How can I generate big data sample for Postgresql using generate_series and random?

Question

I want to generate big data sample (almost 1 million records) for studying tuplesort.c's polyphase merge in postgresql, and I hope the schema as follows:

CREATE TABLE Departments (code VARCHAR(4), UNIQUE (code)); CREATE TABLE Towns (   id SERIAL UNIQUE NOT NULL,   code VARCHAR(10) NOT NULL, -- not unique   article TEXT,   name TEXT NOT NULL, -- not unique   department VARCHAR(4) NOT NULL REFERENCES Departments (code),   UNIQUE (code, department) ); 

how to use generate_series and random for do it? thanks a lot!

Answer 1

To insert one million rows into Towns

insert into towns (     code, article, name, department ) select     left(md5(i::text), 10),     md5(random()::text),     md5(random()::text),     left(md5(random()::text), 4) from generate_series(1, 1000000) s(i) 

Since id is a serial it is not necessary to include it.