Install Vertica on CentOS Guide

OS:                          CentOS 6.5 64bit

Vertica:                    7.0 Community Edition

Part 1: OS Configurations Before Install Vertica

1. Disk Readahead

/sbin/blockdev --setra 2048 /dev/sda1

echo '/sbin/blockdev --setra 2048 /dev/sda1' >> /etc/rc.local

Note: I also have sda2 so I also need to execute

/sbin/blockdev --setra 2048 /dev/sda2

echo '/sbin/blockdev --setra 2048 /dev/sda2' >> /etc/rc.local

2. TZ

vi /etc/profile

add the following line

export TZ="Asia/Shanghai"

For all the valid time zone names, please refer to

https://www.vmware.com/support/developer/vc-sdk/visdk400pubs/ReferenceGuide/timezone.html

3. NTP

$ chkconfig --list ntpd

/sbin/service ntpd restart

/sbin/chkconfig ntpd on

4. Disable SELInux

1). Edit /etc/selinux/config and change setting for SELINUX to disabled

(SELINUX=disabled). This disables SELinux at boot time.

2). As root/sudo, type setenforce 0 to disable SELinux immediately.

5. Disable Transparent HugePages

You can check the current setting using the following command, which is displaying the default value of "enabled=[always]".

# cat /sys/kernel/mm/transparent_hugepage/enabled

[always] madvise never

The preferred method to disable Transparent HugePages is to add "transparent_hugepage=never" to the kernel boot line in the "/etc/grub.conf" file.

vi /etc/grub.conf

and add transparent_hugepage=never

For example: 

title Oracle Linux Server (2.6.39-400.24.1.el6uek.x86_64)

        root (hd0,0)

        kernel /vmlinuz-2.6.39-400.24.1.el6uek.x86_64 ro root=/dev/mapper/vg_ol6112-lv_root rd_NO_LUKS  KEYBOARDTYPE=pc KEYTABLE=uk

LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16  rd_NO_DM rd_LVM_LV=vg_ol6112/lv_swap rd_LVM_LV=vg_ol6112/lv_root rhgb quiet numa=off

transparent_hugepage=never

        initrd /initramfs-2.6.39-400.24.1.el6uek.x86_64.img

6. Change I/O Scheduler

echo deadline > /sys/block/sda/queue/scheduler

echo 'echo deadline > /sys/block/sda/queue/scheduler' >> /etc/rc.local

7. Single Node Install Vertica

rpm -ivh vertica-7.0.0-0.x86_64.RHEL5.rpm

8. Run install_vertica to complete installation

cd /opt/vertica/sbin

./install_vertica --hosts 127.0.0.1 --dba-user vertica --dba-user-password vertica

This installs a vertica instance in localhost (127.0.0.1), and create a dba names vertica, and the password is vertica

9. Accept Vertica License

cd /opt/vertica/bin

./adminTools   (The T is uppercase)

and accept the license and EULA etc. Here please note that you can use mouse click to check and accept the EULA.

10. Install VMart example database

cd /opt/vertica/sbin

./install_example VMart

I mainly followed the installation guide, which is difficult to understand. :)
http://my.vertica.com/docs/7.0.x/PDF/HP_Vertica_7.0.x_Install_Guide.pdf
I also referenced the post here: 

http://unixsystems.blogspot.com/2013/08/vertica-installation-tutorial.html

Aha! All Set.

You can try to connect to database

You can also connect it from a windows environment, for example:

 vsql -h 192.168.136.63 -U vertica

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How to install Chrome on CentOS 6.4 and 6.5

I have been always using Chrome, and even I am quite new to linux, I still want to use Chrome even it's not supported in CentOS 6.4 and 6.5, and below are the steps.

First of all, thanks to Rihard, he provides a script to install Chrome, which does 99.9% of the work. It's great!
 http://chrome.richardlloyd.org.uk/

But when I use the script, I still met some problems, maybe it's because I am using the company's internet proxy, or because in China, we cannot access some websites due to great firewall. Anyway, I need to do something to finish the 0.1% work left.

Step1: Follow the instructions here: http://chrome.richardlloyd.org.uk/ , download install_chrome.sh (http://chrome.richardlloyd.org.uk/install_chrome.sh)

Step2: It's better that you switch to root account to run the script, or use sudo ./install_chrome.sh. Assume you are running a root account:

chmod u+x install_chrome.sh

./install_chrome.sh

In this step, I met several problems:
a. connection to https://dl.google.com failed...

I solved this by using a no proxy internet. In our company, we always using proxy. But the connection just failed, so I run the command at home where no proxy is used.

b. download is very slow as shown in the screenshot below

The time estimation goes up to several hours and the progress always hung.

I solved this by using Ctrl C to stop the ./install_chrome.sh, and run this command again. Sometimes it hang at another package, but tried several times, the installation succeeded.

Note for CentOS 6.4: In CentOS 6.4, I see the script installed successfully. But when I click the icon, nothing happened. Then I open a terminal:

cd /usr/bin

./google-chrome

It shows the error:

[sai@localhost bin]$ ./google-chrome

./google-chrome: /usr/lib64/libnss3.so: version `NSS_3.14.3' not found (required by ./google-chrome)

I tried to follow the instructions here but didn't work.

http://www.linuxquestions.org/questions/slackware-14/google-chrome-30-error-nss-4-13-5-upgrade-4175482053/

What I did to solve this problem is: 

I searched and find a link here:

http://rpmfind.net/linux/RPM/centos/updates/6.4/x86_64/Packages/nss-3.14.3-4.el6_4.x86_64.html

And I download and installed it. Now the problem solved. 

[Update on 2014/2/25] Sorry I didn't know the package link will be removed so I didn't save a copy of the package. I tried to find one and put it in the share folder below. Please try it and let me know whether it works for you:
https://drive.google.com/file/d/0B_ZDNNkWG1dYVXpHeDBwaHNBTXc/edit?usp=sharing

Last but not least, 

to uninstall Chrome, please run:

./install_chrome.sh -u

to update Chrome, please run:

sudo yum update google-chrome-stable

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How to Visualize Vertica Query Plan

Vertica uses EXPLAIN command to return the query plan execution strategy to standard output.

Syntax
EXPLAIN { SELECT... | INSERT... | UPDATE...}

Returns
A compact representation of the query plan, laid out hierarchically.

Let's have an example here.
1. Prepare a table
This is preparation work, and if you know a table you can select please skip this step.

1. CREATE SCHEMA SAI;
2. CREATE TABLE T1(c INT);
3. INSERT INTO T1 VALUES(3);
4. INSERT INTO T1 VALUES(4);
5. INSERT INTO T1 VALUES(5);

2. In Vertica console, or a third party tool like DBVisualizer, execute

EXPLAIN SELECT * FROM SAI.T1;

You will get the output like below

3. Install GraphViz and launch GVEdit
For how to install GraphViz and launch GVEdit, please check another POST of mine.
http://sai1983.blogspot.com/2013/12/how-to-install-graphviz-and-launch.html

4. Use GVEdit
a. Copy the code in highlighted in step 2, the codes start from digraph G and all contents in {}
b. click the new icon of GVEdit and paste the content

c. click the right most "Run" button

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How to install GraphViz and launch GVEdit

When study Vertica query plan, it's the first time I hear about GraphViz, it turns out to be a project with history. The official site and a brief introduction is as below:
http://www.graphviz.org/

Graphviz - Graph Visualization Software

Drawing graphs since 1988

Graphviz is open source graph visualization software. Graph visualization is a way of representing structural information as diagrams of abstract graphs and networks. It has important applications in networking, bioinformatics,  software engineering, database and web design, machine learning, and in visual interfaces for other technical domains. 


Question is: if I got an GraphViz codes, how to make it displayed?

Step 1: Please download a package here

http://www.graphviz.org/Download..php

There are many versions and I downloaded Windows msi package

Step 2: launch a command window with administrator access

Please run a command

msiexec /a graphviz-x.xx.msi

And install the software as normal.

Step 3: open a command shell, go to GraphViz installation path, for example mine is:
D:\Program Files (x86)\Graphviz2.34\
Go to the bin folder, and run gvedit.exe

And you will see GVEdit launched!

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SkyDrive How to Share to Everyone

I have been using Microsoft MSN space to manage my photos, and it's called SkyDrive now. SkyDrive now provides more functions and the UI are improved a lot. However, in MSN space it was very easy to share the picture or album you created to others, with SkyDrive it's not easy to find it out. Luckily, I figured out how to make it work:

1. in SkyDrive click "Files"
This will list all your files and folders

2. Check the folder you want to share (it's on the top right corner) and on the right there will display a link button called "Share" on the right

3. It will pop up a modal dialog, and click Get a link and choose "Public" in the option drop down list, 

4. Then click "Crate link", You can see it's now shared with Everyone. All Set!

I am now able to share my pictures and even send the URL to people I know. 

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A Good Regular Expression Tutorial

Regular Expression is powerful and it's one of the tools that all programmers should grasp.














I just started the trip and get into the world, and I found the tutorial by Java website is very useful.
http://docs.oracle.com/javase/tutorial/essential/regex/index.html


The most interesting part is about Quantifiers. There are three types: greedy, reluctant and possessive.

Greedy	Reluctant	Possessive	Meaning
X?	X??	X?+	X, once or not at all
X*	X*?	X*+	X, zero or more times
X+	X+?	X++	X, one or more times
X{n}	X{n}?	X{n}+	X, exactly n times
X{n,}	X{n,}?	X{n,}+	X, at least n times
X{n,m}	X{n,m}?	X{n,m}+	X, at least n but not more than m times

But it doesn't very clearly say how the match works underline. And there is an interesting stack overflow website about it.

http://stackoverflow.com/questions/5319840/greedy-vs-reluctant-vs-possessive-quantifiers

I found this excellent tutorial on regular expressions and while I intuitively understand what "greedy", "reluctant" and "possessive" quantifiers do, there seems to be a serious hole in my understanding.

Specifically, in the following example:

Enter your regex: .*foo  // greedy quantifier
Enter input string to search: xfooxxxxxxfoo
I found the text "xfooxxxxxxfoo" starting at index 0 and ending at index 13.

Enter your regex: .*?foo  // reluctant quantifier
Enter input string to search: xfooxxxxxxfoo
I found the text "xfoo" starting at index 0 and ending at index 4.
I found the text "xxxxxxfoo" starting at index 4 and ending at index 13.

Enter your regex: .*+foo // possessive quantifier
Enter input string to search: xfooxxxxxxfoo
No match found.

The explanation mentions eating the entire input string, letters been consumed, matcher backing off, rightmost occurrence of "foo" has been regurgitated, etc.

Unfortunately, despite the nice metaphors, I still don't understand what is eaten by whom... Do you know of another tutorial that explains (concisely) how regular expressions engines work?

Alternatively, if someone can explain in somewhat different phrasing the following paragraph, that would be much appreciated:

The first example uses the greedy quantifier .* to find "anything", zero or more times, followed by the letters "f" "o" "o". Because the quantifier is greedy, the .* portion of the expression first eats the entire input string. At this point, the overall expression cannot succeed, because the last three letters ("f" "o" "o") have already been consumed (by whom?). So the matcher slowly backs off (from right-to-left?) one letter at a time until the rightmost occurrence of "foo" has been regurgitated (what does this mean?), at which point the match succeeds and the search ends.

The second example, however, is reluctant, so it starts by first consuming (by whom?) "nothing". Because "foo" doesn't appear at the beginning of the string, it's forced to swallow (who swallows?) the first letter (an "x"), which triggers the first match at 0 and 4. Our test harness continues the process until the input string is exhausted. It finds another match at 4 and 13.

The third example fails to find a match because the quantifier is possessive. In this case, the entire input string is consumed by .*+, (how?) leaving nothing left over to satisfy the "foo" at the end of the expression. Use a possessive quantifier for situations where you want to seize all of something without ever backing off (what does back off mean?); it will outperform the equivalent greedy quantifier in cases where the match is not immediately found.

The best answer is: 

A greedy quantifier first matches as much as possible. So the .* matches the entire string. Then the matcher tries to match the f following, but there are no characters left. So it "backtracks", making the greedy quantifier match one less thing (leaving the "o" at the end of the string unmatched). That still doesn't match the f in the regex, so it "backtracks" one more step, making the greedy quantifier match one less thing again (leaving the "oo" at the end of the string unmatched). That still doesn't match the fin the regex, so it backtracks one more step (leaving the "foo" at the end of the string unmatched). Now, the matcher finally matches the f in the regex, and the o and the next o are matched too. Success!

A reluctant or "non-greedy" quantifier first matches as little as possible. So the .* matches nothing at first, leaving the entire string unmatched. Then the matcher tries to match the f following, but the unmatched portion of the string starts with "x" so that doesn't work. So the matcher backtracks, making the non-greedy quantifier match one more thing (now it matches the "x", leaving "fooxxxxxxfoo" unmatched). Then it tries to match the f, which succeeds, and the o and the next o in the regex match too. Success!

In your example, it then starts the process over with the remaining unmatched portion of the string, following the same process.

A possessive quantifier is just like the greedy quantifier, but it doesn't backtrack. So it starts out with.* matching the entire string, leaving nothing unmatched. Then there is nothing left for it to match with the f in the regex. Since the possessive quantifier doesn't backtrack, the match fails there.

Thanks to the people who provide the question and answer on the stack verflow website. 

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How to install custom recovery Team Win Recovery Project (TWRP) in Android

Team Win Recovery Project (TWRP) custom recovery is one of the best recovery tool to use. I suggest everyone to install it, it can help you install update, backup, wipe cache and support many nice features, and it support touch screen which is very convenient. Its official website is: http://teamw.in/project/twrp2


To install TWRP, there are two ways:
The easiest way is to install an app called "GooManager" from Google Play.
https://play.google.com/store/apps/details?id=com.s0up.goomanager

But in case your network doesn't support you very well to download rom via GooManager, you need to manually install TWRP, and below are the steps:
1. Go to official site http://teamw.in/project/twrp2 to find the TWRP image for your device

2. Download it

For example, mine is: openrecovery-twrp-2.6.3.4-hammerhead.img

3. go to the android SDK installation folder, go to directory platform tools
for example, mine is: D:\Program Files (x86)\Android\android-sdk\platform-tools

4. Copy the download image into this folder

5. Press Shift key and at the same time, right click your mouse you will see a menu item "Open Command Window here"

6. boot your device to fast boot mode and connect it to USB
For my device, I power off my device, and then simultaneously press power and volume down button button it will to go fast boot mode

7 execute command fastboot flash recovery recoveryfilename.img
for example, I execuste
fastboot flash recovery openrecovery-twrp-2.6.3.4-hammerhead.img

8. In fast boot mode, select Recovery mode



9. Go! You will now see the TWRP installed.
10. Last you can delete the img file in the SDK platform-tools folder.

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OK, Google! How to enable Google Now in China

I have got the Nexus 5 and it's very cool that you say "OK Google" to trigger voice search function, you can also speak to use Google Now to find interesting things for you. But Google Now is not available in China, and by default you will see in Android system settings it says Google Now is not supported in China. But the great fire wall cannot stop us, and below is the way you can do it.

The prerequisite is that you have a rooted device. 

1. Please download a third party market app and install it. I recommend Cool Market, the best one I have ever used.
Download link: cool market

2. After installation, search in cool market an app called "market unlocker". Run it and turn on
1) Enable Unlocker
2) Auto Unlocker

3. Turn off location
Go to Settings, under "PERSONAL" there is "Location" icon, click it and turn it off.

4. Clear Data and Cache of Google apps
Very importantly, please turn off your WiFi in this step
Go to Settings-->Apps, slice to ALL apps, clear cache of three Google apps
1) Google Play services (Click manage space, and then clear all data)

2) Google Play Store (Click clear data)

3) Google Search (Clear data)

Now reboot your device

1. go to Google Play to initialize it.
2. long lick the "Up" icon in home screen and click Google now.

Wait Google Now to be initialized. After this, you can enable locations service and google now will be there with you.

OK, Google!