Default (generic) toaster re-implemented using Toaster API.

Default Toaster could be replaced with custom toaster by
SET TOASTER clause in CREATE TABLE or ALTER TABLE expression

Added src/backend/access/toast/README.toastapi

0003_toaster_default patch

Author: Nikita Malakhov

contrib/amcheck/verify_heapam.c

@@ -10,7 +10,7 @@
  */
 #include "postgres.h"
 
-#include "access/detoast.h"
+#include "access/toasterapi.h"
 #include "access/genam.h"
 #include "access/heapam.h"
 #include "access/heaptoast.h"
@@ -24,6 +24,8 @@
 #include "storage/procarray.h"
 #include "utils/builtins.h"
 #include "utils/fmgroids.h"
+#include "access/toast_helper.h"
+#include "catalog/toasting.h"
 
 PG_FUNCTION_INFO_V1(verify_heapam);
 

contrib/dummy_toaster/dummy_toaster--1.0.sql

@@ -12,3 +12,4 @@ LANGUAGE C;
 CREATE TOASTER dummy_toaster  HANDLER dummy_toaster_handler;
 
 COMMENT ON TOASTER dummy_toaster IS 'dummy_toaster is a dummy toaster';
+

contrib/dummy_toaster/dummy_toaster.c

@@ -1,7 +1,7 @@
 /*-------------------------------------------------------------------------
  *
  * dummy_toaster.c
- *		Dummy toaster for Toaster API.
+ *		Dummy toaster - sample toaster for Toaster API.
  *
  * Portions Copyright (c) 2016-2021, PostgreSQL Global Development Group
  * Portions Copyright (c) 1990-1993, Regents of the University of California
@@ -14,6 +14,26 @@
 #include "postgres.h"
 #include "fmgr.h"
 #include "access/toasterapi.h"
+#include "access/heaptoast.h"
+#include "access/htup_details.h"
+#include "catalog/pg_toaster.h"
+#include "commands/defrem.h"
+#include "utils/builtins.h"
+#include "utils/syscache.h"
+#include "access/toast_compression.h"
+#include "access/xact.h"
+#include "catalog/binary_upgrade.h"
+#include "catalog/catalog.h"
+#include "catalog/dependency.h"
+#include "catalog/heap.h"
+#include "catalog/index.h"
+#include "catalog/namespace.h"
+#include "catalog/pg_am.h"
+#include "catalog/pg_namespace.h"
+#include "catalog/pg_opclass.h"
+#include "catalog/pg_type.h"
+#include "catalog/toasting.h"
+#include "miscadmin.h"
 #include "nodes/makefuncs.h"
 
 PG_MODULE_MAGIC;
@@ -22,68 +42,106 @@ PG_FUNCTION_INFO_V1(dummy_toaster_handler);
 #define MAX_DUMMY_CHUNK_SIZE 1024
 
 /*
- * Dummy Toaster is a sample custom toaster for developers to show Toaster API
- * functionality and correct way to add new Toasters to PgSQL.
- */
-
-
-/*
- * Dummy detoast function, does nothing
+ * Dummy Detoast function, receives single varatt_custom pointer,
+ * detoasts it to varlena.
+ *
  */
 static Datum
-dummy_detoast(Relation toast_rel, Datum toast_ptr,
+dummy_detoast(Datum toast_ptr,
 			 int offset, int length)
 {
+	struct varlena *attr = (struct varlena *) DatumGetPointer(toast_ptr);
 	struct varlena *result;
-	result = palloc(0);
+
+	Assert(VARATT_IS_EXTERNAL(attr));
+	Assert(VARATT_IS_CUSTOM(attr));
+
+	result = palloc(VARATT_CUSTOM_GET_DATA_RAW_SIZE(attr));
+	SET_VARSIZE(result, VARATT_CUSTOM_GET_DATA_RAW_SIZE(attr));
+	memcpy(VARDATA(result), VARATT_CUSTOM_GET_DATA(attr),
+		   VARATT_CUSTOM_GET_DATA_RAW_SIZE(attr) - VARHDRSZ);
+
 	return PointerGetDatum(result);
 }
 
 /*
- * Dummy Toast function, does nothing
+ * Dummy Toast function, receives varlena pointer, creates single varatt_custom
+ * varlena size is limited to 1024 bytes
  */
 static Datum
 dummy_toast(Relation toast_rel, Oid toasterid,
 		   Datum value, Datum oldvalue,
 		   int max_inline_size,  int options)
 {
+	struct varlena			*attr;
 	struct varlena			*result;
-	result = palloc(0);
+	int	len;
+	attr = pg_detoast_datum((struct varlena*)DatumGetPointer(value));
+
+	if(VARSIZE_ANY_EXHDR(attr) > MAX_DUMMY_CHUNK_SIZE)
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_DATA_CORRUPTED),
+				 errmsg_internal("Data <%d> size exceeds MAX_DUMMY_CHUNK_SIZE <%d>",
+								 (int)VARSIZE_ANY_EXHDR(attr), MAX_DUMMY_CHUNK_SIZE)));
+
+	}
+
+	len = VARATT_CUSTOM_SIZE(VARSIZE_ANY_EXHDR(attr));
+
+	if (max_inline_size > 0 && len > max_inline_size)
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_DATA_CORRUPTED),
+				 errmsg_internal("Data <%d> size exceeds max inline size <%d>",
+								 len, max_inline_size)));
+	}
+
+	result = palloc(len);
+
+	SET_VARTAG_EXTERNAL(result, VARTAG_CUSTOM);
+	VARATT_CUSTOM_SET_DATA_RAW_SIZE(result, VARSIZE_ANY_EXHDR(attr) + VARHDRSZ);
+	VARATT_CUSTOM_SET_DATA_SIZE(result, len);
+	VARATT_CUSTOM_SET_TOASTERID(result, toasterid);
+
+	memcpy(VARATT_CUSTOM_GET_DATA(result), VARDATA_ANY(attr),
+		   VARSIZE_ANY_EXHDR(attr));
+
+	if ((char*)attr != DatumGetPointer(value))
+		pfree(attr);
+
 	return PointerGetDatum(result);
 }
 
 /*
- * Dummy deltoast function, does nothing
+ * Dummy delete function
  */
 static void
 dummy_delete(Datum value, bool is_speculative)
 {
 }
 
 /*
- * Dummy init function, does nothing
+ * Dummy Validate, always returns True
+ *
  */
-static void
-dummy_toast_init(Relation rel, Datum reloptions, LOCKMODE lockmode,
-				 bool check, Oid OIDOldToast)
+static bool
+dummy_toaster_validate(Oid typeoid, char storage, char compression,
+                                        Oid amoid, bool false_ok)
 {
+	bool result = true;
+	return result;
 }
 
 /*
  * Dummy validation function, always returns TRUE
  */
-static bool
-dummy_toaster_validate(Oid typeoid,  char storage, char compression,
-					 Oid amoid, bool false_ok)
+static void
+dummy_toast_init(Relation rel, Oid toastoid, Oid toastindexoid, Datum reloptions, LOCKMODE lockmode,
+						   bool check, Oid OIDOldToast)
 {
-	return true;
 }
 
-/*
- * Dummy toaster handler.
- * All Toaster functions declared in toasterapi.h and implemented in Custom
- * Toasters must be assigned to TsrRoutine structure
- */
 Datum
 dummy_toaster_handler(PG_FUNCTION_ARGS)
 {
@@ -95,7 +153,7 @@ dummy_toaster_handler(PG_FUNCTION_ARGS)
 	tsr->detoast = dummy_detoast;
 	tsr->deltoast = dummy_delete;
 	tsr->get_vtable = NULL;
-	tsr->toastervalidate = NULL;
+	tsr->toastervalidate = dummy_toaster_validate;
 
 	PG_RETURN_POINTER(tsr);
 }