Author Archives: ronaldpringadi

Knowing your exception class name

You’re staring at a generic catch (Exception e) and you don’t know which actual exception is being thrown. The trick is to log the runtime class so you can replace the generic catch with a specific one: 12345} catch (Exception … Continue reading

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SELinux directory permission

To check SELinux directory permission you need to -z for example 1ls -Z /var/www/html If something is incorrect you can re-adjust some of the directory permission: 1chcon -R -t httpd_sys_content_t /var/www/html

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RedHat / Centos Firewall

To add an exception to firewall In RedHat/CentOS 6 12345iptables –line -vnL iptables -A INPUT -p tcp –dport 80 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A INPUT -p tcp -s 192.168.0.0/16 -j ACCEPT iptables -D INPUT -p tcp -s … Continue reading

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Bash string comparison

1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465#!/bin/bash function test(){ echo "" echo "TEST $1" echo "VAR_1: $VAR_1 VAR_2: $VAR_2 " if [ "$VAR_1" = "false" ]; then echo " VAR_1 is false"; fi if [ "$VAR_2" = "false" ]; then echo " VAR_2 is false"; fi … Continue reading

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Show postgres lock

You’re staring at a query that won’t finish, or a deploy that hangs on a migration, or a UI request that just sits there. Postgres is almost certainly waiting on a lock that another transaction holds. The classic query for … Continue reading

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Apache Lucene: The Search Engine Hiding Inside Half the Internet

If you’ve ever used Elasticsearch, Solr, or even some features in big platforms like Twitter or LinkedIn, chances are you’ve been touching Apache Lucene without knowing it. It’s the quiet workhorse — a Java library that does one thing extraordinarily … Continue reading

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Check all table size in Postgres

You want a quick “which tables are eating my disk?” overview — usually before a vacuum, an archive purge, or a capacity-planning conversation. Here’s a one-shot query that joins information_schema.tables against pg_class to show every public table with its estimated … Continue reading

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Synchronize a postgres table through bash and csv

Please note that the csv export process does not escape commas. 1234567891011121314151617181920212223242526272829303132333435#!/bin/bash DIR=’/root/sql_dump’ mkdir -p "$DIR" cd "$DIR" SIZE=100000 #START=611244350 START=0 END=$((START + SIZE)) STOP=189097000 TABLNAME="schema.tablename" while [[ $START -lt $STOP ]] && [[ $END -le $STOP ]]; do   … Continue reading

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Export and Import Postgres query to CSV

# =========================================================== # Export to CSV # =========================================================== # export PGPASSWORD=”YOURPASSWORD” # psql -U YOURUSERNAME -h YOURHOSTNAME -d YOURDBNAME-t -A -F”,” -c “select * from YOURTABLENAME limit 2″ > output.csv # =========================================================== # Import # =========================================================== # export PGPASSWORD=”YOURPASSWORD” # … Continue reading

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Assorted postgres queries

Get table sizes: SELECT relname AS objectname, relkind AS objecttype, reltuples AS “#entries”, pg_size_pretty(relpages::bigint*8*1024) AS size FROM pg_class WHERE relpages >= 8 ORDER BY relpages DESC;

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