maytasm commented on code in PR #20815:
URL: https://github.com/apache/druid/pull/20815#discussion_r4456399974
##########
server/src/main/java/org/apache/druid/query/ResultLevelCachingQueryRunner.java:
##########
@@ -206,6 +209,27 @@ private byte[] fetchResultsFromResultLevelCache(
return null;
}
+ private byte[] computeResultLevelCacheKey()
+ {
+ final byte[] queryCacheKey = strategy.computeResultLevelCacheKey(query);
+ if (!cacheConfig.isIncludeDatasourceAndIntervalsInResultLevelCacheKey()) {
+ return queryCacheKey;
+ }
+ // The cached value still starts with the ETag, which is checked before
the entry is used. Adding the datasource
+ // and intervals to the key gives queries that differ only by interval or
datasource their own entries, instead of
+ // one shared entry that each of them overwrites.
+ final CacheKeyBuilder builder = new
CacheKeyBuilder(RESULT_LEVEL_CACHE_KEY_WITH_DATASOURCE_AND_INTERVALS)
+ .appendByteArray(queryCacheKey);
+ final byte[] dataSourceCacheKey = query.getDataSource().getCacheKey();
+ if (dataSourceCacheKey != null) {
+ builder.appendByteArray(dataSourceCacheKey);
Review Comment:
- A collision is very unlikely. One query's key would have to equal another
query's key followed by bytes shaped exactly like a datasource cache key.
Although is possible as you pointed out.
- Despite that, the ETag still catches it. Each cache value starts with an
ETag, a SHA-1 of the segment IDs, the clipped query intervals and the query
cache key (CachingClusteredClient.computeResultLevelCachingEtag, around line
821). Segment IDs include the datasource and interval, so a collision between
different datasources or intervals fails the ETag check. It then behaves like
today's default: a miss, and the entry gets overwritten.
- It's a simple fix so let me push a change
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