wwgist

# -*- coding: utf-8 -*-
# При вызове метода __new__ каждый раз возвращается один и тот же объект.
# Хранится объект в классовой переменной.


# переопределение __new__ (поверхностно)
class C(object):
    instance = None
    def __new__(cls):
        if cls.instance is None:

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# MySQL hints

mysql [OPTIONS] [database]
mysqladmin [OPTIONS] command command....

-u  >   user
-p  >   password
-D  >   database
-h  >   host
-P  >   port

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# PostgreSQL hints

psql [option...] [dbname [username]]

-U  >   username    (default=unix_user) VEVAR=PGUSER
-W  >   password
-w  >   no-password
-d  >   dbname              VEVAR=PGDATABASE
-h  >   hostname    (default=unix_socket/localhost) VEVAR=PGHOST
-p  >   port        (default=default)

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Latency Comparison Numbers
--------------------------
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
Send 1K bytes over 1 Gbps network        10,000   ns    0.01 ms
Read 4K randomly from SSD*              150,000   ns    0.15 ms