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One of my most frequently used commands

- by Kevin Smith

On a Linux or UNIX server this is one of my most frequently used commands. find . -name "*.htm" -exec grep -iH "alter session" {} \; It is an easy way to find a string you know is in a group of files, but don't know or can't remember which file it is in. For the example above, I knew that WebCenter Content sends a bunch of alter session commands to the database when it opens a new database connection. I wanted to find where these were defined and what all the alter session commands were. So, I ran these commands: cd /opt/oracle/middleware/Oracle_ECM1/ucm/idc/resources/core find . -name "*.htm" -exec grep -iH "alter session" {} \; And the results were: ./tables/query.htm: ALTER SESSION SET optimizer_mode = ?./tables/query.htm: ALTER SESSION SET NLS_LENGTH_SEMANTICS = ?./tables/query.htm: ALTER SESSION SET NLS_SORT = ?./tables/query.htm: ALTER SESSION SET NLS_COMP = ?./tables/query.htm: ALTER SESSION SET CURSOR_SHARING = ?./tables/query.htm: ALTER SESSION SET EVENTS '30579 trace name context forever, level 2'./tables/query.htm: ALTER SESSION SET NLS_DATE_FORMAT = ?./tables/query.htm: alter session set events '30579 trace name context forever, level 2' I could then go edit the query.htm file and find the include that contained all the ALTER SESSION commands.

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How to 301 redirect from old query string urls to CakePHP Canonical urls?

- by Daniel Bingham

I currently have a .htaccess file that looks like this: RewriteCond %{QUERY_STRING} ^action=view&item=([0-9]+)$ RewriteRule ^index\.php$ /index.php?url=item/%1 [R=301] RewriteCond %{REQUEST_FILENAME} !-d RewriteCond %{REQUEST_FILENAME} !-f RewriteRule ^(.*)$ index.php?url=$1 [QSA,L] It is meant to 301 redirect my old query string based URLs to new CakePHP urls. This will successfully send users to the correct page. However, Google doesn't seem to like it (see below). I previously tried doing this: RewriteCond %{QUERY_STRING} ^action=view&item=([0-9]+)$ RewriteRule ^index\.php$ /item/%1 [R=301] RewriteCond %{REQUEST_FILENAME} !-d RewriteCond %{REQUEST_FILENAME} !-f RewriteRule ^(.*)$ index.php?url=$1 [QSA,L] But that fails. The second rewrite rule doesn't seem to catch the rewritten URL. It goes straight through. Using the first version wouldn't be a problem, except that I suspect that is what is choking up Google. It hasn't indexed my sitemap full of the new URLs. My old sitemap had been fully indexed and all the URLs are in Google's index. But it isn't following the redirects from the old URLs to the new. I have a 'not followed' error for every one of the query urls that was in my old sitemap. Am I properly using a 301 redirect here? Is it the weird rewrite rule? What can I do to send both Google and users to the proper page and save my page rank?

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Generalise variable usage inside code

- by Shirish11

I would like to know if it is a good practice to generalize variables (use single variable to store all the values). Consider simple example Strings querycre,queryins,queryup,querydel; querycre = 'Create table XYZ ...'; execute querycre ; queryins = 'Insert into XYZ ...'; execute queryins ; queryup = 'Update XYZ set ...'; execute queryup; querydel = 'Delete from XYZ ...'; execute querydel ; and Strings query; query= 'Create table XYZ ... '; execute query ; query= 'Insert into XYZ ...'; execute query ; query= 'Update XYZ set ...'; execute query ; query= 'Delete from XYZ ...'; execute query ; In first case I use 4 strings each storing data to perform the actions mentioned in their suffixes. In second case just 1 variable to store all kinds the data. Having different variables makes it easier for someone else to read and understand it better. But having too many of them makes it difficult to manage. Also does having too many variables hamper my performance?

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Which database to use for quickly and pygtk

- by usher

I'm writing application using quickly Pygtk and glade. this application should have database connection (such as MySQL) for reading and writing data from the local or outsourcing machine \ server. However, in my machine there is MySQL installed, but when releasing the app it sould be installed on another ubuntu machine, which may not have mysql and moreover not the same database with the required database name and structure.... So my questions are: Is it a good choice using mysql as database 1.2 If not what is? Is it posible to embeding mysql or other database program during the installation from ubuntu software center? 2.2 If it's posible: hwo(any tutorial?) Where to store secure data outside the mysql (or whatever) for conecting the database every time a user launch the application

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How to choose between Tell don't Ask and Command Query Separation?

- by Dakotah North

The principle Tell Don't Ask says: you should endeavor to tell objects what you want them to do; do not ask them questions about their state, make a decision, and then tell them what to do. The problem is that, as the caller, you should not be making decisions based on the state of the called object that result in you then changing the state of the object. The logic you are implementing is probably the called object’s responsibility, not yours. For you to make decisions outside the object violates its encapsulation. A simple example of "Tell, don't Ask" is Widget w = ...; if (w.getParent() != null) { Panel parent = w.getParent(); parent.remove(w); } and the tell version is ... Widget w = ...; w.removeFromParent(); But what if I need to know the result from the removeFromParent method? My first reaction was just to change the removeFromParent to return a boolean denoting if the parent was removed or not. But then I came across Command Query Separation Pattern which says NOT to do this. It states that every method should either be a command that performs an action, or a query that returns data to the caller, but not both. In other words, asking a question should not change the answer. More formally, methods should return a value only if they are referentially transparent and hence possess no side effects. Are these two really at odds with each other and how do I choose between the two? Do I go with the Pragmatic Programmer or Bertrand Meyer on this?

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Recompiling an old fortran 2/4\66 program that was compiled for os\2 need it to run in dos

- by Mike Hansen

I am helping an old scientist with some problems and have 1 program that he found and modified about 20 yrs. ago, and runs fine as a 32 bit os\2 executable but i need it to run under dos! I am not a programmer but a good hardware & software man, so I'am pretty stupid about this problem, but here go's I have downloaded 6 different compilers watcom77,silverfrost ftn95,gfortran,2 versions of g77 and f80. Watcom says it is to old of program,find older compiler,silverfrost opens it,debugs, etc. but is changing all the subroutines from "real" to "complex" and vice-vesa,and the g77's seem to install perfectly (library links and etc.) but wont even compile the test.f programs.My problem is 1; to recompile "as is" or "upgrade" the code? PROGRAM xconvlv INTEGER N,N2,M PARAMETER (N=2048,N2=2048,M=128) INTEGER i,isign REAL data(n),respns(m),resp(n),ans(n2),t3(n),DUMMY OPEN(UNIT=1, FILE='C:\QKBAS20\FDATA1.DAT') DO 1 i=1,N READ(1,*) T3(i), data(i), DUMMY continue CLOSE(UNIT-1) do 12 i=1,N respns(i)=data(i) resp(i)=respns(i) continue isign=-1 call convlv(data,N,resp,M,isign,ans) OPEN(UNIT=1,FILE='C:\QKBAS20\FDATA9.DAT') DO 14 i=1,N WRITE(1,*) T3(i), ans(i) continue END SUBROUTINE CONVLV(data,n,respns,m,isign,ans) INTEGER isign,m,n,NMAX REAL data(n),respns(n) COMPLEX ans(n) PARAMETER (NMAX=4096) * uses realft, twofft INTEGER i,no2 COMPLEX fft (NMAX) do 11 i=1, (m-1)/2 respns(n+1-i)=respns(m+1-i) continue do 12 i=(m+3)/2,n-(m-1)/2 respns(i)=0.0 continue call twofft (data,respns,fft,ans,n) no2=n/2 do 13 i=1,no2+1 if (isign.eq.1) then ans(i)=fft(i)*ans(i)/no2 else if (isign.eq.-1) then if (abs(ans(i)) .eq.0.0) pause ans(i)=fft(i)/ans(i)/no2 else pause 'no meaning for isign in convlv' endif continue ans(1)=cmplx(real (ans(1)),real (ans(no2+1))) call realft(ans,n,-1) return END SUBROUTINE realft(data,n,isign) INTEGER isign,n REAL data(n) * uses four1 INTEGER i,i1,i2,i3,i4,n2p3 REAL c1,c2,hli,hir,h2i,h2r,wis,wrs DOUBLE PRECISION theta,wi,wpi,wpr,wr,wtemp theta=3.141592653589793d0/dble(n/2) cl=0.5 if (isign.eq.1) then c2=-0.5 call four1(data,n/2,+1) else c2=0.5 theta=-theta endif (etc.,etc., etc.) SUBROUTINE twofft(data,data2,fft1,fft2,n) INTEGER n REAL data1(n,data2(n) COMPLEX fft1(n), fft2(n) * uses four1 INTEGER j,n2 COMPLEX h1,h2,c1,c2 c1=cmplx(0.5,0.0) c2=cmplx(0.0,-0.5) do 11 j=1,n fft1(j)=cmplx(data1(j),data2(j) continue call four1 (fft1,n,1) fft2(1)=cmplx(aimag(fft1(1)),0.0) fft1(1)=cmplx(real(fft1(1)),0.0) n2=n+2 do 12 j=2,n/2+1 h1=c1*(fft1(j)+conjg(fft1(n2-j))) h2=c2*(fft1(j)-conjg(fft1(n2-j))) fft1(j)=h1 fft1(n2-j)=conjg(h1) fft2(j)=h2 fft2(n2-j)=conjg(h2) continue return END SUBROUTINE four1(data,nn,isign) INTEGER isign,nn REAL data(2*nn) INTEGER i,istep,j,m,mmax,n REAL tempi,tempr DOUBLE PRECISION theta, wi,wpi,wpr,wr,wtemp n=2*nn j=1 do 11 i=1,n,2 if(j.gt.i)then tempr=data(j) tempi=data(j+1) (etc.,etc.,etc.,) continue mmax=istep goto 2 endif return END There are 4 subroutines with this that are about 3 pages of code and whould be much easier to e-mail to someone if their able to help me with this.My e-mail is [email protected] , or if someone could tell me where to get a "working" compiler that could recompile this? THANK-YOU, THANK-YOU,and THANK-YOU for any help with this! The errors Iam getting are; 1.In a call to CONVLV from another procedure,the first argument was of a type REAL(kind=1), it is now a COMPLEX(kind=1) 2.In a call to REALFT from another procedure, ... COMPLEX(kind=1) it is now a REAL(kind=1) 3.In a call to TWOFFT from...COMPLEX(kind-1) it is now a REAL(kind=1) 4.In a previous call to FOUR1, the first argument was of a type REAL(kind=1) it is now a COMPLEX(kind=1).

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Syntax error in INSERT INTO statement

- by user454563

I wrote a program that connects to MS Access. When I fill in the fields and add a new item to Access the program fails. The exception is "Syntax error in INSERT INTO statement" Here is the relevant code. **************************************************************** AdoHelper.cs **************************************************************** using System; using System.Collections.Generic; using System.Text; using System.Data; using System.Data.OleDb; namespace Yad2 { class AdoHelper { //get the connection string from the app.config file //Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\Yad2.accdb static string connectionString = Properties.Settings.Default.DBConnection.ToString(); //declare the db connection static OleDbConnection con = new OleDbConnection(connectionString); /// <summary> /// To Execute queries which returns result set (table / relation) /// </summary> /// <param name="query">the query string</param> /// <returns></returns> public static DataTable ExecuteDataTable(string query) { try { con.Open(); OleDbCommand command = new OleDbCommand(query, con); System.Data.OleDb.OleDbDataAdapter tableAdapter = new System.Data.OleDb.OleDbDataAdapter(command); DataTable dt = new DataTable(); tableAdapter.Fill(dt); return dt; } catch (Exception ex) { throw ex; } finally { con.Close(); } } /// <summary> /// To Execute update / insert / delete queries /// </summary> /// <param name="query">the query string</param> public static void ExecuteNonQuery(string query) { try { con.Open(); System.Data.OleDb.OleDbCommand command = new System.Data.OleDb.OleDbCommand(query, con); command.ExecuteNonQuery(); } catch (Exception ex) { throw ex; } finally { con.Close(); } } /// <summary> /// To Execute queries which return scalar value /// </summary> /// <param name="query">the query string</param> public static object ExecuteScalar(string query) { try { con.Open(); System.Data.OleDb.OleDbCommand command = new System.Data.OleDb.OleDbCommand(query, con); /// here is the Excaption !!!!!!!!! return command.ExecuteScalar(); } catch { throw; } finally { con.Close(); } } } } **************************************************************************** **************************************************************************** DataQueries.cs **************************************************************************** using System; using System.Collections.Generic; using System.Text; using System.Data; namespace Yad2 { class DataQueries { public static DataTable GetAllItems() { try { string query = "Select * from Messages"; DataTable dt = AdoHelper.ExecuteDataTable(query); return dt; } catch (Exception ex) { throw ex; } } public static void AddNewItem(string mesNumber, string title , string mesDate , string contactMail , string mesType , string Details ) { string query = "Insert into Messages values(" + mesNumber + " , '" + title + "' , '" + mesDate + "' , '" + contactMail + "' , , '" + mesType + "' , '" + Details + "')"; AdoHelper.ExecuteNonQuery(query); } public static void DeleteDept(int mesNumber) { string query = "Delete from Item where MessageNumber=" + mesNumber; AdoHelper.ExecuteNonQuery(query); } } } *********************************************************************************************** plase help me .... why the program falls ?

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how to cause linux system datetime to run faster than real world datetime?

- by JamesThomasMoon1979

Background I want to monitor a running linux system over several days. It's a custom gentoo build and with much custom software on board. This software has ongoing maintenance timers and cron scripts and other clock driven events. I need to verify these scheduled events are working. Problem Waiting for the system to step through daily and weekly activity is a long wait time. And modifying all clock-based timers on the system would be time consuming. Yet, I often want to test a system's end-to-end scheduled activities without waiting a week. Potential Solution Have the linux system under test appear to run through it's daily cycle of activity within just a few hours. My Question for Serverfault Is there a way to cause the system's time to run faster than real world time? My first thought is manipulating the ntp daemon to repeatedly and smoothly increment the clock . Any other ideas? And yes, I know this may have strange side affects. However, the system has no important or time critical interactions with systems outside of itself. And this may be a valuable testing technique.

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Why are snapshots considered as temporary backups not real backups?

- by Samselvaprabu

I am using VMware ESXi. In our team we use to provide snapshots for long term backup. Then we faced issues like memory spillover and the server got hang up. I started reading in VMware knowledgebase articles and everywhere. Everywhere it was recommended not to have snapshots for a long time. Even VMware advised to keep snapshots for maximum of three days. But our team kept asking us to have at least two permanent snapshots (till deleting the VM). Sometimes we may use the VM for a year). one snapshot is for fresh machine state. (So when we complete testing an application, we will revert back to fresh state and install another application) (If I did not allow that, I may often need to host the VM.) Next snapshot for keeping the VM in some state (maybe they would have found an issue and keep that state for some time. Or they may install prerequisites for the application and keep the machine ready for testing.) Logically, their needs seems to be fair. But if I allow that, I am to permit them to hold the snapshots for long time. We are not using our VM as a mail server or database server. Why is keeping snapshots for long time having an adverse effect? Why are snapshots considered as temporary backups, not real backups?

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Is there a program to show programs loading during the boot process in real time?

- by Gary M. Mugford

Hi all, There are any number of programs that will show me WHAT will run during the boot process for Windows XP. I've always been partial to Mike Lin's version but there are several others, some of which are quite possibly superior. That's not the issue. What I'd really like is a program that would load first and then would list the programs that were about to load and then check them off as the programs loaded. This isn't something I necessarily need for myself. But certain family members get click happy as soon as they see the icon they eventually want to run and end up clicking on it. THIRTY TWO TIMES in one memorable crash-inducing spasm. If there was some way for 'progress' to be shown during the loading of from the various spots Windows auto-loads from, PLUS a BIG BANNER saying "Please do not move the mouse or click on anything until done.", I think I might cut down on my early morning family support calls significantly. I've tried a variety of searches, but I couldn't find the ones that show in real time in the forest of links to programs that will show the list after the fact. Any leads? If not, do any of you who write the after-the-fact listers want to take a shot at producing a utility to do what I think would be a relatively popular utility? Best of the season to all of you and yours. Thanks in advance for any replies, GM

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Anyone have real world experience with Rackspace Cloud Sites at high scale?

- by Allara

I have a pure web service application layer using .NET. I was originally planning to use Amazon EC2, but rolling my own autoscaling procedures is a bit intimidating, and the scaling isn't very granular from a cost perspective. If the app is successful, we could be looking at relatively high scale (millions of requests per month). The app uses Amazon SimpleDB as the database layer. As a test, I have the app running successfully in Rackspace Cloud Sites. Performance seems to be equal to (if not better than) a standard EC2 instance, even with the added latency of the SimpleDB requests travelling to the Rackspace network. However, testing at this stage is at a very low scale. My question is this: has anyone had real-world experience running a high scale application on Rackspace Cloud Sites? Moreover, once you pass the "included" 10,000 compute cycles per month, does the overall cost seem to be lower than rolling lots of EC2 instances? My assumption would be that with completely smooth scaling (i.e. only adding compute resources as needed), the cost could be lower on average. However, their stated goal of calibrating 10,000 CCs as a single 1.2 Ghz CPU seems on average to be much more expensive than EC2. I like the idea of no-touch scaling, but is it too good to be true?

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How to boost playback volume in real time on media recorded with a very low volume.

- by L Marksman

I have never heard a satisfactory answer to this often misunderstood question, let me explain. Lets say I have a sound card and earphones/speakers that can play back audio loud enough in most cases. This is great but the problem is that you always find people who do not know how to record audio, from Youtube video's to music. So now you end up with a audio playback that only uses 10% or less of the capacity of your sound hardware, in vista/win 7 you will see this frequently in the mixer with the volume pushed up to max but the green sound level only goes up a millimeter or two. I am looking for (preferably free) software or a method to boost the sound level of any audio from any source in real time to use more of my hardware capacity similar to what VLC media player can do. Oh and please, do not tell me it is impossible. I am not trying to boost the volume past what my hardware is capable of, I am just trying to use my hardware's full capacity. Also please do not tell met to buy new hardware, I know I can use hardware amplification, I don't want to (like many others) spend money on a simple little problem like this. Thanks!

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Postfix not sending/allowing receiving of messages after server (hardware) changed

- by 537mfb

We had na old notebook runing Ubuntu 12.04 working as a web/ftp/mail server and it worked but since the notebook was a notebook and pretty old and unreliable, a desktop was bought to replace it before it stopped working all together. Due to issues with the new desktop's vídeo card, we couldn't use Ubuntu 12.04 so we installed Ubuntu 13.10 and wen't about configuring it. Since we removed the notebook from the network, we kept the same Computer Name and local IP address to make things as close to the old server as possible configuration-wise. However, something has gone wrong since Postfix is throwing error 451 4.3.0 lookup faillure on every attempt to send a mail, and no email can be received either. Our main.cf file is a copy of the one we were using (and working) on the old server (notice we use EHCP) # See /usr/share/postfix/main.cf.dist for a commented, more complete version # Debian specific: Specifying a file name will cause the first # line of that file to be used as the name. The Debian default # is /etc/mailname. #myorigin = /etc/mailname smtpd_banner = $myhostname ESMTP $mail_name powered by Easy Hosting Control Panel (ehcp) on Ubuntu, www.ehcp.net biff = no # appending .domain is the MUA's job. append_dot_mydomain = no # Uncomment the next line to generate "delayed mail" warnings #delay_warning_time = 4h readme_directory = no myhostname = m21-traducoes.com.pt relayhost = mydestination = localhost, 89.152.248.139 mynetworks = 127.0.0.0/8, 192.168.0.0/16, 172.16.0.0/16, 10.0.0.0/8, 89.152.248.0/24 virtual_alias_domains = virtual_alias_maps = proxy:mysql:/etc/postfix/mysql-virtual_forwardings.cf, proxy:mysql:/etc/postfix/mysql-virtual_email2email.cf transport_maps = proxy:mysql:/etc/postfix/mysql-virtual_transports.cf virtual_mailbox_domains = proxy:mysql:/etc/postfix/mysql-virtual_domains.cf virtual_mailbox_maps = proxy:mysql:/etc/postfix/mysql-virtual_mailboxes.cf virtual_mailbox_base = /home/vmail virtual_uid_maps = static:5000 virtual_gid_maps = static:5000 smtpd_sasl_auth_enable = yes smtpd_sasl_security_options = noanonymous broken_sasl_auth_clients = yes smtpd_recipient_restrictions = permit_mynetworks,permit_sasl_authenticated,check_client_access hash:/var/lib/pop-before-smtp/hosts,reject_unauth_destination smtp_use_tls = yes smtpd_use_tls = yes smtpd_tls_auth_only = no smtpd_tls_CAfile = /etc/postfix/cacert.pem smtpd_tls_cert_file = /etc/postfix/smtpd.cert smtpd_tls_key_file = /etc/postfix/smtpd.key smtpd_tls_loglevel = 1 smtpd_tls_received_header = yes smtpd_tls_session_cache_timeout = 3600s tls_random_source = dev:/dev/urandom virtual_create_maildirsize = yes virtual_mailbox_extended = yes virtual_mailbox_limit_maps = proxy:mysql:/etc/postfix/mysql-virtual_mailbox_limit_maps.cf virtual_mailbox_limit_override = yes virtual_maildir_limit_message = "The user you are trying to reach is over quota." virtual_overquota_bounce = yes debug_peer_list = sender_canonical_maps = debug_peer_level = 1 proxy_read_maps = $local_recipient_maps $mydestination $virtual_alias_maps $virtual_alias_domains $virtual_mailbox_maps $virtual_mailbox_domains $relay_recipient_maps $canonical_maps $sender_canonical_maps $recipient_canonical_maps $relocated_maps $mynetworks $virtual_mailbox_limit_maps $transport_maps alias_maps = hash:/etc/aliases smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated,check_client_access hash:/var/lib/pop-before-smtp/hosts,reject_unauth_destination smtpd_destination_concurrency_limit = 2 smtpd_destination_rate_delay = 1s smtpd_extra_recipient_limit = 10 disable_vrfy_command = yes smtpd_delay_reject = yes smtpd_helo_required = yes smtpd_error_sleep_time = 1s smtpd_soft_error_limit = 10 smtpd_hard_error_limit = 20 This configuration was working before but now everytime i try to send a mail in squirrelmail it reports: Message not sent. Server replied: Requested action aborted: error in processing 451 4.3.0 <[email protected]>: Temporary lookup failure And i can't send mail to it from outsider either. Any ideas? EDIT: Here are some issues MXToolBox reports to my domain, answering hopefully to @Teun Vink: BlackList Mail Server Web Server DNS Error 4 0 2 0 Warnings 0 0 0 3 Passed 0 6 3 12 So the domain is on some blacklist, but that doesn't explain the error at all No mail server issues found (except it's not working) Those two web server errors it's because i don't have HTTPS workin (No SSL Certificate) so the test fails Those 3 DNS warnings we're already there when it was working with the other machine and are related to stuff i can't control: SOA Refresh Value is outside of the recommended range SOA Expire Value out of recommended range SOA NXDOMAIN Value too high I've searched and as far as i can tell only the guys who sold the retail can change those values and they won't. Edit2: I half solved the issue.on the new machine postfix was installed but postfix-mysql waasn't so he couldn't connect to the database (rookie mistake). After fixing that, i can now send mails to the outsider without any issues, however i am still not able to receive mails from utside. The sender doesn't get any message warning about the non-delivery but the message doesn't fall in the inbox and the log shows: Nov 13 15:11:57 m21-traducoes postfix/smtpd[5872]: NOQUEUE: reject: RCPT from re lay4.ptmail.sapo.pt[212.55.154.24]: 451 4.3.5 <relay4.ptmail.sapo.pt[212.55.154. 24]>: Client host rejected: Server configuration error; from=<[email protected]> to=<[email protected]> proto=SMTP helo=<sapo.pt> Nov 13 15:11:57 m21-traducoes postfix/smtpd[5872]: disconnect from relay4.ptmail .sapo.pt[212.55.154.24]

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How to reduce Entity Framework 4 query compile time?

- by Rup

Summary: We're having problems with EF4 query compilation times of 12+ seconds. Cached queries will only get us so far; are there any ways we can actually reduce the compilation time? Is there anything we might be doing wrong we can look for? Thanks! We have an EF4 model which is exposed over the WCF services. For each of our entity types we expose a method to fetch and return the whole entity for display / edit including a number of referenced child objects. For one particular entity we have to .Include() 31 tables / sub-tables to return all relevant data. Unfortunately this makes the EF query compilation prohibitively slow: it takes 12-15 seconds to compile and builds a 7,800-line, 300K query. This is the back-end of a web UI which will need to be snappier than that. Is there anything we can do to improve this? We can CompiledQuery.Compile this - that doesn't do any work until first use and so helps the second and subsequent executions but our customer is nervous that the first usage shouldn't be slow either. Similarly if the IIS app pool hosting the web service gets recycled we'll lose the cached plan, although we can increase lifetimes to minimise this. Also I can't see a way to precompile this ahead of time and / or to serialise out the EF compiled query cache (short of reflection tricks). The CompiledQuery object only contains a GUID reference into the cache so it's the cache we really care about. (Writing this out it occurs to me I can kick off something in the background from app_startup to execute all queries to get them compiled - is that safe?) However even if we do solve that problem, we build up our search queries dynamically with LINQ-to-Entities clauses based on which parameters we're searching on: I don't think the SQL generator does a good enough job that we can move all that logic into the SQL layer so I don't think we can pre-compile our search queries. This is less serious because the search data results use fewer tables and so it's only 3-4 seconds compile not 12-15 but the customer thinks that still won't really be acceptable to end-users. So we really need to reduce the query compilation time somehow. Any ideas? Profiling points to ELinqQueryState.GetExecutionPlan as the place to start and I have attempted to step into that but without the real .NET 4 source available I couldn't get very far, and the source generated by Reflector won't let me step into some functions or set breakpoints in them. The project was upgraded from .NET 3.5 so I have tried regenerating the EDMX from scratch in EF4 in case there was something wrong with it but that didn't help. I have tried the EFProf utility advertised here but it doesn't look like it would help with this. My large query crashes its data collector anyway. I have run the generated query through SQL performance tuning and it already has 100% index usage. I can't see anything wrong with the database that would cause the query generator problems. Is there something O(n^2) in the execution plan compiler - is breaking this down into blocks of separate data loads rather than all 32 tables at once likely to help? Setting EF to lazy-load didn't help. I've bought the pre-release O'Reilly Julie Lerman EF4 book but I can't find anything in there to help beyond 'compile your queries'. I don't understand why it's taking 12-15 seconds to generate a single select across 32 tables so I'm optimistic there's some scope for improvement! Thanks for any suggestions! We're running against SQL Server 2008 in case that matters and XP / 7 / server 2008 R2 using RTM VS2010.

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Same SELECT used in an INSERT has different execution plan

- by amacias

A customer complained that a query and its INSERT counterpart had different execution plans, and of course, the INSERT was slower. First lets look at the SELECT : SELECT ua_tr_rundatetime, ua_ch_treatmentcode, ua_tr_treatmentcode, ua_ch_cellid, ua_tr_cellid FROM (SELECT DISTINCT CH.treatmentcode AS UA_CH_TREATMENTCODE, CH.cellid AS UA_CH_CELLID FROM CH, DL WHERE CH.contactdatetime > SYSDATE - 5 AND CH.treatmentcode = DL.treatmentcode) CH_CELLS, (SELECT DISTINCT T.treatmentcode AS UA_TR_TREATMENTCODE, T.cellid AS UA_TR_CELLID, T.rundatetime AS UA_TR_RUNDATETIME FROM T, DL WHERE T.treatmentcode = DL.treatmentcode) TRT_CELLS WHERE CH_CELLS.ua_ch_treatmentcode(+) = TRT_CELLS.ua_tr_treatmentcode; The query has 2 DISTINCT subqueries. The execution plan shows one with DISTICT Placement transformation applied and not the other. The view in Step 5 has the prefix VW_DTP which means DISTINCT Placement. -------------------------------------------------------------------- | Id | Operation | Name | Cost (%CPU) -------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 272K(100) |* 1 | HASH JOIN OUTER | | 272K (1) | 2 | VIEW | | 4408 (1) | 3 | HASH UNIQUE | | 4408 (1) |* 4 | HASH JOIN | | 4407 (1) | 5 | VIEW | VW_DTP_48BAF62C | 1660 (2) | 6 | HASH UNIQUE | | 1660 (2) | 7 | TABLE ACCESS FULL | DL | 1644 (1) | 8 | TABLE ACCESS FULL | T | 2744 (1) | 9 | VIEW | | 267K (1) | 10 | HASH UNIQUE | | 267K (1) |* 11 | HASH JOIN | | 267K (1) | 12 | PARTITION RANGE ITERATOR| | 266K (1) |* 13 | TABLE ACCESS FULL | CH | 266K (1) | 14 | TABLE ACCESS FULL | DL | 1644 (1) -------------------------------------------------------------------- Query Block Name / Object Alias (identified by operation id): ------------------------------------------------------------- 1 - SEL$1 2 - SEL$AF418D5F / TRT_CELLS@SEL$1 3 - SEL$AF418D5F 5 - SEL$F6AECEDE / VW_DTP_48BAF62C@SEL$48BAF62C 6 - SEL$F6AECEDE 7 - SEL$F6AECEDE / DL@SEL$3 8 - SEL$AF418D5F / T@SEL$3 9 - SEL$2 / CH_CELLS@SEL$1 10 - SEL$2 13 - SEL$2 / CH@SEL$2 14 - SEL$2 / DL@SEL$2 Predicate Information (identified by operation id): --------------------------------------------------- 1 - access("CH_CELLS"."UA_CH_TREATMENTCODE"="TRT_CELLS"."UA_TR_TREATMENTCODE") 4 - access("T"."TREATMENTCODE"="ITEM_1") 11 - access("CH"."TREATMENTCODE"="DL"."TREATMENTCODE") 13 - filter("CH"."CONTACTDATETIME">SYSDATE@!-5) The outline shows PLACE_DISTINCT(@"SEL$3" "DL"@"SEL$3") indicating that the QB3 is the one that got the transformation. Outline Data ------------- /*+ BEGIN_OUTLINE_DATA IGNORE_OPTIM_EMBEDDED_HINTS OPTIMIZER_FEATURES_ENABLE('11.2.0.3') DB_VERSION('11.2.0.3') ALL_ROWS OUTLINE_LEAF(@"SEL$2") OUTLINE_LEAF(@"SEL$F6AECEDE") OUTLINE_LEAF(@"SEL$AF418D5F") PLACE_DISTINCT(@"SEL$3" "DL"@"SEL$3") OUTLINE_LEAF(@"SEL$1") OUTLINE(@"SEL$48BAF62C") OUTLINE(@"SEL$3") NO_ACCESS(@"SEL$1" "TRT_CELLS"@"SEL$1") NO_ACCESS(@"SEL$1" "CH_CELLS"@"SEL$1") LEADING(@"SEL$1" "TRT_CELLS"@"SEL$1" "CH_CELLS"@"SEL$1") USE_HASH(@"SEL$1" "CH_CELLS"@"SEL$1") FULL(@"SEL$2" "CH"@"SEL$2") FULL(@"SEL$2" "DL"@"SEL$2") LEADING(@"SEL$2" "CH"@"SEL$2" "DL"@"SEL$2") USE_HASH(@"SEL$2" "DL"@"SEL$2") USE_HASH_AGGREGATION(@"SEL$2") NO_ACCESS(@"SEL$AF418D5F" "VW_DTP_48BAF62C"@"SEL$48BAF62C") FULL(@"SEL$AF418D5F" "T"@"SEL$3") LEADING(@"SEL$AF418D5F" "VW_DTP_48BAF62C"@"SEL$48BAF62C" "T"@"SEL$3") USE_HASH(@"SEL$AF418D5F" "T"@"SEL$3") USE_HASH_AGGREGATION(@"SEL$AF418D5F") FULL(@"SEL$F6AECEDE" "DL"@"SEL$3") USE_HASH_AGGREGATION(@"SEL$F6AECEDE") END_OUTLINE_DATA */ The 10053 shows there is a comparative of cost with and without the transformation. This means the transformation belongs to Cost-Based Query Transformations (CBQT). In SEL$3 the optimization of the query block without the transformation is 6659.73 and with the transformation is 4408.41 so the transformation is kept. GBP/DP: Checking validity of GBP/DP for query block SEL$3 (#3) DP: Checking validity of distinct placement for query block SEL$3 (#3) DP: Using search type: linear DP: Considering distinct placement on query block SEL$3 (#3) DP: Starting iteration 1, state space = (5) : (0) DP: Original query DP: Costing query block. DP: Updated best state, Cost = 6659.73 DP: Starting iteration 2, state space = (5) : (1) DP: Using DP transformation in this iteration. DP: Transformed query DP: Costing query block. DP: Updated best state, Cost = 4408.41 DP: Doing DP on the original QB. DP: Doing DP on the preserved QB. In SEL$2 the cost without the transformation is less than with it so it is not kept. GBP/DP: Checking validity of GBP/DP for query block SEL$2 (#2) DP: Checking validity of distinct placement for query block SEL$2 (#2) DP: Using search type: linear DP: Considering distinct placement on query block SEL$2 (#2) DP: Starting iteration 1, state space = (3) : (0) DP: Original query DP: Costing query block. DP: Updated best state, Cost = 267936.93 DP: Starting iteration 2, state space = (3) : (1) DP: Using DP transformation in this iteration. DP: Transformed query DP: Costing query block. DP: Not update best state, Cost = 267951.66 To the same query an INSERT INTO is added and the result is a very different execution plan. INSERT INTO cc (ua_tr_rundatetime, ua_ch_treatmentcode, ua_tr_treatmentcode, ua_ch_cellid, ua_tr_cellid)SELECT ua_tr_rundatetime, ua_ch_treatmentcode, ua_tr_treatmentcode, ua_ch_cellid, ua_tr_cellidFROM (SELECT DISTINCT CH.treatmentcode AS UA_CH_TREATMENTCODE, CH.cellid AS UA_CH_CELLID FROM CH, DL WHERE CH.contactdatetime > SYSDATE - 5 AND CH.treatmentcode = DL.treatmentcode) CH_CELLS, (SELECT DISTINCT T.treatmentcode AS UA_TR_TREATMENTCODE, T.cellid AS UA_TR_CELLID, T.rundatetime AS UA_TR_RUNDATETIME FROM T, DL WHERE T.treatmentcode = DL.treatmentcode) TRT_CELLSWHERE CH_CELLS.ua_ch_treatmentcode(+) = TRT_CELLS.ua_tr_treatmentcode;----------------------------------------------------------| Id | Operation | Name | Cost (%CPU)----------------------------------------------------------| 0 | INSERT STATEMENT | | 274K(100)| 1 | LOAD TABLE CONVENTIONAL | | |* 2 | HASH JOIN OUTER | | 274K (1)| 3 | VIEW | | 6660 (1)| 4 | SORT UNIQUE | | 6660 (1)|* 5 | HASH JOIN | | 6659 (1)| 6 | TABLE ACCESS FULL | DL | 1644 (1)| 7 | TABLE ACCESS FULL | T | 2744 (1)| 8 | VIEW | | 267K (1)| 9 | SORT UNIQUE | | 267K (1)|* 10 | HASH JOIN | | 267K (1)| 11 | PARTITION RANGE ITERATOR| | 266K (1)|* 12 | TABLE ACCESS FULL | CH | 266K (1)| 13 | TABLE ACCESS FULL | DL | 1644 (1)----------------------------------------------------------Query Block Name / Object Alias (identified by operation id):------------------------------------------------------------- 1 - SEL$1 3 - SEL$3 / TRT_CELLS@SEL$1 4 - SEL$3 6 - SEL$3 / DL@SEL$3 7 - SEL$3 / T@SEL$3 8 - SEL$2 / CH_CELLS@SEL$1 9 - SEL$2 12 - SEL$2 / CH@SEL$2 13 - SEL$2 / DL@SEL$2Predicate Information (identified by operation id):--------------------------------------------------- 2 - access("CH_CELLS"."UA_CH_TREATMENTCODE"="TRT_CELLS"."UA_TR_TREATMENTCODE") 5 - access("T"."TREATMENTCODE"="DL"."TREATMENTCODE") 10 - access("CH"."TREATMENTCODE"="DL"."TREATMENTCODE") 12 - filter("CH"."CONTACTDATETIME">SYSDATE@!-5)Outline Data------------- /*+ BEGIN_OUTLINE_DATA IGNORE_OPTIM_EMBEDDED_HINTS OPTIMIZER_FEATURES_ENABLE('11.2.0.3') DB_VERSION('11.2.0.3') ALL_ROWS OUTLINE_LEAF(@"SEL$2") OUTLINE_LEAF(@"SEL$3") OUTLINE_LEAF(@"SEL$1") OUTLINE_LEAF(@"INS$1") FULL(@"INS$1" "CC"@"INS$1") NO_ACCESS(@"SEL$1" "TRT_CELLS"@"SEL$1") NO_ACCESS(@"SEL$1" "CH_CELLS"@"SEL$1") LEADING(@"SEL$1" "TRT_CELLS"@"SEL$1" "CH_CELLS"@"SEL$1") USE_HASH(@"SEL$1" "CH_CELLS"@"SEL$1") FULL(@"SEL$2" "CH"@"SEL$2") FULL(@"SEL$2" "DL"@"SEL$2") LEADING(@"SEL$2" "CH"@"SEL$2" "DL"@"SEL$2") USE_HASH(@"SEL$2" "DL"@"SEL$2") USE_HASH_AGGREGATION(@"SEL$2") FULL(@"SEL$3" "DL"@"SEL$3") FULL(@"SEL$3" "T"@"SEL$3") LEADING(@"SEL$3" "DL"@"SEL$3" "T"@"SEL$3") USE_HASH(@"SEL$3" "T"@"SEL$3") USE_HASH_AGGREGATION(@"SEL$3") END_OUTLINE_DATA */ There is no DISTINCT Placement view and no hint.The 10053 trace shows a new legend "DP: Bypassed: Not SELECT"implying that this is a transformation that it is possible only for SELECTs. GBP/DP: Checking validity of GBP/DP for query block SEL$3 (#4) DP: Checking validity of distinct placement for query block SEL$3 (#4) DP: Bypassed: Not SELECT. GBP/DP: Checking validity of GBP/DP for query block SEL$2 (#3) DP: Checking validity of distinct placement for query block SEL$2 (#3) DP: Bypassed: Not SELECT. In 12.1 (and hopefully in 11.2.0.4 when released) the restriction on applying CBQT to some DMLs and DDLs (like CTAS) is lifted.This is documented in BugTag Note:10013899.8 Allow CBQT for some DML / DDLAnd interestingly enough, it is possible to have a one-off patch in 11.2.0.3. SQL> select DESCRIPTION,OPTIMIZER_FEATURE_ENABLE,IS_DEFAULT 2 from v$system_fix_control where BUGNO='10013899'; DESCRIPTION ---------------------------------------------------------------- OPTIMIZER_FEATURE_ENABLE IS_DEFAULT ------------------------- ---------- enable some transformations for DDL and DML statements 11.2.0.4 1

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How do I restart MySQL in monit when page contains specific text?

- by Tyler

How do I check if a web page contains the text "Error connecting to database" and if the text exists in the page restart the database? Here's what I have so far but it isn't working: check host website.com with address website.com group database start program = "/usr/bin/service mysql start" stop program = "/usr/bin/service mysql stop" if url http://website.com content == "Error connecting to database" then restart

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Trouble with Debian Lenny and Sphinx

- by Ando

I've very basic understanding of linux systems, but I've a server which was setup a while ago to host some web apps. Recently I decided to test out and implement Sphinx but unfortunately I cant get the install to work. I'm running a Debian Lenny distro and when I try to install sphinx it says - checking MySQL include files... configure: error: missing include files. ****************************************************************************** ERROR: cannot find MySQL include files. Check that you do have MySQL include files installed. The package name is typically 'mysql-devel'. If include files are installed on your system, but you are still getting this message, you should do one of the following: 1) either specify includes location explicitly, using --with-mysql-includes; 2) or specify MySQL installation root location explicitly, using --with-mysql; 3) or make sure that the path to 'mysql_config' program is listed in your PATH environment variable. To disable MySQL support, use --without-mysql option. ****************************************************************************** I do have mysql 5.1 installed but I can't find the include files, AND one more thing.. I read around the net that I probably need libmysqlclient15-dev but when I try to install that using apt-get i receive the following error. The following packages were automatically installed and are no longer required: libxcb-aux0 libts-0.0-0 libxcb-atom1 ttf-dejavu-extra hunspell-en-us g++-4.3 libmysql++3 libnspr4-0d libdirectfb-1.0-0 libxcb-event1 libasound2 libstdc++6-4.3-dev libhunspell-1.2-0 ttf-dejavu libmozjs2d conkeror-spawn-process-helper libnss3-1d Use 'apt-get autoremove' to remove them. The following NEW packages will be installed: libmysqlclient15-dev 0 upgraded, 1 newly installed, 0 to remove and 276 not upgraded. Need to get 7590 kB of archives. After this operation, 26.3 MB of additional disk space will be used. WARNING: The following packages cannot be authenticated! libmysqlclient15-dev Install these packages without verification [y/N]? Y Err http://ftp.us.debian.org/debian/ lenny/main libmysqlclient15-dev amd64 5.0.51a-24+lenny5 404 Not Found [IP: 35.9.37.225 80] Err http://security.debian.org/ lenny/updates/main libmysqlclient15-dev amd64 5.0.51a-24+lenny5 404 Not Found [IP: 149.20.20.6 80] Failed to fetch http://security.debian.org/pool/updates/main/m/mysql-dfsg-5.0/libmysqlclient15-dev_5.0.51a-24+lenny5_amd64.deb 404 Not Found [IP: 149.20.20.6 80] E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing? Can you help me out by suggesting how to install the required packages and run the Sphinx.

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Ubuntu server; Backup of server and MySql database, and Solr database

- by Camran

How is backup done on ubuntu servers? I have a server (Ubuntu 9.10) which has apache2 installed, php5, mysql etc... The website is a classifieds website where all classifieds are stored in mysql and Solr. I need to backup this server with all information to be able to fully restore it if something goes wrong. How should I start? Is it an automated task, or will I do backups manually? (prefer manually) Thanks

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SQL server timeout 2000 from C# .NET

- by Johnny Egeland

I have run into a strange problem using SQL Server 2000 and two linked server. For two years now our solution has run without a hitch, but suddenly yesterday a query synchronizing data from one of the databases to the other started timing out. I connect to a server in the production network, which is linked to a server containing orders I need data from. The query contains a few joins, but basically this summarizes what is done: INSERT INTO ProductionDataCache (column1, column2, ...) SELECT tab1.column1, tab1.column2, tab2.column1, tab3.column1 ... FROM linkedserver.database.dbo.Table1 AS tab1 JOIN linkedserver.database.dbo.Table2 AS tab2 ON (...) JOIN linkedserver.database.dbo.Tabl32 AS tab3 ON (...) ... WHERE tab1.productionOrderId = @id ORDER BY ... Obviously my first attempt to fix the problem was to increase the timeout limit from the original 5 minutes. But when I arrived at 30 minutes and still got a timeout, I started to suspect something else was going on. A query just does not go from executing in less than 5 minutes to over 30 minutes over night. I outputted the SQL query (which was originally in the C# code) to my logs, and decided to execute the query in the Query Analyzer directly on the database server. To my big surprise, the query executed correctly in less than 10 seconds. So I isolated the SQL execution in a simple test program, and observed the same query time out both on the server originally running this solution AND when running it locally on the database server. Also I have tried to create a Stored Procedure and execute this from the program, but this also times out. Running it in Query Analyzer works fine in less than a few seconds. It seems that the problem only occurs when I execute this query from the C# program. Has anyone seen such behavior before, and found a solution for it? UPDATE: I have now used SQL Profiler on the server. The obvious difference is that when executing the query from the .NET program, it shows up in the log as "exec sp_executesql N'INSERT INTO ...'", but when executing from Query Analyzer it occurs as a normal query in the log. Further I tried to connect the SQL Query Analyzer using the same SQL user as the program, and this triggered the problem in Query Analyzer as well. So it seems the problem only occurs when connecting via TCP/IP using a sql user.

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pyODBC and Unicode Problem

- by Aviv Giladi

Hey guys, I'm working with pyODBC communicate with a MS SQL 2005 Express server. The table to which i'm trying to save the data consists of nvarchar columns. query = u"INSERT INTO tblPersons (name, birthday, gender) VALUES('" query = query + name + u"', '" query = query + birthday + u"', '" query = query + gender + u"')" cur.execute(query ) The variables name, birthrday and gende are read from an Excel file and they are Unicode strings. When I execute the query and either look at the table with SQL Server Management Studio or execute a query that fetches the data that was just inserted, all the data that was written in a non-English languages turn into question marks. The data that was written in English is preserved and appears in the table in the correct way. I tried adding CHARSET=UTF16 to my connection string, but had no luck with that. I can use UTF-8 which works fine but as a working convention, I need all the data saved in my DB to be UTF16. Thanks!

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Powershell - Splitting variable into chunks

- by Andrew

I have written a query in Powershell interrogating a F5 BIG-IP box through it's iControl API to bring back CPU usage etc. Using this code (see below) I can return the data back into a CSV format which is fine. However the $csvdata variable contains all the data. I need to be able to take this variable and for each line split each column of data into a seperate variable. The output currently looks like this: timestamp,"Utilization" 1276181160,2.3282800000e+00 Any advice would be most welcome $SystemStats = (Get-F5.iControl).SystemStatistics ### Allocate a new Query Object and add the inputs needed $Query = New-Object -TypeName iControl.SystemStatisticsPerformanceStatisticQuery $Query.object_name = $i $Query.start_time = $startTime $Query.end_time = 0 $Query.interval = $interval $Query.maximum_rows = 0 ### Make method call passing in an array of size one with the specified query $ReportData = $SystemStats.get_performance_graph_csv_statistics( (,$Query) ) ### Allocate a new encoder and turn the byte array into a string $ASCII = New-Object -TypeName System.Text.ASCIIEncoding $csvdata = $ASCII.GetString($ReportData[0].statistic_data)

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Tab Sweep: Primefaces3, @DataSourceDefinition, JPA Extensions, EclipseLink, Typed Query, Ajax, ...

- by arungupta

Recent Tips and News on Java, Java EE 6, GlassFish & more : • JSF2 + Primefaces3 + EJB3 & JPA2 Integration Project (@henk53) • The state of @DataSourceDefinition in Java EE (@henk53) • Java Persistence API (JPA) Extensions Reference for EclipseLink (EclipseLink) • JavaFX 2.2 Pie Chart with JPA 2.0 (John Yeary) • Typed Query RESTful Service Example (John Yeary) • How to set environment variables in GlassFish admin console (Jelastic) • Architect Enterprise Applications with Java EE (Oracle University) • Glassfish – Basic authentication (Marco Ghisellini) • Solving GlassFish 3.1/JSF PWC4011 warning (Rafael Nadal) • PrimeFaces AJAX Enabled (John Yeary)

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My father wants to learn PHP-MySQL to port his application. What I should do to help?

- by adijiwa

My father is a doctor/physician. About 15 years ago he started writing an application to handle his patient's medical records in his clinic at home. The app has the ability to input patient's medical records (obviously), search patients by some criteria, manage medicine stocks, output receipt to printer, and some more CRUDs. He wrote it in dBase III+. A few years later he migrated to FoxPro 2.6 for DOS and finally in a few more years he rewrote his app in Visual FoxPro 9. And now (actually two years ago) he wants to rewrite it in PHP, but he don't know how. The Visual FoxPro version of this app is still running and has no serious problem except sometimes it performs slowly. Usually there are 1-5 concurrent users. The binary and database files are shared via windows share. He did all the coding as a hobby and for free (it is for his own clinic after all). He also use this app in two other offices he managed. Some reasons of why he wants to rewrite in PHP-MySQL: He wants to learn Easier to deploy (?) Easier client setup, need only a browser What should I do to help my father? How should he start? I explored some options: I let my father learn PHP and MySQL (and HTML (and JavaScript?)) from scratch. I create/bundle framework. I'm thinking on bundling CodeIgniter and a web UI framework (any suggestion?) especially to reduce effort on writing presentation codes. What do you think? tl;dr My father (a doctor) wants to rewrite his Visual FoxPro app in PHP-MySQL. He knows very little of PHP and MySQL but he wants to learn. What should I do to help? How should he start? Some facts: My father is 50 years old. His first encounter with a PC is in early 1980s. It was IBM PC with Intel 8088. He knows BASIC. He taught me how to use DOS and how to program with BASIC. The other language he knows fairly well is dBase/FoxPro. I got my bachelor CS degree last year. I know the internals of my father's app because sometime he wants me to help him writing his app. Sorry for my english.

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Creating database connections - Do it once or for each query?

- by webnoob

At the moment I create a database connection when my web page is first loaded. I then process the page and run any queries against that conection. Is this the best way to do it or should I be creating a database connection each time I run a query? p.s It makes more sense to me to create 1 connection and use it but I don't know if this can cause any other issues. I am using C# (ASP.NET) with MSSQL.

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Are elements returned by Linq-to-Entities query streamed from the DB one at the time or are they retrieved all at once?

- by carewithl

Are elements returned by Linq-to-Entities query streamed from the database one at the time ( as they are requested ) or are they retrieved all at once: SampleContext context = new SampleContext(); // SampleContext derives from ObjectContext var search = context.Contacts; foreach (var contact in search) { Console.WriteLine(contact.ContactID); // is each Contact retrieved from the DB // only when foreach requests it? } thank you in advance

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