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Indexes in databases are similar to indexes in books. In a book, an index allows you to find information quickly without reading the entire book. In a database, an index allows the database program to find data in a table without scanning the entire table.
Indexes improve performance in areas such as:
- Aggregated and verbatim reporting when filtering on fields with indexes.
- Searching in individual reporting and in survey data editing (when search fields are indexed).
- Data imports where the key field is indexed.
Note: Indexes should be used only when needed since responses take longer to store the more indexes there are. This can lead to slightly poorer performance in interviewing. Also, the database will be unavailable for other processes the first time it is regenerated after the index property is set. We therefore recommend against setting new indexes and regenerating the survey while respondents are answering the survey.
Note also however that some functionality in Reportal, for example Hitlists and hierarchies, require the question to be indexed.