SERVER-72542 Avoid redundant index traversal during full validation

(cherry picked from commit 571cfa3561d657445ae694bf6a7b120f202b5250)

5 files changed, 32 insertions, 55 deletions

diff --git a/src/mongo/db/catalog/collection_validation.cpp b/src/mongo/db/catalog/collection_validation.cpp
index dbd119c9ade..1bf11131960 100644
--- a/src/mongo/db/catalog/collection_validation.cpp
+++ b/src/mongo/db/catalog/collection_validation.cpp
@@ -95,14 +95,11 @@ void _validateIndexesInternalStructure(OperationContext* opCtx,
 
         auto& curIndexResults = (results->indexResultsMap)[descriptor->indexName()];
 
-        int64_t numValidated;
-        iam->validate(opCtx, &numValidated, &curIndexResults);
+        iam->validate(opCtx, nullptr, &curIndexResults);
 
         if (!curIndexResults.valid) {
             results->valid = false;
         }
-
-        curIndexResults.keysTraversedFromFullValidate = numValidated;
     }
 }
 
@@ -134,33 +131,6 @@ void _validateIndexes(OperationContext* opCtx,
         auto& curIndexResults = (results->indexResultsMap)[descriptor->indexName()];
         curIndexResults.keysTraversed = numTraversedKeys;
 
-        // If we are performing a full index validation, we have information on the number of index
-        // keys validated in _validateIndexesInternalStructure (when we validated the internal
-        // structure of the index). Check if this is consistent with 'numTraversedKeys' from
-        // traverseIndex above.
-        if (validateState->isFullIndexValidation()) {
-            invariant(opCtx->lockState()->isCollectionLockedForMode(validateState->nss(), MODE_X));
-
-            // The number of keys counted in _validateIndexesInternalStructure, when checking the
-            // internal structure of the index.
-            const int64_t numIndexKeys = curIndexResults.keysTraversedFromFullValidate;
-
-            // Check if currIndexResults is valid to ensure that this index is not corrupted or
-            // comprised (which was set in _validateIndexesInternalStructure). If the index is
-            // corrupted, there is no use in checking if the traversal yielded the same key count.
-            if (curIndexResults.valid) {
-                if (numIndexKeys != numTraversedKeys) {
-                    curIndexResults.valid = false;
-                    string msg = str::stream()
-                        << "number of traversed index entries (" << numTraversedKeys
-                        << ") does not match the number of expected index entries (" << numIndexKeys
-                        << ")";
-                    results->errors.push_back(msg);
-                    results->valid = false;
-                }
-            }
-        }
-
         if (!curIndexResults.valid) {
             results->valid = false;
         }
diff --git a/src/mongo/db/catalog/validate_results.h b/src/mongo/db/catalog/validate_results.h
index 83af552e4d9..03f7389d9ab 100644
--- a/src/mongo/db/catalog/validate_results.h
+++ b/src/mongo/db/catalog/validate_results.h
@@ -45,7 +45,6 @@ struct IndexValidateResults {
     std::vector<std::string> errors;
     std::vector<std::string> warnings;
     int64_t keysTraversed = 0;
-    int64_t keysTraversedFromFullValidate = 0;
 };
 
 using ValidateResultsMap = std::map<std::string, IndexValidateResults>;
diff --git a/src/mongo/db/index/index_access_method.cpp b/src/mongo/db/index/index_access_method.cpp
index ac4ba3a2671..cf276f8f6fc 100644
--- a/src/mongo/db/index/index_access_method.cpp
+++ b/src/mongo/db/index/index_access_method.cpp
@@ -415,9 +415,13 @@ RecordId AbstractIndexAccessMethod::findSingle(OperationContext* opCtx,
 void AbstractIndexAccessMethod::validate(OperationContext* opCtx,
                                          int64_t* numKeys,
                                          IndexValidateResults* fullResults) const {
-    long long keys = 0;
-    _newInterface->fullValidate(opCtx, &keys, fullResults);
-    *numKeys = keys;
+    if (numKeys) {
+        long long keys = 0;
+        _newInterface->fullValidate(opCtx, &keys, fullResults);
+        *numKeys = keys;
+    } else {
+        _newInterface->fullValidate(opCtx, nullptr, fullResults);
+    }
 }
 
 bool AbstractIndexAccessMethod::appendCustomStats(OperationContext* opCtx,
diff --git a/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_sorted_impl.cpp b/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_sorted_impl.cpp
index 52be28c2183..93839c1d4ab 100644
--- a/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_sorted_impl.cpp
+++ b/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_sorted_impl.cpp
@@ -1459,7 +1459,9 @@ void SortedDataInterfaceUnique::fullValidate(OperationContext* opCtx,
         numKeys += UniqueIndexData(it->second, _rsKeyFormat).size();
         ++it;
     }
-    *numKeysOut = numKeys;
+    if (numKeysOut) {
+        *numKeysOut = numKeys;
+    }
 }
 
 bool SortedDataInterfaceBase::appendCustomStats(OperationContext* opCtx,
@@ -1599,7 +1601,9 @@ void SortedDataInterfaceStandard::fullValidate(OperationContext* opCtx,
         ++numKeys;
         ++it;
     }
-    *numKeysOut = numKeys;
+    if (numKeysOut) {
+        *numKeysOut = numKeys;
+    }
 }
 
 std::unique_ptr<mongo::SortedDataInterface::Cursor> SortedDataInterfaceStandard::newCursor(
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_index.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_index.cpp
index 9d009390762..bae8e9888de 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_index.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_index.cpp
@@ -348,25 +348,25 @@ void WiredTigerIndex::fullValidate(OperationContext* opCtx,
         }
     }
 
-    auto cursor = newCursor(opCtx);
-    long long count = 0;
-    LOGV2_TRACE_INDEX(20094, "fullValidate");
-
-    const auto requestedInfo = TRACING_ENABLED ? Cursor::kKeyAndLoc : Cursor::kJustExistance;
-
-    KeyString::Value keyStringForSeek =
-        IndexEntryComparison::makeKeyStringFromBSONKeyForSeek(BSONObj(),
-                                                              getKeyStringVersion(),
-                                                              getOrdering(),
-                                                              true, /* forward */
-                                                              true  /* inclusive */
-        );
-
-    for (auto kv = cursor->seek(keyStringForSeek, requestedInfo); kv; kv = cursor->next()) {
-        LOGV2_TRACE_INDEX(20095, "fullValidate {kv}", "kv"_attr = kv);
-        count++;
-    }
     if (numKeysOut) {
+        auto cursor = newCursor(opCtx);
+        long long count = 0;
+        LOGV2_TRACE_INDEX(20094, "fullValidate");
+
+        const auto requestedInfo = TRACING_ENABLED ? Cursor::kKeyAndLoc : Cursor::kJustExistance;
+
+        KeyString::Value keyStringForSeek =
+            IndexEntryComparison::makeKeyStringFromBSONKeyForSeek(BSONObj(),
+                                                                  getKeyStringVersion(),
+                                                                  getOrdering(),
+                                                                  true, /* forward */
+                                                                  true  /* inclusive */
+            );
+
+        for (auto kv = cursor->seek(keyStringForSeek, requestedInfo); kv; kv = cursor->next()) {
+            LOGV2_TRACE_INDEX(20095, "fullValidate {kv}", "kv"_attr = kv);
+            count++;
+        }
         *numKeysOut = count;
     }
 }