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  • Can't sync filesystem without reboot

    - by Fabio
    I'm having an issue with a linux server. Once a week the running mysql instance hangs and there is no way to fully stop it. If I kill it, it remains in zombie status and init does not reap its pid. The server is used for staging deployments and some internal tools, so it's not under heavy load. The only process constantly used id mysql and for this I think that it's the only process which suffer of this issue. I've searched system logs for errors and the only thing I found is this error (repeated a couple of times) in dmesg output: [706560.640085] INFO: task mysqld:31965 blocked for more than 120 seconds. [706560.640198] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [706560.640312] mysqld D ffff88032fd93f40 0 31965 1 0x00000000 [706560.640317] ffff880242a27d18 0000000000000086 ffff88031a50dd00 ffff880242a27fd8 [706560.640321] ffff880242a27fd8 ffff880242a27fd8 ffff88031e549740 ffff88031a50dd00 [706560.640325] ffff88031a50dd00 ffff88032fd947f8 0000000000000002 ffffffff8112f250 [706560.640328] Call Trace: [706560.640338] [<ffffffff8112f250>] ? __lock_page+0x70/0x70 [706560.640344] [<ffffffff816cb1b9>] schedule+0x29/0x70 [706560.640347] [<ffffffff816cb28f>] io_schedule+0x8f/0xd0 [706560.640350] [<ffffffff8112f25e>] sleep_on_page+0xe/0x20 [706560.640353] [<ffffffff816c9900>] __wait_on_bit+0x60/0x90 [706560.640356] [<ffffffff8112f390>] wait_on_page_bit+0x80/0x90 [706560.640360] [<ffffffff8107dce0>] ? autoremove_wake_function+0x40/0x40 [706560.640363] [<ffffffff8112f891>] filemap_fdatawait_range+0x101/0x190 [706560.640366] [<ffffffff81130975>] filemap_write_and_wait_range+0x65/0x70 [706560.640371] [<ffffffff8122e441>] ext4_sync_file+0x71/0x320 [706560.640376] [<ffffffff811c3e6d>] do_fsync+0x5d/0x90 [706560.640379] [<ffffffff811c40d0>] sys_fsync+0x10/0x20 [706560.640383] [<ffffffff816d495d>] system_call_fastpath+0x1a/0x1f When this happens the only way to make everything working again is a full reboot, but in order to do that I'm forced to use this command after I've manually stopped all running processes echo b > /proc/sysrq-trigger otherwise normal reboot process hangs forever. I've tracked reboots script and I've found out that also the reboot process hangs on a sync call, this one in /etc/init.d/sendsigs (I'm on ubuntu) # Flush the kernel I/O buffer before we start to kill # processes, to make sure the IO of already stopped services to # not slow down the remaining processes to a point where they # are accidentily killed with SIGKILL because they did not # manage to shut down in time. sync I'm almost sure that the cause of this is an hardware issue (the RAID controller???) also because I've other two machines with the same hardware and software configuration and they don't suffer of this, but I can't find any hint in syslog or dmesg. I've also installed smartmontools and mcelog packages but none of them did report any issue. What can I do to track the cause of this issue? Today is happened again, here is the status of system after triggering a reboot init---console-kit-dae---64*[{console-kit-dae}] +-dbus-daemon +-mcelog +-mysqld---{mysqld} +-newrelic-daemon---newrelic-daemon---11*[{newrelic-daemon}] +-ntpd +-polkitd---{polkitd} +-python3 +-rpc.idmapd +-rpc.statd +-rpcbind +-sh---rc---S20sendsigs---sync +-smartd +-snmpd +-sshd---sshd---zsh---sudo---zsh---pstree +-sshd---sshd---zsh---sudo---zsh And here is the status of sync process # ps aux | grep sync root 3637 0.1 0.0 4352 372 ? D 05:53 0:00 sync i.e. Uninterruptible sleep... Hardware specs as reported by lshw I think the raid controller is a fake raid. I usually don't deal with hardware (and for the record I don't have physical access to it) description: Computer product: X7DBP () vendor: Supermicro version: 0123456789 serial: 0123456789 width: 64 bits capabilities: smbios-2.4 dmi-2.4 vsyscall32 configuration: administrator_password=disabled boot=normal frontpanel_password=unknown keyboard_password=unknown power-on_password=disabled uuid=53D19F64-D663-A017-8922-0030487C1FEE *-core description: Motherboard product: X7DBP vendor: Supermicro physical id: 0 version: PCB Version serial: 0123456789 *-firmware description: BIOS vendor: Phoenix Technologies LTD physical id: 0 version: 6.00 date: 05/29/2007 size: 106KiB capacity: 960KiB capabilities: pci pnp upgrade shadowing escd cdboot bootselect edd int13floppy2880 acpi usb ls120boot zipboot biosbootspecification *-storage description: RAID bus controller product: 631xESB/632xESB SATA RAID Controller vendor: Intel Corporation physical id: 1f.2 bus info: pci@0000:00:1f.2 version: 09 width: 32 bits clock: 66MHz capabilities: storage pm bus_master cap_list configuration: driver=ahci latency=0 resources: irq:19 ioport:18a0(size=8) ioport:1874(size=4) ioport:1878(size=8) ioport:1870(size=4) ioport:1880(size=32) memory:d8500400-d85007ff

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  • Load average is have been high over some period

    - by user111196
    We have a dedicated MySQL server and below is the a snapshot of the top. The load average has been staying at nearly 100 for an hour plus ready. top - 20:54:28 up 7:31, 2 users, load average: 83.08, 96.88, 106.23 Tasks: 278 total, 2 running, 274 sleeping, 2 stopped, 0 zombie Cpu0 : 18.8%us, 10.2%sy, 0.0%ni, 70.9%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu1 : 51.2%us, 4.3%sy, 0.0%ni, 44.2%id, 0.0%wa, 0.0%hi, 0.3%si, 0.0%st Cpu2 : 9.0%us, 10.3%sy, 0.0%ni, 80.6%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu3 : 18.8%us, 7.4%sy, 0.0%ni, 73.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu4 : 7.8%us, 8.8%sy, 0.0%ni, 83.4%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu5 : 10.3%us, 8.4%sy, 0.0%ni, 81.4%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu6 : 6.2%us, 7.5%sy, 0.0%ni, 86.2%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu7 : 6.2%us, 6.2%sy, 0.0%ni, 87.3%id, 0.0%wa, 0.0%hi, 0.3%si, 0.0%st Cpu8 : 8.8%us, 10.4%sy, 0.0%ni, 80.5%id, 0.0%wa, 0.0%hi, 0.3%si, 0.0%st Cpu9 : 63.7%us, 4.6%sy, 0.0%ni, 12.2%id, 0.0%wa, 4.3%hi, 15.2%si, 0.0%st Cpu10 : 9.2%us, 10.2%sy, 0.0%ni, 80.6%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu11 : 17.3%us, 5.9%sy, 0.0%ni, 76.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu12 : 8.0%us, 8.7%sy, 0.0%ni, 83.3%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu13 : 10.9%us, 7.4%sy, 0.0%ni, 81.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu14 : 6.2%us, 6.9%sy, 0.0%ni, 86.9%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu15 : 4.8%us, 6.1%sy, 0.0%ni, 89.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 33009800k total, 23174396k used, 9835404k free, 120604k buffers Swap: 35061752k total, 0k used, 35061752k free, 16459540k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 3341 mysql 20 0 14.3g 4.6g 4240 S 417.8 14.5 1673:51 mysqld 24406 root 20 0 15008 1292 876 R 0.3 0.0 0:00.19 top 1 root 20 0 4080 852 608 S 0.0 0.0 0:01.92 init 2 root 15 -5 0 0 0 S 0.0 0.0 0:00.00 kthreadd 3 root RT -5 0 0 0 S 0.0 0.0 0:00.32 migration/0 4 root 15 -5 0 0 0 S 0.0 0.0 0:00.29 ksoftirqd/0 5 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/0 6 root RT -5 0 0 0 S 0.0 0.0 0:03.21 migration/1 7 root 15 -5 0 0 0 S 0.0 0.0 0:00.07 ksoftirqd/1 8 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/1 9 root RT -5 0 0 0 S 0.0 0.0 0:00.17 migration/2 10 root 15 -5 0 0 0 S 0.0 0.0 0:00.03 ksoftirqd/2 11 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/2 12 root RT -5 0 0 0 S 0.0 0.0 0:00.32 migration/3 13 root 15 -5 0 0 0 S 0.0 0.0 0:00.02 ksoftirqd/3 14 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/3 15 root RT -5 0 0 0 S 0.0 0.0 0:00.10 migration/4 16 root 15 -5 0 0 0 S 0.0 0.0 0:00.04 ksoftirqd/4 17 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/4 18 root RT -5 0 0 0 S 0.0 0.0 0:00.35 migration/5 We have also tried to run this command. What else command can help us diagnose the exact problem of this high load? netstat -nat |grep 3306 | awk '{print $6}' | sort | uniq -c | sort -n 1 LISTEN 1 SYN_RECV 410 ESTABLISHED 964 TIME_WAIT Output of vmstat 1: ---------------memory--------------- --swap-- --io-- --system-- -----cpu------ r b swpd free buff cache si so bi bo in cs us sy id wa st 2 0 0 12978936 30944 15172360 0 0 259 3 184 265 6 6 77 12 0

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  • How to Achieve OC4J RMI Load Balancing

    - by fip
    This is an old, Oracle SOA and OC4J 10G topic. In fact this is not even a SOA topic per se. Questions of RMI load balancing arise when you developed custom web applications accessing human tasks running off a remote SOA 10G cluster. Having returned from a customer who faced challenges with OC4J RMI load balancing, I felt there is still some confusions in the field how OC4J RMI load balancing work. Hence I decide to dust off an old tech note that I wrote a few years back and share it with the general public. Here is the tech note: Overview A typical use case in Oracle SOA is that you are building web based, custom human tasks UI that will interact with the task services housed in a remote BPEL 10G cluster. Or, in a more generic way, you are just building a web based application in Java that needs to interact with the EJBs in a remote OC4J cluster. In either case, you are talking to an OC4J cluster as RMI client. Then immediately you must ask yourself the following questions: 1. How do I make sure that the web application, as an RMI client, even distribute its load against all the nodes in the remote OC4J cluster? 2. How do I make sure that the web application, as an RMI client, is resilient to the node failures in the remote OC4J cluster, so that in the unlikely case when one of the remote OC4J nodes fail, my web application will continue to function? That is the topic of how to achieve load balancing with OC4J RMI client. Solutions You need to configure and code RMI load balancing in two places: 1. Provider URL can be specified with a comma separated list of URLs, so that the initial lookup will land to one of the available URLs. 2. Choose a proper value for the oracle.j2ee.rmi.loadBalance property, which, along side with the PROVIDER_URL property, is one of the JNDI properties passed to the JNDI lookup.(http://docs.oracle.com/cd/B31017_01/web.1013/b28958/rmi.htm#BABDGFBI) More details below: About the PROVIDER_URL The JNDI property java.name.provider.url's job is, when the client looks up for a new context at the very first time in the client session, to provide a list of RMI context The value of the JNDI property java.name.provider.url goes by the format of a single URL, or a comma separate list of URLs. A single URL. For example: opmn:ormi://host1:6003:oc4j_instance1/appName1 A comma separated list of multiple URLs. For examples:  opmn:ormi://host1:6003:oc4j_instanc1/appName, opmn:ormi://host2:6003:oc4j_instance1/appName, opmn:ormi://host3:6003:oc4j_instance1/appName When the client looks up for a new Context the very first time in the client session, it sends a query against the OPMN referenced by the provider URL. The OPMN host and port specifies the destination of such query, and the OC4J instance name and appName are actually the “where clause” of the query. When the PROVIDER URL reference a single OPMN server Let's consider the case when the provider url only reference a single OPMN server of the destination cluster. In this case, that single OPMN server receives the query and returns a list of the qualified Contexts from all OC4Js within the cluster, even though there is a single OPMN server in the provider URL. A context represent a particular starting point at a particular server for subsequent object lookup. For example, if the URL is opmn:ormi://host1:6003:oc4j_instance1/appName, then, OPMN will return the following contexts: appName on oc4j_instance1 on host1 appName on oc4j_instance1 on host2, appName on oc4j_instance1 on host3,  (provided that host1, host2, host3 are all in the same cluster) Please note that One OPMN will be sufficient to find the list of all contexts from the entire cluster that satisfy the JNDI lookup query. You can do an experiment by shutting down appName on host1, and observe that OPMN on host1 will still be able to return you appname on host2 and appName on host3. When the PROVIDER URL reference a comma separated list of multiple OPMN servers When the JNDI propery java.naming.provider.url references a comma separated list of multiple URLs, the lookup will return the exact same things as with the single OPMN server: a list of qualified Contexts from the cluster. The purpose of having multiple OPMN servers is to provide high availability in the initial context creation, such that if OPMN at host1 is unavailable, client will try the lookup via OPMN on host2, and so on. After the initial lookup returns and cache a list of contexts, the JNDI URL(s) are no longer used in the same client session. That explains why removing the 3rd URL from the list of JNDI URLs will not stop the client from getting the EJB on the 3rd server. About the oracle.j2ee.rmi.loadBalance Property After the client acquires the list of contexts, it will cache it at the client side as “list of available RMI contexts”.  This list includes all the servers in the destination cluster. This list will stay in the cache until the client session (JVM) ends. The RMI load balancing against the destination cluster is happening at the client side, as the client is switching between the members of the list. Whether and how often the client will fresh the Context from the list of Context is based on the value of the  oracle.j2ee.rmi.loadBalance. The documentation at http://docs.oracle.com/cd/B31017_01/web.1013/b28958/rmi.htm#BABDGFBI list all the available values for the oracle.j2ee.rmi.loadBalance. Value Description client If specified, the client interacts with the OC4J process that was initially chosen at the first lookup for the entire conversation. context Used for a Web client (servlet or JSP) that will access EJBs in a clustered OC4J environment. If specified, a new Context object for a randomly-selected OC4J instance will be returned each time InitialContext() is invoked. lookup Used for a standalone client that will access EJBs in a clustered OC4J environment. If specified, a new Context object for a randomly-selected OC4J instance will be created each time the client calls Context.lookup(). Please note the regardless of the setting of oracle.j2ee.rmi.loadBalance property, the “refresh” only occurs at the client. The client can only choose from the "list of available context" that was returned and cached from the very first lookup. That is, the client will merely get a new Context object from the “list of available RMI contexts” from the cache at the client side. The client will NOT go to the OPMN server again to get the list. That also implies that if you are adding a node to the server cluster AFTER the client’s initial lookup, the client would not know it because neither the server nor the client will initiate a refresh of the “list of available servers” to reflect the new node. About High Availability (i.e. Resilience Against Node Failure of Remote OC4J Cluster) What we have discussed above is about load balancing. Let's also discuss high availability. This is how the High Availability works in RMI: when the client use the context but get an exception such as socket is closed, it knows that the server referenced by that Context is problematic and will try to get another unused Context from the “list of available contexts”. Again, this list is the list that was returned and cached at the very first lookup in the entire client session.

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  • Shrink NTFS Windows 7 Partition with GParted

    - by user15961
    I am running a dual-boot system with Windows 7 and Ubuntu 10.10. Initially I allocated about 20GB for my Ubuntu partition; however, I quickly ran out of that space and am now looking to expand my partition. Currently my NTFS partition (450GB) has about 130GB of free space. I tried using GParted to shrink the partition but encountered the following error. I booted into windows so I could run chkdsk but the countdown freezes at 1 upon reboot. I tried multiple methods to resolve that issue but nothing seems to work. Finally I gave up, and now I just want to know what is the best way for me to force GParted to shrink the partition regardless of the errors. I don't really have anything important and I don't mind risking the data. I just don't want to wipe the entire NTFS partition because I don't have a Windows install CD and might require Windows later on for some programs. I tried using sudo ntfsresize but that spews out the same error as GParted... Any ideas? Check and repair file system (ntfs) on /dev/sda2 00:00:09 ( ERROR ) calibrate /dev/sda2 00:00:00 ( SUCCESS ) path: /dev/sda2 start: 36944325 end: 976771119 size: 939826795 (448.14 GiB) check file system on /dev/sda2 for errors and (if possible) fix them 00:00:09 ( ERROR ) ntfsresize -P -i -f -v /dev/sda2 ntfsresize v2.0.0 (libntfs 10:0:0) Device name : /dev/sda2 NTFS volume version: 3.1 Cluster size : 4096 bytes Current volume size: 481191318016 bytes (481192 MB) Current device size: 481191319040 bytes (481192 MB) Checking for bad sectors ... Checking filesystem consistency ... Cluster 63468 is referenced multiple times! Cluster 63469 is referenced multiple times! Cluster 63465 is referenced multiple times! Cluster 63466 is referenced multiple times! Cluster 63467 is referenced multiple times! Cluster 165621 is referenced multiple times! Cluster 165622 is referenced multiple times! Cluster 165623 is referenced multiple times! Cluster 165624 is referenced multiple times! ERROR: Filesystem check failed! ERROR: 9 clusters are referenced multiply times. NTFS is inconsistent. Run chkdsk /f on Windows then reboot it TWICE! The usage of the /f parameter is very IMPORTANT! No modification was and will be made to NTFS by this software until it gets repaired.

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  • Random select rows via JPA

    - by Ke
    In Mysql, SELECT id FROM table ORDER BY RANDOM() LIMIT 5 this sql can select 5 random rows. How to do this via JPA Query (Hibernate as provider, Mysql database)? Thanks.

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  • Tuning recommendations from mysqltuner.pl: query_cache_limit

    - by knorv
    The mysqltuner.pl script gives me the following recommendation: query_cache_limit (> 1M, or use smaller result sets) And MySQL status output shows: mysql> SHOW STATUS LIKE 'Qcache%'; +-------------------------+------------+ | Variable_name | Value | +-------------------------+------------+ | Qcache_free_blocks | 12264 | | Qcache_free_memory | 1001213144 | | Qcache_hits | 3763384 | | Qcache_inserts | 54632419 | | Qcache_lowmem_prunes | 0 | | Qcache_not_cached | 6656246 | | Qcache_queries_in_cache | 55280 | | Qcache_total_blocks | 122848 | +-------------------------+------------+ 8 rows in set (0.00 sec) From the status output above, how can I judge whether or nor the suggested increase in query_cache_limit is needed?

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  • NNTP usenet download messages

    - by stighy
    Hi stackoverflow gurus! I would like to download usenet messages to my personal Mysql database, so without using any newsreader. At the moment i'm using IpWorks component for .NET . I've created a simple app in Vb.Net, It works, but it's realy slow... to download and to do the INSERT INTO . Anyone know some better method to "massive" download message and insert it into a simple mysql table ? Thanks in advance !

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  • Foreign keys vs partitioning

    - by Industrial
    Hi! Since foreign keys are not supported by partitioned mySQL databases for the moment, I would like to hear some pro's and con's for a read-heavy application that will handle around 1-400 000 rows per table. Unfortunately, I dont have enough experience yet in this area to make the conclusion by myself... Thanks a lot! References: http://stackoverflow.com/questions/1537219/how-to-handle-foreign-key-while-partitioning http://stackoverflow.com/questions/2496140/mysql-partitioning-with-foreign-keys

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  • Importing wikipedia database dumb - kills navicat - anyone got any ideas?

    - by Ali
    Ok guys I've downloaded the wikipedia xml dump and its a whopping 12 GB of data :\ for one table and I wanted to import it into mysql databse on my localhost - however its a humongous file 12GB and obviously navicats taking its sweet time in importing it or its more likely its hanged :(. Is there a way to include this dump or atleast partially at most you know bit by bit. Let me correct that its 21 GB of data - not that it helps :\ - does any one have any idea of importing humongous files like this into MySQL database.

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  • Convert SQL query to Ruby help

    - by Verloren
    Hey all, I need to query my database table to find which employee has the most support tickets related to them. I can do this just fine using this MySQL query: SELECT employee_id, COUNT(id) AS number_of_tickets FROM tickets GROUP BY employee_id ORDER BY number_of_tickets DESC LIMIT 1; How would write this in Ruby-on-Rails? Thanks very much for your assistance. I use Ruby version 1.8.6, Rails version 2.2.2 and MySQL Server version 5.0.

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  • How to install python2.6-devel package under CentOs 5

    - by Creotiv
    I need to install mysql-python under python2.6. mysql-python package needs python2.6-devel package that depends on the libpython2.6.so.1.0(64bit) I found on the net some python2.6-devel packages, but can't find libpython2.6 Server architecture is x86_64. Maybe someone have this lib, or know where i can find it. Thanks for help)

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  • How to fill a drop down menu

    - by shinjuo
    I want to populate a drop down menu with a column from a MySQL database. I have the rest of my database set up, but at the moment it is just a text entry box and it would be easier just to select the actually entry from a list. Also does anyone know of a good tutorial or site that has tutorials and example codes for PHP and MySQL

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  • Database design for heavy timed data logging

    - by user293995
    Hi, I have an application where I receive each data 40.000 rows. I have 5 million rows to handle (500 Mb MySQL 5.0 database). Actually, thoses rows are stored in the same table = slow to update, hard to backup, ... Which king of scheme is used in such application to allow long term accessibility to the datas without problems with too big tables, easy backup, fast read / write ? Is postgresql better than mysql for such purpose ? Thanks in advance BEst regards

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  • 4 Minute Delay Between New User Registration and Receipt of Activation Email

    - by John
    Hello, I am using a PHP/MySQL login script that sends a new user an activation email. When a new user registers, the info is put into MySQL pretty much instantly, but then it takes about 4 minutes for the activation email to arrive in the new user's inbox. It seems like sites like Facebook and Twitter can get out an activation email instantly when a new user registers. Is there anything that I could do to make the activation email that I'm using arrive instantly or really fast? Thanks in advance, John

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  • Ruby on rails active-record generated SQL on Postgres

    - by jpartogi
    Dear all, Why does Ruby on rails generated more queries in the background on Postgres than MySQL? I haven't tried deploying Rails on production with Postgres yet, but I am just afraid this generated queries would affect the performance. Do you find Rails with Postgres is slower than MySQL, knowing that it produce more query on the background? Or it is relatively the same?

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  • ODBC vs MySQLClient

    - by Matt
    I'm currently using ODBC to connect to my MySQL database, using C#. I've been told that using the MySql Connector would be better, and faster, and not dependent on Windows. Can someone shed some light on this please? I've been unable to find anything on the net so far

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  • How to display a date as iso 8601 format with PHP

    - by Matthew James Taylor
    I'm trying to display a datetime from my MySQL database as an iso 8601 formated string with PHP but it's coming out wrong. 17 Oct 2008 is coming out as: 1969-12-31T18:33:28-06:00 which is clearly not correct (the year should be 2008 not 1969) This is the code I'm using: <?= date("c", $post[3]) ?> $post[3] is the datetime (CURRENT_TIMESTAMP) from my MySQL database. Any ideas what's going wrong?

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  • ALTER TABLE error

    - by Travis
    Can someone explain to me why I am receiving the following error? I want to rename the column "exerciseID" to "ID" in a mysql table using the following syntax. ALTER TABLE `exercises` CHANGE `exerciseID` `ID` INT( 11 ) NOT NULL AUTO_INCREMENT However I receive the following error: MySQL said: #1025 - Error on rename of './balance/#sql-de_110e' to './balance/exercises' (errno: 150) Any suggestions would be much appreciated

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  • Good tool to visualise database schema?

    - by Mat
    Are there any good tools for visualising a pre-existing database schema? I'm using MySQL if it matters. I'm currently using MySQL Workbench to process an SQL create script dump, but it's clunky, slow and a manual process to drag all the tables about (which would be okay if it wasn't so slow).

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  • What exactly this error is?

    - by user144842
    Database i am using is MySQL 5.1. I specified, i believe, right connectionstring in my web.config. but when i run my web app. it throws this exception:- MySql.Data.MySqlClient.MySqlException: The user specified as a definer ('root'@'%') does not exist Any help. Why am i getting this?

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  • Need help with this SQL

    - by Bragaadeesh
    Hi guys, I am very very new to mysql. I am trying to execute the following query. update share set holder = 22 where SHARE_ID IN (select SHARE_ID from SHARE WHERE holder=1 LIMIT 10) When I try to execute the above query I am getting this error #1235 - This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME subquery'

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  • Combining two UPDATE Commands - Performance ?

    - by Johannes
    If I want to update two rows in a MySQL table, using the following two command: UPDATE table SET Col = Value1 WHERE ID = ID1 UPDATE table SET Col = Value2 WHERE ID = ID2` I usually combine them into one command, so that I do not to have to contact the MySQL server twice from my C client: UPDATE table SET Col = IF( ID = ID1 , Value1 , Value2) WHERE ID=ID1 OR ID=ID2 Is this really a performance gain? Background Information: I am using a custom made fully C written high-performance heavily loaded webserver.

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