# A Survey on Big IoT Data Indexing: Potential Solutions, Recent Advancements, and Open Issues
## 5 Existing Indexing Techniques
### Metric Indexing Techniques
\begin{table}
\begin{tabular}{l p{142.3 pt}} \hline \hline
**Indexing Structure** & **Application** \\ \hline LSH & \(\bullet\) Pattern matching \\  & \(\bullet\) Recommendation retrieval \\  & \(\bullet\) Text processing \\  & \(\bullet\) Natural language processing \\  & \(\bullet\) Reducing the dimensionality of data \\  & \(\bullet\) Image/Video retrieval \\  & \(\bullet\) Content similarity deployment and discovery \\ \hline Kernelized LSH & \(\bullet\) Content-based retrieval \\  & \(\bullet\) Speaker search \\  & \(\bullet\) Image classification \\ \hline Robust Discrete Spectral Hashin & \(\bullet\) Image semantic indexing \\  & \(\bullet\) Image retrieval \\ \hline Spectral Hashing & \(\bullet\) Image retrieval \\  & \(\bullet\) Detection of region-duplication forgery in digital images \\  & \(\bullet\) Fast approximate nearest neighbor \\  & \(\bullet\) Classification \\ \hline Kernel Based Supervised Hashing & \(\bullet\) Person re-identification \\  & \(\bullet\) Similarity search \\  & \(\bullet\) Image retrieval \\ \hline Label-regularized Max-margin Partition & \(\bullet\) Classification for large-scale datasets \\ \hline Bit-Scalable Deep Hashin & \(\bullet\) Similarity learning for image retrieval and person re-identification \\ \hline Asymmetric Deep Supervised Hashing & \(\bullet\) Image retrieval \\ \hline M-tree & \(\bullet\) Similarity search in multimedia Dataset \\  & \(\bullet\) Accelerator for database query \\  & \(\bullet\) Recommendation System \\  & \(\bullet\) Indexing the music data \\  & \(\bullet\) Classification \\ \hline Slim-tree & \(\bullet\) Video indexing and similarity search \\ \hline SFC \& Kd-tree & \(\bullet\) Data cleaning and data mining \\ \hline Hollow-tree & \(\bullet\) Store and retrieve large volumes of complex data \\ \hline AMDS & \(\bullet\) Multimedia retrieval \\  & \(\bullet\) Computational biology \\  & \(\bullet\) Location-based services \\ \hline VP-tree & \(\bullet\) Pattern recognition and image processing \\  & \(\bullet\) Image indexing and retrieval \\  & \(\bullet\) Storing neuronal morphology data \\  & \(\bullet\) Similarity search on cloud computing \\  & \(\bullet\) Malware detection \\  & \(\bullet\) Clustering \\ \hline mVP-tree & \(\bullet\) Images retrieval in airport video monitoring systems \\ \hline MM-tree & \(\bullet\) Image retrieval \\ \hline XM-tree & \(\bullet\) Web Information Retrieval \\ \hline Ball-tree & \(\bullet\) Face sketch recognition \\  & \(\bullet\) Classification in high dimensions \\  & \(\bullet\) Clustering and matching for object class recognition \\ \hline BCCF-tree & \(\bullet\) Image indexing and retrieval for person re-identification \\  & \(\bullet\) Indexing IoT sensor data \\ \hline GH-tree & \(\bullet\) Image Search by Content \\ \hline GNAT-tree & \(\bullet\) Indexing and similarity search of face-images data \\ \hline SPB-tree & \(\bullet\) Multimedia retrieval \\  & \(\bullet\) Pattern recognition \\  & \(\bullet\) Computational biology \\ \hline X-tree & \(\bullet\) Image coding \\  & \(\bullet\) Classification \\ \hline Kd-tree & \(\bullet\) Search and synchronization of sensor nodes \\ \hline R-tree & \(\bullet\) Classification \\  & \(\bullet\) Spatial indexing for the IoT data management \\  & \(\bullet\) Images search and retriever \\  & \(\bullet\) Geographical search \\ \hline Hilbert R-tree & \(\bullet\) Visualization of 3D massive data \\ \hline \hline \end{tabular}
\end{table} 
Table 17: Application area of the indexing structures.