SERVER-72518 Make 5% random-cursor $sample cutoff configurable

4 files changed, 37 insertions, 1 deletions

diff --git a/src/mongo/db/pipeline/pipeline_d.cpp b/src/mongo/db/pipeline/pipeline_d.cpp
index bb146b1cb94..f0d4d224f42 100644
--- a/src/mongo/db/pipeline/pipeline_d.cpp
+++ b/src/mongo/db/pipeline/pipeline_d.cpp
@@ -516,7 +516,17 @@ StatusWith<unique_ptr<PlanExecutor, PlanExecutor::Deleter>> PipelineD::createRan
     // function because double-locking forces any PlanExecutor we create to adopt a NO_YIELD policy.
     invariant(opCtx->lockState()->isCollectionLockedForMode(coll->ns(), MODE_IS));
 
-    static const double kMaxSampleRatioForRandCursor = 0.05;
+    auto* clusterParameters = ServerParameterSet::getClusterParameterSet();
+    auto* randomCursorSampleRatioParam =
+        clusterParameters
+            ->get<ClusterParameterWithStorage<InternalQueryCutoffForSampleFromRandomCursorStorage>>(
+                "internalQueryCutoffForSampleFromRandomCursor");
+
+    auto maxSampleRatioClusterParameter =
+        randomCursorSampleRatioParam->getValue(expCtx->ns.tenantId());
+
+    const double kMaxSampleRatioForRandCursor = maxSampleRatioClusterParameter.getSampleCutoff();
+
     if (!expCtx->ns.isTimeseriesBucketsCollection()) {
         if (sampleSize > numRecords * kMaxSampleRatioForRandCursor || numRecords <= 100) {
             return nullptr;
diff --git a/src/mongo/db/query/SConscript b/src/mongo/db/query/SConscript
index bb1b4efda4c..a2c337ce8bd 100644
--- a/src/mongo/db/query/SConscript
+++ b/src/mongo/db/query/SConscript
@@ -267,6 +267,7 @@ env.Library(
     LIBDEPS_PRIVATE=[
         '$BUILD_DIR/mongo/db/server_base',
         '$BUILD_DIR/mongo/db/service_context',
+        '$BUILD_DIR/mongo/idl/cluster_server_parameter',
         '$BUILD_DIR/mongo/util/pcre_wrapper',
         'memory_util',
     ],
diff --git a/src/mongo/db/query/query_knobs.idl b/src/mongo/db/query/query_knobs.idl
index 64d8b782359..d4ca334491f 100644
--- a/src/mongo/db/query/query_knobs.idl
+++ b/src/mongo/db/query/query_knobs.idl
@@ -26,6 +26,9 @@
 # it in the license file.
 #
 
+imports:
+  - "mongo/idl/cluster_server_parameter.idl"
+
 global:
   cpp_namespace: "mongo"
   cpp_includes:
@@ -61,6 +64,21 @@ enums:
             # Use a prefix of sha256 redaction strategy
             kSha256RedactionStrategy: "sha256"
 
+structs:
+  InternalQueryCutoffForSampleFromRandomCursorStorage:
+    description: "A specification for the 'internalQueryCutoffForSampleFromRandomCursor' cluster-wide configuration parameter type."
+    inline_chained_structs: true
+    chained_structs:
+      ClusterServerParameter: clusterServerParameter
+    fields:
+      sampleCutoff:
+        description: "The configuration for random-cursor sample cutoffs."
+        type: double
+        default: 0.05
+        validator:
+          gt: 0.0
+          lte: 1.0
+
 server_parameters:
 
   #
@@ -1076,6 +1094,12 @@ server_parameters:
       gte: 0
     on_update: plan_cache_util::clearSbeCacheOnParameterChange
 
+  internalQueryCutoffForSampleFromRandomCursor:
+    description: "The maximum sample ratio for random cursor."
+    set_at: cluster
+    cpp_varname: "internalQueryCutoffForSampleFromRandomCursor"
+    cpp_vartype: InternalQueryCutoffForSampleFromRandomCursorStorage
+
   internalQueryGlobalProfilingFilter:
     description: "Enables the setProfilingFilterGlobally command."
     set_at: [ startup ]
diff --git a/src/mongo/db/sorter/SConscript b/src/mongo/db/sorter/SConscript
index a52da1d0c7a..5f88dabdc58 100644
--- a/src/mongo/db/sorter/SConscript
+++ b/src/mongo/db/sorter/SConscript
@@ -13,6 +13,7 @@ sorterEnv.CppUnitTest(
     ],
     LIBDEPS=[
         '$BUILD_DIR/mongo/db/exec/document_value/document_value',
+        '$BUILD_DIR/mongo/db/query/query_knobs',
         '$BUILD_DIR/mongo/db/service_context',
         '$BUILD_DIR/mongo/db/storage/encryption_hooks',
         '$BUILD_DIR/mongo/db/storage/storage_options',