{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Writing to PostgreSQL\n",
    "\n",
    "1. Insure PostgreSQL is actually installed on the system, \n",
    "2. There is a database called demo created on the said system\n",
    "\n",
    "The cell below creates a dataframe that will be stored within postgreSQL"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "2.0.4\n"
     ]
    }
   ],
   "source": [
    "#\n",
    "# Writing to PostgreSQL database\n",
    "#\n",
    "import transport\n",
    "from transport import providers\n",
    "import pandas as pd\n",
    "_data = pd.DataFrame({\"name\":['James Bond','Steve Rogers','Steve Nyemba'],'age':[55,150,44]})\n",
    "pgw = transport.get.writer(provider=providers.POSTGRESQL,database='demo',table='friends')\n",
    "pgw.write(_data,if_exists='replace') #-- default is append\n",
    "print (transport.__version__)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Reading from PostgreSQL\n",
    "\n",
    "The cell below reads the data that has been written by the cell above and computes the average age within a PostreSQL (simple query). \n",
    "\n",
    "- Basic read of the designated table (friends) created above\n",
    "- Execute an aggregate SQL against the table\n",
    "\n",
    "\n",
    "**NOTE**\n",
    "\n",
    "By design **read** object are separated from **write** objects in order to avoid accidental writes to the database.\n",
    "Read objects are created with **transport.get.reader** whereas write objects are created with **transport.get.writer**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "           name  age\n",
      "0    James Bond   55\n",
      "1  Steve Rogers  150\n",
      "2  Steve Nyemba   44\n",
      "--------- STATISTICS ------------\n",
      "   _counts   avg\n",
      "0        3  83.0\n"
     ]
    }
   ],
   "source": [
    "\n",
    "import transport\n",
    "from transport import providers\n",
    "pgr = transport.get.reader(provider=providers.POSTGRESQL,database='demo',table='friends')\n",
    "_df = pgr.read()\n",
    "_query = 'SELECT COUNT(*) _counts, AVG(age) from friends'\n",
    "_sdf = pgr.read(sql=_query)\n",
    "print (_df)\n",
    "print ('--------- STATISTICS ------------')\n",
    "print (_sdf)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "An **auth-file** is a file that contains database parameters used to access the database. \n",
    "For code in shared environments, we recommend \n",
    "\n",
    "1. Having the **auth-file** stored on disk \n",
    "2. and the location of the file is set to an environment variable.\n",
    "\n",
    "To generate a template of the **auth-file** open the **file generator wizard** found at visit https://healthcareio.the-phi.com/data-transport"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'host': 'klingon.io',\n",
       " 'port': 5432,\n",
       " 'username': 'me',\n",
       " 'password': 'foobar',\n",
       " 'provider': 'postgresql',\n",
       " 'database': 'demo',\n",
       " 'table': 'friends'}"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "{\n",
    "    \"host\":\"klingon.io\",\"port\":5432,\"username\":\"me\",\"password\":\"foobar\", \"provider\":\"postgresql\",\n",
    "    \"database\":\"demo\",\"table\":\"friends\"\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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