Database requirements for running the app:

• Postgresql 9.5 or newer
• Create two databases foo and bar
• create a table source with three integer columns (a,b,c) in foo
• and a table dest with three integer columns (a,b,c) in bar

PS: It is necessary to change the database credentials in file lib/manage_db_conn.ex in order to work, it is currently hardcoded there.

Simple web application to accomplish the following on a pre-created database with the necessary table structures:

• opens a connection to the database foo
• fills the table source with 1 million rows where: --column a contains the numbers from 1 to 1e6 --column b has a % 3 --column c has a % 5
• opens a connection to the database bar
• copies the data from table source in foo to table dest in bar using postgresql copy command (without saving data into a file) Then:
• starts a web server that has two endpoints: ./dbs/foo/tables/source and ./dbs/bar/tables/dest --upon a GET request to either of the two it must respond with contents of a corresponding table serialized as CSV and using HTTP chunked encoding. Data must be streamed from the database upon a request, not stored in a file or cached in memory

All the transactions used Streams to give a better performance and support greater amounts of data.

The app can be run by Elixir's cli IEX, here's an example:

Erlang/OTP 20 [erts-9.2.1] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]

Interactive Elixir (1.6.1) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> StreamingChunked.Pipeline.run_pipeline()
inserting into source
copying source into dest
initializing server
{:ok, #PID<0.203.0>}