/* * Repro for a gap in CBR limit propagation: CardinalityEstimator::propagateLimit() has no case for * STAGE_SHARDING_FILTER, so it falls into MONGO_UNREACHABLE_TASSERT(12039700). SHARDING_FILTER is * otherwise a fully supported node (it is estimated via passThroughNodeCard and is absent from both * isNodeUnsupportedByCBR and isNodeUnexpectedByCBR), so nothing bails out before the switch . * * Preconditions for the crash: * - a sharded collection, so the shard plan contains a SHARDING_FILTER, * - a $limit above it, so estimate(LimitNode) calls propagateLimit, * - the limit must be strictly less than the estimated cardinality at the SHARDING_FILTER, else * propagateLimit returns early at the approxGtEq(limitCE, outCE) check. * */ import {ShardingTest} from "jstests/libs/shardingtest.js" ; const st = new ShardingTest({ shards: 2, mongos: 1, rs: { setParameter: { featureFlagCostBasedRanker: true , internalQueryPlanRanker: "costBased" , internalQueryCBRCEMode: "samplingCE" , }, }, }); const db = st.getDB( "test" ); const coll = db[jsTestName()]; coll.drop(); // Hashed shard key on _id so that predicates on 'a' / 'b' cannot be shard-key targeted and the shard // plan retains a SHARDING_FILTER stage. assert.commandWorked( st.s.adminCommand({shardCollection: coll.getFullName(), key: {_id: "hashed" }}), ); // Insert enough documents that a small limit is well below the estimated cardinality. const bulk = coll.initializeUnorderedBulkOp(); for (let i = 0; i < 1000; i++) { bulk.insert({a: i % 50, b: i % 25}); } assert.commandWorked(bulk.execute()); // Two candidate indexes so CBR has more than one plan to rank. assert.commandWorked(coll.createIndexes([{a: 1}, {b: 1}])); // Limit of 5 against a predicate matching ~all documents. The non-explain query is affected too, // not just explain: CBR runs during normal planning. const findRes = db.runCommand({ find: coll.getName(), filter: {a: {$gte: 0}, b: {$gte: 0}}, limit: 5, }); jsTest.log.info( "find result" , {findRes}); assert.commandWorked(findRes, "expected the find to succeed" ); st.stop();