We have just covered the different types of Metamorph index while talking about Metamorph queries. A couple of additional notes covering virtual fields, and compound indexes. These are two different ways of creating a Metamorph index on multiple fields, each having their own use.

Virtual fields are created with string concatentation, with new-line separators. It is used to perform a text search across multiple fields at the same time. The fields are not differentiated between when searching, however the most important fields should typically be first due to the lead bias in LIKEP.

Compound Metamorph indexes allow for the additional indexing of other fields in the data. These should be fixed length fields, typically counter, date, int, double etc. They are used for two purposes. First they will be consulted when filtering the record, which is more efficient than using another index, or post-processing. Secondly it the ORDER BY is completely resolvable with the additional fields in the index then it is used then.