In Apache Solr's managed-schema.xml, using copyField allows you to copy field values during indexing.
For example, let's say we have set up the following copyField:
<copyField source="cat" dest="text"/>
<copyField source="name" dest="text"/>
<copyField source="manu" dest="text"/>
<copyField source="features" dest="text"/>
By doing this, during indexing, the values of the cat, name, manu, and features fields will be copied to the text field. At this time, the destination text field must be multiValued="true".
One reason for doing this is to consolidate multiple distributed field values (in the example above, values from the cat, name, manu, and features fields) into the destination field (in the example above, the text field), aiming to improve search speed by searching one consolidated field instead of individual fields. However, consolidating fields into one may result in the loss of the ability to adjust weights for each field or perform detailed adjustments in analysis.
In Japanese, it is common to use both morphological analysis and character N-gram with the following settings.
<copyField source="title" dest="title_2g"/>
In the above settings, 'title' is used for morphological analysis, and 'title_2g' is used for the 2-gram field.
