Currently, I wanna take Shark’s (Spark SQL) DDL and DML as an reference to design/implement SQLE’s DDL and DML. However, I cannot find its DDL and DML. I can only find several SQLs in Shark paper[1]. [1] shark paper – http://tab.d-thinker.org/showthread.php?tid=2585 Shark’s language is Hive QL. HQL’s DDL and DML can be found at Hive…
How to make fdisk -l display partition sizes by bytes instead of sectors? fdisk does not have such options as far as I know. However, good news is that you can use parted: # parted -l It will print partition info like # parted -l Model: Linux device-mapper (linear) (dm) Disk /dev/mapper/fedora_vm235-swap: 2164MB Sector size…
Differences beween DDL (Data Definition Language) and DML (Data Manipulation Language) Data Definition Language (DDL) statements are used to define the database structure or schema. Data Manipulation Language (DML) statements are used for managing data within schema objects. References:http://www.orafaq.com/faq/what_are_the_difference_between_ddl_dml_and_dcl_commands
What are sequence points in C? The comp.lang.c FAQ explains this quite well. A sequence point is a point in time at which the dust has settled and all side effects which have been seen so far are guaranteed to be complete. The sequence points listed in the C standard are: at the end of…
I prefer Linux Mint (I am using Cinnamon) not automatically mounting a portable storage such as USB disk or iPhone for me and I would like do the mounting manually if I need it. The default behavior of Linux Mint is to automatically mount the disks. How to disable this? The auto mounting on Linux…
A commit is not the HEAD now. and git commit –amend will not work for it. How to change its commit message? You can use git rebase together with git commit –amend as follows. Assume your commit to be edited is 2b8ed. $ git rebase -i 2b8ed^ Change the pick to edit in the line…
I want to attach a disk to a DomU. The Xen DomU is running and should not be rebooted. Hence, changing its configuration file is not an option. How to dynamically attach a disk to running DomU in Xen? To attach phy:vg_xen/vm-228-large to vm-228 as xvdb, run this on Dom0: # xl block-attach vm-228 phy:vg_xen/vm-228-large…
As is known, database schema is a collection of database rules like data type and data relationship. However, this is still a little abstract. So what is database schema in one sentence everyone could understand it clearly. The wikipedia page on Database schema is quite good for understanding the concept. A database schema of a…
I want to add adsense ads to be shown to visitors on desktop only. How to remove AdSense ads for mobile devices? You can achieve this through using “Responsive ad unit” of AdSense. The support article Create a responsive ad unit from AdSense discusses this and gives an example. Check the “Hiding an ad unit”…
We may need to maintain a dev-name branch on git remote server to share your codes. How to create the branch? 1, git checkout -b your_branch_name 2, Do your changes, add commit 3, git push origin your_branch_name References:http://stackoverflow.com/questions/1519006/how-do-you-create-a-remote-git-branch
How to make taglist recognize specific files with certain extensions as C source files? You may try adding this line to your ~/.vimrc: autocmd BufRead,BufNewFile *.c0 set filetype=c Reference: https://stackoverflow.com/questions/9013263/vim-tagslist-plugin-not-detecting-custom-language-racket
How to make ctags recognize specific files with certain extensions such as .c0 or .puc as C source files? You may add this line to your ~/.ctags: –langmap=c:+.c0,c:+.puc
I want to kick off a user such as “bob” on a Linux box which I managed remotely. How to do this? bob may log on the Linux box by various ways: Log on the screen on the Linux box (locally) with a X server. Log on remotely by a ssh shell. Log on by…
Which simple and basic image editors are good on Linux like the paint program on Windows? GIMP is great but too high weighted for normal usage like resizing, cropping, image annotation with text. Pinta is a free and open source drawing/editing program that is easy to edit images. It is available on many Linux distros….
How can I force iPhone to reboot/restart/reset when it locks up completely and does not response? To force an iPhone to restart: Press and hold the iPhone’s power key and home button together. Holding the two keys for around 10~15 seconds until the screen is turned off. Release the buttons once the screen lights up…
Resizing images on Linux with gThumb is easy. However, I have a batch of images inside a folder. Manually resizing them will consume too much time. How to automatically resize them on Linux with a script? You can use convert from ImageMagick together with bash script to resize images inside a directory. mkdir resize; IFS=$(echo…
We have a running HDFS cluster. Currently, the NameNode metadata data directory has only one directory configured in hdfs-site.xml: <property> <name>dfs.namenode.name.dir</name> <value>file:///home/hadoop/hdfs/</value> <description>NameNode directory for namespace and transaction logs storage.</description> </property> We would like to add a new directory for dfs.namenode.name.dir to make replicas of the metadata on a separated disk for higher data reliability….
The “Entering/Leaving…” messages when invoking another make by a make is kind of annoying. Is it possible to suppress these messages and how to suppress them? For GNU make, it is controlled by options: -w, –print-directory Print a message containing the working directory before and after other processing. This may be useful for tracking down…
How to detect whether a .jpg image is almost blank/black on Linux? Here is a bash function that I used to detect whether an image is black on Linux: function isBlank () { mean=`convert $1 -format “%[mean]” info:` echo “$mean” } It uses ImageMagic to generate formatted image characteristics (the mean). If the mean is…
I noticed that some guys’ screen console has a status bar with tab numbers. That will be very useful for 1) know you are using screen rather than a normal terminal. 2) which tab you are working in. Below is my ~/.screenrc: hardstatus alwayslastline hardstatus string ‘%{= kG}[ %{G}%H %{g}][%= %{=kw}%?%-Lw%?%{r}(%{W}%n*%f%t%?(%u)%?%{r})%{w}%?%+Lw%?%?%= %{g}][%{B}%Y-%m-%d %{W}%c %{g}]’ It…