CSV Databases in Perl

On Monday I wrote about using Amazon Athena from Perl. That’s only step one though, because often I find myself needing to dig further.

Athena provides results as CSV. I have a couple tools I use to interact with CSV. The older, which I’ve mentioned before, is a filter that reads CSV on STDIN and writes JSON on STDOUT. I use it with normal shell tools and jq :

#!/usr/bin/env perl use strict; use Text::xSV; use JSON::XS; my $CSV = Text::xSV -> new (); my $JSON = JSON::XS -> new -> canonical -> utf8; $CSV -> read_header(); while ( my $row = $CSV -> fetchrow_hash) { print $JSON -> encode($row) . "

" ; }

Then I might do something like:

cat foo.csv | csv2json | jq .username

The above is handy for little scripts, but what I’ve been enjoying lately is actual SQL, so I have a script to use CSV as a database. I think I’m calling it csvsh . It wraps dbish and leverages DBD::CSV and does some annoying backbends to ease the use of the tool.

#!/usr/bin/env perl use strict; use warnings; use autodie; use Term::ANSIColor; my $csv = shift or die "usage: $0 <path-to-csv>

" ; my $dir = $csv =~ s(^(.*/)([^/]+) )($1 /. $2)r; unless ( - d $dir) { mkdir $dir; link $csv, "$dir/_" ; } chdir $dir; open my $fh, '<' , '_' ; my $header = <$fh> ; close $fh; print colored([ 'bold' ], "table is _, columns are $header" ); system 'dbish' , 'dbi:CSV:f_dir=.' ; END { chdir q(..) ; unlink "$dir/_" ; rmdir $dir; };

I want to make it support a --sql argument at some point but haven’t gotten around to it yet. Here’s an example session of csvsh :

$ csvsh ~/Downloads/3d5f3e2c-f9eb-48bc-9a3f-628a739e011d.csv table is _, columns are "eventname","eventsource","eventtype","sourceipaddress","cnt" Useless localization of scalar assignment at /home/frew/.plenv/versions/5.26.0/lib/perl5/site_perl/ 5.26.0/DBI/Format.pm line 377. DBI::Shell 11.95 using DBI 1.636 WARNING: The DBI::Shell interface and functionality are ======= very likely to change in subsequent versions! Connecting to 'dbi:CSV:f_dir=.' as ''... @dbi:CSV:f_dir=.> SELECT SUM(cnt), eventname FROM _ GROUP BY eventname; SUM,eventname 68,'DescribeInternetGateways' 4,'GetBucketVersioning' 68,'DescribeApplications' 68,'DescribeDBSecurityGroups' 253,'DescribeAutoScalingGroups' 68,'DescribeSpotInstanceRequests' 460,'DescribeAccountAttributes' 3,'DescribeRegions' 260,'GetSendQuota' 68,'DescribeCacheSecurityGroups' 68,'DescribeEnvironments' 68,'DescribeNetworkInterfaces' 264,'GetAccountSummary' 136,'DescribeAddresses' 68,'DescribeVpcs' 68,'DescribeSubnets' [ ... ]

It’s a little noisy at startup, but it still works pretty well.

As with Monday’s post I don’t have much I can link to that adds to this information, so I’ll duplicate the stuff I’m interested in this week:

(The following includes affiliate links.)

I just started the eigth book in The Malazan Series and as usual I’m enjoying it a lot.

In a totally different vein I just ordered a thermocouple in the hopes that it would give me more insight while roasting my coffee and allow me to make my roasts that much better.

Posted Wed, Jun 14, 2017

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