Postgres migration script.

psql-migrate

#!/usr/bin/env sh
set -eu

if [ $# -ne 0 ]; then
  cat <<-USAGE
psql-migrate

Takes a sorted list of filenames from stdin and writes psql migrations sql
to stdout.

usage:
  ls -1v migrations/* | psql-migrate | psql ...

safety:
  * A migration table called 'schema_migrations' will be created.
  * Paths passed to stdin must be relative to the script or absolute.
  * Only migration file basenames are persisted in schema_migrations.
USAGE
  exit 0
fi

migrations=""
while read -r migration; do
  if [ ! -r "$migration" ]; then
    echo "error: '$migration' not readable."
    [ "$migration" = "$(basename "$migration")" ] && echo "Did you forget to include the path?"
    exit -1
  fi
  migrations="${migrations} $migration"
done < /dev/stdin

cat <<-SQL
\set ON_ERROR_STOP ON
create table if not exists schema_migrations (
  migration text not null primary key,
  completed timestamp with time zone not null default now()
);
SQL

for migration in $migrations; do
  filename=$(basename "$migration")
  cat <<-SQL
-- begin migration $filename
do \$$
begin
  perform 1 from schema_migrations where migration = '$filename';
  if not found then
    raise notice 'migration "%", begin', '$filename';
    -- begin sql

$(cat "$migration")

    -- end sql
    insert into schema_migrations values ('$filename');
    raise notice 'migration "%", end', '$filename';
  else
    raise notice 'migration "%" already run, skipping', '$filename';
  end if;
end
\$$;
-- end migration $filename

SQL
done