MongoDB
Discussion of MongoDB and its sponsoring company 10gen.
Soundbites: the Facebook/MySQL/NoSQL/VoltDB/Stonebraker flap, continued
As a follow-up to the latest Stonebraker kerfuffle, Derrick Harris asked me a bunch of smart followup questions. My responses and afterthoughts include:
- Facebook et al. are in effect Software as a Service (SaaS) vendors, not enterprise technology users. In particular:
- They have the technical chops to rewrite their code as needed.
- Unlike packaged software vendors, they’re not answerable to anybody for keeping legacy code alive after a rewrite. That makes migration a lot easier.
- If they want to write different parts of their system on different technical underpinnings, nobody can stop them. For example …
- … Facebook innovated Cassandra, and is now heavily committed to HBase.
- It makes little sense to talk of Facebook’s use of “MySQL.” Better to talk of Facebook’s use of “MySQL + memcached + non-transparent sharding.” That said:
- It’s hard to see why somebody today would use MySQL + memcached + non-transparent sharding for a new project. At least one of Couchbase or transparently-sharded MySQL is very likely a superior alternative. Other alternatives might be better yet.
- As noted above in the example of Facebook, the many major web businesses that are using MySQL + memcached + non-transparent sharding for existing projects can be presumed able to migrate away from that stack as the need arises.
Continuing with that discussion of DBMS alternatives:
- If you just want to write to the memcached API anyway, why not go with Couchbase?
- If you want to go relational, why not go with MySQL? There are many alternatives for scaling or accelerating MySQL — dbShards, Schooner, Akiban, Tokutek, ScaleBase, ScaleDB, Clustrix, and Xeround come to mind quickly, so there’s a great chance that one or more will fit your use case. (And if you don’t get the choice of MySQL flavor right the first time, porting to another one shouldn’t be all THAT awful.)
- If you really, really want to go in-memory, and don’t mind writing Java stored procedures, and don’t need to do the kinds of joins it isn’t good at, but do need to do the kinds of joins it is, VoltDB could indeed be a good alternative.
And while we’re at it — going schema-free often makes a whole lot of sense. I need to write much more about the point, but for now let’s just say that I look favorably on the Big Four schema-free/NoSQL options of MongoDB, Couchbase, HBase, and Cassandra.
What to do about “unstructured data”
We hear much these days about unstructured or semi-structured (as opposed to) structured data. Those are misnomers, however, for at least two reasons. First, it’s not really the data that people think is un-, semi-, or fully structured; it’s databases.* Relational databases are highly structured, but the data within them is unstructured — just lists of numbers or character strings, whose only significance derives from the structure that the database imposes.
*Here I’m using the term “database” literally, rather than as a concise synonym for “database management system”. But see below.
Second, a more accurate distinction is not whether a database has one structure or none — it’s whether a database has one structure or many. The easiest way to see this is for databases that have clearly-defined schemas. A relational database has one schema (even if it is just the union of various unrelated sub-schemas); an XML database, however, can have as many schemas as it contains documents.
One small terminological problem is easily handled, namely that people don’t talk about true databases very often, at least when they’re discussing generalities; rather, they talk about data and DBMS.* So let’s talk of DBMS being “structured” singly or multiply or whatever, just as the databases they’re designed to manage are.
*And they refer to the DBMS as “databases,” because they don’t have much other use for the word.
All that said — I think that single vs. multiple database structures isn’t a bright-line binary distinction; rather, it’s a spectrum. For example: Read more
| Categories: Cassandra, Couchbase, Data models and architecture, HBase, IBM and DB2, MarkLogic, MongoDB, NoSQL, Splunk, Theory and architecture | 19 Comments |
Alternatives for Hadoop/MapReduce data storage and management
There’s been a flurry of announcements recently in the Hadoop world. Much of it has been concentrated on Hadoop data storage and management. This is understandable, since HDFS (Hadoop Distributed File System) is quite a young (i.e. immature) system, with much strengthening and Bottleneck Whack-A-Mole remaining in its future.
Known HDFS and Hadoop data storage and management issues include but are not limited to:
- Hadoop is run by a master node, and specifically a namenode, that’s a single point of failure.
- HDFS compression could be better.
- HDFS likes to store three copies of everything, whereas many DBMS and file systems are satisfied with two.
- Hive (the canonical way to do SQL joins and so on in Hadoop) is slow.
Different entities have different ideas about how such deficiencies should be addressed. Read more
| Categories: Aster Data, Cassandra, Cloudera, Data warehouse appliances, DataStax, EMC, Greenplum, Hadapt, Hadoop, IBM and DB2, MapReduce, MongoDB, Netezza, Parallelization | 22 Comments |
The MongoDB story
Along with CouchDB/Couchbase, MongoDB was one of the top examples I had in mind when I wrote about document-oriented NoSQL. Invented by 10gen, MongoDB is an open source, no-schema DBMS, so it is suitable for very quick development cycles. Accordingly, there are a lot of MongoDB users who build small things quickly. But MongoDB has heftier uses as well, and naturally I’m focused more on those.
MongoDB’s data model is based on BSON, which seems to be JSON-on-steroids. In particular:
- You just bang things into single BSON objects managed by MongoDB; there is nothing like a foreign key to relate objects. However …
- … there are fields, datatypes, and so on within MongoDB BSON objects. The fields are indexed.
- There’s a multi-value/nested-data-structure flavor to MongoDB; for example, a BSON object might store multiple addresses in an array.
- You can’t do joins in MongoDB. Instead, you are encouraged to put what might be related records in a relational database into a single MongoDB object. If that doesn’t suffice, then use client-side logic to do the equivalent of joins. If that doesn’t suffice either, you’re not looking at a good MongoDB use case.
| Categories: Clustering, Data models and architecture, MapReduce, MongoDB, NoSQL, Parallelization | 10 Comments |
10gen company basics
10gen, as you probably knew, is the company behind MongoDB. I’ve talked with Dwight Merriman of 10gen a few times, which is why his thoughts were featured in at least three different posts on NoSQL/document-oriented-database generalities. I also talked a month ago with new 10gen President Max Schireson (who at one point was the #2 guy at MarkLogic) and CTO Eliot Horowitz. After some delay, 10gen gave me permission to post some January, 2011 slides that summarize company status, target markets, customer brags — excuse me, customer success — and so on. Maybe it’s time I actually blogged about 10gen and MongoDB. 🙂
By the way, our vendor client disclosures are a bit out of date in the area of short-request processing data management. The list is actually 10gen /MongoDB, Cloudera/HBase, CodeFutures/dbShards, Couchbase, DataStax/Cassandra, MarkLogic (yes, I count them, even though I didn’t count them as “NoSQL”), salesforce.com/database.com, and Schooner Information Technology.
10gen company highlights include:
- 10gen boasts a couple hundred paying customers total, but that includes small consulting/training deals.
- 10gen has dozens of MongoDB support subscription customers. That figure was around 25 in August.
- Like similar vendors, 10gen plans to add some proprietary code to its MongoDB support subscription services.
- 10gen is bicoastal, having started in New York City but ramping up in Redwood Shores. For one thing, a lot of 10gen’s customers are in the SF Bay area.
- 10gen headcount was 16 or so in August, 25-30 in January.
For a bit more detail, please see the slides linked above. I shall now do a separate post that is actually about MongoDB.
| Categories: Market share and customer counts, MongoDB | 2 Comments |
Notes on document-oriented NoSQL
When people talk about document-oriented NoSQL or some similar term, they usually mean something like:
Database management that uses a JSON model and gives you reasonably robust access to individual field values inside a JSON (JavaScript Object Notation) object.
Or, if they really mean,
The essence of whatever it is that CouchDB and MongoDB have in common.
well, that’s pretty much the same thing as what I said in the first place. 🙂
Of the various questions that might arise, three of the more definitional ones are:
- Why JSON rather than XML?
- What’s with this fluidity between the terms “document” and “object”?
- Are you serious about the lack of joins?
Let me take a crack at each. Read more
| Categories: CouchDB, MapReduce, MarkLogic, MongoDB, NoSQL, Object, Structured documents | 16 Comments |
Notes, links, and comments January 20, 2011
I haven’t done a pure notes/links/comments post for a while. Let’s fix that now. (A bunch of saved-up links, however, did find their way into my recent privacy threats overview.)
First and foremost, the fourth annual New England Database Summit (nee “Day”) is next week, specifically Friday, January 28. As per my posts in previous years, I think well of the event, which has a friendly, gathering-of-the-clan flavor. Registration is free, but the organizers would prefer that you register online by the end of this week, if you would be so kind.
The two things potentially wrong with the New England Database Summit are parking and the rush hour drive home afterwards. I would listen with interest to any suggestions about dinner plans.
One thing I hope to figure out at the Summit or before is what the hell is going on on Vertica’s blog or, for that matter, at Vertica. The recent Mike Stonebraker post that spawned a lot of discussion and commentary has disappeared. Meanwhile, Vertica has had three consecutive heads of marketing leave the company since June, and I don’t know who to talk to there any more. Read more