Cassandra – Cassandra tuning guide

https://tobert.github.io/pages/als-cassandra-21-tuning-guide.html

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Cassandra – Save a table in CSV and loading a CSV to a table in CQLSH

cqlsh:test_keyspace> COPY test_table TO 'test_table.csv' WITH HEADER=true;
cqlsh:test_keyspace> COPY test_table FROM 'test_table.csv' WITH HEADER=true;
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Emacs – Learning Emacs

http://www.jesshamrick.com/2012/09/10/absolute-beginners-guide-to-emacs/

C-h C-h : help
C-g : quit
C-x b : switch buffers
C-x right : right-cycle through buffers
C-x left : left-cycle through buffers
C-x k : kill buffer

C-x 0 : close the active window

C-x 1 : close all windows except the active window
C-x 2 : split the active window vertically into two horizontal windows
C-x 3 : split the active window horizontally into two vertical windows
C-x o : change active window to next window

C-x C-f : open file

C-x C-s : save file
C-x C-w : save file as

C-space : set region mark

C-w : kill region
C-k : kill region between point and end of current line
M-w : kill region without deleting
C-y : yank region from kill ring
M-y : move to previous item in the kill ring
M-Y : move to next item in the kill ring

C-_ : undo

C-s : search forwards
C-r : search backwards
M-% : query replace (‘space’ to replace, ‘n’ to skip, ‘!’ to replace all)
M-q : wrap text

C-left : move one word left

C-right : move one word right
C-up : move one paragraph up
C-down : move one paragraph down
home : move to the beginning of the line
end : move to the end of the line
page up : move up a page
page down : move down a page
M- : move to end of buffer

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RSocket – Resources about RSocket(Next paradigm of communication framework)

https://github.com/linux-china/awesome-rsocket/blob/master/README.md

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Rust – Idiomatic rust

https://github.com/mre/idiomatic-rust

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Java 11 – Enable Java Flight Recorder JVM option example

-XX:StartFlightRecording=\
        disk=true, \
        dumponexit=true, \
        filename=recording.jfr, \
        maxsize=1024m,\
        maxage=1d

Checking running JFR with jcmd

% jcmd PID JFR.check name=1

Dump JFR now

%jcmd PID JFR.dump name=1 filename=dump.jfr
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Spark – join transformation

join—Equivalent to an inner join in RDBMS, this returns a new pair RDD with the elements (K, (V, W)) containing all possible pairs of values from the first and second RDDs that have the same keys. For the keys that exist in only one of the two RDDs, the resulting RDD will have no elements. 


leftOuterJoin—Instead of (K, (V, W)), this returns elements of type (K, (V, Option(W))). The resulting RDD will also contain the elements (key, (v, None)) for those keys that don’t exist in the second RDD. Keys that exist only in the second RDD will have no matching elements in the new RDD. 


rightOuterJoin—This returns elements of type (K, (Option(V), W)); the resulting RDD will also contain the elements (key, (None, w)) for those keys that don’t exist in the first RDD. Keys that exist only in the first RDD will have no matching elements in the new RDD. 


fullOuterJoin—This returns elements of type (K, (Option(V), Option(W)); the resulting RDD will contain both (key, (v, None)) and (key, (None, w)) elements for those keys that exist in only one of the two RDDs. 


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