From 87302920975ff64112ef6964d71cf68b7eaf9cd2 Mon Sep 17 00:00:00 2001
From: Rafa de la Torre <rtorre@carto.com>
Date: Fri, 8 Nov 2019 19:20:08 +0100
Subject: [PATCH] Function to retrieve remote PG server ver

---
 .../CDB_FederatedServerDiagnostics.sql        | 41 ++++++++++++++++---
 test/CDB_FederatedServerDiagnostics.sql       |  2 +
 2 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/scripts-available/CDB_FederatedServerDiagnostics.sql b/scripts-available/CDB_FederatedServerDiagnostics.sql
index fd00e95..e55f90f 100644
--- a/scripts-available/CDB_FederatedServerDiagnostics.sql
+++ b/scripts-available/CDB_FederatedServerDiagnostics.sql
@@ -2,22 +2,53 @@
 -- Private functions
 --------------------------------------------------------------------------------
 
-CREATE OR REPLACE FUNCTION @extschema@.__CDB_FS_Server_Version_PG(server_internal name)
+--
+-- Get the version of a remote PG server
+--
+CREATE OR REPLACE FUNCTION @extschema@.__CDB_FS_Foreign_Server_Version_PG(server_internal name)
 RETURNS text
 AS $$
+DECLARE
+    -- Import pg_settings from pg_catalog
+    remote_schema name := 'pg_catalog';
+    remote_table name := 'pg_settings';
+    local_schema name := @extschema@.__CDB_FS_Create_Schema(server_internal, remote_schema);
+    role_name name := @extschema@.__CDB_FS_Generate_Server_Role_Name(server_internal);
+    remote_server_version text;
 BEGIN
-    -- TODO Implement
-    RETURN '14.0';
+    -- Import the foreign pg_settings table
+    IF NOT EXISTS (
+        SELECT * FROM pg_class
+        WHERE relnamespace = (SELECT oid FROM pg_namespace WHERE nspname = local_schema)
+        AND relname = remote_table
+    ) THEN
+        EXECUTE format('IMPORT FOREIGN SCHEMA %I LIMIT TO (%I) FROM SERVER %I INTO %I',
+                    remote_schema, remote_table, server_internal, local_schema);
+    END IF;
+
+    BEGIN
+        EXECUTE format('
+            SELECT setting FROM %I.%I WHERE name = ''server_version'';
+        ', local_schema, remote_table) INTO remote_server_version;
+    EXCEPTION WHEN OTHERS THEN
+        RAISE EXCEPTION 'Not enough permissions to access the server "%"',
+                        @extschema@.__CDB_FS_Extract_Server_Name(server_internal);
+    END;
+
+    RETURN remote_server_version;
 END
 $$
 LANGUAGE PLPGSQL VOLATILE PARALLEL UNSAFE;
 
 
+--
+-- Collect and return diagnostics info from a remote PG into a jsonb
+--
 CREATE OR REPLACE FUNCTION @extschema@.__CDB_FS_Server_Diagnostics_PG(server_internal name)
 RETURNS jsonb
 AS $$
 DECLARE
-    remote_server_version text := @extschema@.__CDB_FS_Server_Version_PG(server_internal);
+    remote_server_version text := @extschema@.__CDB_FS_Foreign_Server_Version_PG(server_internal);
 BEGIN
     RETURN jsonb_build_object('server_version', remote_server_version);
 END
@@ -31,7 +62,7 @@ LANGUAGE PLPGSQL VOLATILE PARALLEL UNSAFE;
 --------------------------------------------------------------------------------
 
 --
--- TODO: function documentation
+-- Collect and return diagnostics info from a remote PG into a jsonb
 --
 CREATE OR REPLACE FUNCTION @extschema@.CDB_Federated_Server_Diagnostics(server TEXT)
 RETURNS jsonb
diff --git a/test/CDB_FederatedServerDiagnostics.sql b/test/CDB_FederatedServerDiagnostics.sql
index e26b615..a94776d 100644
--- a/test/CDB_FederatedServerDiagnostics.sql
+++ b/test/CDB_FederatedServerDiagnostics.sql
@@ -44,6 +44,8 @@ SELECT '1.3', cartodb.CDB_Federated_Server_Diagnostics(server => 'loopback') @>
 -- ===================================================================
 \set QUIET on
 SELECT 'D1', cartodb.CDB_Federated_Server_Unregister(server => 'loopback'::text);
+-- Reconnect, using a new session in order to close FDW connections
+\connect
 DROP DATABASE cdb_fs_tester;
 
 -- Drop role