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You can improve the performance of your query by using the different types of fields for different purposes. For example, your query will run much faster (this can be up to ten times faster) if you add selection criteria to the key fields, rather than to the data fields.

Virtual fields are fields which do not physically exist, but are calculated whenever they are required. For example, your file may contain a person's date of birth, but not their age. If the age is defined as a virtual field and if you include age in your query, then it is calculated each time that person's record is retrieved. This means that if you include the age in your query, it may take a longer time to run. It is better not to include virtual fields in a query unless you need them.

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