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CacheStrategy: Improve Javadocs. (#9280) 

* CacheStrategy: Improve Javadocs.

* Update processing/src/main/java/org/apache/druid/query/CacheStrategy.java

Co-Authored-By: Suneet Saldanha <44787917+suneet-s@users.noreply.github.com>

Co-authored-by: Suneet Saldanha <44787917+suneet-s@users.noreply.github.com>
This commit is contained in:
Gian Merlino 2020-02-28 11:30:58 -08:00 committed by GitHub
parent c294e0b7c6
commit 81d8be6e39
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1 changed files with 15 additions and 7 deletions
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processing/src/main/java/org/apache/druid/query/CacheStrategy.java
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@ -30,13 +30,15 @@ import java.util.List;
import java.util.concurrent.ExecutorService;
/**
* Handles caching-related tasks for a particular query type.
*
* Generally returned by the toolchest method {@link QueryToolChest#getCacheStrategy}.
*/
@ExtensionPoint
public interface CacheStrategy<T, CacheType, QueryType extends Query<T>>
{
/**
* Returns the given query is cacheable or not.
* Returns whether the given query is cacheable or not.
* The {@code willMergeRunners} parameter can be used for distinguishing the caller is a broker or a data node.
*
* @param query the query to be cached
@ -48,21 +50,27 @@ public interface CacheStrategy<T, CacheType, QueryType extends Query<T>>
boolean isCacheable(QueryType query, boolean willMergeRunners);
/**
* Computes the cache key for the given query
* Computes the per-segment cache key for the given query. Because this is a per-segment cache key, it should only
* include parts of the query that affect the results for a specific segment (i.e., the results returned from
* {@link QueryRunnerFactory#createRunner}).
*
* @param query the query to compute a cache key for
* @param query the query to be cached
*
* @return the cache key
* @return the per-segment cache key
*/
byte[] computeCacheKey(QueryType query);
/**
* Computes the result level cache key for the given query.
* Some implementations may include query parameters that might not be used in {@code computeCacheKey} for same query
* Computes the result-level cache key for the given query. The result-level cache will tack on datasource and
* interval details, so this key does not need to include datasource and interval. But it should include anything
* else that might affect the results of the query.
*
* Some implementations will need to include query parameters that are not used in {@link #computeCacheKey} for the
* same query.
*
* @param query the query to be cached
*
* @return the result level cache key
* @return the result-level cache key
*/
byte[] computeResultLevelCacheKey(QueryType query);