Make OpenDBFromPool docs explicit about closing the *sql.DB

#2295

Author: jackc

stdlib/sql.go

@@ -216,7 +216,8 @@ func OpenDB(config pgx.ConnConfig, opts ...OptionOpenDB) *sql.DB {
 
 // OpenDBFromPool creates a new *sql.DB from the given *pgxpool.Pool. Note that this method automatically sets the
 // maximum number of idle connections in *sql.DB to zero, since they must be managed from the *pgxpool.Pool. This is
-// required to avoid acquiring all the connections from the pgxpool and starving any direct users of the pgxpool.
+// required to avoid acquiring all the connections from the pgxpool and starving any direct users of the pgxpool. Note
+// that closing the returned *sql.DB will not close the *pgxpool.Pool.
 func OpenDBFromPool(pool *pgxpool.Pool, opts ...OptionOpenDB) *sql.DB {
 	c := GetPoolConnector(pool, opts...)
 	db := sql.OpenDB(c)