Revert "SERVER-58104 Prevent the balancer from calculating split points in sessions collection if shard key is not _id"

This reverts commit 01549c7e5d425f48c5c9533d2655e20d992d9eef.

2 files changed, 0 insertions, 62 deletions

diff --git a/jstests/sharding/balancing_sessions_collection_reshard.js b/jstests/sharding/balancing_sessions_collection_reshard.js
deleted file mode 100644
index e5a8c3b096b..00000000000
--- a/jstests/sharding/balancing_sessions_collection_reshard.js
+++ /dev/null
@@ -1,55 +0,0 @@
-/*
- * Tests that the balancer does not split the chunks for the sessions collection
- * if the shard key is not _id.
- */
-(function() {
-    "use strict";
-
-    let numShards = 2;
-    const kMinNumChunks = 2;
-    const clusterName = jsTest.name();
-    const st = new ShardingTest({
-        name: clusterName,
-        shards: numShards,
-        other:
-            {configOptions: {setParameter: {minNumChunksForSessionsCollection: kMinNumChunks}}}
-    });
-
-    let waitForBalancerToRun = function() {
-        let lastRoundNumber =
-            assert.commandWorked(st.s.adminCommand({balancerStatus: 1})).numBalancerRounds;
-        st.startBalancer();
-
-        assert.soon(function() {
-            let res = assert.commandWorked(st.s.adminCommand({balancerStatus: 1}));
-            return res.mode == "full" && res.numBalancerRounds - lastRoundNumber > 1;
-        });
-
-        st.stopBalancer();
-    };
-
-    const kSessionsNs = "config.system.sessions";
-    let configDB = st.s.getDB("config");
-
-    jsTest.log("Verify that the sessions collection is successfully dropped.");
-
-    assert.commandWorked(configDB.runCommand({drop: "system.sessions"}));
-
-    jsTest.log("Verify that the sessions collection is successfully recreated and resharded.");
-
-    assert.commandWorked(st.s.adminCommand({enableSharding: "config"}));
-    assert.commandWorked(st.s.adminCommand({shardCollection: kSessionsNs, key: {oldRoles: 1}}));
-
-    jsTest.log("Verify that balancer does not fail after resharding.");
-    waitForBalancerToRun();
-
-    jsTest.log(
-        "Verify that there is a single chunk for the collection and the bounds are the resharded key.");
-    assert.eq(1, configDB.chunks.count({ns: kSessionsNs}));
-
-    let doc = configDB.chunks.findOne({ns: kSessionsNs});
-    assert(doc.min.hasOwnProperty("oldRoles"));
-    assert(doc.max.hasOwnProperty("oldRoles"));
-
-    st.stop();
-}());
diff --git a/src/mongo/db/s/balancer/balancer_chunk_selection_policy_impl.cpp b/src/mongo/db/s/balancer/balancer_chunk_selection_policy_impl.cpp
index 15bf7093fbf..b113735802f 100644
--- a/src/mongo/db/s/balancer/balancer_chunk_selection_policy_impl.cpp
+++ b/src/mongo/db/s/balancer/balancer_chunk_selection_policy_impl.cpp
@@ -234,13 +234,6 @@ void getSplitCandidatesToEnforceTagRanges(const ChunkManager* cm,
 void getSplitCandidatesForSessionsCollection(OperationContext* opCtx,
                                              const ChunkManager* cm,
                                              SplitCandidatesBuffer* splitCandidates) {
-    // Do not compute split points if shard key is not _id,
-    // since the split points depend on _id.id.
-    const auto& keyPattern = cm->getShardKeyPattern().getKeyPattern();
-    if (!KeyPattern::isIdKeyPattern(keyPattern.toBSON())) {
-        return;
-    }
-
     const auto minNumChunks = minNumChunksForSessionsCollection.load();
 
     if (cm->numChunks() >= minNumChunks) {