- Create
UNLOGGED
table. This reduces the amount of data written to persistent storage by up to 2x. - Set
WITH (autovacuum_enabled=false)
on the table. This saves CPU time and IO bandwidth on useless vacuuming of the table (since we neverDELETE
orUPDATE
the table). - Insert rows with
COPY FROM STDIN
. This is the fastest possible approach to insert rows into table. - Minimize the number of indexes in the table, since they slow down inserts. Usually an index
on
time timestamp with time zone
is enough. - Add
synchronous_commit = off
topostgresql.conf
. - Use table inheritance for fast removal of old data:
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
import os | |
def split(filehandler, delimiter=',', row_limit=10000, | |
output_name_template='output_%s.csv', output_path='.', keep_headers=True): | |
""" | |
Splits a CSV file into multiple pieces. | |
A quick bastardization of the Python CSV library. | |
Arguments: |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Latency Comparison Numbers (~2012) | |
---------------------------------- | |
L1 cache reference 0.5 ns | |
Branch mispredict 5 ns | |
L2 cache reference 7 ns 14x L1 cache | |
Mutex lock/unlock 25 ns | |
Main memory reference 100 ns 20x L2 cache, 200x L1 cache | |
Compress 1K bytes with Zippy 3,000 ns 3 us | |
Send 1K bytes over 1 Gbps network 10,000 ns 10 us | |
Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
function go() { | |
var userId = prompt('Username?', 'Guest'); | |
checkIfUserExists(userId); | |
} | |
var USERS_LOCATION = 'https://SampleChat.firebaseIO-demo.com/users'; | |
function userExistsCallback(userId, exists) { | |
if (exists) { | |
alert('user ' + userId + ' exists!'); |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
import logging | |
import cStringIO | |
import csv | |
DEBUG = False | |
def data2csv(data): | |
si = cStringIO.StringIO() | |
cw = csv.writer(si, delimiter='\t',lineterminator="\n") | |
for row in data: |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
""" | |
Minimal character-level Vanilla RNN model. Written by Andrej Karpathy (@karpathy) | |
BSD License | |
""" | |
import numpy as np | |
# data I/O | |
data = open('input.txt', 'r').read() # should be simple plain text file | |
chars = list(set(data)) | |
data_size, vocab_size = len(data), len(chars) |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
import csv | |
import sys | |
import os | |
# example usage: python split.py example.csv 200 | |
# above command would split the `example.csv` into smaller CSV files of 200 rows each (with header included) | |
# if example.csv has 401 rows for instance, this creates 3 files in same directory: | |
# - `example_1.csv` (row 1 - 200) | |
# - `example_2.csv` (row 201 - 400) | |
# - `example_3.csv` (row 401) |
type below:
brew update
brew install redis
To have launchd start redis now and restart at login:
brew services start redis
def sha256Hash(text: String) : String = java.security.MessageDigest.getInstance("SHA-256").digest(text.getBytes()).map(0xFF & ).map { "%02x".format() }.foldLeft(""){_ + _}
def sha256Hash(text: String) : String = String.format("%064x", new java.math.BigInteger(1, java.security.MessageDigest.getInstance("SHA-256").digest(text.getBytes("UTF-8"))))
verify via:
scala> sha256Hash("Rusty is a cowboy!")