# Study on Effective Temporal Data Retrieval Leveraging Complex Indexed Architecture
## 4 Indexing
### Proposed Solution--Master Index Extension & Partitioning  
When dealing with index structures, various access methods can be used to locate data. Index Unique scan (IUS) is used if the condition reflects the unique constraint by using an equality sign. If the multiple values can be produced, either as the result of the range condition or by using the non-unique index, the Index Range scan (IRS) method is used, naturally, if the order of the attributes in the index and reflecting the query is suitable. There are also many other methods, like Full Scan based on the fact that the data are already sorted in the leaf layer, so the ordering is not necessary to be performed, Fast Full scan, where all suitable data are in the index, however, the attribute order forming index is not suitable, thus the index is scanned fully. The specific access path is defined by the Skip Scan, which can be preferred if the query lacks the leading attribute of the index. It is based on the index in index architecture for the composite definition [16]. As stated, if the index is not suitable or even if there is no index covering the conditions, at all (e.g., supervised by the function call), the whole data block set associated with the table must be searched by executing the Table Access Full method. It can have many severe limitations and constraints, mostly if there is a fragmentation present if the associated block amount is higher in comparison with current real demands. All of these factors have significant performance limitations. The Master index was firstly defined in [24]. It uses the index just as the data locators. Generally, any index structure can be used, holding any data. By using the proposed techniques covering NULL values inside the index, any index type can be used. The spirit of the Master index is to locate data by extracting the block identifier from the ROWID values in the leaf layer. Thanks to that, just relevant data blocks are accessed. Migrated rows are secured, as well, although the ROWID pointers are not used to address them, however, there is a pointer inside the block, which is associated with the index itself, thus the security and whole data frame can be accessed forming a reliability layer. If at  
Figure 9: NULL categorization model—proposed architecture. least one record is pointed to the block, it is completely loaded and the whole block is scanned for either data themselves or for locating migrated rows. It removes the limitation of the memory Buffer cache problem covered in [9]. Specific index structure can be used, as well, based on the B+tree data structure, however, it points only to the data block, not the direct row position. Leaf layer automatically removes the duplicate pointers by sorting the data based on the index set, as well as pointers. A proposed solution dealing with NULL can be used, as well, individual categories are used in the separate module, in which the block definition pointers can be used, as well. The architecture of the Master indexing extended by the NULL pointer module categorization is in Figure 10. Communication interconnection of the modules is black colored, data flow in individual phases is shown green. The processing consists of several phases. The first phase represents the query definition and its representation in the database system. Server process of the instance memory is contacted (first phase), where the syntactic and semantic check is done. In the second phase, the existing index set is processed to identify a suitable index to access the data. The third phase represents the decision. If the suitable index to cover the query exists, processing is shifted to the fourth phase, the particular index is used and result set is created. Vice versa, if there is no suitable index to serve the query, the Master index module is contacted to select the most suitable index. Such index is used for the relevant blocks holding data extraction in the fifth phase. Partitioning enhances the performance, manageability, and availability of a wide variety of applications.