Add timestamp methods

This change adds [new milestone database methods][1] for fetching milestones by timestamp. In order to make this performant, this change also adds a new index to the `m.mtime` (modified timestamp) field. [1]: share/sharedb#262
share · Jan 30, 2019 · 46ef109 · 46ef109
1 parent e630382
commit 46ef109
Show file tree

Hide file tree

Showing 5 changed files with 388 additions and 329 deletions.
diff --git a/README.md b/README.md
@@ -123,7 +123,8 @@ const milestoneDb = new MongoMilestoneDB({
 * 4101 - Must provide valid collection name
 * 4102 - Must provide valid ID
 * 4103 - Must provide valid snapshot
-* 4104 - Must provide valid integer version
+* 4104 - Must provide valid integer version or null
+* 4105 - Must provide valid integer timestamp or null
 
 ### 5100 - Internal error - DB
 

diff --git a/lib/mongo-milestone-db.js b/lib/mongo-milestone-db.js
@@ -57,13 +57,21 @@ class MongoMilestoneDB extends MilestoneDB {
   }
 
   getMilestoneSnapshot(collectionName, id, version, callback) {
-    if (!collectionName) return process.nextTick(callback, new InvalidCollectionNameError());
-    if (!id) return process.nextTick(callback, new InvalidIdError());
-    if (!this._isValidVersion(version)) {
-      return process.nextTick(callback, new InvalidVersionError());
-    }
+    this._getMilestoneSnapshotByVersion(collectionName, id, version)
+      .then(snapshot => process.nextTick(callback, null, snapshot))
+      .catch(error => process.nextTick(callback, error));
+  }
+
+  getMilestoneSnapshotAtOrBeforeTime(collection, id, timestamp, callback) {
+    const isAfterTimestamp = false;
+    this._getMilestoneSnapshotByTimestamp(collection, id, timestamp, isAfterTimestamp)
+      .then(snapshot => process.nextTick(callback, null, snapshot))
+      .catch(error => process.nextTick(callback, error));
+  }
 
-    this._getMilestoneSnapshot(collectionName, id, version)
+  getMilestoneSnapshotAtOrAfterTime(collection, id, timestamp, callback) {
+    const isAfterTimestamp = true;
+    this._getMilestoneSnapshotByTimestamp(collection, id, timestamp, isAfterTimestamp)
       .then(snapshot => process.nextTick(callback, null, snapshot))
       .catch(error => process.nextTick(callback, error));
   }
@@ -79,19 +87,52 @@ class MongoMilestoneDB extends MilestoneDB {
       });
   }
 
-  _getMilestoneSnapshot(collectionName, id, version) {
-    return this._collection(collectionName)
-      .then((collection) => {
-        const query = {d: id};
-        if (version != null) {
-          query.v = {$lte: version};
-        }
+  _getMilestoneSnapshotByVersion(collectionName, id, version) {
+    if (!id) return Promise.reject(new InvalidIdError());
+    if (!this._isValidVersion(version)) {
+      return Promise.reject(new InvalidVersionError());
+    }
+
+    const query = {d: id};
+    if (version != null) {
+      query.v = {$lte: version};
+    }
 
-        const sort = {v: -1};
+    const options = {
+      sort: {v: -1},
+    };
 
-        return collection
-          .findOne(query, {sort: sort});
-      })
+    return this._getMilestoneSnapshotByQuery(collectionName, query, options);
+  }
+
+  _getMilestoneSnapshotByTimestamp(collectionName, id, timestamp, isAfterTimestamp) {
+    if (!id) return Promise.reject(new InvalidIdError());
+    if (!this._isValidTimestamp(timestamp)) {
+      return Promise.reject(new InvalidTimestampError());
+    }
+
+    const nullSortOrder = isAfterTimestamp ? -1 : 1;
+
+    const query = {d: id};
+    const options = {
+      limit: 1,
+      sort: {'m.mtime': nullSortOrder},
+    };
+
+    if (timestamp !== null) {
+      const comparator = isAfterTimestamp ? {$gte: timestamp} : {$lte: timestamp};
+      query['m.mtime'] = comparator;
+      options.sort['m.mtime'] = -nullSortOrder;
+    }
+
+    return this._getMilestoneSnapshotByQuery(collectionName, query, options);
+  }
+
+  _getMilestoneSnapshotByQuery(collectionName, query, options) {
+    if (!collectionName) return Promise.reject(new InvalidCollectionNameError());
+
+    return this._collection(collectionName)
+      .then(collection => collection.findOne(query, options))
       .then(MongoMilestoneDB._databaseRepresentationToSnapshot);
   }
 
@@ -129,7 +170,10 @@ class MongoMilestoneDB extends MilestoneDB {
           // collection this won't be a problem, but this is a dangerous mechanism.
           // Perhaps we should only warn instead of creating the indexes, especially
           // when there is a lot of data in the collection.
-          return collection.createIndex({d: 1, v: 1}, {background: true, unique: true});
+          return Promise.all([
+            collection.createIndex({d: 1, v: 1}, {background: true, unique: true}),
+            collection.createIndex({'m.mtime': 1}, {background: true}),
+          ]);
         }
 
         return Promise.resolve();
@@ -227,6 +271,14 @@ class InvalidVersionError extends Error {
   }
 }
 
+class InvalidTimestampError extends Error {
+  constructor() {
+    super();
+    this.code = 4105;
+    this.message = 'Must provide valid integer timestamp or null';
+  }
+}
+
 class MongoClosedError extends Error {
   constructor() {
     super();