Create numbered migration files, 1-create_users.sql, 2-create_accounts.sql, put them in the MIGRATIONS_LOCATION directory.

pgmigrations.erb.sh

#!/bin/bash

export PGPASSWORD=<%= password %>

USER=<%= user %>
DATABASE=<%= database %>
HOST=<%= host %>
MIGRATIONS_TABLE=<%= migrations_table %>
MIGRATIONS_LOCATION=<%= migrations_location %>

function execute_sql {
  psql -U $USER -d $DATABASE -h localhost -t -c "$1"
}

function ensure_migrations_table {
	execute_sql "CREATE TABLE IF NOT EXISTS $MIGRATIONS_TABLE (version integer UNIQUE);"
}

function check_migration_version {
	local version=`execute_sql "SELECT version FROM migrations ORDER BY version DESC LIMIT 1;"`
	if [ -z $version ]; then
		echo 0
	else	
		echo $version
	fi
}

function add_migration {
	execute_sql "INSERT INTO $MIGRATIONS_TABLE VALUES ($1)"
}

function check_dry_run {
	if [ -z $DRY_RUN ]; then
		echo "Running migrations!"
	else
		echo "Running in DRY_RUN mode. No migrations will actually execute"
	fi
}

function run_migrations {
	local current_version=`check_migration_version`
	echo "Current migration version is: $current_version"
	for f in `ls $MIGRATIONS_LOCATION/*.sql | sort -V`
	do
		local version=`echo $f | grep -Po '\d+'`
		if [ $version -gt $current_version ]; then
			local migration=`cat $f`
			echo "Running migration $f"
			echo
			if [ -z $DRY_RUN ]; then
				execute_sql "$migration"
				result=$?
				if [ $result -eq 0 ]; then
				    add_migration $version
				else
				    exit $result
				fi
			fi
		else
			echo "Skipping migration $f"
		fi
	done
}

ensure_migrations_table
check_dry_run
run_migrations

export PGPASSWORD=