diff options
| -rw-r--r-- | src/mongo/db/query/classic_plan_cache.cpp | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/src/mongo/db/query/classic_plan_cache.cpp b/src/mongo/db/query/classic_plan_cache.cpp index aa3f150291c..31ac6d13550 100644 --- a/src/mongo/db/query/classic_plan_cache.cpp +++ b/src/mongo/db/query/classic_plan_cache.cpp @@ -149,7 +149,13 @@ bool shouldCacheQuery(const CanonicalQuery& query) { // We don't read or write from the plan cache for explain. This ensures that explain queries // don't affect cache state, and it also makes sure that we can always generate information // regarding rejected plans and/or trial period execution of candidate plans. - if (query.getExplain()) { + // + // In order to be able to correctly measure 'executionTimeMillis' stats we should only skip + // caching top-level plans. Otherwise, if we were to skip caching inner pipelines for $lookup + // queries, we could run through the multi-planner for each document coming from the outer side, + // completely skewing the 'executionTimeMillis' stats. + tassert(6497600, "expCtx is null", query.getExpCtxRaw()); + if (query.getExplain() && query.getExpCtxRaw()->subPipelineDepth == 0) { return false; } |