From d54acf1b792de6f7a8b82e49a1e94a7c24c938b0 Mon Sep 17 00:00:00 2001
From: Neil Shweky <neilshweky@gmail.com>
Date: Thu, 4 Nov 2021 18:08:24 +0000
Subject: SERVER-59597 remove unneeded checks in scan

---
 src/mongo/db/exec/sbe/stages/ix_scan.cpp |  4 ---
 src/mongo/db/exec/sbe/stages/scan.cpp    | 58 ++++++++++++++------------------
 2 files changed, 26 insertions(+), 36 deletions(-)

diff --git a/src/mongo/db/exec/sbe/stages/ix_scan.cpp b/src/mongo/db/exec/sbe/stages/ix_scan.cpp
index 9e73305f0a1..b913c5575d9 100644
--- a/src/mongo/db/exec/sbe/stages/ix_scan.cpp
+++ b/src/mongo/db/exec/sbe/stages/ix_scan.cpp
@@ -326,10 +326,6 @@ PlanState IndexScanStage::getNext() {
     // state in case it yields as the state will be completely overwritten after the call.
     disableSlotAccess();
 
-    if (!_cursor) {
-        return trackPlanState(PlanState::IS_EOF);
-    }
-
     checkForInterrupt(_opCtx);
 
     if (_firstGetNext) {
diff --git a/src/mongo/db/exec/sbe/stages/scan.cpp b/src/mongo/db/exec/sbe/stages/scan.cpp
index 5a50224861a..ea4c7ba85fe 100644
--- a/src/mongo/db/exec/sbe/stages/scan.cpp
+++ b/src/mongo/db/exec/sbe/stages/scan.cpp
@@ -303,7 +303,7 @@ void ScanStage::open(bool reOpen) {
             _cursor = _coll->getCursor(_opCtx, _forward);
         }
     } else {
-        _cursor.reset();
+        MONGO_UNREACHABLE_TASSERT(5959701);
     }
 
     _open = true;
@@ -317,10 +317,6 @@ PlanState ScanStage::getNext() {
     // case it yields as the state will be completely overwritten after the next() call.
     disableSlotAccess();
 
-    if (!_cursor) {
-        return trackPlanState(PlanState::IS_EOF);
-    }
-
     checkForInterrupt(_opCtx);
 
     auto res = _firstGetNext && _seekKeyAccessor;
@@ -761,39 +757,37 @@ void ParallelScanStage::open(bool reOpen) {
         _coll = restoreCollection(_opCtx, *_collName, _collUuid, *_catalogEpoch);
     }
 
-    if (_coll) {
-        {
-            stdx::unique_lock lock(_state->mutex);
-            if (_state->ranges.empty()) {
-                auto ranges = _coll->getRecordStore()->numRecords(_opCtx) / 10240;
-                if (ranges < 2) {
-                    _state->ranges.emplace_back(Range{RecordId{}, RecordId{}});
-                } else {
-                    if (ranges > 1024) {
-                        ranges = 1024;
-                    }
-                    auto randomCursor = _coll->getRecordStore()->getRandomCursor(_opCtx);
-                    invariant(randomCursor);
-                    std::set<RecordId> rids;
-                    while (ranges--) {
-                        auto nextRecord = randomCursor->next();
-                        if (nextRecord) {
-                            rids.emplace(nextRecord->id);
-                        }
-                    }
-                    RecordId lastid{};
-                    for (auto id : rids) {
-                        _state->ranges.emplace_back(Range{lastid, id});
-                        lastid = id;
+    {
+        stdx::unique_lock lock(_state->mutex);
+        if (_state->ranges.empty()) {
+            auto ranges = _coll->getRecordStore()->numRecords(_opCtx) / 10240;
+            if (ranges < 2) {
+                _state->ranges.emplace_back(Range{RecordId{}, RecordId{}});
+            } else {
+                if (ranges > 1024) {
+                    ranges = 1024;
+                }
+                auto randomCursor = _coll->getRecordStore()->getRandomCursor(_opCtx);
+                invariant(randomCursor);
+                std::set<RecordId> rids;
+                while (ranges--) {
+                    auto nextRecord = randomCursor->next();
+                    if (nextRecord) {
+                        rids.emplace(nextRecord->id);
                     }
-                    _state->ranges.emplace_back(Range{lastid, RecordId{}});
                 }
+                RecordId lastid{};
+                for (auto id : rids) {
+                    _state->ranges.emplace_back(Range{lastid, id});
+                    lastid = id;
+                }
+                _state->ranges.emplace_back(Range{lastid, RecordId{}});
             }
         }
-
-        _cursor = _coll->getCursor(_opCtx);
     }
 
+    _cursor = _coll->getCursor(_opCtx);
+
     _open = true;
 }
 
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