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MongoDB queries don’t always return all matching documents

engineering.meteor.com

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Re: MongoDB queries don’t always return all matching documents

#131

Post by catnaroek »

Lazare wrote: post #124
spriggan3 wrote: post #76

Earlier quoted context omitted.

> Why on earth would you use a database that makes so little in the way of guarantees about what results you get from it? Because some people can't stand having to work with SQL,migrations,schema and constraints, it's as simple as that ( That's not my opinion,that's just the rational behind MongoDB). Even if you use Postgres with the Json column type, you still need to write SQL queries and schemas. In the context of…

> Because some people can't stand having to work with SQL,migrations,schema and constraints The thing is, if you actually try and write an app using MongoDB, you will rapidly find that you: 1) Have migrations (except they're going to be some scary ad hoc nodejs script that loop through your document store and modify fields on the fly). 2) Have schemas (except they'll be implicit and undocumented) 3) Constraints (exce…

Exactly. While the process of designing the structure of your data can make you feel like “you're not getting real work done”, in the long run, it actually prevents headaches caused by inconsistent data. Data always has a structure, it's just that some people are too lazy or mentally feeble to figure out what it is.

Re: MongoDB queries don’t always return all matching documents

#132

Post by joeblau »

im_down_w_otp wrote: post #16

Said it before, will say it again... "MongoDB is the core piece of architectural rot in every single teetering and broken data platform I've worked with." The fundamental problem is that MongoDB provides almost no stable semantics to build something deterministic and reliable on top of it. That said. It is really, really easy to use.

I worked at a Data Analytics start up in Palo Alto back in 2011 and we had 8 or 9 databases in our arsenal for storing different types of data. MongoDB was by far the worst and most unstable database we had. It was so bad that for the presidential debate, I had to stay up and flip servers all night because even though the shards were perfectly distributed, the database would crash and fail over to two other machines which couldn't handle our entire social media stream. We ended up calling some guys from MongoDB in to help us troubleshoot the issue and the guy basically said "Yeah we know that's a limitation; you should probably buy more machines to distribute the load." I like the concept of Mongo, but there are other more robust NoSQL databases to choose from.

Re: MongoDB queries don’t always return all matching documents

#133

Post by hardwaresofton »

If you're currently using MongoDB in your stack and are finding yourselves outgrowing it or worried that an issue like this might pop up, you owe it to yourself to check out RethinkDB:

https://rethinkdb.com/

It's quite possibly the best document store out right now. Many others in this thread have said good things about it, but give it a try and you'll see.

Here's a technical comparison of RethinkDB and Mongo: https://rethinkdb.com/docs/comparison-tables/

Here's the aphyr review of RethinkDB (based on 2.2.3): https://aphyr.com/posts/330-jepsen-rethinkdb-2-2-3-reconfigu...

Re: MongoDB queries don’t always return all matching documents

#134

Post by themartorana »

catnaroek wrote: post #127
Pxtl wrote: post #101

Earlier quoted context omitted.

Because postgres doesn't focus on the first-five-minutes experience the way Mongo does. Even the name is hard to say. Mongo is a dumb, dead-end platform, but they know how important ease-of-use is.

> Mongo is a dumb, dead-end platform, but they know how important ease-of-use is. By “ease of use”, do you mean “ease of making something that seems to work” or “ease of making something that actually works”? I've never used a schema-free database, and ended up thinking to myself “I'm completely sure this database can't possibly contain garbage data”. Or do programmers simply not care about data integrity anymore?

Prototyping on Mongo is bad. MySQL takes 10 seconds to install. I'm imagining with the public Docker registry, so does Postgres.

How many times have you promised to fix something later and then later comes and...

Prototyping is not an excuse for laziness. It does feel like some programmers don't care.

Re: MongoDB queries don’t always return all matching documents

#135

Post by pgaddict »

ruw1090 wrote: post #22

While I love to hate on MongoDB as much as the next guy, this behavior is consistent with read-committed isolation. You'd have to be using Serializable isolation in an RDBMS to avoid this anomaly.

Quoting from the very first paragraph of the blog post:

> Specifically, if a document is updated while the query is running, MongoDB may not return it from the query — even if it matches both before and after the update!

How's that compatible with READ COMMITTED isolation level?

Re: MongoDB queries don’t always return all matching documents

#136

Post by brightball »

hardwaresofton wrote: post #133

If you're currently using MongoDB in your stack and are finding yourselves outgrowing it or worried that an issue like this might pop up, you owe it to yourself to check out RethinkDB: https://rethinkdb.com/ It's quite possibly the best document store out right now. Many others in this thread have said good things about it, but give it a try and you'll see. Here's a technical comparison of RethinkDB and Mongo: https:…

How does it compare to Couchbase? That seems to be lighting the world on fire in that space lately.

Re: MongoDB queries don’t always return all matching documents

#138

Post by rdtsc »

m_mueller wrote: post #118
spriggan3 wrote: post #76

Earlier quoted context omitted.

> Why on earth would you use a database that makes so little in the way of guarantees about what results you get from it? Because some people can't stand having to work with SQL,migrations,schema and constraints, it's as simple as that ( That's not my opinion,that's just the rational behind MongoDB). Even if you use Postgres with the Json column type, you still need to write SQL queries and schemas. In the context of…

So my question is then: Why not use CouchDB instead? I don't see what Mongo gives you over that and CouchDB is at least dependable and predictable in its operation.

CouchDB is too reliable and actually fsyncs your documents to disk. That is plain boring. I like to live on the edge and have some documents go to /dev/null once in a while. Life is just more exciting that way ;-)

/s

Re: MongoDB queries don’t always return all matching documents

#139

Post by themartorana »

tomphoolery wrote: post #69
eloff wrote: post #41

Earlier quoted context omitted.

As a guy who works on ACID database internals, I'm appalled that people use MongoDB. You want a document store? Use Postgres. Why on earth would you use a database that makes so little in the way of guarantees about what results you get from it? I think most people have really low load and concurrency, so things seem to work. When things get busier you're in for a world of pain. Look I get that's it's easy to use and…

Postgres wasn't always a great document store...there was definitely a time period where if you wanted to take a document-oriented approach to data modeling, MongoDB was a good way to go. JSONB was only added in the last minor version of Postgres, and while the JSON and HSTORE types were available, it didn't give you quite the same speed. Now that JSONB is a thing, I think the two databases are more comparable as a d…

A text/blob field with a normalized key column or two were always vastly superior. We're talking about data loss at an incredible level. I mean, a new Jepsen test comes out and this community goes bonkers over how database X might suffer a split-brain problem for a few milliseconds under an extreme condition but Mongo on a single instance has never been safe, and people are making excuses for it.

Re: MongoDB queries don’t always return all matching documents

#140

Post by [deleted] »

threeseed wrote: post #110
hinkley wrote: post #90

Earlier quoted context omitted.

Are there NoSQL alternatives that have a worse track record than Mongo?

Cassandra, HBase etc had checkered pasts with plenty of their own data loss and inconsistency bugs. Now they are considered two of the most rock solid NoSQL databases. The hatred towards MongoDB really is pretty irrational given just how popular the database is.

[deleted]
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