winstonjs · ne0c0de · Feb 18, 2021 · Feb 18, 2021
diff --git a/README.md b/README.md
@@ -58,6 +58,7 @@ defaults to false.
 * __metaKey:__ Configure which key is used to store metadata in the logged info object.
 Defaults to `'metadata'` to remain compatible with the [metadata format](https://github.com/winstonjs/logform/blob/master/examples/metadata.js)
 * __expireAfterSeconds:__ Seconds before the entry is removed. Works only if __capped__ is not set.
+* __partialFilterExpression:__ Optional condition for the entry to be removed. Works only if __capped__ is not set and __expireAfterSeconds__ is set.
 
 *Metadata:* Logged as a native JSON object in 'meta' property.
 

diff --git a/lib/winston-mongodb.d.ts b/lib/winston-mongodb.d.ts
@@ -141,7 +141,14 @@ declare module 'winston-mongodb' {
         * @memberof MongoDBConnectionOptions
         */
        expireAfterSeconds?: number;
+       /**
+        * Optional condition for the entry to be removed. Works only if capped is not set and expireAfterSeconds is set.
+        *
+        * @type {*}
+        * @memberof MongoDBConnectionOptions
+        */
+       partialFilterExpression?: any;
     }
-    
+
     const MongoDB: MongoDBTransportInstance;
 }
diff --git a/lib/winston-mongodb.js b/lib/winston-mongodb.js
@@ -51,6 +51,8 @@ const helpers = require('./helpers');
  * after transport shut down.
  * @param {number} options.expireAfterSeconds Seconds before the entry is removed.
  * Do not use if capped is set.
+ * @param {Object} options.partialFilterExpression Condition for the entry to be removed.
+ * Do not use if capped is set or expireAfterSeconds is not set.
  */
 let MongoDB = exports.MongoDB = function(options) {
   Transport.call(this, options);
@@ -79,6 +81,7 @@ let MongoDB = exports.MongoDB = function(options) {
   this.decolorize = options.decolorize;
   this.leaveConnectionOpen = options.leaveConnectionOpen;
   this.expireAfterSeconds = !this.capped && options.expireAfterSeconds;
+  this.partialFilterExpression = !this.capped && this.expireAfterSeconds && options.partialFilterExpression ? options.partialFilterExpression : null;
   this.metaKey = options.metaKey || 'metadata';
   if (this.storeHost) {
     this.hostname = os.hostname();
@@ -113,15 +116,22 @@ let MongoDB = exports.MongoDB = function(options) {
       if (self.expireAfterSeconds) {
         indexOpts.expireAfterSeconds = self.expireAfterSeconds;
       }
+      if (self.partialFilterExpression) {
+        indexOpts.partialFilterExpression = self.partialFilterExpression;
+      }
       return col.indexInformation({full: true}).then(info=>{
         info = info.filter(i=>i.name === ttlIndexName);
         if (info.length === 0) { // if its a new index then create it
           return col.createIndex({timestamp: -1}, indexOpts);
-        } else { // if index existed with the same name check if expireAfterSeconds param has changed
+        } else { // if index existed with the same name check if expireAfterSeconds or partialFilterExpression param has changed
           if (info[0].expireAfterSeconds !== undefined &&
               info[0].expireAfterSeconds !== self.expireAfterSeconds) {
             return col.dropIndex(ttlIndexName)
             .then(()=>col.createIndex({timestamp: -1}, indexOpts));
+          } else if (info[0].partialFilterExpression !== undefined &&
+              JSON.stringify(info[0].partialFilterExpression) !== JSON.stringify(self.partialFilterExpression)) {
+            return col.dropIndex(ttlIndexName)
+                .then(()=>col.createIndex({timestamp: -1}, indexOpts));
           }
         }
       });