Error when adding computed index field: InvalidOperationException contextDatabase

Question

I add a custom computed field to the fieldmap node in the Lucene Search config like so:

<fieldNames hint="raw:AddFieldByFieldName">
 <field fieldName="my_field" indexType="UNTOKENIZED" returnType="stringCollection" />
</fieldNames>

I also registered my custom computed field like so:

<fields hint="raw:AddComputedIndexField">
 <field fieldName="my_field" indexType="UNTOKENIZED" returnType="stringCollection">MyAssembly.MyField,MyAssembly</field>
</fields>

After saving and building the solution I got this error when logging into Sitecore:

contextDatabase

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.InvalidOperationException: contextDatabase

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[InvalidOperationException: contextDatabase]
Sitecore.Forms.Core.Dependencies.DefaultImplItemRepository..ctor(Database contextDatabase, Database masterDatabase) +103

Further Information: Sitecore 8.2 update 6.

Answer 1

I am not sure what the issue was but in the end to fix this I had to update by field to:

<fieldNames hint="raw:AddFieldByFieldName">
    <field fieldName="my_field" indexType="UNTOKENIZED" returnType="stringCollection" storageType="YES" settingType="Sitecore.ContentSearch.LuceneProvider.LuceneSearchFieldConfiguration, Sitecore.ContentSearch.LuceneProvider">
        <analyzer type="Sitecore.ContentSearch.LuceneProvider.Analyzers.LowerCaseKeywordAnalyzer, Sitecore.ContentSearch.LuceneProvider" />
    </field>
</fieldNames>

I thought it might be the self-closing tag but I tried just updating that and that that didn't resolve the issue so i'm assuming it is either the settingType attribute or child node that solved this issue.

If anyone has a better solution please let me know.