Foreign Table: Persistent Postgres table for managing external data queried by DuckDB readers

include/pgduckdb/pgduckdb_foreign_tables.hpp

@@ -0,0 +1,28 @@
+#pragma once
+
+#include <string>
+
+#include "pgduckdb/pg/declarations.hpp"
+
+namespace pgduckdb {
+
+// The name of the foreign server that we use for DuckDB foreign tables.
+#define DUCKDB_FOREIGN_SERVER_NAME "duckdb"
+
+void ValidateForeignIdentifier(const char *identifier, const char *context);
+
+std::string BuildForeignTableFunctionCall(const char *reader, const char *location, void *options);
+
+bool EnsureForeignTableLoaded(Oid relid);
+
+void UnloadedForeignTable(Oid relid);
+
+void ResetForeignTableCache();
+
+bool IsForeignTableLoaded(Oid relid);
+
+bool pgduckdb_is_foreign_relation(Oid relation_oid);
+
+const char *ForeignTableServerName();
+
+} // namespace pgduckdb

include/pgduckdb/pgduckdb_ruleutils.h

@@ -15,8 +15,9 @@ char *pgduckdb_get_tabledef(Oid relation_id);
 char *pgduckdb_get_alter_tabledef(Oid relation_oid, AlterTableStmt *alter_stmt);
 char *pgduckdb_get_rename_relationdef(Oid relation_oid, RenameStmt *rename_stmt);
 bool pgduckdb_is_not_default_expr(Node *node, void *context);
-List *pgduckdb_db_and_schema(const char *postgres_schema_name, const char *duckdb_table_am_name);
-const char *pgduckdb_db_and_schema_string(const char *postgres_schema_name, const char *duckdb_table_am_name);
+List *pgduckdb_db_and_schema(const char *postgres_schema_name, const char *duckdb_table_am_name, bool is_ddb_foreign);
+const char *pgduckdb_db_and_schema_string(const char *postgres_schema_name, const char *duckdb_table_am_name,
+                                          bool is_ddb_foreign);
 bool pgduckdb_is_duckdb_row(Oid type_oid);
 bool pgduckdb_is_unresolved_type(Oid type_oid);
 bool pgduckdb_is_fake_type(Oid type_oid);

sql/pg_duckdb--1.0.0--1.1.0.sql

@@ -103,3 +103,14 @@ CREATE FUNCTION duckdb.create_simple_secret(
 RETURNS TEXT
 SET search_path = pg_catalog, pg_temp
 LANGUAGE C AS 'MODULE_PATHNAME', 'pgduckdb_create_simple_secret';
+
+CREATE SERVER duckdb
+TYPE 'foreign_table'
+FOREIGN DATA WRAPPER duckdb;
+
+GRANT USAGE ON FOREIGN SERVER duckdb TO public;
+
+DROP EVENT TRIGGER IF EXISTS duckdb_alter_table_trigger;
+CREATE EVENT TRIGGER duckdb_alter_foreign_table_trigger ON ddl_command_end
+    WHEN tag IN ('ALTER TABLE', 'ALTER FOREIGN TABLE')
+    EXECUTE FUNCTION duckdb._alter_table_trigger();