[pr-review] Lighten docs & validate SQL dialect

Signed-off-by: Étienne Lafarge <etienne.lafarge@gmail.com>

docs/install.md

@@ -380,13 +380,13 @@ Using such a storage backend is particularly useful if your release information
 weighs more than 1MB (in which case, it can't be stored in ConfigMaps/Secrets
 because of internal limits in Kubernetes' underlying etcd key-value store).
 
-To enable the SQL backend, you'll need to [deploy an SQL
-database](./sql-storage.md) and init Tiller with the following options:
+To enable the SQL backend, you'll need to deploy a SQL database and init Tiller
+with the following options:
 
 ```shell
 helm init \
   --override \
-    'spec.template.spec.containers[0].args'='{--storage=sql,--sql-dialect=postgres,--sql-connection-string=postgresql://tiller-postgres:5432/helm?user=helm&password=changemeforgodssake&sslmode=disable}'
+    'spec.template.spec.containers[0].args'='{--storage=sql,--sql-dialect=postgres,--sql-connection-string=postgresql://tiller-postgres:5432/helm?user=helm&password=changeme}'
 ```
 
 **PRODUCTION NOTES**: it's recommended to change the username and password of

docs/sql-storage.md

@@ -1,89 +0,0 @@
-# Store release information in an SQL database
-
-You may be willing to store release information in an SQL database - in
-particular, if your releases weigh more than 1MB and therefore [can't be stored in ConfigMaps or Secrets](https://github.com/helm/helm/issues/1413).
-
-We recommend using [PostgreSQL](https://www.postgresql.org/).
-
-This document describes how to deploy `postgres` atop Kubernetes. This being
-said, using an out-of-cluster (managed or not) PostreSQL instance is totally
-possible as well.
-
-Here's a Kubernetes manifest you can apply to get a minimal PostreSQL pod
-running on your Kubernetes cluster. **Don't forget to change the credentials
-and, optionally, enable TLS in production deployments**.
-
-```yaml
-apiVersion: v1
-kind: Service
-metadata:
-  name: tiller-postgres
-  namespace: kube-system
-spec:
-  ports:
-    - port: 5432
-  selector:
-    app: helm
-    name: postgres
----
-apiVersion: apps/v1
-kind: StatefulSet
-metadata:
-  name: tiller-postgres
-  namespace: kube-system
-spec:
-  serviceName: tiller-postgres
-  selector:
-    matchLabels:
-      app: helm
-      name: postgres
-  replicas: 1
-  template:
-    metadata:
-      labels:
-        app: helm
-        name: postgres
-    spec:
-      containers:
-        - name: postgres
-          image: postgres:11-alpine
-          imagePullPolicy: Always
-          ports:
-            - containerPort: 5432
-          env:
-          - name: POSTGRES_DB
-            value: helm
-          - name: POSTGRES_USER
-            value: helm
-          - name: POSTGRES_PASSWORD
-            value: changemeforgodssake
-          - name: PGDATA
-            value: /var/lib/postgresql/data/pgdata
-          resources:
-            limits:
-              memory: 128Mi
-            requests:
-              cpu: 50m
-              memory: 128Mi
-          volumeMounts:
-            - mountPath: /var/lib/postgresql/data
-              name: tiller-postgres-data
-  volumeClaimTemplates:
-  - metadata:
-      name: tiller-postgres-data
-    spec:
-      accessModes: ["ReadWriteOnce"]
-      storageClassName: default
-      resources:
-        requests:
-          storage: 5Gi
-```
-
-Once postgres is deployed, you'll need to install Tiller using `helm init`, with
-a few custom CLI flags:
-
-```shell
-helm init \
-  --override \
-    'spec.template.spec.containers[0].args'='{--storage=sql,--sql-dialect=postgres,--sql-connection-string=postgresql://tiller-postgres:5432/helm?user=helm&password=changemeforgodssake&sslmode=disable}'
-```

pkg/storage/driver/sql.go

@@ -43,6 +43,10 @@ var labelMap = map[string]string{
 	"NAME":        "name",
 }
 
+var supportedSQLDialects = map[string]struct{}{
+	"postgres": struct{}{},
+}
+
 // SQLDriverName is the string name of this driver.
 const SQLDriverName = "SQL"
 
@@ -113,6 +117,10 @@ type Release struct {
 
 // NewSQL initializes a new memory driver.
 func NewSQL(dialect, connectionString string, logger func(string, ...interface{})) (*SQL, error) {
+	if _, ok := supportedSQLDialects[dialect]; !ok {
+		return nil, fmt.Errorf("%s dialect isn't supported, only \"postgres\" is available for now", dialect)
+	}
+
 	db, err := sqlx.Connect(dialect, connectionString)
 	if err != nil {
 		return nil, err