Add federated server list remotes

Includes: - CDB_Federated_Server_List_Remote_Schemas - CDB_Federated_Server_List_Remote_Tables
2019-10-29 18:26:36 +01:00
parent e22aaee5f5
commit 144c4e722b
5 changed files with 286 additions and 29 deletions
--- a/scripts-available/CDB_FederatedServer_ListRemote.sql
+++ b/scripts-available/CDB_FederatedServer_ListRemote.sql
@@ -0,0 +1,114 @@
+--------------------------------------------------------------------------------
+-- Private functions
+--------------------------------------------------------------------------------
+CREATE OR REPLACE FUNCTION @extschema@.__CDB_FS_List_Foreign_Schemas_PG(server_internal name)
+RETURNS TABLE(remote_schema name)
+AS $$
+DECLARE
+    -- Import schemata from the information schema
+    --
+    -- "The view schemata contains all schemas in the current database
+    -- that the current user has access to (by way of being the owner
+    -- or having some privilege)."
+    -- See https://www.postgresql.org/docs/11/infoschema-schemata.html
+    --
+    -- "The information schema is defined in the SQL standard and can
+    -- therefore be expected to be portable and remain stable"
+    -- See https://www.postgresql.org/docs/11/information-schema.html
+    inf_schema name := 'information_schema';
+    remote_table name := 'schemata';
+    local_schema name := @extschema@.__CDB_FS_Create_Schema(server_internal, inf_schema);
+BEGIN
+    -- Import the foreign schemata if not done
+    IF NOT EXISTS (
+        SELECT * FROM pg_class
+        WHERE relnamespace = (SELECT oid FROM pg_namespace WHERE nspname = local_schema)
+        AND relname = remote_table
+    ) THEN
+        EXECUTE format('IMPORT FOREIGN SCHEMA %I LIMIT TO (%I) FROM SERVER %I INTO %I', inf_schema, remote_table, server_internal, local_schema);
+    END IF;
+
+    -- Return the result we're interested in
+    RETURN QUERY EXECUTE format('SELECT schema_name::name AS remote_schema FROM %I.%I', local_schema, remote_table);
+END
+$$
+LANGUAGE PLPGSQL VOLATILE PARALLEL UNSAFE;
+
+
+CREATE OR REPLACE FUNCTION @extschema@.__CDB_FS_List_Foreign_Tables_PG(server_internal name, remote_schema name)
+RETURNS TABLE(remote_table name)
+AS $func$
+DECLARE
+    -- Import `tables` from the information schema
+    --
+    -- "The view tables contains all tables and views defined in the
+    -- current database. Only those tables and views are shown that
+    -- the current user has access to (by way of being the owner or
+    -- having some privilege)."
+    -- https://www.postgresql.org/docs/11/infoschema-tables.html
+
+    -- Create local target schema if it does not exists
+    inf_schema name := 'information_schema';
+    remote_table name := 'tables';
+    local_schema name := @extschema@.__CDB_FS_Create_Schema(server_internal, inf_schema);
+BEGIN
+    -- Import the foreign `tables` if not done
+    IF NOT EXISTS (
+        SELECT * FROM pg_class
+        WHERE relnamespace = (SELECT oid FROM pg_namespace WHERE nspname = local_schema)
+        AND relname = 'tables'
+    ) THEN
+        EXECUTE format('IMPORT FOREIGN SCHEMA %I LIMIT TO (%I) FROM SERVER %I INTO %I', inf_schema, remote_table, server_internal, local_schema);
+    END IF;
+
+    -- Return the result we're interested in
+    -- Note: in this context, schema names are not to be quoted
+    RETURN QUERY EXECUTE format($q$SELECT table_name::name AS remote_table FROM %I.%I WHERE table_schema = '%s'$q$, local_schema, remote_table, remote_schema);
+END
+$func$
+LANGUAGE PLPGSQL VOLATILE PARALLEL UNSAFE;
+
+
+--------------------------------------------------------------------------------
+-- Public functions
+--------------------------------------------------------------------------------
+
+--
+-- List remote schemas in a federated server that the current user has access to.
+--
+CREATE OR REPLACE FUNCTION @extschema@.CDB_Federated_Server_List_Remote_Schemas(remote_server name)
+RETURNS TABLE(remote_schema name)
+AS $$
+DECLARE
+    server_internal name := @extschema@.__CDB_FS_Generate_Server_Name(input_name := remote_server, check_existence := true);
+    server_type name := @extschema@.__CDB_FS_server_type(server_internal);
+BEGIN
+    CASE server_type
+    WHEN 'postgres_fdw' THEN
+        RETURN QUERY SELECT @extschema@.__CDB_FS_List_Foreign_Schemas_PG(server_internal);
+    ELSE
+        RAISE EXCEPTION 'Not implemented server type % for remote server %', server_type, remote_server;
+    END CASE;
+END
+$$
+LANGUAGE PLPGSQL VOLATILE PARALLEL UNSAFE;
+
+--
+-- List remote tables in a federated server that the current user has access to.
+--
+CREATE OR REPLACE FUNCTION @extschema@.CDB_Federated_Server_List_Remote_Tables(remote_server name, remote_schema name)
+RETURNS TABLE(remote_table name)
+AS $$
+DECLARE
+    server_internal name := @extschema@.__CDB_FS_Generate_Server_Name(input_name := remote_server, check_existence := true);
+    server_type name := @extschema@.__CDB_FS_server_type(server_internal);
+BEGIN
+    CASE server_type
+    WHEN 'postgres_fdw' THEN
+        RETURN QUERY SELECT @extschema@.__CDB_FS_List_Foreign_Tables_PG(server_internal, remote_schema);
+    ELSE
+        RAISE EXCEPTION 'Not implemented server type % for remote server %', server_type, remote_server;
+    END CASE;
+END
+$$
+LANGUAGE PLPGSQL VOLATILE PARALLEL UNSAFE;