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5.3.4. Full Text Filter
The Lucene-based Query API uses the
cache flag of @FullTextFilterDef, set to FilterCacheModeType.INSTANCE_AND_DOCIDSETRESULTS which automatically caches the filter instance and wraps the filter around a Hibernate specific implementation of CachingWrapperFilter. Unlike Lucene's version of this class, SoftReferences are used with a hard reference count (see discussion about filter cache). The hard reference count is adjusted using default.filter.cache_docidresults.size (defaults to 5). Wrapping is controlled using the @FullTextFilterDef.cache parameter. There are three different values for this parameter:
| Value | Definition |
|---|---|
| FilterCacheModeType.NONE | No filter instance and no result is cached by the Query Module. For every filter call, a new filter instance is created. This setting addresses rapidly changing data sets or heavily memory constrained environments. |
| FilterCacheModeType.INSTANCE_ONLY | The filter instance is cached and reused across concurrent Filter.getDocIdSet() calls. DocIdSet results are not cached. This setting is useful when a filter uses its own specific caching mechanism or the filter results change dynamically due to application specific events making DocIdSet caching in both cases unnecessary. |
| FilterCacheModeType.INSTANCE_AND_DOCIDSETRESULTS | Both the filter instance and the DocIdSet results are cached. This is the default value. |
Filters should be cached in the following situations:
- The system does not update the targeted entity index often (in other words, the IndexReader is reused a lot).
- The Filter's DocIdSet is expensive to compute (compared to the time spent to execute the query).
