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  • How to implement the setup rules like Clash of Clan?

    - by user25959
    Now I'm already implement the setup build rules which the building could move by unit grid width and height. But the validation detection is poor efficiency. The algorithm cost me 10~12(ms) in average when I move the building. Here is my approach to that: 1.Basic Grid, it is a two dimensional array. Grid[row][column], so that I can save info for each grid. Like whether is it in occupied or excluded. 2.Exclude Space, this is a space which limit same building numbers in space.

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  • Microsoft Sql Server 2008 R2 System Databases

    For a majority of software developers little time is spent understanding the inner workings of the database management systems (DBMS) they use to store data for their applications.  I personally place myself in this grouping. In my case, I have used various versions of Microsoft’s SQL Server (2000, 2005, and 2008 R2) and just recently learned how valuable they really are when I was preparing to deliver a lecture on "SQL Server 2008 R2, System Databases". Microsoft Sql Server 2008 R2 System DatabasesSo what are system databases in MS SQL Server, and why should I know them? Microsoft uses system databases to support the SQL Server DBMS, much like a developer uses config files or database tables to support an application. These system databases individually provide specific functionality that allows MS SQL Server to function. Name Database File Log File Master master.mdf mastlog.ldf Resource mssqlsystemresource.mdf mssqlsystemresource.ldf Model model.mdf modellog.ldf MSDB msdbdata.mdf msdblog.ldf Distribution distmdl.mdf distmdl.ldf TempDB tempdb.mdf templog.ldf Master DatabaseIf you have used MS SQL Server then you should recognize the Master database especially if you used the SQL Server Management Studio (SSMS) to connect to a user created database. MS SQL Server requires the Master database in order for DBMS to start due to the information that it stores. Examples of data stored in the Master database User Logins Linked Servers Configuration information Information on User Databases Resource DatabaseHonestly, until recently I never knew this database even existed until I started to research SQL Server system databases. The reason for this is due largely to the fact that the resource database is hidden to users. In fact, the database files are stored within the Binn folder instead of the standard MS SQL Server database folder path. This database contains all system objects that can be accessed by all other databases.  In short, this database contains all system views and store procedures that appear in all other user databases regarding system information. One of the many benefits to storing system views and store procedures in a single hidden database is the fact it improves upgrading a SQL Server database; not to mention that maintenance is decreased since only one code base has to be mainlined for all of the system views and procedures. Model DatabaseThe Model database as the name implies is the model for all new databases created by users. This allows for predefining default database objects for all new databases within a MS SQL Server instance. For example, if every database created by a user needs to have an “Audit” table when it is  created then defining the “Audit” table in the model will guarantees that the table will be located in every new database create after the model is altered. MSDB DatabaseThe MSDBdatabase is used by SQL Server Agent, SQL Server Database Mail, SQL Server Service Broker, along with SQL Server. The SQL Server Agent uses this database to store job configurations and SQL job schedules along with SQL Alerts, and Operators. In addition, this database also stores all SQL job parameters along with each job’s execution history.  Finally, this database is also used to store database backup and maintenance plans as well as details pertaining to SQL Log shipping if it is being used. Distribution DatabaseThe Distribution database is only used during replication and stores meta data and history information pertaining to the act of replication data. Furthermore, when transactional replication is used this database also stores information regarding each transaction. It is important to note that replication is not turned on by default in MS SQL Server and that the distribution database is hidden from SSMS. Tempdb DatabaseThe Tempdb as the name implies is used to store temporary data and data objects. Examples of this include temp tables and temp store procedures. It is important to note that when using this database all data and data objects are cleared from this database when SQL Server restarts. This database is also used by SQL Server when it is performing some internal operations. Typically, SQL Server uses this database for the purpose of large sort and index operations. Finally, this database is used to store row versions if row versioning or snapsot isolation transactions are being used by SQL Server. Additionally, I would love to hear from others about their experiences using system databases, tables, and objects in a real world environments.

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  • Brightness fn key adjustment problems

    - by npCoder
    My brightness function key controls work after setting grub boot parameter to "acpi_osi=" but using them I cannot adjust the brightness higher than around 70% (there is empty bar left over and I can't adjust higher) unless I go to Brightness & Lock settings manually than I can use the slider to adjust it higher... I primarily use intel_backlight to adjust my backlight and I am running Linux kernel 3.14.1 on Ubuntu 14.04 LTS on an ASUS X550LA Laptop when I try: cd /sys/class/backlight/intel_backlight cat max_brightness 937 cat brightness 811 It seems that I can only adjust to a maximum of 811 using the fn brightness controls If I instead do cd /sys/class/backlight/acpi_video0 cat max_brightness 10 cat brightness 4 cat actual_brightness 10 With the FN keys actual_brightness is not equal to the value returned from brightness on acip_video0 (which is always 4) but on intel_backlight actual_brightness = brightness The adjustment problem seemingly arises because both intel_backlight and acpi_video0 are trying to adjust brightness

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  • Microsoft Sql Server 2008 R2 System Databases

    For a majority of software developers little time is spent understanding the inner workings of the database management systems (DBMS) they use to store data for their applications.  I personally place myself in this grouping. In my case, I have used various versions of Microsoft’s SQL Server (2000, 2005, and 2008 R2) and just recently learned how valuable they really are when I was preparing to deliver a lecture on "SQL Server 2008 R2, System Databases". Microsoft Sql Server 2008 R2 System DatabasesSo what are system databases in MS SQL Server, and why should I know them? Microsoft uses system databases to support the SQL Server DBMS, much like a developer uses config files or database tables to support an application. These system databases individually provide specific functionality that allows MS SQL Server to function. Name Database File Log File Master master.mdf mastlog.ldf Resource mssqlsystemresource.mdf mssqlsystemresource.ldf Model model.mdf modellog.ldf MSDB msdbdata.mdf msdblog.ldf Distribution distmdl.mdf distmdl.ldf TempDB tempdb.mdf templog.ldf Master DatabaseIf you have used MS SQL Server then you should recognize the Master database especially if you used the SQL Server Management Studio (SSMS) to connect to a user created database. MS SQL Server requires the Master database in order for DBMS to start due to the information that it stores. Examples of data stored in the Master database User Logins Linked Servers Configuration information Information on User Databases Resource DatabaseHonestly, until recently I never knew this database even existed until I started to research SQL Server system databases. The reason for this is due largely to the fact that the resource database is hidden to users. In fact, the database files are stored within the Binn folder instead of the standard MS SQL Server database folder path. This database contains all system objects that can be accessed by all other databases.  In short, this database contains all system views and store procedures that appear in all other user databases regarding system information. One of the many benefits to storing system views and store procedures in a single hidden database is the fact it improves upgrading a SQL Server database; not to mention that maintenance is decreased since only one code base has to be mainlined for all of the system views and procedures. Model DatabaseThe Model database as the name implies is the model for all new databases created by users. This allows for predefining default database objects for all new databases within a MS SQL Server instance. For example, if every database created by a user needs to have an “Audit” table when it is  created then defining the “Audit” table in the model will guarantees that the table will be located in every new database create after the model is altered. MSDB DatabaseThe MSDBdatabase is used by SQL Server Agent, SQL Server Database Mail, SQL Server Service Broker, along with SQL Server. The SQL Server Agent uses this database to store job configurations and SQL job schedules along with SQL Alerts, and Operators. In addition, this database also stores all SQL job parameters along with each job’s execution history.  Finally, this database is also used to store database backup and maintenance plans as well as details pertaining to SQL Log shipping if it is being used. Distribution DatabaseThe Distribution database is only used during replication and stores meta data and history information pertaining to the act of replication data. Furthermore, when transactional replication is used this database also stores information regarding each transaction. It is important to note that replication is not turned on by default in MS SQL Server and that the distribution database is hidden from SSMS. Tempdb DatabaseThe Tempdb as the name implies is used to store temporary data and data objects. Examples of this include temp tables and temp store procedures. It is important to note that when using this database all data and data objects are cleared from this database when SQL Server restarts. This database is also used by SQL Server when it is performing some internal operations. Typically, SQL Server uses this database for the purpose of large sort and index operations. Finally, this database is used to store row versions if row versioning or snapsot isolation transactions are being used by SQL Server. Additionally, I would love to hear from others about their experiences using system databases, tables, and objects in a real world environments.

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  • certain files not syncing

    - by Josh
    I have UbuntuOne set up to sync a one folder with a number of subfolders. For some reason some of the subfolders have stopped syncing. Within one subfolder with 6 subfolders in it, some are showing up empty (they shouldn't be) and some are showing up with only some of the files they should contain. I have synced recently, and newer files are showing up in other subfolders. There's just some problem with these particular folders. They are not especially big nor do they have especially big files in them. Thoughts?

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  • replacing Zorin OS 8 with ubuntu 14.04

    - by Paul John
    I was trying to replace Zorin OS 8 with ubuntu 14.04 (32 bits). What I have tried: I took an empty pen drive and downloaded Ubuntu 14.04 iso file on to this pen drive. I then restarted my laptop (Lenovo N 3000) and pressed F12 I then selected the USB drive in the boot options. After sometime I got the Zorin flash screen again. I know I am "fundamentally" wrong in the manner how I am executing this installation process. If you could please provide me a stepwise instruction.

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  • Why is Ubuntu unmounting my primary hard drive?

    - by Twisol
    I'm running Ubuntu 10.10 on my laptop (an Asus G73j), dual-booting Windows 7 if that matters. After using the computer for couple of hours or so, I get a popup complaining that a file was unmounted, then my GNOME desktop panels disappear. I can't save any unsaved work (the file browser shows "Filesystem" as totally empty), and other programs break in odd ways (like Chrome can't browse to any new pages, but keeps current ones going... at least I still have Pandora to listen to when this happens!). I've tried looking in the system logs to no avail; I'm assuming that it can't write any errors to the logs because, of course, the logs are on the primary hard drives. This started happening maybe a few days ago. Yesterday I upgraded from 10.4, but I believe it was happening before then. Any advice for figuring this out?

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  • Unable to start GRUB2 on Triple boot Macbook Pro with OS X Lion, Windows 7 and Ubuntu

    - by Shravan
    I installed Windows 7 using Bootcamp. Then I created a partition from the empty space in the Windows partition and another 4GB partition for the linux swap using GParted. I installed Ubuntu 12.04 LTS in the the newly created partition from the Windows partition. Now GRUB2 does not load and I can only see the blinking cursor on the top right when selecting "Windows HD" from the 'option' key at the start up. OS X works fine but nothing else. Could someone please help me fix this? I am attaching the boot-info from the boot-repair tool. http://paste.ubuntu.com/1040169/

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  • How to detect GLSL warnings?

    - by msell
    After compiling a shader with glCompileShader, I can call glGetShaderiv with GL_COMPILE_STATUS to check if the shader compiled successfully. I can also call glGetShaderInfoLog to get information about possible errors, warnings or other info. The information log returned by this function is unspecified. In a tool where users can write their own shaders, I would like to print all errors and warnings from the compilation, but nothing if no warnings or errors were found. The problem is that the GL_COMPILE_STATUS returns only false if the compilation failed and true otherwise. If no problems were found, some drivers return empty info log from glGetShaderInfoLog, but some drivers can return something else such as "No errors.", which I do not want to print to the user. How is this problem generally solved?

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  • How to find the occurrence of particular character in string - CHARINDEX

    - by Vipin
    Many times while writing SQL, we need to find if particular character is present in the column data. SQL server possesses an in-built function to do this job - CHARINDEX(character_to_search, string, [starting_position]) Returns the position of the first occurrence of the character in the string. NOTE - index starts with 1. So, if character is at the starting position, this function would return 1. Returns 0 if character is not found. Returns 0 if 'string' is empty. Returns NULL if string is NULL. A working example of the function is SELECT CHARINDEX('a', fname) a_First_occurence, CHARINDEX('a', fname, CHARINDEX('a', fname)) a_Second_occurrence FROM Users WHERE fname = 'aka unknown' OUTPUT ------- a_First_occurence a_Second_occurrence 1 3

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  • How to shade a texture two different colors?

    - by Venesectrix
    To give an example of what I'm asking about, I'll use Saints Row 3 since I've been playing that lately. In that game you can customize your looks and your car's appearance a lot. Your coat can have a primary color and a trim color. Your car can have a primary color and a stripe color, etc. Is there just a single coat texture that is being shaded two different colors somehow or are they overlaying a transparent second texture for the trim/stripes that gets shaded differently? If it's just one texture I'd like to know how it's done. If it's two different textures it seems like it's a waste of space. The second texture would be the same size as the first one but mostly transparent if you just wanted to lay it on top of the first one. Or are they just carefully positioning a second, smaller texture so that it aligns properly with the first one?

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  • How to access shared folders in Ubuntu VM(Oracle Virtualbox) and link them to the home folder(Answered)

    - by Njihia
    I have configured a shared folder between the Windows host and Ubuntu guest. The folder mounts at start up but its empty(It also has a padlock sign.). I have to run the command below to access its content(the padlock sign disappears). sudo mount.vboxsf media ~/media How can i configure it to be run automatically at start up. I've tried adding to the start up programs but nothing happens. Am new to Linux so try to put your answer in a layman's language. Thanks.

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  • Gnome 3 Shell extensions not working on Ubuntu 12.4 [closed]

    - by user63960
    Possible Duplicate: Gnome Shell Extension Empty I just upgraded to Ubuntu 12.4 running on a Win 7 box via VBox and switched the user interface to Gnome 3 but have a problem. In Advanced Settings (gnome tweak), the Shell Extensions window has no listings and the Theme window shows a "caution" triangle next to the Shell theme drop box. I have re-installed the default extensions using the Noobs Lab posted instructions: sudo apt-get install shell-extensions3.4 sudo apt-get install gnome-shell-extensions The commands appear to complete without error. Symptoms are: Gnome 2 visual appearance and no window borders or controls. To close a window, I have to click the window indicator in the sys tray and select the close menu item. Any ideas?

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  • How to prevent a Gtk.SourceView from grabbing the URI of a file

    - by laboleite
    I'm making a text editor using GTK3 in Vala. I need to drag a file and, when I drop it into the application window, the application opens that file. I'm using a Gtk.Notebook that contains the Gtk.SourceView's. It works when I drop a file into an empty Gtk.Notebook, but when there is at least one Gtk.SourceView's appended on it, the SourceView grab the URI of the file, shows it and the window can't handle the opening of the file. In this case, what can I do to prevent a Gtk.SourceView from grabbing the uri of a file when I drop a file into a Gtk.SourceView. PS: I tried to use the drag_dest_unset() inside the SourceView derived class. It worked, the SourceView didn't grab the URI and the window could open the file, but the application showed a message like this, in runtime: Gtk-WARNING **: Can't set a target list on a widget until you've called gtk_drag_dest_set() to make the widget into a drag destination

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  • Problems installing Ubuntu on unallocated space

    - by Adam
    I've been trying to install Ubuntu on some unallocated space, but I'm getting confused with the manual partition setup. I didn't want to try the other options for it suggested that everything on my drive would be erased (but I might be wrong) I have an old(ish) laptop with a 60GB hard-drive. Theres a Windows 7 partition of 30GB, followed by 20GB of unallocated space, then HP's Windows recovery partition of under 10GB. Do I need to format the empty space in windows first? What's the recommended method in this case?

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  • Dell Vostro 1510 trackpad

    - by user18055
    A week ago I moved totally from Windows 7 to Ubuntu. I've been really happy with the transition bar one annoying glitch. My trackpad sometimes works, sometimes doesn't. All other hardware including peripherals work flawlessly, including a Logitech ball mouse, Wacom Bamboo pen and touch and wireless Logitech keyboard and mouse combo. I can't see any pattern to when and why the trackpad works. Occasionally on rebooting, it will work, but then I can reboot 10x in a row and it won't work, then I leave it a day, then reboot and it works flawlessly. Any ideas on a solution or appropriate method for me to deb it? My knowledge of Ubuntu/Linux is sketchy at best so I could do with a little help :)

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  • I'm trying to install postgresql on 12.04, and it's just not working

    - by Pointy
    I've got a new installation and I'm trying to get Postgresql working. The database was installed and I started a restoration from a dump on another machine, but that ran into problems because I had forgotten to install the "contrib" package. I used "pg_dropcluster" to drop the old cluster so I could start from scratch, and that's when things went weird. The first manifestation of this was that /etc/postgresql was just empty. I uninstalled the postgresql package and reinstalled, several times, to no avail. Is there something I can do to figure out why apt is confused here? I've done this many times on many systems and never seen anything like this happen.

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  • How to connect to the internet via command line or graphical utility given I can't click at the top of the screen?

    - by Ben
    My Ubuntu 12.04 installation has an input problem resulting preventing me from clicking near the top of the screen. That is, there is an unclickable area, circa 60 pixels high and stretching all the way across the screen. I will ask about this in a later question. For now, I would just like to be able to connect to the internet, given this limitation. I am able to access the network connections application by hitting the super key and typing "network connections". There is a LAN and a wireless network available. The network icon in the bar at the top of the screen shows an empty wedge, which I suppose means that wireless is off. I've attached the cable for the Ethernet connection, but it does not seem to have connected automatically. How can I figure out what's going on? (I'll happily edit in the output of any relevant terminal commands.) Thank you.

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  • mounting linux partition after installing windows

    - by varsketiz
    I installed windows 7 and my grub is gone. I'm trying to follow: https://help.ubuntu.com/community/RecoveringUbuntuAfterInstallingWindows but I can't mount my ubuntu partion. sudo fdisk -l Device Boot Start End Blocks Id System /dev/sda1 * 1 13 102400 7 HPFS/NTFS Partition 1 does not end on cylinder boundary. /dev/sda2 13 4863 38958080 7 HPFS/NTFS /dev/sda3 4864 14594 78157825 5 Extended /dev/sda5 14220 14594 2999296 82 Linux swap / Solaris Gparted shows my Extended partition as empty/unallocated space (???). How can I mount it? sudo mount -t ext3 /dev/sda3 /media/ubuntu mount: wrong fs type, bad option, bad superblock on /dev/sda3, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so

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  • Getting photos and music on/off samsung/google galaxy nexus (ice cream sandwich) phone

    - by wim
    I am having trouble to access the filesystem on my phone. It just worked in previous version of Ubuntu, but now it appears empty whether it is mounted with MTP or PTP. I have followed a few guides on building and reinstalling libmtp etc without success. This answer did not help for me, either, and gMTP just hangs when I click the connect button. I know I can use wifi e.g. airdroid to access my photos, but this is too slow and a bit clumsy for me, and downloaded photos lose their original timestamps. Has anyone had success connecting to this phone on 12.04 ??

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  • How to detect a touch on transparent area of an image in a (libgdx) stage?

    - by Usman
    Can some one please help to detect a touch on an image which I am using as an actor in a stage. The image is actually a long diagnol brush which has plenty of transparent area. The problem is when I touche the transparent area of the brush image it is also triggering the clicklistener of the image. I need the click listener should only be called when the finger actually touched the visible image not the area which is empty. I am using libgdx-0.9.4 libraries. Here is my simple piece of code. import com.badlogic.gdx.scenes.scene2d.ui.Image; import com.badlogic.gdx.scenes.scene2d.ui.ClickListener; Image brushImg = new Image(ImageCache.getTexture("brush")); brushImg.width = mStage.width()*0.75f; brushImg.height = mStage.height()*0.75f; brushImg.setClickListener(new ClickListener() { @Override public void click(Actor actor, float x, float y) { SoundFactory.play("brush"); }

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  • Bubble shooter search alghoritm

    - by Fofole
    So I have a Matrix of NxM. At a given position (for ex. [2][5]) I have a value which represents a color. If there is nothing at that point the value is -1. What I need to do is after I add a new point, to check all his neighbours with the same color value and if there are more than 2, set them all to -1. If what I said doesn't make sense what I'm trying to do is an alghoritm which I use to destroy all the same color bubbles from my screen, where the bubbles are memorized in a matrix where -1 means no bubble and {0,1,2,...} represent that there is a bubble with a specific color. This is what I tried and failed: public class Testing { static private int[][] gameMatrix= {{3, 3, 4, 1, 1, 2, 2, 2, 0, 0}, {1, 4, 1, 4, 2, 2, 1, 3, 0, 0}, {2, 2, 4, 4, 3, 1, 2, 4, 0, 0}, {0, 1, 2, 3, 4, 1, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, }; static int Rows=6; static int Cols=10; static int count; static boolean[][] visited=new boolean[15][15]; static int NOCOLOR = -1; static int color = 1; public static void dfs(int r, int c, int color, boolean set) { for(int dr = -1; dr <= 1; dr++) for(int dc = -1; dc <= 1; dc++) if(!(dr == 0 && dc == 0) && ok(r+dr, c+dc)) { int nr = r+dr; int nc = c+dc; // if it is the same color and we haven't visited this location before if(gameMatrix[nr][nc] == color && !visited[nr][nc]) { visited[nr][nc] = true; count++; dfs(nr, nc, color, set); if(set) { gameMatrix[nr][nc] = NOCOLOR; } } } } static boolean ok(int r, int c) { return r >= 0 && r < Rows && c >= 0 && c < Cols; } static void showMatrix(){ for(int i = 0; i < gameMatrix.length; i++) { System.out.print("["); for(int j = 0; j < gameMatrix[0].length; j++) { System.out.print(" " + gameMatrix[i][j]); } System.out.println(" ]"); } System.out.println(); } static void putValue(int value,int row,int col){ gameMatrix[row][col]=value; } public static void main(String[] args){ System.out.println("Initial Matrix:"); putValue(1, 4, 1); putValue(1, 5, 1); showMatrix(); for(int n = 0; n < 15; n++) for(int m = 0; m < 15; m++) visited[n][m] = false; //reset count count = 0; //dfs(bubbles.get(i).getRow(), bubbles.get(i).getCol(), color, false); // get the contiguous count dfs(5,1,color,false); //if there are more than 2 set the color to NOCOLOR for(int n = 0; n < 15; n++) for(int m = 0; m < 15; m++) visited[n][m] = false; if(count > 2) { //dfs(bubbles.get(i).getRow(), bubbles.get(i).getCol(), color, true); dfs(5,1,color,true); } System.out.println("Matrix after dfs:"); showMatrix(); } }

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  • What does Visual studio debugger do, when condition should give error

    - by zacharmarz
    I'm debugging some code and I need to break everytime, when character in string (const char *) is equal to something. So I put there breakpoint and attach condition like: s[0] == 'e'. But code I'm debugging is in CRT and there is possibility, that s == 0 is true. So "addressing empty pointer" should give some kind of error. Yes - I could give there condition s != 0, but it would not be such fun :) And I'm curious, what will debugger do when trying to evaluate this condition? How it will behave internally? Obviously it's not giving any error nor stopping on this breakpoint when s == 0 Thanks for your answer.

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  • Presenting Beginning PowerShell at SQL Saturday 149 MN

    - by merrillaldrich
    I am happy to be presenting a session on beginning PowerShell for DBAs at my new home town’s SQL Saturday! (I moved from Seattle to Saint Paul, MN a short time ago.) I will be sharpening this presentation up to make sure anyone who comes will not go away empty handed. BTW, WOW, the schedule is up and I must admit I did not expect nine tracks of awesome. This looks amazing. My session is geared toward helping those DBAs who have not seen PowerShell, or perhaps may find PowerShell syntax opaque or...(read more)

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  • Developing Schema Compare for Oracle (Part 6): 9i Query Performance

    - by Simon Cooper
    All throughout the EAP and beta versions of Schema Compare for Oracle, our main request was support for Oracle 9i. After releasing version 1.0 with support for 10g and 11g, our next step was then to get version 1.1 of SCfO out with support for 9i. However, there were some significant problems that we had to overcome first. This post will concentrate on query execution time. When we first tested SCfO on a 9i server, after accounting for various changes to the data dictionary, we found that database registration was taking a long time. And I mean a looooooong time. The same database that on 10g or 11g would take a couple of minutes to register would be taking upwards of 30 mins on 9i. Obviously, this is not ideal, so a poke around the query execution plans was required. As an example, let's take the table population query - the one that reads ALL_TABLES and joins it with a few other dictionary views to get us back our list of tables. On 10g, this query takes 5.6 seconds. On 9i, it takes 89.47 seconds. The difference in execution plan is even more dramatic - here's the (edited) execution plan on 10g: -------------------------------------------------------------------------------| Id | Operation | Name | Bytes | Cost |-------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 108K| 939 || 1 | SORT ORDER BY | | 108K| 939 || 2 | NESTED LOOPS OUTER | | 108K| 938 ||* 3 | HASH JOIN RIGHT OUTER | | 103K| 762 || 4 | VIEW | ALL_EXTERNAL_LOCATIONS | 2058 | 3 ||* 20 | HASH JOIN RIGHT OUTER | | 73472 | 759 || 21 | VIEW | ALL_EXTERNAL_TABLES | 2097 | 3 ||* 34 | HASH JOIN RIGHT OUTER | | 39920 | 755 || 35 | VIEW | ALL_MVIEWS | 51 | 7 || 58 | NESTED LOOPS OUTER | | 39104 | 748 || 59 | VIEW | ALL_TABLES | 6704 | 668 || 89 | VIEW PUSHED PREDICATE | ALL_TAB_COMMENTS | 2025 | 5 || 106 | VIEW | ALL_PART_TABLES | 277 | 11 |------------------------------------------------------------------------------- And the same query on 9i: -------------------------------------------------------------------------------| Id | Operation | Name | Bytes | Cost |-------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 16P| 55G|| 1 | SORT ORDER BY | | 16P| 55G|| 2 | NESTED LOOPS OUTER | | 16P| 862M|| 3 | NESTED LOOPS OUTER | | 5251G| 992K|| 4 | NESTED LOOPS OUTER | | 4243M| 2578 || 5 | NESTED LOOPS OUTER | | 2669K| 1440 ||* 6 | HASH JOIN OUTER | | 398K| 302 || 7 | VIEW | ALL_TABLES | 342K| 276 || 29 | VIEW | ALL_MVIEWS | 51 | 20 ||* 50 | VIEW PUSHED PREDICATE | ALL_TAB_COMMENTS | 2043 | ||* 66 | VIEW PUSHED PREDICATE | ALL_EXTERNAL_TABLES | 1777K| ||* 80 | VIEW PUSHED PREDICATE | ALL_EXTERNAL_LOCATIONS | 1744K| ||* 96 | VIEW | ALL_PART_TABLES | 852K| |------------------------------------------------------------------------------- Have a look at the cost column. 10g's overall query cost is 939, and 9i is 55,000,000,000 (or more precisely, 55,496,472,769). It's also having to process far more data. What on earth could be causing this huge difference in query cost? After trawling through the '10g New Features' documentation, we found item 1.9.2.21. Before 10g, Oracle advised that you do not collect statistics on data dictionary objects. From 10g, it advised that you do collect statistics on the data dictionary; for our queries, Oracle therefore knows what sort of data is in the dictionary tables, and so can generate an efficient execution plan. On 9i, no statistics are present on the system tables, so Oracle has to use the Rule Based Optimizer, which turns most LEFT JOINs into nested loops. If we force 9i to use hash joins, like 10g, we get a much better plan: -------------------------------------------------------------------------------| Id | Operation | Name | Bytes | Cost |-------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 7587K| 3704 || 1 | SORT ORDER BY | | 7587K| 3704 ||* 2 | HASH JOIN OUTER | | 7587K| 822 ||* 3 | HASH JOIN OUTER | | 5262K| 616 ||* 4 | HASH JOIN OUTER | | 2980K| 465 ||* 5 | HASH JOIN OUTER | | 710K| 432 ||* 6 | HASH JOIN OUTER | | 398K| 302 || 7 | VIEW | ALL_TABLES | 342K| 276 || 29 | VIEW | ALL_MVIEWS | 51 | 20 || 50 | VIEW | ALL_PART_TABLES | 852K| 104 || 78 | VIEW | ALL_TAB_COMMENTS | 2043 | 14 || 93 | VIEW | ALL_EXTERNAL_LOCATIONS | 1744K| 31 || 106 | VIEW | ALL_EXTERNAL_TABLES | 1777K| 28 |------------------------------------------------------------------------------- That's much more like it. This drops the execution time down to 24 seconds. Not as good as 10g, but still an improvement. There are still several problems with this, however. 10g introduced a new join method - a right outer hash join (used in the first execution plan). The 9i query optimizer doesn't have this option available, so forcing a hash join means it has to hash the ALL_TABLES table, and furthermore re-hash it for every hash join in the execution plan; this could be thousands and thousands of rows. And although forcing hash joins somewhat alleviates this problem on our test systems, there's no guarantee that this will improve the execution time on customers' systems; it may even increase the time it takes (say, if all their tables are partitioned, or they've got a lot of materialized views). Ideally, we would want a solution that provides a speedup whatever the input. To try and get some ideas, we asked some oracle performance specialists to see if they had any ideas or tips. Their recommendation was to add a hidden hook into the product that allowed users to specify their own query hints, or even rewrite the queries entirely. However, we would prefer not to take that approach; as well as a lot of new infrastructure & a rewrite of the population code, it would have meant that any users of 9i would have to spend some time optimizing it to get it working on their system before they could use the product. Another approach was needed. All our population queries have a very specific pattern - a base table provides most of the information we need (ALL_TABLES for tables, or ALL_TAB_COLS for columns) and we do a left join to extra subsidiary tables that fill in gaps (for instance, ALL_PART_TABLES for partition information). All the left joins use the same set of columns to join on (typically the object owner & name), so we could re-use the hash information for each join, rather than re-hashing the same columns for every join. To allow us to do this, along with various other performance improvements that could be done for the specific query pattern we were using, we read all the tables individually and do a hash join on the client. Fortunately, this 'pure' algorithmic problem is the kind that can be very well optimized for expected real-world situations; as well as storing row data we're not using in the hash key on disk, we use very specific memory-efficient data structures to store all the information we need. This allows us to achieve a database population time that is as fast as on 10g, and even (in some situations) slightly faster, and a memory overhead of roughly 150 bytes per row of data in the result set (for schemas with 10,000 tables in that means an extra 1.4MB memory being used during population). Next: fun with the 9i dictionary views.

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