When you use the CBR Query Optimization feature, the IBM Content Search Services (CSS) server throws a timeout exception.
The CBR Query Optimization feature specifies how searches that combine both a content-based retrieval (CBR) search and a relational search on a database (DB) are executed. To provide control over how combined searches are executed, the CBRQueryOptimization property can be set on the object store. When the property is set to dynamic switching mode, the Content Platform Engine dynamically determines whether to issue the CBR search first or the DB search first, optimizing performance for these types of searches. For detailed feature information, see CBR Query Optimization.
When using this feature in dynamic switching mode, a timeout in the form of an exception might be returned with the following message:
CBR_TS_COST_ESTIMATION_QUERY_TIMEOUT : A timeout has been received from the IBM Content Search Services server
while it is running a cost estimation query "{0}" against IBM Content Search Services index {1}.
where {0} is the CBR query submitted and {1} is full-text index that is being searched.
If you want combined searches to operate in dynamic switching mode, increase the timeout value on the CSS server. The tradeoff of a higher timeout is that it will take longer for the CSS server to estimate the number of CBR hits. However, the overall benefit of operating in dynamic switching mode might more than make up for the extra estimation time. For example, if your query takes 300 seconds to return without dynamic switching mode versus 60 seconds (including a CSS timeout increase from 30 to 40 seconds), it is more beneficial to increase the timeout and use dynamic switching mode as your overall query time is faster.
To increase the timeout value on one or more CSS servers:
<estimationQueryTimeoutMS>40000</estimationQueryTimeoutMS>