perl script without using DBI

Question

I have to make a perl script populate a database in PostgreSQL without using DBI or any sort of database interface model. I am a beginner to scripting so naturally, I'v been stuck on this for quite a while. I only have this much so far.

    open my $pipe, '|-', "psql -d postgres -U postgres", @options or die;
    # NOT SURE WHAT TO DO AFTER THIS

    close $pipe;

edit 1: Now i'm trying to do this.

 for ($count = $iters; $count >= 1; $count--) {
    $randdecimal = rand();
    $pipe "INSERT INTO random_table (runid, random_number) VALUES ($runid, $randdecimal)";
 }

but it gives me a syntax error

You may be better off generating a big sql file, and just shelling out to postgres to read it. Interacting statement-by-statement via open could get horribly complicated. — Neil Slater
– Neil Slater, Commented Apr 13, 2013 at 15:52
print $pipe "SELECT * FROM TheTable;\n", but you'd be better off using DBI by a large margin. What you are attempting is not sensible. — Jonathan Leffler
– Jonathan Leffler, Commented Apr 13, 2013 at 15:53
Could you elaborate one that please or maybe provide an example? — user1943079
– user1943079, Commented Apr 13, 2013 at 15:53
If you're asking me, the answer is no. I like you too much to be willing to inflict the pain of processing SQL via pipes in Perl. — Jonathan Leffler
– Jonathan Leffler, Commented Apr 13, 2013 at 15:55
but all i need to do is insert into a table an arbitrary number of times. Nothing more than that — user1943079
– user1943079, Commented Apr 13, 2013 at 16:06

Richard Huxton · Accepted Answer · 2013-04-13 17:32:38Z

2

Like the others say, DBI is much better than printing to a pipe.

However, there is a halfway house. Just print all your SQL to STDOUT and then do something like:

myscript.pl | psql -v ON_ERROR_STOP=1 --single-transaction -f -

This lets you easily check your script output / send it to a file. The psql options stop on the first error, wrap everything in a transaction and read from STDIN. You might want the usual -h/-U options too.

Personally, I tend to have two terminals open and just write to a .sql file then \i from a psql prompt. I like having a record of what command I ran.

answered Apr 13, 2013 at 17:32

Richard Huxton

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