I am making a web app using the Django framework and would like some opinion regarding which database to use.
PostgreSQL works very nicely with Django and I think (please do correct me if I'm wrong) MySQL requires a bit more time and effort to work with Django.
My database in a single table will have around 60 million entries and it does read and write per request once but will sometimes require two reads making it I guess in a sense more read heavy.
Total expected DB size: around 10 tables each with around ~50 million entries.
My question is that will PostgreSQL suffice for having such a large number of entries while performing both read and writes or should I switch to MySQL because I heard MySQL is more advantageous to read heavy tasks.
Thank You.
Both MySQL and PostgreSQL are free to download and install. Install then, tune the servers for the expected load, insert 100 million rows of random data, and take some measurements.
PostgreSQL, when configured correctly for your hardware, will perform fine. (PostgreSQL's default settings are very conservative.) Its query optimizer and indexing options are far superior to MySQL.
Related
I have a Redshift datawarehouse that is pulling data in from multiple sources.
One is my from MySQL and the others are some cloud based databases that get pulled in.
When querying in redshift, the query response is significantly slower than the same mysql table(s).
Here is an example:
SELECT *
FROM leads
WHERE id = 10162064
In mysql this takes .4 seconds. In Redshift it takes 4.4 seconds.
The table has 11 million rows. "id" is indexed in mysql and in redshift it is not since it is a columnar system.
I know that Redshift is a columnar data warehouse (which is relatively new to me) and Mysql is a relational database that is able to utilize indexes. I'm not sure if Redshift is the right tool for us for reporting, or if we need something else. We have about 200 tables in it from 5 different systems and it is currently at 90 GB.
We have a reporting tool sitting on top that does native queries to pull data. They are pretty slow but are also pulling a ton of data from multiple tables. I would expect some slowness with these, but with a simple statement like above, I would expect it to be quicker.
I've tried some different DIST and SORT key configurations but see no real improvement.
I've run vacuum and analyze with no improvement.
We have 4 nodes, dc2.large. Currently only using 14% storage. CPU utilization is frequently near 100%. Database connections averages about 10 at any given time.
The datawarehouse just has exact copies of the tables from our integration with the other sources. We are trying to do near real-time reporting with this.
Just looking for advice on how to improve performance of our redshift via configuration changes, some sort of view or dim table architecture, or any other tips to help me get the most out of redshift.
I've worked with clients on this type of issue many times and I'm happy to help but this may take some back and forth to narrow in on what is happening.
First I'm assuming that "leads" is a normal table, not a view and not an external table. Please correct if this assumption isn't right.
Next I'm assuming that this table isn't very wide and that "select *" isn't contributing greatly to the speed concern. Yes?
Next question is wide this size of cluster for a table of only 11M rows? I'd guess it is that there are other much larger data sets on the database and that this table isn't setting the size.
The first step of narrowing this down is to go onto the AWS console for Redshift and find the query in question. Look at the actual execution statistics and see where the query is spending its time. I'd guess it will be in loading (scanning) the table but you never know.
You also should look at STL_WLM_QUERY for the query in question and see how much wait time there was with the running of this query. Queueing can take time and if you have interactive queries that need faster response times then some WLM configuration may be needed.
It could also be compile time but given the simplicity of the query this seems unlikely.
My suspicion is that the table is spread too thin around the cluster and there are lots of mostly empty blocks being read but this is just based on assumptions. Is "id" the distkey or sortkey for this table? Other factors likely in play are cluster load - is the cluster busy when this query runs? WLM is one place that things can interfere but disk IO bandwidth is a share resource and if some other queries are abusing the disks this will make every query's access to disk slow. (Same is true of network bandwidth and leader node workload but these don't seem to be central to your issue at the moment.)
As I mentioned resolving this will likely take some back and forth so leave comments if you have additional information.
(I am speaking from a knowledge of MySQL, not Redshift.)
SELECT * FROM leads WHERE id = 10162064
If id is indexed, especially if it is a Unique (or Primary) key, 0.4 sec sounds like a long network delay. I would expect 0.004 as a worst-case (with SSDs and `PRIMARY KEY(id)).
(If leads is a VIEW, then let's see the tables. 0.4s may be be reasonable!)
That query works well for a RDBMS, but not for a columnar database. Face it.
I can understand using a columnar database to handle random queries on various columns. See also MariaDB's implementation of "Columnstore" -- that would give you both RDBMS and Columnar in a single package. Still, they are separate enough that you can't really intermix the two technologies.
If you are getting 100% CPU in MySQL, show us the query, its EXPLAIN, and SHOW CREATE TABLE. Often, a better index and/or query formulation can solve that.
For "real time reporting" in a Data Warehouse, building and maintaining Summary Tables is often the answer.
Tell us more about the "exact copy" of the DW data. In some situations, the Summary tables can supplant one copy of the Fact table data.
I need to start off by pointing out that by no means am I a database expert in any way. I do know how to get around to programming applications in several languages that require database backends, and am relatively familiar with MySQL, Microsoft SQL Server and now MEMSQL - but again, not an expert at databases so your input is very much appreciated.
I have been working on developing an application that has to cross reference several different tables. One very simple example of an issue I recently had, is I have to:
On a daily basis, pull down 600K to 1M records into a temporary table.
Compare what has changed between this new data pull and the old one. Record that information on a separate table.
Repopulate the table with the new records.
Running #2 is a query similar to:
SELECT * FROM (NEW TABLE) LEFT JOIN (OLD TABLE) ON (JOINED FIELD) WHERE (OLD TABLE.FIELD) IS NULL
In this case, I'm comparing the two tables on a given field and then pulling the information of what has changed.
In MySQL (v5.6.26, x64), my query times out. I'm running 4 vCPUs and 8 GB of RAM but note that the rest of my configuration is default configuration (did not tweak any parameters).
In MEMSQL (v5.5.8, x64), my query runs in about 3 seconds on the first try. I'm running the exact same virtual server configuration with 4 vCPUs and 8 GB of RAM, also note that the rest of my configuration is default configuration (did not tweak any parameters).
Also, in MEMSQL, I am running a single node configuration. Same thing for MySQL.
I love the fact that using MEMSQL allowed me to continue developing my project, and I'm coming across even bigger cross-table calculation queries and views that I can run that are running fantastically on MEMSQL... but, in an ideal world, i'd use MySQL. I've already come across the fact that I need to use a different set of tools to manage my instance (i.e.: MySQL Workbench works relatively well with a MEMSQL server but I actually need to build views and tables using the open source SQL Workbench and the mysql java adapter. Same thing for using the Visual Studio MySQL connector, works, but can be painful at times, for some reason I can add queries but can't add table adapters)... sorry, I'll submit a separate question for that :)
Considering both virtual machines are exactly the same configuration, and SSD backed, can anyone give me any recommendations on how to tweak my MySQL instance to run big queries like the one above on MySQL? I understand I can also create an in-memory database but I've read there might be some persistence issues with doing that, not sure.
Thank you!
The most likely reason this happens is because you don't have index on your joined field in one or both tables. According to this article:
https://www.percona.com/blog/2012/04/04/join-optimizations-in-mysql-5-6-and-mariadb-5-5/
Vanilla MySQL only supports nested loop joins, that require the index to perform well (otherwise they take quadratic time).
Both MemSQL and MariaDB support so-called hash join, which does not require you to have indexes on the tables, but consumes more memory. Since your dataset is negligibly small for modern RAM sizes, that extra memory overhead is not noticed in your case.
So all you need to do to address the issue is to add indexes on joined field in both tables.
Also, please describe the issues you are facing with the open source tools when connect to MemSQL in a separate question, or at chat.memsql.com, so that we can fix it in the next version (I work for MemSQL, and compatibility with MySQL tools is one of the priorities for us).
I am looking for a free SQL database able to handle my data model. The project is a production database working in a local network not connected to the internet without any replication. The number of application connected at the same times would be less than 10.
The data volume forecast for the next 5 years are:
3 tables of 100 millions rows
2 tables of 500 millions rows
20 tables with less than 10k rows
My first idea was to use MySQL, but I have found around the web several articles saying that MySQL is not designed for big database. But, what is the meaning of big in this case?
Is there someone to tell me if MySQL is able to handle my data model?
I read that Postgres would be a good alternative, but require a lot of hours for tuning to be efficient with big tables.
I don't think so that my project would use NOSQL database.
I would know if someone has some experience to share with regarding MySQL.
UPDATE
The database will be accessed by C# software (max 10 at the same times) and web application (2-3 at the same times),
It is important to mention that only few update will be done on the big tables, only insert query. Delete statements will be only done few times on the 20 small tables.
The big tables are very often used for select statement, but the most often in the way to know if an entry exists, not to return grouped and ordered batch of data.
I work for Percona, a company that provides consulting and other services for MySQL solutions.
For what it's worth, we have worked with many customers who are successful using MySQL with very large databases. Terrabytes of data, tens of thousands of tables, tables with billions of rows, transaction load of tens of thousands of requests per second. You may get some more insight by reading some of our customer case studies.
You describe the number of tables and the number of rows, but nothing about how you will query these tables. Certainly one could query a table of only a few hundred rows in a way that would not scale well. But this can be said of any database, not just MySQL.
Likewise, one could query a table that is terrabytes in size in an efficient way. It all depends on how you need to query it.
You also have to set specific goals for performance. If you want queries to run in milliseconds, that's challenging but doable with high-end hardware. If it's adequate for your queries to run in a couple of seconds, you can be a lot more relaxed about the scalability.
The point is that MySQL is not a constraining factor in these cases, any more than any other choice of database is a constraining factor.
Re your comments.
MySQL has referential integrity checks in its default storage engine, InnoDB. The claim that "MySQL has no integrity checks" is a myth often repeated over the years.
I think you need to stop reading superficial or outdated articles about MySQL, and read some more complete and current documentation.
MySQLPerformanceBlog.com
High Performance MySQL, 3rd edition
MySQL 5.6 manual
MySQL has a two important (and significantly different) database engines - MyISAM and InnoDB. A limits depends on usage - MyISAM is nontransactional - there is relative fast import, but it is too simple (without own memory cache) and JOINs on tables higher than 100MB can be slow (due too simple MySQL planner - hash joins is supported from 5.6). InnoDB is transactional and is very fast on operations based on primary key - but import is slower.
Current versions of MySQL has not good planner as Postgres has (there is progress) - so complex queries are usually much better on PostgreSQL - and really simple queries are better on MySQL.
Complexity of PostgreSQL configuration is myth. It is much more simple than MySQL InnoDB configuration - you have to set only five parameters: max_connection, shared_buffers, work_mem, maintenance_work_mem and effective_cache_size. Almost all is related to available memory for Postgres on server. Usually work for 5 minutes. On my experience a databases to 100GB is usually without any problems on Postgres (probably on MySQL too). There are two important factors - how speed you expect and how much memory and how fast IO you have.
With large databases you have to have a experience and knowledges for any database technology. All is fast when you are in memory, and when ratio database size/memory is higher, then much more work you have to do to get good results.
First of all, MySQLs table size is only limited by the allowed file size limit of your OS which is I. The terra bytes on any modern OS. That would pose no problems. Most important are questions like this:
What kind of queries will you run?
Are the large table records updated frequently or basically archives for history data?
What is your hardware budget?
What is the kind of query speed you need?
Are you familiar with table partitioning, archive tables, config tuning?
How fast do you need to write (expected inserts per second)
What language will you use to connect to the db (Java, .net, Ruby etc)
What platform are you most familiar with?
Will you run queries which might cause table scans such like '%something%' which would have to go through every single row and take forever
MySQL is used by Facebook, google, twitter and others with large tables and 100,000,000 is not much in the age of social media. MySQL has very little drawbacks (even though I prefer postgresql in most cases) like altering large tables by adding a new index for example. That might send your company in a couple days forced vacation if you don't have a replica in the meantime. Is there a reason why NoSQL is not an option? Sometimes hybrid approaches are a good choice like having your relational business logic in MySQL and huge statistical tables in a NoSQL database like MongoDb which can scale by adding new servers in minutes (MySQL can too but it's more complicated). Now MongoDB can have a indexed column which can be searched by in blistering speed.
Bejond the bottom line: you need to answer the above questions first to make a very informed decision. If you have huge tables and only search on indexed keys almost any database will do - if you expect many changes to the structure down the road you want to use a different approach.
Edit:
Based on your update you just posted I doubt you would run into problems.
I have a MySQL database with a few (five to be precise) huge tables. It is essentially a star topology based data warehouse. The table sizes range from 700GB (fact table) to 1GB and whole database goes upto 1 terabyte. Now I have been given a task of running analytics on these tables which might even include joins.
A simple analytical query on this database can be "find number of smokers per state and display it in descending order" this requirement could be converted in a simple query like
select state, count(smokingStatus) as smokers
from abc
having smokingstatus='current smoker'
group by state....
This query (and many other of same nature) takes a lot of time to execute on this database, time taken is in order of tens of hours.
This database is also heavily used for insertion which means every few minutes there are thousands of rows getting added.
In such a scenario how can I tackle this querying problem?
I have looked in Cassandra which seemed easy to implement but I am not sure if it is going to be as easy for running analytical queries on the database especially when I have to use "where clause and group by construct"
Have Also looked into Hadoop but I am not sure how can I implement RDBMS type queries. I am not too sure if I want to right away invest in getting at least three machines for name-node, zookeeper and data-nodes!! Above all our company prefers windows based solutions.
I have also thought of pre-computing all the data in a simpler summary tables but that limits my ability to run different kinds of queries.
Are there any other ideas which I can implement?
EDIT
Following is the mysql environment setup
1) master-slave setup
2) master for inserts/updates
3) slave for reads and running stored procedures
4) all tables are innodb with files per table
5) indexes on string as well as int columns.
Pre-calculating values is an option but since requirements for this kind of ad-hoc aggregated values keeps changing.
Looking at this from the position of attempting to make MySQL work better rather than positing an entirely new architectural system:
Firstly, verify what's really happening. EXPLAIN the queries which are causing issues, rather than guessing what's going on.
Having said that, I'm going to guess as to what's going on since I don't have the query plans. I'm guessing that (a) your indexes aren't being used correctly and you're getting a bunch of avoidable table scans, (b) your DB servers are tuned for OLTP, not analytical queries, (c) writing data while reading is causing things to slow down greatly, (d) working with strings just sucks and (e) you've got some inefficient queries with horrible joins (everyone has some of these).
To improve things, I'd investigate the following (in roughly this order):
Check the query plans, make sure the existing indexes are being used correctly - look at the table scans, make sure the queries actually make sense.
Move the analytical queries off the OLTP system - the tunings required for fast inserts and short queries are very different to those for the sorts of queries which potentially read most of a large table. This might mean having another analytic-only slave, with a different config (and possibly table types - I'm not sure what the state of the art with MySQL is right now).
Move the strings out of the fact table - rather than having the smoking status column with string values of (say) 'current smoker', 'recently quit', 'quit 1+ years', 'never smoked', push these values out to another table, and have the integer keys in the fact table (this will help the sizes of the indexes too).
Stop the tables from being updated while the queries are running - if the indexes are moving while the query is running I can't see good things happening. It's (luckily) been a long time since I cared about MySQL replication, so I can't remember if you can batch up the writes to the analytical query slave without too much drama.
If you get to this point without solving the performance issues, then it's time to think about moving off MySQL. I'd look at Infobright first - it's open source/$$ & based on MySQL, so it's probably the easiest to put into your existing system (make sure the data is going to the InfoBright DB, then point your analytical queries to the Infobright server, keep the rest of the system as it is, job done), or if Vertica ever releases its Community Edition. Hadoop+Hive has a lot of moving parts - its pretty cool (and great on the resume), but if it's only going to be used for the analytic portion of you system it may take more care & feeding than other options.
1 TB is not that big. MySQL should be able to handle that. At least simple queries like that shouldn't take hours! Can't be very helpful without knowing the larger context, but I can suggest some questions that you might ask yourself, mostly related to how you use your data:
Is there a way you can separate the reads and writes? How many read so you do per day and how many writes? Can you live with some lag, e.g write to a new table each day and merge it to the existing table at the end of the day?
What are most of your queries like? Are they mostly aggregation queries? Can you do some partial aggregation beforehand? Can you pre-calculate number of new smokers every day?
Can you use hadoop for the aggregation process above? Hadoop is kinda good at that stuff. Basically use hadoop just for daily or batch processing and store the results into the DB.
On the DB side, are you using InnoDB or MyISAM? Are the indices on String columns? Can you make it ints etc.?
Hope that helps
MySQL is have a serious limitation what prevent him to be able to perform good on such scenarious. The problem is a lack of parralel query capability - it can not utilize multiple CPUs in the single query.
Hadoop has an RDMBS like addition called Hive. It is application capable of translate your queries in Hive QL (sql like engine) into the MapReduce jobs. Since it is actually small adition on top of Hadoop it inherits its linear scalability
I would suggest to deploy hive alongside MySQL, replicate daily data to there and run heavy aggregations agains it. It will offload serious part of the load fro MySQL. You still need it for the short interactive queries, usually backed by indexes. You need them since Hive is iherently not-interactive - each query will take at least a few dozens of seconds.
Cassandra is built for the Key-Value type of access and does not have scalable GroupBy capability build-in. There is DataStax's Brisk which integrate Cassandra with Hive/MapReduce but it might be not trivial to map your schema into Cassandra and you still not get flexibility and indexing capabiilties of the RDBMS.
As a bottom line - Hive alongside MySQL should be good solution.
Can any one guide me about my query?, i m making application for banking sector with fuzzy logic. i have to import table with 100 million rows daily. and i am using MySql for this application which is processing slowly. so is there any another server for handling my database which can access fast?
We roughly load about half that many rows a day in our RDBMS (Oracle) and it would not occur to me to implement such a thing without access to DBA knowledge about my RDBMS. We fine-tune this system several times a month and we still encounter new issues all the time. This is such a non-trivial task that the only valid answer is:
Don't play around, have your managers get a DBA who knows their business!
Note: Our system has been in place for 10 years now. It hasn't been built in a day...
100 million rows daily?
You have to be realistic. I doubt any single instance of any database out there can handle this type of thouroughput efficiently. You should probably look at clustering options and other optimising techniques such as splitting data in two diffent DB's (sharding).
MySQL Enterprise has a bunch of features built-in that could ease and moniter the clustering process, but I think MySQL community edition supports it too.
Good-luck!
How are you doing it?
One hugh transaction?
Perhaps try to make small transactions in chunks of 100 or 1000.
Is there an index on that table? Drop the index before starting the improt (if that is possible due to unique costraints etc.) and rebuild the index after the import.
An other option would perhaps be an in memory database.
Well it seems your business' main logic does not depend on importing those 100mio rows into a database, otherwise you wouldn't be stuck with doing this by yourself, right? (correct me if I'm wrong)
Are you sure you need to import those rows into a database when the main business doesn't need to? What kind of questions are you going to ask of the date? Can't you maybe keep the log files on a bunch of servers and query them with eg Hadoop? Or can you aggregate the information contained in the log files and only store a condensed version?
I'm also asking this because it sounds like you're planning to perform some at least moderately sophisticated analysis on the data and the trouble with this amount of data won't stop once you have it in a DB.