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MongoDB queries don’t always return all matching documents

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

#121

Post by orthecreedence »

threeseed wrote: post #114
Joeboy wrote: post #9

Earlier quoted context omitted.

> don't use mongo, it's just hype I'm kind of curious as to where this hype is. I've almost never heard anybody say anything positive about mongodb. All I ever see is people saying it's terrible / hilarious for various reasons.

The hatred for MongoDB mostly comes from the PostgreSQL supporters camp. The rest of us are just using whatever tool makes sense. MongoDB is the fastest database I've ever used. The easiest to get running, stable and scaled out. The best documentation by far and has excellent integration e.g. Spark, Hadoop. If you are doing Big Data it's a great tool in the arsenal.

It's fast because it doesn't actually save your data when you ask it to. It saves it later, when it feels like it, maybe. Also, the hate I have for Mongo is from first-hand experience with the wretched thing. The scaling is insane. The next jump after your first server is like 9 servers (2 repsets w/ 3 servers each w/ 3 config nodes). I don't have that kind of cash laying around for servers, especially when instance-for-instance, Postgres can handle easily 10x the write load of mongo.

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

#122

Post by [deleted] »

PeCaN wrote: post #50
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…

MongoDB: Because /dev/null doesn't support sharding.

[deleted]

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

#123

Post by glasser »

paradox95 wrote: post #115

Should an infrastructure company be advertising the fact that it didn't research the technology it chose to use to build its own infrastructure? All these people saying Mongo is garbage are all likely neckbeards sysadmins. Unless you're hiring database admin and sysadmins, Postgres (unless managed - then you have a different set of scaling problems) or any other tradition SQL store is not a viable alternative. This a…

My goal in writing this post was not to convince people to use or not use MongoDB, but to document an edge case that may affect people who happen to use it for whatever reason, which as far as I could tell was inadequately documented elsewhere.

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

#124

Post by Lazare »

spriggan3 wrote: post #76
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…

> 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 (except they'll be hidden inside your app logic, and violating them will cause data corruption).

The biggest lie about NoSQL databases is that they're schemaless. If you're EVER going to read the data back and do anything with it, it has a schema.

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

#125

Post by Lazare »

im_down_w_otp wrote: post #77
tomphoolery wrote: post #69

Earlier quoted context omitted.

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…

Is that actually true? I mean the part about Postgres might be, I don't know. But was there a time when MongoDB was a good way to go? Was there ever a time when it actually worked consistently well at something that was database shaped? Because I started dealing with it in ~2010 I think, and it wasn't a suitable database for anything other than toy projects or throw-away data back then, and while it's many versions n…

> But was there a time when MongoDB was a good way to go?

Not in any way, shape, or form. Keep in mind, as bad as it is now, it was vastly worse when it launched.

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

#126

Post by rgo »

Everytime I hear arguments for going back to relational databases, I remember all the scalability problems I lived through for 15 years in relational hell before switching to Mongo.

The thing about relational databases is that they do everything for you. You just lay the schema out (with ancient E-R tools maybe) load your relational data, write the queries, indexes, that's it.

The problem was scalability, or any tough performance situation really. That's when you realized RDBMSs were huge lock-ins, in the sense that they would require an enormous amount of time to figure out how to optimize queries and db parameters so that they could do that magic outer join for you. I remember queries that would take 10x more time to finish just by changing the order of tables in a FROM. I recall spending days trying different Oracle hints just to see if that would make any difference. And the SQL-way, with PK constraints and things like triggers, just made matters worse by claiming the database was actually responsible for maintaining data consistency. SQL, with its naturalish language syntax, was designed so that businessman could inquire the database directly about their business, but somehow that became a programming interface, and finally things like ORMs where invented that actually translated code into English so that a query compiler could translate that back into code. Insane!

Mongo, like most NoSQL, forces you to denormalize and do data consistency in your code, moving data logic into solid models that are tested and versioned from day one. That's the way it's supposed to be done, it sorta screams take control over your data goddammit. So, yes, there's a long way to go with Mongo or any generalistic NoSQL database really, but RDBMS seems a step back even if your data is purely relational.

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

#127

Post by catnaroek »

Pxtl wrote: post #101
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…

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?

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

#128

Post by catnaroek »

spriggan3 wrote: post #76
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…

> 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 real question is “How come these people are allowed anywhere near data stores?” SQL isn't ideal, but how many of the alternatives are better at protecting the integrity of your data?

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

#129

Post by paradox95 »

glasser wrote: post #123
paradox95 wrote: post #115

Should an infrastructure company be advertising the fact that it didn't research the technology it chose to use to build its own infrastructure? All these people saying Mongo is garbage are all likely neckbeards sysadmins. Unless you're hiring database admin and sysadmins, Postgres (unless managed - then you have a different set of scaling problems) or any other tradition SQL store is not a viable alternative. This a…

My goal in writing this post was not to convince people to use or not use MongoDB, but to document an edge case that may affect people who happen to use it for whatever reason, which as far as I could tell was inadequately documented elsewhere.

Only the first line was directed at you - and it was more in jest. Everything else was directed more at the other commenters and Mongo detractors in general.

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

#130

Post by [deleted] »

toomuchtodo wrote: post #86
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…

Who knew you'd need to learn how to use tools to use them!

[deleted]
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