postgres bindng docs (#813)

concepts/bindings/README.md

@@ -23,15 +23,17 @@ Every binding has its own unique set of properties. Click the name link to see t
 |------|:----------------:|:-----------------:|--------|
 | [Cron (Scheduler)](../../reference/specs/bindings/cron.md) | ✅ | ✅ | Experimental |
 | [HTTP](../../reference/specs/bindings/http.md)           |    | ✅ | Experimental |
+| [InfluxDB](../../reference/specs/bindings/influxdb.md)       |    | ✅ | Experimental |
 | [Kafka](../../reference/specs/bindings/kafka.md)         | ✅ | ✅ | Experimental |
 | [Kubernetes Events](../../reference/specs/bindings/kubernetes.md) | ✅ |    | Experimental |
 | [MQTT](../../reference/specs/bindings/mqtt.md)           | ✅ | ✅ | Experimental |
+| [PostgreSql](../../reference/specs/bindings/postgres.md)       |    | ✅ | Experimental |
 | [RabbitMQ](../../reference/specs/bindings/rabbitmq.md)   | ✅ | ✅ | Experimental |
 | [Redis](../../reference/specs/bindings/redis.md)         |    | ✅ | Experimental |
 | [Twilio](../../reference/specs/bindings/twilio.md)       |    | ✅ | Experimental |
 | [Twitter](../../reference/specs/bindings/twitter.md)       | ✅ | ✅ | Experimental |
 | [SendGrid](../../reference/specs/bindings/sendgrid.md)       |    | ✅ | Experimental |
-| [InfluxDB](../../reference/specs/bindings/influxdb.md)       |    | ✅ | Experimental |
+
 
 ### Amazon Web Service (AWS)
 

reference/specs/bindings/postgres.md

@@ -0,0 +1,125 @@
+# PostgrSQL Binding Spec
+
+```yaml
+apiVersion: dapr.io/v1alpha1
+kind: Component
+metadata:
+  name: <NAME>
+  namespace: <NAMESPACE>
+spec:
+  type: bindings.postgres
+  metadata:
+  - name: url # Required
+    value: <CONNECTION_STRING>
+```
+
+> **Note:** In production never place passwords or secrets within Dapr components. For information on securely storing and retrieving secrets refer to [Setup Secret Store](../../../howto/setup-secret-store)
+
+The PostgrSQL binding uses [pgx connection pool](https://github.com/jackc/pgx) internally so the `url` parameter can be any valid connection string, either in a `DSN` or `URL` format:
+
+**Example DSN**
+
+```shell
+user=dapr password=secret host=dapr.example.com port=5432 dbname=dapr sslmode=verify-ca
+```
+
+**Example URL**
+
+```shell
+postgres://dapr:secret@dapr.example.com:5432/dapr?sslmode=verify-ca
+```
+
+Both methods also support connection pool configuration variables:
+
+* `pool_min_conns`: integer 0 or greater
+* `pool_max_conns`: integer greater than 0
+* `pool_max_conn_lifetime`: duration string
+* `pool_max_conn_idle_time`: duration string
+* `pool_health_check_period`: duration string
+
+## Output Binding Supported Operations
+
+* `exec`
+* `query`
+* `close`
+
+### exec
+
+The `exec` operation can be used for DDL operations (like table creation), as well as `INSERT`, `UPDATE`, `DELETE` operations which return only metadata (e.g. number of affected rows).
+
+**Request**
+
+```json
+{
+  "operation": "exec",
+  "metadata": {
+    "sql": "INSERT INTO foo (id, c1, ts) VALUES (1, 'demo', '2020-09-24T11:45:05Z07:00')"
+  }
+}
+```
+
+**Response**
+
+```json
+{
+  "metadata": {
+    "operation": "exec",
+    "duration": "294µs", 
+    "start-time": "2020-09-24T11:13:46.405097Z",
+    "end-time": "2020-09-24T11:13:46.414519Z",
+    "rows-affected": "1",
+    "sql": "INSERT INTO foo (id, c1, ts) VALUES (1, 'demo', '2020-09-24T11:45:05Z07:00')"
+  }
+}
+```
+
+### query
+
+The `query` operation is used for `SELECT` statements, which returns the metadata along with data in a form of an array of row values.
+
+**Request**
+
+```json
+{
+  "operation": "query",
+  "metadata": {
+    "sql": "SELECT * FROM foo WHERE id < 3"
+  }
+}
+```
+
+**Response**
+
+```json
+{
+  "metadata": {
+    "operation": "query",
+    "duration": "432µs", 
+    "start-time": "2020-09-24T11:13:46.405097Z",
+    "end-time": "2020-09-24T11:13:46.420566Z",
+    "sql": "SELECT * FROM foo WHERE id < 3"
+  },
+  "data": "[
+    [0,\"test-0\",\"2020-09-24T04:13:46Z\"],
+    [1,\"test-1\",\"2020-09-24T04:13:46Z\"],
+    [2,\"test-2\",\"2020-09-24T04:13:46Z\"]
+  ]"
+}
+```
+
+### close
+
+Finally, the `close` operation can be used to explicitly close the DB connection and return it to the pool. This operation doesn't have any response.
+
+**Request**
+
+```json
+{
+  "operation": "close"
+}
+```
+
+
+> Note, the PostgreSql binding itself doesn't prevent SQL injection, like with any database application, validate the input before executing query.
+
+