Re: C api mysql_store_result vs mysql_use_result
- Original Message - From: Alex Schaft al...@quicksoftware.co.za If I were to do a select count(*) from x where y prior to doing select * from x where y to get a number of records, how would this impact performance on the server itself? Would the first query be the one to do the most processing, with the second one being faster, or would both have to do the same amount of work? Heh. The amount of work put into parsing and executing would be the same, except if you can compose your count query to use only indexed fields. Easily checked with an explain of both queries, I'd say. Also, do consider if you really need a %complete progress indicator, or if a simple record counter with no indicated endpoint will do. That is, do your users need to know how long it's going to take, or do they just want assurance that the process didn't hang? -- Bier met grenadyn Is als mosterd by den wyn Sy die't drinkt, is eene kwezel Hy die't drinkt, is ras een ezel -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
Re: C api mysql_store_result vs mysql_use_result
On 2012/02/09 01:40 PM, Johan De Meersman wrote: - Original Message - From: Alex Schaftal...@quicksoftware.co.za If I were to do a select count(*) from x where y prior to doing select * from x where y to get a number of records, how would this impact performance on the server itself? Would the first query be the one to do the most processing, with the second one being faster, or would both have to do the same amount of work? Heh. The amount of work put into parsing and executing would be the same, except if you can compose your count query to use only indexed fields. Easily checked with an explain of both queries, I'd say. Also, do consider if you really need a %complete progress indicator, or if a simple record counter with no indicated endpoint will do. That is, do your users need to know how long it's going to take, or do they just want assurance that the process didn't hang? From the user's perspective, they just need to know the process didn't hang. The count() query is more for getting memory requirements upfront. Can I handle it all, or do I need to break it down into pages? -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
conditional updating
I want to update a date field in a record. if the date in the field is -00-00 I want to change it to the current date. I would appreciate suggestions or links on how to do this. Yup, tried reading the manual, but need a bit of help. I will be updating another field at the same time. bill -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
Re: conditional updating
untested: update set mydate = IF(mydate = '-00-00', now(), mydate) - michael dykman On Thu, Feb 9, 2012 at 8:14 AM, william drescher will...@techservsys.com wrote: I want to update a date field in a record. if the date in the field is -00-00 I want to change it to the current date. I would appreciate suggestions or links on how to do this. Yup, tried reading the manual, but need a bit of help. I will be updating another field at the same time. bill -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql -- - michael dykman - mdyk...@gmail.com May the Source be with you. -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
Re: conditional updating
Update table set mydate=now() where mydate='-00-00'; should do it. Sent from my iPad On Feb 9, 2012, at 7:15 AM, william drescher will...@techservsys.com wrote: I want to update a date field in a record. if the date in the field is -00-00 I want to change it to the current date. I would appreciate suggestions or links on how to do this. Yup, tried reading the manual, but need a bit of help. I will be updating another field at the same time. bill -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
Re: C api mysql_store_result vs mysql_use_result
- Original Message - From: Alex Schaft al...@quicksoftware.co.za From the user's perspective, they just need to know the process didn't hang. The count() query is more for getting memory requirements upfront. Can I handle it all, or do I need to break it down into pages? Then just use the cursor-based api (I guess that's mysql_use_result) all the time, and you won't have any memory problems at all. If you need to retrieve pages (as in, the third block of 10 results, for instance) LIMIT is your friend. Do read the documentation on limit, though - there's performance caveats when you use order by and similar. -- Bier met grenadyn Is als mosterd by den wyn Sy die't drinkt, is eene kwezel Hy die't drinkt, is ras een ezel -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
Re: conditional updating
On 2/9/2012 8:22 AM, Johnny Withers wrote: Update table set mydate=now() where mydate='-00-00'; should do it. can't do that because the record is selected by other criteria. Thanks bill -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
Re: conditional updating
Am 09.02.2012 14:55, schrieb william drescher: On 2/9/2012 8:22 AM, Johnny Withers wrote: Update table set mydate=now() where mydate='-00-00'; should do it. can't do that because the record is selected by other criteria. so explain the criteria, show us the query usually you do exatcly the same WHERE as for the select and add and mydate='-00-00' signature.asc Description: OpenPGP digital signature
Re: conditional updating
On 2/9/2012 8:18 AM, Michael Dykman wrote: untested: update set mydate = IF(mydate = '-00-00', now(), mydate) - michael dykman Thank you very much ! bill On Thu, Feb 9, 2012 at 8:14 AM, william drescher will...@techservsys.com wrote: I want to update a date field in a record. if the date in the field is -00-00 I want to change it to the current date. I would appreciate suggestions or links on how to do this. Yup, tried reading the manual, but need a bit of help. I will be updating another field at the same time. bill -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
Re: conditional updating
So, add your other criteria to the where clause, you failed to say there were other conditions in your first email. Sent from my iPad On Feb 9, 2012, at 7:56 AM, william drescher will...@techservsys.com wrote: On 2/9/2012 8:22 AM, Johnny Withers wrote: Update table set mydate=now() where mydate='-00-00'; should do it. can't do that because the record is selected by other criteria. Thanks bill -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
Re: conditional updating
He did mention that there was another field he was updating, which implies that the state of the date field was not the only condition. - michael On Thu, Feb 9, 2012 at 9:22 AM, Johnny Withers joh...@pixelated.net wrote: So, add your other criteria to the where clause, you failed to say there were other conditions in your first email. Sent from my iPad On Feb 9, 2012, at 7:56 AM, william drescher will...@techservsys.com wrote: On 2/9/2012 8:22 AM, Johnny Withers wrote: Update table set mydate=now() where mydate='-00-00'; should do it. can't do that because the record is selected by other criteria. Thanks bill -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql -- - michael dykman - mdyk...@gmail.com May the Source be with you. -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
Re: Tuning mysql
Grant emailgr...@gmail.com wrote: I'm running mysql on Gentoo with 4GB RAM and I'm wondering if I should change any settings. I'm using mysql with a website on the same server so I have skip-networking, and I increased key_buffer and innodb_buffer_pool_size from 16M to 256M. Everything else is default. Should I consider changing these or any other settings? pt-variable-advisor from percona-toolkit (http://www.percona.com/downloads/percona-toolkit/2.0.3/) Giovanni -- /* * SnB - Hosting and software solutions * http://www.snb.it */ -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
Re: Tuning mysql
Good advice, all of it. What hasn't been said and should be noted: in most cases, the bottleneck is the queries themselves. You will generally get a lot more boost from tuning those than from any configuration tweaking (excepting the pathological cases). - michael dykman On Thu, Feb 9, 2012 at 10:52 AM, Giovanni Bechis bi...@snb.it wrote: Grant emailgr...@gmail.com wrote: I'm running mysql on Gentoo with 4GB RAM and I'm wondering if I should change any settings. I'm using mysql with a website on the same server so I have skip-networking, and I increased key_buffer and innodb_buffer_pool_size from 16M to 256M. Everything else is default. Should I consider changing these or any other settings? pt-variable-advisor from percona-toolkit (http://www.percona.com/downloads/percona-toolkit/2.0.3/) Giovanni -- /* * SnB - Hosting and software solutions * http://www.snb.it */ -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql -- - michael dykman - mdyk...@gmail.com May the Source be with you. -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
Re: conditional updating
It implied to me there were two fields to update based on the date being a given value. Read it how you like. Sent from my iPad On Feb 9, 2012, at 9:34 AM, Michael Dykman mdyk...@gmail.com wrote: He did mention that there was another field he was updating, which implies that the state of the date field was not the only condition. - michael On Thu, Feb 9, 2012 at 9:22 AM, Johnny Withers joh...@pixelated.net wrote: So, add your other criteria to the where clause, you failed to say there were other conditions in your first email. Sent from my iPad On Feb 9, 2012, at 7:56 AM, william drescher will...@techservsys.com wrote: On 2/9/2012 8:22 AM, Johnny Withers wrote: Update table set mydate=now() where mydate='-00-00'; should do it. can't do that because the record is selected by other criteria. Thanks bill -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql -- - michael dykman - mdyk...@gmail.com May the Source be with you. -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
About mysql++3.1.0 SET TRANSACTION ISOLATION LEVEL
Hello:
I foud a question about function of transaction.
In this function switch not have break
Transaction::Transaction(Connection conn, IsolationLevel level,
IsolationScope scope, bool consistent) :
conn_(conn),
finished_(true) // don't bother rolling it back if ctor fails
{
// Set the transaction isolation level and scope as the user wishes
Query q(conn_.query(SET ));
if (scope == session) q SESSION ;
if (scope == global) q GLOBAL ;
q TRANSACTION ISOLATION LEVEL ;
switch (level) {
case read_uncommitted: q READ UNCOMMITTED;
case read_committed:q READ COMMITTED;
case repeatable_read:q REPEATABLE READ;
case serializable: q SERIALIZABLE;
}
Qiufeng Chen
陈秋丰
360平台研发部
[说明: 说明: 说明: 说明: 2-1-26 邮件格]
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Installing Mysql-Workbench
Dear All, I researched about data modelling designing Schema diagrams need a tool to design Schema diagrams. Today i download the source code of Mysql-Workbench ( mysql-workbench-gpl-5.2.37-src ), but when i run the ./configure command i am facing the below issue :- checking for GNOME... configure: error: Package requirements (gtkmm-2.4 = 2.12) were not met: Requested 'gtkmm-2.4 = 2.12' but version of gtkmm is 2.10.10 Consider adjusting the PKG_CONFIG_PATH environment variable if you installed software in a non-standard prefix. Alternatively, you may set the environment variables GNOME_CFLAGS and GNOME_LIBS to avoid the need to call pkg-config. See the pkg-config man page for more details. I know I need to meet some dependencies , and is there any link that first installs all dependencies 7 then mysql-workbench because my yum install dependencies does not find the corresponding packages. Thanks in Advance. -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
