
Ask HN: PostgreSQL or MySQL? - ReD_CoDE
I have four questions related to SQL<p>1. PostgreSQL or MySQL? And why?<p>2. Is it possible to build a hybrid database schema? For example, SQLite+JSON?<p>3. Is it possible to convert XML(XMI) schema to SQLite schema automatically?<p>4. Is it possible to build a custom file format based on SQLite or hybrid one based on SQLite+JSON?
======
nbouscal
The following isn’t the top reason I recommend Postgres, but is the reason I
think least likely to be echoed in a dozen other comments:

Postgres has some of the best documentation of any software product I’ve ever
used. If someone wants to learn about SQL or databases, I always have to
restrain myself from recommending that they just read the Postgres manual
front to back. It’s comprehensive, it’s well written, it’s easy to navigate,
and almost every explanation comes with several clear examples. It’s hard to
overstate how valuable a property that is for a product as central to your
architecture as your primary transactional database.

~~~
Zelphyr
Too many Open Source developers discount the value of documentation. I all too
often hear, "It's Open Source so the community should step up and write the
documentation." To which I counter that the best person/people to at least
start the documentation are the ones who build the product as they're the most
knowledgeable about it. The community will gladly contribute. I personally
believe that great documentation was a big reason for PHP's success in the
early days.

~~~
otterley
Same for all of the GNU software distribution, Sun Microsystems’ products, and
SGI’s. Even MSDN has had pretty good documentation.

I miss the days when I could understand how something worked just by reading
the official documentation first.

To this day, in my open source projects, I do not accept contributions that
lack either documentation updates or test cases.

~~~
linux2647
> I miss the days when I could understand how something worked just by reading
> the official documentation first.

This is probably why I don’t read much documentation when I’m working with a
library, et al. Never thought about it until I read the parent

------
matthewmacleod
On the first point, default to using Postgres unless you have a particular
reason not to. In general, it offers more and better-executed features. There
are some scenarios where MySQL offers a benefit and this advice doesn’t apply,
but it’s unlikely you will need to worry about that if you’re in a “what
database do I use” position.

Your other questions are a bit too vague to be answerable. It’s possible to
build anything you want, including custom file formats or schema converters,
if you want to invest the time. You might have more useful responses if you
explain the use case instead of the solution you already have in mind.

~~~
dfsegoat
As someone who has transitioned from MySQL->pg, this makes total sense to me.
Partitioning is still a bit better in MySQL IMO (many types / options) - but
pg is nearly there.

~~~
quicksilver03
Did you mean replication rather than partitioning perhaps?

I've found MySQL replication quite easy to use, whereas PostgreSQL has been
rather clunkier in my experience. However, I've had the exact opposite
experience with respect to partitioning.

~~~
evanelias
MySQL partitioning shines with one specific use-case: time-based data
retention. e.g., by using RANGE partitioning over a temporal value, you can
very efficiently drop large amounts of old data when no longer needed, and can
automate this fairly easily.

For anything else, MySQL partitioning rule-of-thumb is you'll have a bad time,
mainly for performance reasons.

~~~
photonios
Postgres's support for table partitioning got a massive boost in the last
major release (11.x): [https://www.postgresql.org/docs/current/ddl-
partitioning.htm...](https://www.postgresql.org/docs/current/ddl-
partitioning.html)

------
jerrytsai
I will respond only to Q1, taking the perspective of analytics and data
science.

Answer: PostgreSQL > MySQL

Postgres implementation of SQL includes a few useful clauses that are useful
for analytics that MySQL does not support.

It used to be that MySQL had no window functions, and that made it wholly
inferior to Postgres when it came to analytics. However, it seems MySQL began
supporting window functions two years ago, so that is no longer a reason to
choose one over the other.

There are at least two features supported in Postgres that are not available
in MySQL that I use often enough to care:

• SELECT DISTINCT ON

• FULL OUTER JOIN

Having these saves dev time. It is possible to implement either using MySQL,
but your code will be more verbose, creating more opportunities for error.

If you care about analyzing the data for data-scientific purposes, you would
be better off using Postgres. It isn't just the couple of extra clauses. It's
also having more (useful) indexing choices and little choices like being able
to use two pipes (||) to concatenate strings instead of CONCAT().

~~~
raymondgh
Having consulted for hundreds of analysts writing SQL to explore their data
and create reports, I would agree with this assessment. Additionally, I tend
to avoid recommending MySQL because of a strange behavior when using Group By.
In Postgres, every column must be either aggregated or grouped by when using a
grouping expression. In MySQL, this requirement is not present, and the
ambiguity of the query is resolved by returning basically random results which
are quite often misunderstood to represent the desired report. In other words,
you can screw up in MySQL easily and not notice, whereas in Postgres, you’ll
get an error message.

[https://stackoverflow.com/questions/1023347/mysql-
selecting-...](https://stackoverflow.com/questions/1023347/mysql-selecting-a-
column-not-in-group-by)

~~~
dawkins
This was in older versions. From 5.7 ONLY_FULL_GROUP_BY is enabled by default.

------
nmpennypacker
Personally,PostgreSQL. Both have their advantages and disadvantages, but my
standard arguments in favor of Postgres are that it: 1\. Enforces data types
natively. I've shot myself in the foot before with MySQL and 'polluting' data.
2\. JSONB support makes it easy to use a 'hybrid' schema if you want NoSQL-
like behavior or a junk drawer to shove JSON into.

Regarding your conversion questions, it's common to have an app that
communicates with several databases, but I don't know of any architecture that
would allow ACID transactions in two engines simultaneously.

As far as converting data, it all depends on what your development preferences
are. I work mostly in the Ruby ecosystem, and I can tell you that I've used
ActiveRecord to a Postgres database, and exported the results into a SQLite
file. I'm sure it would be possible to use an XML parser like Nokogiri to
convert XML into a SQLite file as well. If you prefer another major
programming language, the tools likely exist to accomplish the same thing.

~~~
johannes1234321
> 1\. Enforces data types natively.

Quite a while ago MySQL changed the default to be strict on types and not
doing truncations anymore. Recently it also (finally) got check constraints.

> 2\. JSONB support makes it easy to use a 'hybrid' schema

MySQL has a JSON data type with validation, binary storage, efficient updates
and efficient replication.

~~~
perlgeek
My experiences are with a pretty old mysql version (5.5, iirc), but that
version allowed inserts without supplying a value to a column that is NOT NULL
and has no default value.

If that's the _strict_ mode, I shudder to think what the lax mode must be...
:(

And upgrade to MariaDB 10.3 caught those cases, so at least there's some
progress in the mysql/mariadb ecosystem.

> MySQL has a JSON data type with validation, binary storage, efficient
> updates and efficient replication.

Postgres has, in addition, indexes over expression, which allows you to build
indexes for specific queries into JSONB.

(I'd argue that if you need indexes, it's typically better to extract that
data into the regular table and not keep it in the json, but it can still save
your butt if you need to react quickly to a requirement change and no time for
a data migration).

~~~
johannes1234321
> My experiences are with a pretty old mysql version (5.5, iirc), but that
> version allowed inserts without supplying a value to a column that is NOT
> NULL and has no default value.

With recent MySQL:

create table ttt (col int not null); insert into ttt () values(); ERROR: 1364:
Field 'col' doesn't have a default value

> Postgres has, in addition, indexes over expression, which allows you to
> build indexes for specific queries into JSONB.

MySQL has that, too. I consider this quite useful, especially since MySQL also
supports indexing an array of values from a JSON document. (Given `{"colors":
["red", "green", "blue" ]}` a search for `JSON_CONTAINS('$.colors', 'red')`
benefits from the index.

------
dragonsh
Given the progress both Mariadb and postgresql has made I think you will not
go wrong with either. In both you have support for json now which one you
chose depends on your use case.

 _Mariadb_ \- If you want easy horizontal scalability with master-master
replication go with mariadb.

 _Postgresql_ \- If you want reliable and powerful sql-92 compliance and
willing to work with master-slave go for postgresql. You can do master to
master with postgre-Xl [1]. But still given the ease of use with which you can
work with galera cluster I would not recommend postgresql for master-master.

Anyways for your other questions:

2\. SQLite already supports json type [2] so its not SQLite+JSON its just
SQLite.

3\. Yes you can write a simple python script to do it.

4\. Why to use a custom file format when SQLite has its own format with
support for json.

[1] [https://www.postgres-xl.org/](https://www.postgres-xl.org/)

[2] [https://www.sqlite.org/json1.html](https://www.sqlite.org/json1.html)

~~~
dikei
In my experience, master-master replication with Galera is more troublesome
than its worth. It's better to use the simple master-standby solution with
automated fail-over.

------
madhadron
1\. Do you have experience running PostgreSQL or MySQL in production? Use what
you know. Do you have friends or colleagues with that experience? Use what
they know. Is the stack you end up using predominantly used with one or the
other, so you have lots more people in the community who will have hit issues
you might have? Use that one. Failing any of those? Default to PostgreSQL.

2\. I think you mean SQL+JSON, and the answer is PostgreSQL's JSONB columns,
or dumping blobs into rows in MySQL (just keep your row sizes below 4kb).

3\. Possible? Yes. A good idea? Almost never. Trees and relations are quite
mathematically different, and you will need to specify quite a bit of the
mapping to make it come out in a way you would actually want to work with.

4\. Not really...generally you would have a SQLite database. If you need stuff
that doesn't go in well as a blob, you would put it in a file and include a
reference in the database.

~~~
tmk1108
Can you expand on the 4kb part of row sizes? I have been experimenting with
storing json in MySQL tables and I'm curious about this limit

~~~
madhadron
MySQL expects rows to be fairly small, which leads to decisions about how the
system handles loading data. You can put larger blobs in, but it may have
adverse performance implications.

------
gtsteve
When considering between PostgreSQL and MySQL bear in mind that client-side
drivers are licensed differently. I believe the MySQL connector is still GPL
licensed; it used to be LGPL and then the license was changed with little
fanfare. Commentators called this "weaponising the GPL". The goal is to get
you to buy the enterprise version of MySQL.

I know MySQL way better but at a brief look I can see Postgres drivers are
licensed more liberally.

~~~
CameronNemo
Actually the goal is to get you to unwittingly use the GPL connectors, then
backcharge you after an audit.

------
jtolmar
> 2\. Is it possible to build a hybrid database schema? For example,
> SQLite+JSON?

Postgres and MySQL both have JSON support that can do fancy things which
includes indexes, but it's extra work and I don't think it actually gains you
anything. I'd recommend using regular old columns for anything you ever plan
to want a query on. But if you have other stuff, it's perfectly reasonable to
dump a bunch of random garbage into a JSON column. People use this for things
like user settings, and are generally happy with it.

> 4\. Is it possible to build a custom file format based on SQLite or hybrid
> one based on SQLite+JSON?

SQLite is already basically a file format. You can store JSON blobs in strings
somewhere inside it if that's convenient.

~~~
sb8244
Postgres jsonb column type has worked great without much effort. The old JSON
type wasn't great and required special index, but that's decently in the past
now. Not sure of MySQL in this aspect.

------
ausjke
If you ask this at HN most likely it will be PostgreSQL.

If you ask scripting language it got to be python or javascript here.

I use HN daily and noticed as a group, HN readers do in general have their
preference on things like this.

By all means, MySQL's market share is much larger than PostgreSQL, and MySQL
8+ is very impressive. I compared both and eventually picked MySQL for my
projects, even though I really _hate_ Oracle.

~~~
apple4ever
You could use Percona MySQL, which isn't by Oracle and is much better anyway.

------
partoa
1\. Depends. If you have a lot of update queries, MySQL wins
[[https://eng.uber.com/mysql-migration/](https://eng.uber.com/mysql-
migration/)]. MySQL also has better replication and sharding support at the
moment.

2\. PostgreSQL and MYSQL also sport JSON... JSON functions can be a little
tricky. Still, they work.

3\. Depends on the structure of your XML. Might even possible to use RegEx to
achieve this objective. XML to JSON is easier though. That can be saved in
JSON fields in a DB.

4\. You can build a custom file based on anything. The only catch, the SQLite
client will only read a valid SQLite file. As such, you have to know what
you're doing.

[Edit] Formating

~~~
jiggawatts
That's incredibly well written, constructive feedback by the Uber team! I
wonder if the Postgres team has taken this on board and attempted to resolve
some of the design issues, e.g.: by moving the cache in-process.

~~~
jeltz
The Uber team betrays their lack of knowledge about PostgreSQL in the article,
so take it with a huge grain of salt. I recommend reading Markus Winand's
article.

[https://use-the-index-luke.com/blog/2016-07-29/on-ubers-choi...](https://use-
the-index-luke.com/blog/2016-07-29/on-ubers-choice-of-databases)

But that does not mean though that there are not also real issues with table
bloat in PostgreSQL, and they are being worked on by creating a new storage
engine with a different MVCC implementation.

------
jstewartmobile
#1: depends on your scenario. Postgres is more like Oracle--there are types of
query it can do natively that would have to be externally assisted with MySQL.
MySQL is simpler, has all kinds of warts, but scales decently.

Here's why uber moved to MySQL: [https://eng.uber.com/mysql-
migration/](https://eng.uber.com/mysql-migration/)

#2-4: My use of SQLite has always been very basic, so no idea. Per SQLite's
author: " _SQLite does not compete with client /server databases. SQLite
competes with fopen()._"

~~~
baragiola
That's a very interesting article. Does anybody knows if Postgres 10 and 11
addressed any of those issues?

~~~
estsauver
[https://news.ycombinator.com/item?id=14222721](https://news.ycombinator.com/item?id=14222721)
is a continued discussion of the response.

------
glax
For me postgresql's schema, EXPLAIN, Column modification and UUID. But most of
the time I stick to sqlite, it satisfies most of the project with low
footprint and require for installation restricted servers.

~~~
barrkel
Every time I've used sqlite for any kind of throwaway web app, I've regretted
it due to the almost complete lack of support for concurrent operations.
Sqlite is for file formats, not anything that might have concurrent writes.

~~~
asdkhadsj
TIL. I really thought SQLite had better support for concurrent behavior.

Do you know if the problem you cite is distinct separate processes of SQLite?
Ie, can a single process (aka one web app) handle concurrent behavior properly
with SQLite? Or will it fail even in that scenario?

~~~
Spooky23
Why write code to deal with that complexity when you can just use pg or MySQL?

~~~
asdkhadsj
Because depending on the use case you don't want to run a 2nd server. For
example, I work on some FOSS that lets users self host. The intention is for
minimally experienced users to self host, as well as host on small
laptops/etc. For obvious reasons, spinning up a full database has issues -
requiring them to install Docker or etc is not feasible.

With that said, knowing how DB concurrency behaves in inherently concurrent
applications (anything HTTP facing, for example) seems vital. If it needs to
be not concurrent, it's paramount to know that.

To be clear, knowing how and when the concurrency breaks down does not mean
advocating for it. Merely that if concurrency wasn't supported, you may need
to write your applications differently to properly lock the non-threadsafe
behavior.

------
evanelias
To echo a few other commenters here, a major point of consideration is your
team's experience and broader technical network. Generally speaking, either
Postgres or MySQL is likely fine for most applications. But you'll have a
better time with whichever one you can most smoothly build on, operate, and
hire for.

Separate from that, and with the disclaimer that my career has been heavily
MySQL-oriented, although I try to provide a balanced perspective:

MySQL can be a good choice for OLTP-heavy workloads, such as a high volume of
relatively straightforward queries. It also supports a very wide variety of
replication options. In some aspects, MySQL is simpler to operate than pg.
(This can be a point of contention, as MySQL is more idiosyncratic and this
leads to some land-mines that are well-known to the community, but unclear
from the manual alone.)

At this point there are also many hundreds (thousands?) of engineers and DBAs
worldwide who have extensive experience working on massive-scale MySQL
deployments. This may or may not be relevant to your project, depending what
you're building and its eventual best-case size.

MySQL is admittedly less "batteries included". Although MySQL/InnoDB does
support things like windowing functions, fulltext, geospatial, etc they're not
necessarily a best-in-class implementation yet. In a MySQL shop, if you need
OLAP, you're better off doing ETL into a separate column store or Hadoop
cluster; if you need fulltext search, you're better off using a separate
search index system like Solr; etc. Depending on your point-of-view, this
approach is either "more UNIXy" or a major operational headache, or both :)

Meanwhile Postgres may be a better choice if you want to handle a bunch of
things using a single piece of software: mixed OLTP + OLAP workloads, fulltext
search, geospatial. It also has some interesting indexing features MySQL
lacks, such as partial indexes, and ability to index an entire nested JSON
structure in a single index.

Postgres gets major points for having a true open source development model,
cleaner core code, better adherence to SQL standards, etc. Conceptually, it is
very well-aligned with the textbook description of a relational database. Its
adherents love it, sometimes fanatically so, which can be a mixed bag to
outsiders. I sometimes feel parallels to the Mac user community in the late
90s/early 00s: it's probably a better choice for many use-cases, but
personally I raise an eyebrow to suggestions that it's the universal best
choice for all possible situations.

------
mayankkaizen
I'm not a very tech savvy and know very little about databases. But I have
read countless posts/comments over the years and everywhere everyone
recommends postgres.

Again, I have no clue about other database systems, but postgres documentation
is just awesome. I believe you can practically everything from its
documentation.

~~~
gonational
I find a comment like this to be underrated; it’s like a meta-analysis.

------
fouc
1\. Both are great, they're both absolutely fantastic products!

PostgreSQL does have slightly more popularity nowadays, especially since they
came out with JSONB support first and have more advanced features built-in.

------
steffann
I have used PostgreSQL+JSONB and it works great. Doing indexes on JSON fields
adds a lot of value.

~~~
cagmz
What do you use the JSONB column for?

We've loved the flexibility of JSONB while our schema wasn't nailed down, but
eventually migrated many fields to be columns for ease of reading and writing
nested objects.

------
buboard
There was an Uber engineering post years ago about why they switched to mysql.
Not sure how relevant it is today

[https://eng.uber.com/mysql-migration/](https://eng.uber.com/mysql-migration/)

~~~
pmart123
[https://use-the-index-luke.com/blog/2016-07-29/on-ubers-choi...](https://use-
the-index-luke.com/blog/2016-07-29/on-ubers-choice-of-databases)

------
markuman123
Use what you're most comfort with, not what others are.

Postgres and MySQL (MariaDB/Percona) are both big players with a huge
community.

Maybe consider to use Mariadb or Percona instead of MySQL to avoid oracle
vendor lock in.

------
pabl0rg
EXPLAIN is almost useless on mysql, but very helpful in postgres.

EXPLAIN is a very useful command once you have some degree of success (users).

~~~
johannes1234321
EXPLAIN with the JSON or TREE formats in MySQL got a lot better. Also MySQL's
optimzer traces give lots of information more
[https://dev.mysql.com/doc/internals/en/optimizer-
tracing.htm...](https://dev.mysql.com/doc/internals/en/optimizer-tracing.html)

------
dragonwriter
1\. Mostly, Postgres, as it's superior in most areas, but MySQL seems to still
have advantages in replication (and, if you are hosting in AWS, there Aurora
Serverless MySQL offering supports somethings, like their own Data API, that
the equivalent Postgres offering doesn't yet which may tip the balance.

> Is it possible to build a hybrid database schema? For example, SQLite+JSON?

Yes, but many DBs will hold JSON natively and, conversely, lots of DB data
fits nicely in JSON. What's the motivating use case?

> 4\. Is it possible to build a custom file format based on SQLite or hybrid
> one based on SQLite+JSON?

Not sure what you are asking here; SQLite has its own file format.i suppose,
as with many combined formats these days, you could stop that together with a
folder of JSON documents and call it a custom format. What's the motivating
use case?

~~~
reilly3000
Aurora PG Serverless is out as of July, but I’ve read some horror stories
about it so far.

~~~
dragonwriter
Don't know about horror stories, but Aurora PG Serverless doesn't (yet?) have
the Data API support (which enables a couple of other Aurora serverless
features) that Aurora MySQL Serverless has, and IIRC has some other feature
limitations that aren't directly tied to Data API.

~~~
nitesmeh
Data API now supports Aurora PG Serverless, [https://aws.amazon.com/about-
aws/whats-new/2019/09/amazon-au...](https://aws.amazon.com/about-aws/whats-
new/2019/09/amazon-aurora-serverless-postgresql-now-supports-data-api/)

------
ReD_CoDE
Thank you all, I've tried to read all the comments. I think I have to clarify
the questions I asked:

1\. Is related to our upcoming startup, we chose MySQL + Redis, but some said
use PostgreSQL

(However, my friend explained that MySQL before v8 was weak and after v8 has
tried to come back to its salad days, this is why he chose MySQL)

2-3-4: In the industry, especially in the industry I'm active, Digital Built
Environment Industry, there's a lot of invaluable schemas, especially XML(XMI)
that I feel "these schemas convert structured data to semi-structured data"
which is not good and efficient

For this reason, I'm thinking of SQL (Server) and SQLite (File) to preserve
structured data

There's a vitally important schema in the built environment industry called
Industry Foundation Classes (IFC) [1] which is based on EXPRESS/STEP and also
has XML(XMI) schema too, but I want to convert the schema to SQL and SQLite

A friend did an invaluable job and after years introduced a correct method to
convert it to SQL [2][3] but don't have any idea of developing the schema
based on SQLite [4] that will accelerate the IFC development

[1] [https://www.buildingsmart.org/about/what-is-openbim/ifc-
intr...](https://www.buildingsmart.org/about/what-is-openbim/ifc-
introduction/)

[2] [https://forums.buildingsmart.org/t/ifc-for-relational-
databa...](https://forums.buildingsmart.org/t/ifc-for-relational-databases-
ifcsql/1524)

[3] [https://forums.buildingsmart.org/t/store-modify-and-
retrieve...](https://forums.buildingsmart.org/t/store-modify-and-retrieve-ifc-
data-with-ifcsql/1558)

[4] [https://forums.buildingsmart.org/t/ifc-sqlite-
project/1359](https://forums.buildingsmart.org/t/ifc-sqlite-project/1359)

------
OldHand2018
For point 3 (Is it possible to convert XML(XMI) schema to SQLite schema
automatically?), are you asking about a tool that takes an XML schema and
gives you back an SQL schema?

I haven't heard of anything, but I would imagine it exists. I have, on the
other hand, done a fair amount of XML to SQL conversion and have found that
generating a good schema involves understanding the data so you know what to
denormalize. You don't really want to have thousands of tables, each
representing an XML tag. That would make your database very hard to use.

Trial and error, and a good knowledge of what kind of questions you are going
to be asking your database to answer...

------
pbhowmic
Answering Q1: MySQL over Postgres. Postgres has 2 critical things going
against it \- The query optimizer is a mess \- It's implementation of
secondary indexes is not cache friendly, so it can be slow

~~~
taffer
I don't know what you're trying to say. PostgreSQL makes no distinction
between primary and secondary indexes. MySQL, which only knows clustered
indexes (see "Unreasonable Defaults" [1]) has to make such a distinction, so
that when you use a secondary index it also has to go through the primary
index in addition to the secondary index. Also

[1] [https://use-the-index-luke.com/blog/2014-01/unreasonable-
def...](https://use-the-index-luke.com/blog/2014-01/unreasonable-defaults-
primary-key-clustering-key)

------
LordHeini
I would also recommend Postgres for the features alone. Like the full text
search.

One reason not mentioned often is the vast amount of plugins which can do lots
of useful things.

Like PostGis or TimescaleDb which all work really well.

~~~
johannes1234321
Instead of requiring a plugin, MySQL has good GIS support natively built-in.

------
karmakaze
As previously mentioned, I agree that there is much less difference between
them than there used to be. Use what you know or have access to those who
know.

Personally I prefer PostgreSQL and the main benefit of using MySQL is how easy
it is to set up replication and operate in master-slave, master-master, or
group replication.

For high write volumes, TokuDB and now RocksDB do work well, the former for
sequential writes and the latter is LSM Tree based.

------
zelly
Postgres is a long-term support stack at this point, like the JVM. Too many
people rely on it. You need a very good reason to pick anything else.

------
teunispeters
1\. PostgreSQL. Fast, reliable, (relatively) small (for some reason mysql got
a lot bigger). Had a few historic problems with replication but I think that's
been resolved. I dealt a lot with large scale large data sets and I wouldn't
recommend mysql for that at all, except if they were very simple and relations
were either not used or used minimally. There are better database systems than
either, but I can't think of a less reliable one than MySQL. If you use PHP
though, mysql is easier.

(I'm going to assume the rest of the questions are SQL related and not SQLite,
which is a particular binary format)

2\. why? SQL + json would make some sense, sometimes. I haven't needed it - I
just do SQL. Others have better answers.

3\. There are tools to do some XML to and from SQL. YMMV. I always rolled my
own.

4\. it's always possible. Is it worth it? I used CSV with embedded json for a
long time with archival storage because it was reversably parseable and could
scale time-based databases somewhat reasonably. There are smarter ways to do
this too ...

~~~
evanelias
> I dealt a lot with large scale large data sets and I wouldn't recommend
> mysql for that at all

Was your use-case transaction processing (OLTP) or analytics (OLAP)? There are
a ton of examples of massive-scale MySQL deployments for OLTP... Facebook,
YouTube, Pinterest, Slack, Uber, Wikipedia, GitHub, Yelp, Etsy, Shopify,
Booking.com, Wordpress.com, Tumblr, Box, Dropbox, Alibaba, Square, Venmo... a
large chunk of the internet, in other words :)

~~~
chrisgarand
It seems most people on HN (and to their credit, they also admit), they have
limited recent experience with MySQL, so they don't know that they are 99%
functionally equivalent (with edge cases being better for one or the other).

------
tyingq
You don't mention SQLite in question 1, but then include it in questions 2-4.

Did you maybe mean "SQL" and not "SQLite" here?

------
mighty_bander
For very simple usage, you won't see a lot of difference, but I would go with
postgres. It has a lot of features that MySql doesn't, and isn't any harder to
set up and use.

Point 2: as long as you also write software to deal with it, I guess so.
Postgres has a JSON type. This question makes me want to ask what you are
trying to accomplish.

Point 3: Yes, probably, and for all I know there's something out there to do
it for you. I'm assuming basic usage; there is undoubtedly some weird corner
of xmi that makes it a Turing-complete language or something equally ill-
advised. So writing a schema converter for very basic stuff is probably quite
easy, but really filling in all the junk is possibly less so.

4 appears to be a repeat of 2.

------
dezzeus
I'm going to write a couple of things about the first point.

Several years ago, a knowledgable guy told me that the most compelling reason
for choosing between PostgreSQL and MySQL was the expected I/O: "for read-
intensive workloads (e.g. blogs), choose MySQL; for mixed workloads (e.g.
forums), choose PostgreSQL".

But I honestly don't know if that may still be valid as of today.

Nowadays, I think that for basic things, it doesn't really matter; but for
peculiar things, Postgres may have some advantages (both technically and not).
Also keep in mind that, for some popular scopes, SQLite is likely everything
you really need.

~~~
evanelias
> Several years ago, a knowledgable guy told me that the most compelling
> reason for choosing between PostgreSQL and MySQL was the expected I/O: "for
> read-intensive workloads (e.g. blogs), choose MySQL; for mixed workloads
> (e.g. forums), choose PostgreSQL".

This seems a bit backwards. MySQL's main strength is OLTP workloads, including
mixed read-write workloads / high write volumes. A majority of the giant
social networks are using MySQL (or previously used MySQL before moving to in-
house custom databases) and have insane write volumes.

For OLAP workloads, or mixed OLTP/OLAP workloads, Postgres tends to be a
better choice. OLAP is inherently read-heavy, which is why I would disagree
with the advice above.

~~~
madhadron
The biggest social network uses MySQL because they already dumped so much
engineering into it that changing is basically impractical. But it's mostly
used as a key-value store backing a custom graph database.

~~~
evanelias
That is simply not correct. Please understand that I worked on MySQL at
Facebook, so I know what I'm talking about here :)

Facebook developed an entirely new MySQL storage engine (MyRocks, which is a
RocksDB-backed engine for MySQL) and then migrated their largest sharded tiers
to it. This is basically just as much work as developing a new database from
scratch, i.e. more work than something like migrating to Postgres. This
completely debunks the "changing is basically impractical" claim.

And while Facebook's primary db tier (UDB) does have a restricted API / access
pattern, calling it a "key-value store" is a gross oversimplification at best,
or completely inaccurate at worst. Range scans are absolutely core to the UDB
access pattern, for starters.

Many other social networks are also built on MySQL (linkedin, pinterest,
tumblr; and several in China) or previously used MySQL before moving to a
custom in-house db (twitter). I think reddit and instagram are the only two
using pg? And I recall parts of instagram were being moved to mysql, although
I'm way out-of-date on whatever happened there.

~~~
madhadron
> This is basically just as much work as developing a new database from
> scratch, i.e. more work than something like migrating to Postgres. This
> completely debunks the "changing is basically impractical" claim.

I disagree for three reasons:

1\. The long tail of code using MySQL at the company, like at any large
software company, is prohibitive. You would have to maintain MySQL and
PostgreSQL in parallel for years. A new storage engine, on the other hand, is
controlled by one team.

2\. Migrating from InnoDB to MyRocks consists of successively adding MyRocks
replicas, letting them catch up, and removing InnoDB replicas. That is a
dramatically easier proposition than migrating tiers to PostgreSQL.

The fact that RocksDB was a hard technical project is kind of irrelevant. The
new storage engine provided major wins and could be done within a team, while
migrating to PostgreSQL would provide at most small improvements and demand
changes to huge amounts of code and massive data migration projects. That
makes the former project deeply practical and the latter impractical. If the
usual stack back in the day had been the LAPP stack instead of the LAMP stack,
we would be having this discussion the other way.

> calling it a "key-value store" is a gross oversimplification at best

That's fair. The right thing to have said would be that the query patterns
that are used are extremely simple selects over a single table, which is a
place that MySQL has traditionally shone. MySQL's query planner still does
strange things on complex queries from time to time. I had a case about six
months ago where one shard decided it was going to reorder indexes in a query
and load everything in the database's core tables before filtering it down
instead of using the proper index order like the other nine hundred something
shards. Easily fixed once we realized it (we forced the index order in the
query), but the fact that we had to... I have heard that this has all gotten
much better in MySQL 8.0.

~~~
evanelias
You're _severely_ underestimating the amount of effort that went into MyRocks.
The development and deployment was a 3+ year effort spanning quite a few
different teams.

Automating the physical rollout (as you correctly described) is the easy part.
That doesn't account for all the many difficult spots that occurred prior to
it: the massive complexity of mysql storage engine development in general;
huge numbers of various performance edge-cases; converting replication-related
system tables to MyRocks in order to achieve crash-safe replication;
developing online hot-copy for MyRocks from scratch; schema change support;
adding tons of new status vars and system vars; fast bulk import to MyRocks
which is necessary for the replica migration to even be possible; updating
hundreds of thousands of lines of automation code written under the assumption
of InnoDB being the only storage engine in use and using various InnoDBisms...

The MyRocks migration wasn't a project I personally worked on, but I'm very
aware of what was involved. It appears you joined FB PE in 2017 and therefore
missed much of this historical context? I'm not really sure why you would have
such strong opinions about it.

You say that FB is using MySQL because "changing is basically impractical",
but also say MyRocks "provided major wins", which seems to be a contradiction.
In any case, I'm not aware of any pg feature that provides compression ratios
_anywhere_ near that of MyRocks, and pg is only recently even adopting an arch
that supports pluggable storage engines at all. In combination it's really
hard to make a case that FB is using MySQL just due to historical investment
and inability to change.

Honestly I would also not be surprised if FB moves some core tiers off of
MySQL to a pure-RocksDB solution at some point in the future. The number of
intermediate data services and proxies make this sort of thing absolutely
possible. For the same reason, in theory a move to another db like pg would be
completely possible without needing to run both in parallel for years (again,
just talking in theory; moving to pg just doesn't make practical sense).

> The right thing to have said would be that the query patterns that are used
> are extremely simple selects over a single table

For UDB, sure. What about all the other MySQL tiers? The non-UDB MySQL
footprint at FB, despite being a minority of FB's MySQL fleet, is still larger
than the vast majority of other companies' relational database fleets
worldwide. The range of use-cases in the DBaaS (XDB) tier alone spans a
massive combination of different database features and access patterns.

~~~
madhadron
> You say that FB is using MySQL because "changing is basically impractical",
> but also say MyRocks "provided major wins", which seems to be a
> contradiction.

I think I must not be expressing myself clearly. 3+ year projects involving a
large number of teams to get back to where you started are impractical. That's
what migrating to PostgreSQL would be. Perhaps I should have written
"switching from MySQL to PostgreSQL would be impractical"?

~~~
evanelias
Apologies if I'm misunderstanding. To take a step back and paraphrase this
subthread, as I understand it:

* `dezzeus said MySQL was better for read-intensive workloads, Postgres better for mixed read/write

* I replied saying there are a number of huge social networks with insane write rates, which is contrary proof against that claim. (Having personally spent most of the past decade working on massive-scale MySQL at several social networks / UGC sites, this topic is near and dear to my heart...)

* You replied saying, iiuc, that FB is only using MySQL for historical reasons and difficulty of switching. (IMO, your initial comment was tangential to the original topic of comparative read vs write perf anyway. Regardless of why FB is using MySQL, factually they are an example of extremely high write rate, previously via InnoDB for many years. That said, I wasn't the person who downvoted your comment.)

* I replied saying that's inaccurate, as FB demonstrably _does_ have the resources and talent to switch to another DB _if_ there was a compelling reason, and furthermore MySQL+MyRocks provides a combination of feature set + compression levels that other databases (including Postgres) simply cannot match at this time. At FB's scale, this translates to absolutely massive cost savings, meaning that MySQL+MyRocks is a better choice for FB for _technical and business reasons_ rather than just historical reasons or difficulty of switching.

I may have misunderstood, but it definitely felt like your original comments
were throwing shade at MySQL, and/or publicly stating historically inaccurate
reasons for why FB is currently using MySQL.

~~~
madhadron
I think I have done a poor job of communicating, and I'm sorry for it.

------
asdkhadsj
Question on this area. What have you found to be the best way to migrate an
existing app to Postgres?

We plan to migrate to Postgres, but with every LOC written we're entrenching
ourselves into Mysql. We all want Postgres, but at the same time I just can't
see the transition happening with each passing day.

Thoughts?

 _edit_ : I should be clear too. I think our goal would be to not require a
full rewrite spanning weeks. So an active translation layer, or replication..
or something tricky.. but I just don't foresee us being able to spend a month
putting everything on hold so we can migrate.

------
dotdi
My company recently looked at MySQL vs PostgreSQL. While we chose Postgres
there is one thing that stood out in my research, I haven't found any comments
on this:

We were looking at scalable, HA, possibly multi-DC workloads and such, and
yes, relational DBs are not necessarily the right choice, but MySQL looked a
bit better in this regard, especially for master-master replication. There are
several high-profile teams that have huge production deployments running on
MySQL (IIRC Uber and Github) and there are a lot of things to be learned from
them.

~~~
yahyaheee
Did you evaluate Citus as well?

------
darkhorn
You can compare it from here [https://sql-
workbench.eu/dbms_comparison.html](https://sql-
workbench.eu/dbms_comparison.html)

------
throw0101a
Is there a Galera-equivalent system available of Postgres? I.e., multi-master
replication.

I know of BDR, but that doesn't seem to be publicly available for recent
versions of Pg?

~~~
nodesocket
Not sure about master-master, but I've used repmgr[1] to manage a PostgreSQL
master-slave setup and it works pretty well though it is by no-means plug and
play. There are a variety of steps and manual processes to get it up and
running.

[1] [https://repmgr.org/](https://repmgr.org/)

~~~
throw0101a
We find it handy to have multi-master, which leans towards being more active-
active: we have keepalived doing health checks on two systems, and point our
app server(s) at a vIP.

The app server runs Galera's _arbd_ so we don't need three DBs.

------
thunderbong
My first goto database is always SQLite. Only when SQLite is unable to handle
the requirements, for example, too many writes, do I look at PostgreSQL.

------
Arkanosis
Regarding 1): choosing a software stack (or any part thereof) without a clear
use case is a recipe for failure. What's the use case?

~~~
asah
To be fair, often you don't have your requirements completely nailed
beforehand, or they change midway through the project.

That's why I choose Postgres: aside from extreme scale or latency, you can
throw pretty much anything at it. Also, given expert advice, its performance
degrades gracefully i.e. lots of easy ways to optimize and workaround issues.

Example: pg's type system is insanely flexible incl native support for high
speed JSON, latlng, geometry, and more - and types are "batteries included"
incl matching, inspection/extraction (e.g. JSON navigation), conversion,
concurrency and concurrency control, ACID recovery, replication, etc. For
example, it's one way line of code to create an index on the results of a JSON
navigation expression whose result is then converted to another datatype e.g.
timestamptz. Performance is then 100x+ on queries that use that expression.

Pg datetime handling is also world class incl timezones and conversion, query
and manipulation functions. Want the records from last Tuesday across
timezones, given data in seconds-since-the-epoch? The SQL is shorter than in
English.

~~~
yen223
If the requirements are still up in the air, then I would aim to use the
simplest, most evolvable solution. This to me means _no_ database.

~~~
majewsky
If the requirements are still up in the air, but you know that you're going to
be storing _some_ data, definitely go with a database, even if just a single
SQLite file. Using plain files means figuring out the file format, which turns
into a huge mess when requirements get tacked on later. The other option would
be to store a JSON file or a bunch of JSON files in a directory, at which
point you're building a shitty version of either SQL or MongoDB instead of
focusing on your business logic.

~~~
yen223
The grandparent comment is right about one thing: you need to figure out what
your use case is, in order to make a good judgment call. “Some data” can mean
a lot of things. Transactional data? Sure, get a sql database in. Images,
video, or plain json documents? SQL databases are a poor fit there.

One should also consider if they even need to manage data persistence. I’ve
had success using Google Sheets as the backing data storage for a prototype.
Below a certain scale, it is a lot easier to visualise and manipulate data in
a spreadsheet than through a sql client.

~~~
Arkanosis
This. Answer “pg!” without any clue of what the objective is, and you'll end
up with surprises like “oh, you know, this is for a revolutionary concept
where people can check in their source code at different stages of
development, so that they have a history of their changes and can restore an
older version if needed” or “hey, we've followed your expert recommendations
but now we're facing some availability issue after a link to our shiny new
search engine made the front page of HN and Slashdot”. Migrating from pg to
git or SOLR is not really enjoyable, and you can't reuse much of what you've
done (unlike when migrating one SQL database to another).

------
anm89
Although there is already pretty unanimous consensus here, one side note is
that administrating mysql is always a headache in my experience whereas
postgres seems to just work.

Every time I start a new project and I see it's using mysql i sigh a little
bit knowing that I'm going to end up spending hours fighting some dumb
configuration issue.

------
viraptor
What does your app/framework support as a default store (what do the devs use
and test against).

What features do you expect from the db? What versions of each database can
you run?

Have you got an environment where one option is better supported than the
other? (For example AWS aurora cluster and MySQL?)

Do you have an ops team with existing experience with either db?

------
rayrrr
MySQL: Wait a sec, what do I use for this table, InnoDB or MyISAM? What are
the tradeoffs again? Oh, right, do I want ACID transactions or fulltext
search? Man, this tradeoff sucks.

PostgreSQL: Wait a sec, which schema (namespace) should I put this table in?
Man, it's nice to have namespaces within a DB.

~~~
Thaxll
No one has been using MyISAM for the last 10 years.

~~~
rayrrr
Funnily enough, I have not been using MySQL for the last 10 years either,
because I switched to Postgres and never went back.

~~~
evanelias
Fair, but why comment on MySQL's supposed deficiencies if your knowledge of it
is so out-of-date?

~~~
Thaxll
But vanilla PG didn't get good master / slave feature until "recently" so you
were running without replicas in the last 10 years?

[https://www.postgresql.org/about/news/1235/](https://www.postgresql.org/about/news/1235/)

~~~
bjt
Your link is from 9 years ago.

~~~
Thaxll
The release from 9 years ago was not even close to what MySQL was offering at
the time.

------
donatj
MySQL or better yet AuroraDB if you want scalability. MySQL still has a
sizable speed advantage, is easier to learn, maintain, and has a more vibrant
world of tooling. MySQL is also easier to find experienced developers for.
This has been my experience anyway.

------
kibibu
Are you confusing SQLite with SQL?

------
CaptainZapp
Isn't MySQL owned by Oracle?

To each his own, but that would just about answer the question for me.

~~~
hu3
MariaDB isn't.

------
flarg
In case it's not been said already, Oracle own mysql, use mariadb instead

------
dariojcravero
I'd say Postgres because of tools like [https://hasura.io](https://hasura.io)
that let you automatically layer graphql on top of it and jsonb :)

------
no_gravity
I really like the direct DB to filesystem mappings of the MyISAM engine in
MySql. A database is simply a directory. A table is simply 3 files in that
directory:

    
    
        - One for the structure
        - One for the data 
        - One for the indexes
    

You can simply copy a MyISAM database by copying the directory (while the
MySql server is stopped).

MariaDB has forked the MyISAM engine and created the Aria engine. It is a
crash safe version of MyISAM and is now their default engine for all system
tables.

So in contrast to MySql, you can completely disable InnoDB in MariaDB. MySql
does not support that anymore as their system tables are InnoDB.

Especially for non-concurrency workloads, MyISAM and Aria are super fast.

For these reasons, I really like MariaDB.

~~~
juangacovas
You also get "mariabackup" which is a fork of perconabackup for consistent,
physical backups of InnoDB and Aria/MyISAM

------
cweagans
1\. Whatever you feel most comfortable using and administering because the
alternative is dangerous for production.

2\. Probably.

3\. Probably, but you'll probably have to write the code to do it.

4\. Why bother?

------
unixhero
Postgres hands down.

------
based2
MySQL or MariaDB?

------
danmg
Materialized views, common table expressions, outer joins, are all missing in
mysql and essential. The Postgresql's stored procedure language blows mysql
out of the water, and it's possible to use different language backends.

SQLite has json extensions. You need to select them at compile time though, so
you can't just assume they'll be there by default.

~~~
evanelias
MySQL has supported left/right outer joins for as long as I can remember, and
I've been using it continuously since 2003.

MySQL doesn't support _full outer join_ , but it's rarely needed, and you can
often get a similar result using a UNION. (Clunky, I'll admit... but I'd say
the same thing about Postgres recommending against use of _NOT IN_ , which is
a common construct and more readable than an anti-join.)

CTEs were added in MySQL 8.0 (~1.5 years ago).

Agreed on the other points.

~~~
anarazel
> . but I'd say the same thing about Postgres recommending against use of NOT
> IN, which is a common construct and more readable than an anti-join.

The recommendation against that is due to the semantics defined in the
standard. If there is _any_ NULL in the list matched against, the entire a NOT
IN (...) expression also has to evaluate to NULL. Which is extremely confusing
to most people (and has some consequences in how efficient things can be
executed).

------
bob1029
I have quite a bit of experience with #2.

We use a SQLite hybrid with JSON blobs (stored as regular TEXT columns) as the
principal transactional store for our clients' business system state. The
simplicity of this approach (which is definitely not for everyone) is what
made it feasible for our small development team to manage the project as far
as we have. If we were still using a big-boy SQL solution like PostgreSQL or
SQL Server and managing all of the concerns specific to these dependencies
(multiplied by the number of environments we are responsible for deploying
these to), we probably would have been forced to close up shop by now.

Being able to deploy a single binary which brings every dependency (including
the database) it needs along for the ride proved to be a lifesaver for us. The
process before this involved spending an entire day getting SQL Server
configured relative to the service accounts, and whatever ridiculous quirks
may exist in each clients' specific AD. Today, it is literally a 30 second
file extract, sc create, and it's running. We go from RDP into a blank box to
a working production system within 5 minutes. This is also how we've been able
to completely sidestep the docker question, since no one could justify the
added complexity once we got the equation down to: a single binary folder + a
bare-ass Windows Server 2016/19 box = good to go. This is also enabled by .NET
Core's Self-Contained Deployments, so SQLite isn't a free lunch all on its
own.

Again, the above is not for everyone. We are responsible for maintaining
production services running across many client sites, and needed a solution
that could scale not only in terms of our clients' requirements, but also in
terms of our abilities to manage all of these environments all at once.
Managing a hosted SQL service requires direct access to each of these
environments which has tremendous overhead for us due to the email back-and-
forth remote access game that has to be played each time.

If you are in an environment where its just a single instance of the
production/test/qa/development stack, I would absolutely push for a hosted SQL
option like PostgreSQL/MySQL/SQL Server. In these cases you have a single (or
4) points of touch, and it is very reasonable and consistent and all within
your control. If you find yourself in a situation similar to mine, I would
still advocate for the hosted SQL by default unless you are a very brave soul
and understand the risks of going a bit off the beaten path. Disclaimer aside,
there really are some interesting treasures out here. If you can afford to
waste a month, try doing your entire persistence layer in SQLite with JSON
serialized business models where appropriate. Assuming you budgeted for
complete failure, worst case you walk away with a new perspective. Better
case, you end up in the position I find myself in now.

Just don't forget to set PRAGMA journal_mode=WAL; if you decide to go on the
adventure. It makes orders of magnitude difference in concurrent write
throughput (SQL Server was never this fast for us).

------
namewasmypw
MySQL is simply garbage that shouldn't be used under any circumstance.

1\. No transactional DDL 2\. Implicit, confusing coercions 3\. Terrible
Unicode handling 4\. the list goes on

~~~
johannes1234321
1\. Thanks to the new data dictionary in 8.0 there is light at the end of that
tunnel ...

2\. Yeah, MySQL tried to be "simple" and it took a while to be confident for
changing it's default to being strict (the option for opting exists for ages
...) But meanwhile defaults are proper.

3\. Especially the 3 byte Unicode type was a historic mistake. It reduced
required storage space but didn't forsee the need for Emojis and other 4 byte
sequences ... utf8mb4 charset fixes that though

4\. ...

------
telaelit
MongoDB

------
Maledictus
[https://m.youtube.com/watch?v=emgJtr9tIME](https://m.youtube.com/watch?v=emgJtr9tIME)

------
AdrianB1
1\. For small databases (up to a few GB) my personal preference in the past 5
years was MS SQL (Express Edition, free), then PostgreSQL and last is MySQL.
That means the answer to your specific question, PostgreSQL. Why? That is the
order of features, ease of use and performance in my experience, other people
may have seen different.

For larger databases I have no experience with either PostgreSQL or MySQL, I
was spoiled to use MS SQL for up to Terabyte size and that's the largest I've
ever worked with.

~~~
wayneftw
MS SQL Server definitely has some important features that are missing from PG.
Top on that list IMO is real stored procedures that can return multiple
heterogeneous result-sets with simple select statements. Another big one is
client side tools. Query optimization and schema flexibility (being able to
alter things instead of dropping in re-creating) might still be not as good in
PG as well.

You won’t get a ton of agreement from this crowd though, despite the majority
of them probably never having used it.

~~~
leandrod
Only this is not a way to select a DBMS. PostgreSQL adds important features
much faster than competitors, it is free and much leaner and more flexible.

~~~
wayneftw
Free and leaner, yes. More flexible? That’s debatable. As I pointed out, it’s
certainly not more flexible when it come to returning multiple result-sets
from a single procedure.

I think that PG actually did just add a feature called stored procedures
though. So maybe soon for returning multiple heterogeneous selects! It’s one
feature that I’ve been waiting a long time for…

I chose SQL Server in many cases for it’s very high quality, support, superior
ease of use and flexibility. Free and leaner weren’t very high on my list
comparatively. You think those are the best characteristics to go by?

------
kissgyorgy
You don't really benefit from MySQL speed if you are not Facebook, so I would
always start with PostgreSQL.

~~~
jaco8
We use PostgreSQL but also Firebird, which maybe is the great underdog in
opensource databases.

~~~
yardstick
I used InterBase (Firebird predecessor) 15 years ago, and recall it had some
big limits around versioning/lots of updates. To reclaim disk space we’d have
to periodically backup/restore the db. It got so bad/frequent that we moved to
Postgres and haven’t looked back since. I guess if one is considering SQLite
that it’s not too relevant, but is this still an issue with modern Firebird?

~~~
thijsvandien
Many of IB's limitations and bugs have been removed over the years. I think it
was around FB2.5 that it really became a better product than IB ever was. A
cool thing, though, is that it's very backward compatible. If you have
applications that expect IB6, they will happily connect to any version of FB,
even using the old client lib. The pace of development has ramped up since
FB3, which was focused on rearchitecting the core. That's mostly a good thing.
Still, I fear a little that it will also affect reliability.

Not sure exactly what kind of situation got you in trouble, but I haven't had
any issues (ab)using the database myself. Disk space is still not reclaimed.
It does, however, get used when the amount of data grows again, of course.
Effectively the database is always the largest size it ever needed to be, but
no larger. Most of the time, that shouldn't be any issue. If you expect huge
spikes, there are other ways around it.

------
mdellavo
This entirely depends on the domain and data model, and unless you need SQL -
mongodb should be a consideration too.

~~~
madhadron
No. MongoDB has a track record of losing data and not actually providing
durability. It is considered a joke in the professional community.

~~~
mat_keep
interesting: [https://www.mongodb.com/jepsen](https://www.mongodb.com/jepsen)

A lot of MongoDB users who wouldn't be considered a "joke"
[https://www.mongodb.com/who-uses-mongodb](https://www.mongodb.com/who-uses-
mongodb)

Rather than listen to unqualified nonsense, they run tests. And gather facts
to guide technology decisions. and yes, I work for MongoDB - just before
anyone starts whining about disclosure You're welcome

~~~
madhadron
I posted my problems with it as a response to a sibling comment. Since this
was four or five years ago now, maybe all of this has been fixed, but that's
not something I'm going to depend on in production any time soon.

Also, the MongoDB users you list must be taken with a grain of salt. For
example, you list Facebook on that page. Nope. The description is "...adapted
the storage engine API, extending MongoDB into new workloads and new
capabilities." That is, Facebook acquired Parse, which used Mongo. Facebook
ported MongoDB to run on RocksDB. Facebook shut down Parse. End of MongoDB at
Facebook. You list Google, and the mouseover is basically that you can run
MongoDB on GCE. I'm not saying that Mongo is unusual in this behavior. It's
how most people listing "who uses X" build their lists.

