SERVER-57225 Prevent top-level AND optimization from being used for ANDs with many children

2 files changed, 25 insertions, 2 deletions

diff --git a/jstests/core/big_predicate.js b/jstests/core/big_predicate.js
new file mode 100644
index 00000000000..d9d140b31d8
--- /dev/null
+++ b/jstests/core/big_predicate.js
@@ -0,0 +1,20 @@
+/**
+ * Test that a query containing an AND with a lot of clauses can be answered.
+ */
+(function() {
+"use strict";
+
+const coll = db.big_predicate;
+coll.drop();
+
+let filter = {};
+for (let i = 0; i < 2500; ++i) {
+    filter["field" + i] = 123;
+}
+
+assert.commandWorked(coll.insert({foo: 1}));
+assert.commandWorked(coll.insert(filter));
+
+assert.eq(coll.find(filter).itcount(), 1);
+assert.commandWorked(coll.explain().find(filter).finish());
+})();
diff --git a/src/mongo/db/query/sbe_stage_builder_filter.cpp b/src/mongo/db/query/sbe_stage_builder_filter.cpp
index 0cdccc4323a..cedb52a3f5b 100644
--- a/src/mongo/db/query/sbe_stage_builder_filter.cpp
+++ b/src/mongo/db/query/sbe_stage_builder_filter.cpp
@@ -80,6 +80,7 @@ namespace mongo::stage_builder {
 namespace {
 
 struct MatchExpressionVisitorContext;
+const size_t kMaxChildrenForTopLevelAndOptimization = 25;
 
 /**
  * Output of the tree can come from two places:
@@ -131,7 +132,8 @@ struct MatchExpressionVisitorContext {
 
         // If the root node is an $and, store it in 'topLevelAnd'.
         // TODO: SERVER-50673: Revisit how we implement the top-level $and optimization.
-        if (root->matchType() == MatchExpression::AND) {
+        if (root->matchType() == MatchExpression::AND &&
+            root->numChildren() <= kMaxChildrenForTopLevelAndOptimization) {
             topLevelAnd = root;
         }
     }
@@ -165,7 +167,8 @@ struct MatchExpressionVisitorContext {
 
         // If the root node is an $and, store it in 'topLevelAnd'.
         // TODO: SERVER-50673: Revisit how we implement the top-level $and optimization.
-        if (root->matchType() == MatchExpression::AND) {
+        if (root->matchType() == MatchExpression::AND &&
+            root->numChildren() <= kMaxChildrenForTopLevelAndOptimization) {
             topLevelAnd = root;
         }
     }