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  • Does it make sense to use BOTH mongodb and mysql in the same rails application?

    - by Brian Armstrong
    I have a good reason to use mongodb for part of my app. But people generally describe it as not a good fit for "transactional" applications like a bank where transactions have to be exact/consistent, etc. Does it make sense to split the models up in Rails and have some of them use MySql and others mongo? Or will this generally cause more problems than it's worth? I'm not building a banking app or anything, but was thinking it might make sense for my users table or or transactions table (recording revenue) to do that part in MySql.

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  • Can I join between two MySQL tables stores on separate machines?

    - by CuriousCoder
    I have a relatively light query that needs information from a local MySQL table along with another MySQL table which is stored on a physically separate machine (on the same network). I'm keen to avoid setting up replication just to facilitate this light query that only needs executed once a day. Is there any way that I can join with a table on a remote machine using one query? Or run a SELECT INTO into a local table. Notes I'm using C# & .NET 4.

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  • With PHP and AJAX, Can two clients inter-exchange data without MySQL?

    - by Devyn
    Hi, Let's assume I'm developing a AJAX, PHP chess game. During the game, one movement of a player will be notified to the another but we are not saving that information. Normally, we used to store in MySQL every time a player makes movement and show update position to another player. What I want is to reduce MySQL load as much as possible and server is not interested in movements between two players. Server will only save final result like who wins. So what should I do?

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  • Can MySQL reasonably perform queries on billions of rows?

    - by haxney
    I am planning on storing scans from a mass spectrometer in a MySQL database and would like to know whether storing and analyzing this amount of data is remotely feasible. I know performance varies wildly depending on the environment, but I'm looking for the rough order of magnitude: will queries take 5 days or 5 milliseconds? Input format Each input file contains a single run of the spectrometer; each run is comprised of a set of scans, and each scan has an ordered array of datapoints. There is a bit of metadata, but the majority of the file is comprised of arrays 32- or 64-bit ints or floats. Host system |----------------+-------------------------------| | OS | Windows 2008 64-bit | | MySQL version | 5.5.24 (x86_64) | | CPU | 2x Xeon E5420 (8 cores total) | | RAM | 8GB | | SSD filesystem | 500 GiB | | HDD RAID | 12 TiB | |----------------+-------------------------------| There are some other services running on the server using negligible processor time. File statistics |------------------+--------------| | number of files | ~16,000 | | total size | 1.3 TiB | | min size | 0 bytes | | max size | 12 GiB | | mean | 800 MiB | | median | 500 MiB | | total datapoints | ~200 billion | |------------------+--------------| The total number of datapoints is a very rough estimate. Proposed schema I'm planning on doing things "right" (i.e. normalizing the data like crazy) and so would have a runs table, a spectra table with a foreign key to runs, and a datapoints table with a foreign key to spectra. The 200 Billion datapoint question I am going to be analyzing across multiple spectra and possibly even multiple runs, resulting in queries which could touch millions of rows. Assuming I index everything properly (which is a topic for another question) and am not trying to shuffle hundreds of MiB across the network, is it remotely plausible for MySQL to handle this? UPDATE: additional info The scan data will be coming from files in the XML-based mzML format. The meat of this format is in the <binaryDataArrayList> elements where the data is stored. Each scan produces = 2 <binaryDataArray> elements which, taken together, form a 2-dimensional (or more) array of the form [[123.456, 234.567, ...], ...]. These data are write-once, so update performance and transaction safety are not concerns. My naïve plan for a database schema is: runs table | column name | type | |-------------+-------------| | id | PRIMARY KEY | | start_time | TIMESTAMP | | name | VARCHAR | |-------------+-------------| spectra table | column name | type | |----------------+-------------| | id | PRIMARY KEY | | name | VARCHAR | | index | INT | | spectrum_type | INT | | representation | INT | | run_id | FOREIGN KEY | |----------------+-------------| datapoints table | column name | type | |-------------+-------------| | id | PRIMARY KEY | | spectrum_id | FOREIGN KEY | | mz | DOUBLE | | num_counts | DOUBLE | | index | INT | |-------------+-------------| Is this reasonable?

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  • C#+Mysql Runs out of Connections. I am using 'using' and closing all connections immediately.

    - by Cyril Gupta
    In the application that I am making right now, I am getting this error: error connecting: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached. Evidently I am touching max-count in the connection pool. I am dutifully using 'using' with all connection objects and freeing them up immediately when the function is done with them. This is on C#, and I am using the MySql Data Dll. Is there something wrong with the dotnet connector for MySql? Is there a workaround?

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  • pitfalls with mixing storage engines in mysql with django?

    - by Dave Orr
    I'm running a django system over mysql in amazon's cloud, and the database default is innodb. But now I want to put a fulltext index on a couple of tables for searching, which evidently requires myisam. The obvious solution is to just tell mysql to ALTER TABLE to myisam, but are there going to be any issues with that? One that comes to mind is that I'll have to remember to do that any time I build a new version of the database, which should theoretically be rare, but there doesn't seem to be a way to tell django to please set the storage engine at the table level. I guess I could write a migration (we use south). Any other things I might be missing? What could possibly go wrong?

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  • How do you encode an apostrophe so that it's searchable in mysql?

    - by Yegor
    I don't think that was the most clear question, but an example should make it a little clearer. I have a table filled with movie names, some of which contain apostrophes. I have a search box which is used to find movies. If I perform searches via mov_title = '$search_keywords' it all works, but this method will not yield any results for partial searches, so I have to use this mov_title LIKE '%$search_keywords%' This method works fine for titles that are A-Za-z0-9, but if a title has an apostrophe, it's not able to find the movie, even if I do an exact match. Before the titles are stored in the DB, I put them through this: $search_keywords = htmlspecialchars(mysql_escape_string($_GET["search_keywords"])); So in the DB, there is a forward slash before every single apostrophe. The only way to match a movie title with an apostrophe is to physically put a forward slash in front of the apostrophe, in the search box. This seems so trivial, and I'm sure the solution is painfully obvious, but I'm just not seeing it.

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  • MySQL running on an EC2 m1.small instance has high load but low memory usage, possible resolutions?

    - by Tosh
    I have a MySQL server 5.0.75 Ubuntu, on an m1.small instance running on Amazon's EC2 as part of an application. During peak usage the server load will rise very high, while the memory usage stays low and the application server is no longer responsive since it's waiting for query results. The application server has only 5-8 apache processes running (mod_perl processes). The data directory uses only 140MB of data so the MyIsam tables aren't very big. The queries are pretty complicated with some big joins being performed, and the application makes a lot of queries. mysqltuner reports everything OK except "Maximum possible memory usage: 1.7G (99% of installed RAM)" but I'm nowhere close to using that. My question is, where should I be looking to fix this? Is this something that can be tuned away, or do I just need a larger instance/server? Googling indicates either or also upgrading MySQL server. Any pointers in the right direction would be greatly appreciated, thanks! EDIT: I just discovered this in my slow queries log: # Time: 101116 11:17:00 # User@Host: user[pass] @ [host] # Query_time: 4063 Lock_time: 1035 Rows_sent: 0 Rows_examined: 19960174 SELECT * FROM contacts WHERE contacts.contact_id IN (SELECT external_id FROM contact_relations WHERE external_table = 'contacts' AND contact_id IN (SELECT contact_id FROM contacts WHERE (company_name like '%%butan%%%' OR country like '%%butan%%%' OR city like '%%butan%%%' OR email1 like '%%butan%%%') AND (company_name is not null and company_name != ''))); Which actually brings up a different but related question: If I have a contact table containing: John Smith,The Fun Factory,555-1212,[email protected] What's the best way to search for that record using "factory" as a search key? Fulltext rarely seems to find items in the middle of a word, for example "actor" should bring up "Factory"

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  • Using a variable in a mysql query, in a C++ MFC program.

    - by D.Gaughan
    Hi, after extensive trawling of the internet I still havent found any solution for this problem. I`m writing a small C++ app that connects to an online database and outputs the data in a listbox. I need to enable a search function using an edit box, but I cant get the query to work while using a variable. My code is: res = mysql_perform_query (conn, "select distinct artist from Artists"); //res = mysql_perform_query (conn, "select album from Artists where artist = ' ' "); while((row = mysql_fetch_row(res)) != NULL){ CString str; UpdateData(); str = ("%s\n", row[0]); UpdateData(FALSE); m_list_control.AddString(str); } the first "res = " line is working fine, but I need the second one to work. I have a member variable m_search_edit set up for the edit box, but any way I try to include it in the sql statement causes errors. eg. res = mysql_perform_query (conn, "select album from Artists where artist = '"+m_search_edit+" ' "); causes this error: error C2664: 'mysql_perform_query' : cannot convert parameter 2 from 'class CString' to 'char *' No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called" And when I convert m_search_edit to a char* it gives me a " Cannot add 2 pointers" error. Any way around this???

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  • How can I kill MySQL queries every 60 seconds in Windows?

    - by Ethan Allen
    I want to check my MySQL server every minute and kill queries that have run longer than 150 seconds. The main reason I want to do this is because I don't want queries from certain people to lock up the DB for everyone else. I know this is not the ultimate solution to the problem, but at least it's a fallback in case something goes wrong with a query. I don't have a slave DB (this is just an at-home project). I'd like to schedule a script to run that does this for me. I'm unfamiliar with Perl or Ruby and I need it done on my Windows 2008 Server box. I've looked into creating a simple cmd line script, but that doesn't seem to be possible. I know currently I can do something like this but I have to do it manually: mysqladmin processlist mysqladmin kill Anyone have any ideas or examples on how I could do this?

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  • How do I select a random record efficiently in MySQL?

    - by user198729
    mysql> EXPLAIN SELECT * FROM urls ORDER BY RAND() LIMIT 1; +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ | 1 | SIMPLE | urls | ALL | NULL | NULL | NULL | NULL | 62228 | Using temporary; Using filesort | +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ The above doesn't qualify as efficient,how should I do it properly?

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  • Reading data from a MySQL database into a HTML Table?

    - by Michael McKay
    So i am working on a project and need some advice. I have a MySQL database that stores events, i know how to code this functionality in PHP but im just stuck of a few specifics. As the project that I am creating is a timetable, the most important attributes are the day of the event, starting time and finishing time. Once i have read this data from the MYSQL database using my PHP script, how do i go about inserting these events in to a html timetable? Lets say i have record like below in my events table: Event ID = 01 Event Day = Monday Event Start = 12:00 Event End = 14:00 How would I then put that into a html table, bearing in mind that i may have mutiple events for a day?

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  • A very interesting MYSQL problem (related to indexing, million records, algorithm.)

    - by terence410
    This problem is pretty hard to describe and therefore difficult to search the answer. I hope some expert could share you opinions on that. I have a table with around 1 million of records. The table structure is similar to something like this: items{ uid (primary key, bigint, 15) updated (indexed, int, 11) enabled (indexed, tinyint, 1) } The scenario is like this. I have to select all of the records everyday and do some processing. It takes around 3 second to handle each item. I have written a PHP script to fetch 200 items each time using the following. select * from items where updated unix_timestamp(now()) - 86400 and enabled = 1 limit 200; I will then update the "updated" field of the selected items to make sure that it wont' be selected again within one day. The selected query is something like that. update items set updated = unix_timestamp(now()) where uid in (1,2,3,4,...); Then, the PHP will continue to run and process the data which doesn't require any MYSQL connection anymore. Since I have million records and each record take 3 seconds to process, it's definitely impossible to do it sequentially. Therefore, I will execute the PHP in every 10 seconds. However, as time goes by and the table growth, the select getting much slower. Sometimes, it take more than 100 seconds to run! Do you guys have any suggestion how may I solve this problem?

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  • How can I join 3 tables with mysql & php?

    - by steven
    check out the page [url]http://www.mujak.com/test/test3.php[/url] It pulls the users Post,username,xbc/xlk tags etc which is perfect... BUT since I am pulling information from a MyBB bulletin board system, its quite different. When replying, people are are allowed to change the "Thread Subject" by simplying replying and changing it. I dont want it to SHOW the changed subject title, just the original title of all posts in that thread. By default it repies with "RE:thread title". They can easily edit this and it will show up in the "Subject" cell & people wont know which thread it was posted in because they changed their thread to when replying to the post. So I just want to keep the orginial thread title when they are replying. Make sense~?? Tables:mybb_users Fields:uid,username Tables:mybb_userfields Fields:ufid Tables:mybb_posts Fields:pid,tid,replyto,subject,ufid,username,uid,message Tables:mybb_threads Fields:tid,fid,subject,uid,username,lastpost,lastposter,lastposteruid I haev tried multiple queries with no success: $result = mysql_query(" SELECT * FROM mybb_users LEFT JOIN (mybb_posts, mybb_userfields, mybb_threads) ON ( mybb_userfields.ufid=mybb_posts.uid AND mybb_threads.tid=mybb_posts.tid AND mybb_users.uid=mybb_userfields.ufid ) WHERE mybb_posts.fid=42"); $result = mysql_query(" SELECT * FROM mybb_users LEFT JOIN (mybb_posts, mybb_userfields, mybb_threads) ON ( mybb_userfields.ufid=mybb_posts.uid AND mybb_threads.tid=mybb_posts.tid AND mybb_users.uid=mybb_posts.uid ) WHERE mybb_threads.fid=42"); $result = mysql_query(" SELECT * FROM mybb_posts LEFT JOIN (mybb_userfields, mybb_threads) ON ( mybb_userfields.ufid=mybb_posts.uid AND mybb_threads.tid=mybb_posts.tid ) WHERE mybb_posts.fid=42");

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  • MYSQL - Adding result set A to result set B? Please see my example

    - by BlackberryFan
    I have two mysql tables. They are laid out in this manner: user_info id | emailContact _______________________ 1 | [email protected] 3 | [email protected] user_biz_info id | emailContact _________________________ 8 | [email protected] 9 | [email protected] What kind of join would I use to create a result set of information like this: id | emailContact ________________________________ 1 - [email protected] 3 - [email protected] 8 - [email protected] 9 - [email protected] I have tried the following: SELECT p.id, p.emailContact, b.id, b.emailContact FROM user_info p, user_business_info b But it seems that this is an incorrect approach. Would someone be able to suggest the correct approach in this or possibly point me in the direction of some tutorials that cover this type of mysql join, as this is what I assume is needed in this case. Thanks for your time in reading through my question!!

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  • Best way to have unique key over 500M varchar(255) records in mysql/innodb?

    - by taw
    I have url column with unique key over it - but its performance on updates is absolutely atrocious. I suspect that's because the index doesn't all fit in memory. So I was thinking, how about adding a column of md5(url) with 16 bytes of binary data and unique-keying that instead. What would be the best datatype for that? I'd love to be able to just see 32-character hex hash, while mysql would convert it to/from 16 binary bytes and index that, as programs using the database might have some troubles with arbitrary binary data that I'd rather avoid if possible (also I'm a bit afraid that mysql might get some strange ideas about character sets and for example overalocating storage for that by 3:1 because it thinks it might need utf8, how do I avoid that for cure?).

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  • is there a limit of merge tables with Mysql ?

    - by sysko
    I'm working on a database with mysql 5.0 for an open source project it's used to stored sentences in specific languages and their translations in other languages I used to have a big table "sentences" and "sentences_translations" (use to join sentences to sentences) table but has we have now near one million entries, this begin to be a bit slow, moreover, most of request are made using a "where lang =" so I've decided to create a table by language sentences_LANGUAGECODE and sentences_translation_LANGSOURCE_LANGTARGET and to create merge table like this sentences_ENG_OTHERS which merge sentences_ENG_ARA sentences_ENG_DEU etc... when we want to have the translations in all languages of an english sentence sentences_OTHERS_ENG when we want to have only the english translations of some sentences I've created a script to create all these tables (they're around 31 languages so more than 60 merge table), I've tested, that works really great a request which use to take 160ms now take only 30 :) but I discover that all my merge table after the 15th use to have "NULL" as type of storage engine instead of MRG_MYISAM, and if delete one, then I can create an others, using FLUSH table between each creation also allow me to create more merge tables so is this a limitation from mysql ? can we override it ? thanks for your answers

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  • Do I need the text "_size" in the my.cnf file for mysql 5.1?

    - by chongman
    This is a pretty simple question about setting parameters in the my.cnf file for mysql 5.1. This page gives me the parameters I can tune: http://dev.mysql.com/doc/refman/5.0/en/server-parameters.html and so I think I would need to write key_buffer_size = 256M But when I open my current my.cnf, it has the line: key_buffer = 16M My question is, do I need "key_buffer_size" or "key_buffer" or does it not matter which I use? And, how would I know if something in the my.cnf is incorrect? Where's the daemon start log file? I am running ubuntu; I think version 8.04 LTS

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