From ee08d86e202e58f488d1303341839a831e9bfc68 Mon Sep 17 00:00:00 2001
From: Benety Goh <benety@mongodb.com>
Date: Fri, 20 Nov 2020 16:39:11 -0500
Subject: SERVER-52525 extract index_key_validate::validateIndexSpecTTL() from
 createIndexes command

---
 src/mongo/db/catalog/index_key_validate.cpp | 51 +++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

(limited to 'src/mongo/db/catalog/index_key_validate.cpp')

diff --git a/src/mongo/db/catalog/index_key_validate.cpp b/src/mongo/db/catalog/index_key_validate.cpp
index 829a2b7392c..14e0ca05bdd 100644
--- a/src/mongo/db/catalog/index_key_validate.cpp
+++ b/src/mongo/db/catalog/index_key_validate.cpp
@@ -610,6 +610,57 @@ StatusWith<BSONObj> validateIndexSpecCollation(OperationContext* opCtx,
     return indexSpec;
 }
 
+Status validateIndexSpecTTL(const BSONObj& indexSpec) {
+    if (!indexSpec.hasField(IndexDescriptor::kExpireAfterSecondsFieldName)) {
+        return Status::OK();
+    }
+
+    const BSONElement expireAfterSecondsElt =
+        indexSpec[IndexDescriptor::kExpireAfterSecondsFieldName];
+    if (!expireAfterSecondsElt.isNumber()) {
+        return {ErrorCodes::CannotCreateIndex,
+                str::stream() << "TTL index '" << IndexDescriptor::kExpireAfterSecondsFieldName
+                              << "' option must be numeric, but received a type of '"
+                              << typeName(expireAfterSecondsElt.type())
+                              << "'. Index spec: " << indexSpec};
+    }
+
+    if (expireAfterSecondsElt.safeNumberLong() < 0) {
+        return {ErrorCodes::CannotCreateIndex,
+                str::stream() << "TTL index '" << IndexDescriptor::kExpireAfterSecondsFieldName
+                              << "' option cannot be less than 0. Index spec: " << indexSpec};
+    }
+
+    const std::string tooLargeErr = str::stream()
+        << "TTL index '" << IndexDescriptor::kExpireAfterSecondsFieldName
+        << "' option must be within an acceptable range, try a lower number. Index spec: "
+        << indexSpec;
+
+    // There are two cases where we can encounter an issue here.
+    // The first case is when we try to cast to millseconds from seconds, which could cause an
+    // overflow. The second case is where 'expireAfterSeconds' is larger than the current epoch
+    // time.
+    try {
+        auto expireAfterMillis =
+            duration_cast<Milliseconds>(Seconds(expireAfterSecondsElt.safeNumberLong()));
+        if (expireAfterMillis > Date_t::now().toDurationSinceEpoch()) {
+            return {ErrorCodes::CannotCreateIndex, tooLargeErr};
+        }
+    } catch (const AssertionException&) {
+        return {ErrorCodes::CannotCreateIndex, tooLargeErr};
+    }
+
+    const BSONObj key = indexSpec["key"].Obj();
+    if (key.nFields() != 1) {
+        return {ErrorCodes::CannotCreateIndex,
+                str::stream() << "TTL indexes are single-field indexes, compound indexes do "
+                                 "not support TTL. Index spec: "
+                              << indexSpec};
+    }
+
+    return Status::OK();
+}
+
 GlobalInitializerRegisterer filterAllowedIndexFieldNamesInitializer(
     "FilterAllowedIndexFieldNames", [](InitializerContext* service) {
         if (filterAllowedIndexFieldNames)
-- 
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