What is the fastest/most performant SQL driver for Python? - python

I know of PyMySQLDb, is that pretty much the thinnest/lightest way of accessing MySql?

The fastest is SQLAlchemy.
"Say what!?"
Well, a nice ORM, and I like SQLAlchemy, you will get your code finished much faster. If your code then runs 0.2 seconds slower isn't really gonna make any noticeable difference. :)
Now if you get performance problems, then you can look into improving the code. But choosing the access module after who in theory is "fastest" is premature optimization.

The lightest possible way is to use ctypes and directly call into the MySQL API, of course, without using any translation layers. Now, that's ugly and will make your life miserable unless you also write C, so yes, the MySQLDb extension is the standard and most performant way to use MySQL while still using the Python Database API. Almost anything else will be built on top of that or one of its predecessors.
Of course, the connection layer is rarely where all of the database speed problems come from. That's mostly from misusing the API you have or building a bad database or queries.

MySQLDb is faster while SQLAlchemy makes code more user friendly -:)

Related

Bad practice to have ORMs with NoSQL stores?

I use Redis (redis-py) inside my Python platform. Recently it was suggested that I switch to an ORM.
E.g.: python-stdnet, rom or redisco
Is use of ORMs considered bad practice in the NoSQL world?
Ultimately the question boils down to at what layer do you want to write code.
Do you want to write code that manipulates data structures in a remote database, or do you want to write higher-level code that uses the abstractions built on top of those data structures? You can think of it as a similar question about relational databases as do you want to write SQL, or do you want to write higher-level code?
Personally, despite using rom myself for a variety of tasks (I am the author), I also directly manipulate Redis in the same projects where it makes sense.
Comments pointing out that the R in ORM is for relational are technically correct. That doesn't mean there aren't valid uses and reasons for libraries that abstract redis away.
There are some great libraries that make interfacing with a redis feel much nicer and more idiomatic to the language you are using. For ruby libraries like ohm or redis-native_hash (disclosure: I wrote that one) do just that. For python there are tools like redisco and surely others. These make persisting objects to redis very simple and make working with redis feel much more ruby-ish or python-ish.
Here are a few more benefits from using even the most basic abstraction, like a very thin wrapper you might write and keep in your application:
Switching redis clients will be easier. Maybe you'll never do this, but if you did, changing your calls to redis in one place (your wrapper) is much simpler than changing them everywhere you use redis.
Implementing things you might need for scaling, like sharding or connection pooling, is likely going to be easier if your calls are made through some abstraction.
Replacing redis with some other key/value store or data structure server would be simpler if an abstraction is in place.
I'm not advocating using an object mapping library or building your own abstraction, just pointing out there are valid reasons why you would. Its up to you to evaluate your needs and pick what works best for you. There is nothing wrong with calling redis directly either.

which databases can be used better for pyqt application

i want to create application in windows. i need to use databases which would be preferable best for pyqt application
like
sqlalchemy
mysql
etc.
I would use SQLite every time unless performance became an obvious big problem.
It comes with Python
You don't need to worry about installing it on a target machine or having an existing installation which might clash (including a potential port clash - SQLite doesn't use a port)
It's fairly small (doesn't increase the installed size too much)
Then, a much less obvious choice that I would very much consider making: adding Django to the mix. Django's model system could make for much simpler management, depending on the type of data you're working with. Also, in the case where I've considered it (I just haven't got to that stage of development yet) it means I can reuse the models I've got on the server and a good bit of code from there too.
Obviously in this case you could need to be careful about what you expose; business-critical processing stuff that you don't want to share, potential security holes in server code which you've helpfully provided the code for, etc.
SQlite is fine for a single user.
If you are going over a network to talk to a central database, then you need a database woith a decent Python lirary.
Take a serious look at MySQL if you need/want SQL.
Otherwise, there is CouchDB in the Not SQL camp, which is great if you are storing documents, and can express searches as Map/reduce functions. Poor for adhoc queries.
If you want a relational database I'd recommend you to use SQLAlchemy, as you then get a choice as well as an ORM. Bu default go with SQLite, as per other recommendations here.
If you don't need a relational database, take a look at ZODB. It's an awesome Python-only object-oriented database.
i guess its totally upto you ..but as far as i am concerned i personlly use sqlite, becoz it is easy to use and amazingly simple syntax whereas for MYSQL u can use it for complex apps and has options for performance tuning. but in end its totally upto u and wt your app requires

Pros and cons of using sqlite3 vs custom table implementation

I noticed that a significant part of my (pure Python) code deals with tables. Of course, I have class Table which supports the basic functionality, but I end up adding more and more features to it, such as queries, validation, sorting, indexing, etc.
I to wonder if it's a good idea to remove my class Table, and refactor the code to use a regular relational database that I will instantiate in-memory.
Here's my thinking so far:
Performance of queries and indexing would improve but communication between Python code and the separate database process might be less efficient than between Python functions. I assume that is too much overhead, so I would have to go with sqlite which comes with Python and lives in the same process. I hope this means it's a pure performance gain (at the cost of non-standard SQL definition and limited features of sqlite).
With SQL, I will get a lot more powerful features than I would ever want to code myself. Seems like a clear advantage (even with sqlite).
I won't need to debug my own implementation of tables, but debugging mistakes in SQL are hard since I can't put breakpoints or easily print out interim state. I don't know how to judge the overall impact of my code reliability and debugging time.
The code will be easier to read, since instead of calling my own custom methods I would write SQL (everyone who needs to maintain this code knows SQL). However, the Python code to deal with database might be uglier and more complex than the code that uses pure Python class Table. Again, I don't know which is better on balance.
Any corrections to the above, or anything else I should think about?
SQLite does not run in a separate process. So you don't actually have any extra overhead from IPC. But IPC overhead isn't that big, anyway, especially over e.g., UNIX sockets. If you need multiple writers (more than one process/thread writing to the database simultaneously), the locking overhead is probably worse, and MySQL or PostgreSQL would perform better, especially if running on the same machine. The basic SQL supported by all three of these databases is the same, so benchmarking isn't that painful.
You generally don't have to do the same type of debugging on SQL statements as you do on your own implementation. SQLite works, and is fairly well debugged already. It is very unlikely that you'll ever have to debug "OK, that row exists, why doesn't the database find it?" and track down a bug in index updating. Debugging SQL is completely different than procedural code, and really only ever happens for pretty complicated queries.
As for debugging your code, you can fairly easily centralize your SQL calls and add tracing to log the queries you are running, the results you get back, etc. The Python SQLite interface may already have this (not sure, I normally use Perl). It'll probably be easiest to just make your existing Table class a wrapper around SQLite.
I would strongly recommend not reinventing the wheel. SQLite will have far fewer bugs, and save you a bunch of time. (You may also want to look into Firefox's fairly recent switch to using SQLite to store history, etc., I think they got some pretty significant speedups from doing so.)
Also, SQLite's well-optimized C implementation is probably quite a bit faster than any pure Python implementation.
You could try to make a sqlite wrapper with the same interface as your class Table, so that you keep your code clean and you get the sqlite performences.
If you're doing database work, use a database, if your not, then don't. Using tables, it sound's like you are. I'd recommend using an ORM to make it more pythonic. SQLAlchemy is the most flexible (though it's not strictly just an ORM).

Fast, thread-safe Python ORM?

Can you recommend a high-performance, thread-safe and stable ORM for Python? The data I need to work with isn't complex, so SQLAlchemy is probably an overkill.
If you are looking for something thats high performance, and based on one of your comments "something that can handle >5k queries per second". You need to keep in mind that an ORM is not built specifically for speed and performance, it is built for maintainability and ease of use. If the data is so basic that even SqlAlchemy might be overkill, and your mostly doing writes, it might be easier to just do straight inserts and skip the ORM altogether.
The peewee orm is fast and extremely lightweight, might be a good fit if SQA is too heavy.
SqlAlchemy's SqlSoup module skips most of the tediousness of SqlAlchemy's mapping and session overhead. You can pretty much 'dive' straight in, take a look.
You can use a more declarative layer on top of SQLAlchemy such as Elixir, or look at Storm which is also a bit more declerative than SQLAlchemy.
The latter was developed for and is used by sites such as Ubuntu/Canonical's launchpad, so it should scale well.

Comparing persistent storage solutions in python

I'm starting on a new scientific project which has a lot of data (millions of entries) I'd like to store in an easily and quickly accessible format. I've come across a number of different potential options, but I'm not sure how to pick amongst them. My data can probably just be stored as a dictionary, or potentially a dictionary of dictionaries. Some potential considerations:
Speed. I can't load all the data off disk every time I start a new script, and I'd like as quick access to random entries as possible.
Ease-of-use. This is python. The storage should feel like python.
Stability/maturity. I'd like something that's currently supported, although something that works well but is still in development would be fine.
Ease of installation. My sysadmin should be able to get this running on our cluster.
I don't really care that much about the size of the storage, but it could be a consideration if an option is really terrible on this front. Also, if it matters, I'll most likely be creating the database once, and thereafter only reading from it.
Some potential options that I've started looking at (see this post):
pyTables
ZopeDB
shove
shelve
redis
durus
Any suggestions on which of these might be better for my purposes? Any better ideas? Some of these have a back-end; any suggestions on which file-system back-end would be best?
Might want to give mongodb a shot - the PyMongo library works with dictionaries and supports most Python types. Easy to install, very performant + scalable. MongoDB (and PyMongo) is also used in production at some big names.
A RDBMS.
Nothing is more realiable than using tables on a well known RDBMS. Postgresql comes to mind.
That automatically gives you some choices for the future like clustering. Also you automatically have a lot of tools to administer your database, and you can use it from other software written in virtually any language.
It is really fast.
In the "feel like python" point, I might add that you can use an ORM. A strong name is sqlalchemy. Maybe with the elixir "extension".
Using sqlalchemy you can leave your user/sysadmin choose which database backend he wants to use. Maybe they already have MySql installed - no problem.
RDBMSs are still the best choice for data storage.
I'm working on such a project and I'm using SQLite.
SQLite stores everything in one file and is part of Python's standard library. Hence, installation and configuration is virtually for free (ease of installation).
You can easily manage the database file with small Python scripts or via various tools. There is also a Firefox plugin (ease of installation / ease-of-use).
I find it very convenient to use SQL to filter/sort/manipulate/... the data. Although, I'm not an SQL expert. (ease-of-use)
I'm not sure if SQLite is the fastes DB system for this work and it lacks some features you might need e.g. stored procedures.
Anyway, SQLite works for me.
if you really just need dictionary-like storage, some of the new key/value or column stores like Cassandra or MongoDB might provide a lot more speed than you'd get with a relational database. Of course if you decide to go with RDBMS, SQLAlchemy is the way to go (disclaimer: I am its creator), but your desired featurelist seems to lean in the direction of "I just want a dictionary that feels like Python" - if you aren't interested in relational queries or strong ACIDity, those facets of RDBMS will probably feel cumbersome.
Sqlite -- it comes with python, fast, widely availible and easy to maintain
If you only need simple (dict like) access mechanisms and need efficiency for processing a lot of data, then HDF5 might be a good option. If you are going to be using numpy then it is really worth considering.
Go with a RDBMS is reliable scalable and fast.
If you need a more scalabre solution and don't need the features of RDBMS, you can go with a key-value store like couchdb that has a good python api.
The NEMO collaboration (building a cosmic neutrino detector underwater) had much of the same problems, and they used mysql and postgresql without major problems.
It really depends on what you're trying to do. An RDBMS is designed for relational data, so if your data is relational, then use one of the various SQL options. But it sounds like your data is more oriented towards a key-value store with very fast random GET operations. If that's the case, compare the benchmarks of the various key-stores, focusing on the GET speed. The ideal key-value store will keep or cache requests in memory, and be able to handle many GET requests concurrently. You may actually want to create your own benchmark suite so you can effectively compare random concurrent GET operations.
Why do you need a cluster? Is the size of each value very large? If not, you shouldn't need a cluster to handle storage of a million entries. But if you're storing large blobs of data, that matters, and you may need something easily supports read slaves and/or transparent partitioning. Some of the key-value stores are document oriented and/or optimized for storing larger values. Redis is technically more storage efficient for larger values due to the indexing overhead required for fast GETs, but that doesn't necessarily mean it's slower. In fact, the extra indexing makes lookups faster.
You're the only one that can truly answer this question, and I strongly recommend putting together a custom benchmark suite to test available options with actual usage scenarios. The data you get from that will give you more insight than anything else.

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