Q: I have a table in pg like so: CREATE TABLE t ( a BIGSERIAL NOT NULL, -- 8 b b SMALLINT, -- 2 b c SMALLINT, -- 2 b d REAL, -- 4 b e REAL, -- 4 b f REAL, -- 4 b g INTEGER, -- 4 b h REAL, -- 4 b i REAL, -- 4 b j SMALLINT, -- 2 b k INTEGER, -- 4 b l I…

Get the current free disk space in PostgreSQL PostgreSQL获取磁盘空间 from eshizhan Here has a simple way to get free disk space without any extended language, just define a function using pgsql. CREATE OR REPLACE FUNCTION sys_df() RETURNS SETOF text[] LANG…

Q:   I have a PostgreSQL table. select * is very slow whereas select id is nice and quick. I think it may be that the size of the row is very large and it's taking a while to transport, or it may be some other factor. I need all of the fields (or nea…

This document describes the installation of PostgreSQL using the source    code distribution. (If you are installing a pre-packaged distribution,    such as an RPM or Debian package, ignore this document and read the    packager's instructions instea…

这个月6号开始,着手解决一个具有实际意义的计算任务.任务数据有9879896条,每条包含30个整数,任务是计算每两条数据之间的斯皮尔相关系数及其P值.原始数据只有500+MB,因此我并不认为这是个多么大的计算任务.随后稍加计算,我还是很惊呆的,要计算(9879896×9879895)÷2≍4.88亿亿组数据,但此时这还只是个数字概念,我也没意识到时间复杂度和空间复杂度的问题. 1. 计算规模初体验 数据格式:9879896行,30列,每列之间以空格符隔开,例如: 0 2 0 2 0 0 0 0…

Google : Op-Amp Level Shifter Level shifting a +/- 2.5V signal to 0 - 5V I have a front end module that generates an (ECG) signal that varies from +/-2.5 V. I want to shift this signal to 0 - 5V. What is the best way to do this? First thing to try is…

Should Your Resume Be One Page or Two? Conventional wisdom suggests that you should keep it short: According to job hunting site The Ladders, recruiters spend roughly six seconds reviewing most resumes. However, new findings by resume writing service…

what are stop words 一.总结 一句话总结:就是在seo的关键词中不要有stop words,不然的话搜索引擎会直接忽略 stop words  most common  words language In computing, stop words are words which are filtered out before or after processing of natural language data (text).[1] Though "stop words&…

奇怪的现象 在paython3中 print(range(10)) 得出的结果是 range(0,10) ,而不是[0,1,2,3,4,5,6,7,8,9] ,为什么呢? 官网原话: In many ways the object returned by range() behaves as if it is a list, but in fact it isn’t. It is an object which returns the successive items of the desire…

http://electronicdesign.com/boards/non-inverting-level-shifter-requires-only-one-op-amp-one-supply-voltage With portable battery-operated devices continuing to add functionality while shrinking in size, printed-circuit-board real estate becomes incre…