all subitem of T subItemSet |
| (5) | For i = 1; i < max_t; i++ { |
| (6) | If length of subitem = i { |
| (7) | If i_hashTable not contain the subitem { |
| (8) | Subitem.count = 1 |
| (9) | Add subitem to i_hashTable |
| (10) | } else { |
| (11) | Subitem.count+ = 1 |
| (12) | Value = subitem.count |
| (13) | Update value of key subitem in i_hashTable |
| (14) | } |
| (15) | } |
| (16) | } |
| (17) | } |
| (18) | If there is an update to the database data, cache the updated data |
| (19) | Cache the updated data to the data set db_delete, db_add, db_update, db_noupdate, respectively |
| (20) | If db_update not null { |
| (21) | Add db_update to db_add |
| (22) | Add db_noupdate to db_delete |
| (23) | } |
| (24) | If db_delete not null { |
| (25) | For each transaction T ∈ db_delete { |
| (26) | Find all subitem of T subItemSet |
| (27) | For each subitem ∈ subItemSet { |
| (28) | Find the subitem key-value |
| (29) | Subitem.count− = 1 |
| (30) | Update value of key subitem in i_hashTable |
| (31) | } |
| (32) | } |
| (33) | } |
| (34) | Produce has_infrequent_subset (c, Lk − 1) |
| (35) | For all (k − 1) subset s of c |
| (36) | If s in Lk − 1 return true; |
| (37) | Else return false |
| (38) | End |
