Author Archives: ronaldpringadi

Delete Postgres Cache

Posted on April 13, 2016 by ronaldpringadi

1234#!/bin/bash sync echo 1 > /proc/sys/vm/drop_caches service postgresql-9.3 restart

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Java Flight Recorder: a profiler that’s already in your JVM

Posted on March 22, 2016 by ronaldpringadi

If you’re running anything on the JVM (Java Virtual Machine) in production and you’ve never opened a Flight Recorder file, you’re leaving a free profiler on the table. Java Flight Recorder (JFR) is a low-overhead event recorder built into the … Continue reading →

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Check which database object depends on (has reference to) your table

Posted on February 12, 2016 by ronaldpringadi

12345678910111213141516SELECT R.TABLE_NAME FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE u INNER JOIN INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS FK     ON U.CONSTRAINT_CATALOG = FK.UNIQUE_CONSTRAINT_CATALOG     AND U.CONSTRAINT_SCHEMA = FK.UNIQUE_CONSTRAINT_SCHEMA     AND U.CONSTRAINT_NAME = FK.UNIQUE_CONSTRAINT_NAME INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE R     ON R.CONSTRAINT_CATALOG = FK.CONSTRAINT_CATALOG     AND … Continue reading →

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Postgres function to devide-and-conquer (iterate) your big query

Posted on February 8, 2016 by ronaldpringadi

Create a postgres function to devide-and-conquer (iterate) your big query 1234567891011121314151617181920212223242526272829303132333435363738394041TRUNCATE TABLE YOUR_NEW_BIG_TABLE; DROP FUNCTION IF EXISTS pg_iterator(); CREATE OR REPLACE FUNCTION pg_iterator()   RETURNS void AS $BODY$ DECLARE     vOffsetRecord INT;     vTotal INT;     vLimit … Continue reading →

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Crontab header

Posted on February 1, 2016 by ronaldpringadi

123456# minute (0-59), # |      hour (0-23), # |      |       day of the month (1-31), # |      |       |       month of the year (1-12), # … Continue reading →

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Add user in mysql

Posted on January 17, 2016 by ronaldpringadi

The classic three-liner for adding a MySQL user, run from a mysql shell connected as root or another account with the CREATE USER privilege. Replace each placeholder with your own value. 123CREATE USER ‘YOUR_USER_NAME’@’CONNECTING_FROM_WHERE’ IDENTIFIED BY ‘THIS_USER_PASSWORD’; GRANT ALL PRIVILEGES … Continue reading →

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Using grep as highlighter

Posted on December 18, 2015 by ronaldpringadi

1$ grep –color -E ‘^|pattern1|pattern2’ file name

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TCL programming

Posted on November 12, 2015 by ronaldpringadi

A reusable expect dispatcher I kept around for running the same kind of operation across a list of servers — untar an index, restart a service, patch a config file. The trick is that the script reads the first command-line … Continue reading →

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Simple unit test is bash file

Posted on October 28, 2015 by ronaldpringadi

Consider the following 3 files: 1. shellTestFramework.sh 1234567891011121314151617181920212223242526272829303132333435363738394041424344454647#!/bin/bash # Copyright (c) Ronald Pringadi # Before each Test function setUpTest(){     #"Please overwrite this function on your unit test. Something that need to be done before each test"     … Continue reading →

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Multithreading in Java using ThreadPoolExecutor

Posted on September 23, 2015 by ronaldpringadi

ThreadWorker is your custom class. 123456789try { ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors.newFixedThreadPool(MAX_THREAD_SIZE); for (int i = 1; i Random randomGenerator = new Random(); executor.submit(new ThreadWorker("worker" + i, randomGenerator.nextInt(10))); LOG.info(i); } } catch (Exception e) { LOG.error("Hmm something is not right.", … Continue reading →

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