Class LRUQueryCache

    • Constructor Summary

      Constructors 
      Constructor Description
      LRUQueryCache​(int maxSize, long maxRamBytesUsed)
      Create a new instance that will cache at most maxSize queries with at most maxRamBytesUsed bytes of memory.
      LRUQueryCache​(int maxSize, long maxRamBytesUsed, Predicate<LeafReaderContext> leavesToCache, float skipCacheFactor)
      Expert: Create a new instance that will cache at most maxSize queries with at most maxRamBytesUsed bytes of memory, only on leaves that satisfy leavesToCache.
    • Constructor Detail

      • LRUQueryCache

        public LRUQueryCache​(int maxSize,
                             long maxRamBytesUsed,
                             Predicate<LeafReaderContext> leavesToCache,
                             float skipCacheFactor)
        Expert: Create a new instance that will cache at most maxSize queries with at most maxRamBytesUsed bytes of memory, only on leaves that satisfy leavesToCache. Also, clauses whose cost is skipCacheFactor times more than the cost of the top-level query will not be cached in order to not slow down queries too much.
      • LRUQueryCache

        public LRUQueryCache​(int maxSize,
                             long maxRamBytesUsed)
        Create a new instance that will cache at most maxSize queries with at most maxRamBytesUsed bytes of memory. Queries will only be cached on leaves that have more than 10k documents and have more than 3% of the total number of documents in the index. This should guarantee that all leaves from the upper tier will be cached while ensuring that at most 33 leaves can make it to the cache (very likely less than 10 in practice), which is useful for this implementation since some operations perform in linear time with the number of cached leaves. Only clauses whose cost is at most 100x the cost of the top-level query will be cached in order to not hurt latency too much because of caching.
    • Method Detail

      • onHit

        protected void onHit​(Object readerCoreKey,
                             Query query)
        Expert: callback when there is a cache hit on a given query. Implementing this method is typically useful in order to compute more fine-grained statistics about the query cache.
        See Also:
        onMiss(java.lang.Object, org.apache.lucene.search.Query)
        WARNING: This API is experimental and might change in incompatible ways in the next release.
      • onQueryCache

        protected void onQueryCache​(Query query,
                                    long ramBytesUsed)
        Expert: callback when a query is added to this cache. Implementing this method is typically useful in order to compute more fine-grained statistics about the query cache.
        See Also:
        onQueryEviction(org.apache.lucene.search.Query, long)
        WARNING: This API is experimental and might change in incompatible ways in the next release.
      • onQueryEviction

        protected void onQueryEviction​(Query query,
                                       long ramBytesUsed)
        Expert: callback when a query is evicted from this cache.
        See Also:
        onQueryCache(org.apache.lucene.search.Query, long)
        WARNING: This API is experimental and might change in incompatible ways in the next release.
      • onDocIdSetCache

        protected void onDocIdSetCache​(Object readerCoreKey,
                                       long ramBytesUsed)
        Expert: callback when a DocIdSet is added to this cache. Implementing this method is typically useful in order to compute more fine-grained statistics about the query cache.
        See Also:
        onDocIdSetEviction(java.lang.Object, int, long)
        WARNING: This API is experimental and might change in incompatible ways in the next release.
      • onDocIdSetEviction

        protected void onDocIdSetEviction​(Object readerCoreKey,
                                          int numEntries,
                                          long sumRamBytesUsed)
        Expert: callback when one or more DocIdSets are removed from this cache.
        See Also:
        onDocIdSetCache(java.lang.Object, long)
        WARNING: This API is experimental and might change in incompatible ways in the next release.
      • onClear

        protected void onClear()
        Expert: callback when the cache is completely cleared.
        WARNING: This API is experimental and might change in incompatible ways in the next release.
      • clearCoreCacheKey

        public void clearCoreCacheKey​(Object coreKey)
        Remove all cache entries for the given core cache key.
      • clearQuery

        public void clearQuery​(Query query)
        Remove all cache entries for the given query.
      • clear

        public void clear()
        Clear the content of this cache.
      • doCache

        public Weight doCache​(Weight weight,
                              QueryCachingPolicy policy)
        Description copied from interface: QueryCache
        Return a wrapper around the provided weight that will cache matching docs per-segment accordingly to the given policy. NOTE: The returned weight will only be equivalent if scores are not needed.
        Specified by:
        doCache in interface QueryCache
        See Also:
        Collector.scoreMode()
      • ramBytesUsed

        public long ramBytesUsed()
        Description copied from interface: Accountable
        Return the memory usage of this object in bytes. Negative values are illegal.
        Specified by:
        ramBytesUsed in interface Accountable
      • getTotalCount

        public final long getTotalCount()
        Return the total number of times that a Query has been looked up in this QueryCache. Note that this number is incremented once per segment so running a cached query only once will increment this counter by the number of segments that are wrapped by the searcher. Note that by definition, getTotalCount() is the sum of getHitCount() and getMissCount().
        See Also:
        getHitCount(), getMissCount()
      • getHitCount

        public final long getHitCount()
        Over the total number of times that a query has been looked up, return how many times a cached DocIdSet has been found and returned.
        See Also:
        getTotalCount(), getMissCount()
      • getMissCount

        public final long getMissCount()
        Over the total number of times that a query has been looked up, return how many times this query was not contained in the cache.
        See Also:
        getTotalCount(), getHitCount()
      • getCacheCount

        public final long getCacheCount()
        Return the total number of cache entries that have been generated and put in the cache. It is highly desirable to have a hit count that is much higher than the cache count as the opposite would indicate that the query cache makes efforts in order to cache queries but then they do not get reused.
        See Also:
        getCacheSize(), getEvictionCount()
      • getEvictionCount

        public final long getEvictionCount()
        Return the number of cache entries that have been removed from the cache either in order to stay under the maximum configured size/ram usage, or because a segment has been closed. High numbers of evictions might mean that queries are not reused or that the caching policy caches too aggressively on NRT segments which get merged early.
        See Also:
        getCacheCount(), getCacheSize()