bytea_appendable_toaster contrib module (extension)

Contrib module implements Custom toaster for non-compressed
bytea columns, which allows fast appending to existing bytea
value. Appended tail is stored directly in toaster pointer,
if there is enough place to do it.
Also modifies concatenation operation for bytea datatype -
byteacat() with append operation for TOASTed values.

Author: Teodor Sigaev <teodor@sigaev.ru>
Author: Oleg Bartunov <obartunov@postgrespro.ru>
Author: Nikita Glukhov <n.gluhov@postgrespro.ru>
Author: Nikita Malakhov <n.malakhov@postgrespro.ru>

Discussion: https://www.postgresql.org/message-id/flat/224711f9-83b7-a307-b17f-4457ab73aa0a@sigaev.ru

Author: Nikita Malakhov

contrib/Makefile

@@ -14,6 +14,7 @@ SUBDIRS = \
 		bloom		\
 		btree_gin	\
 		btree_gist	\
+		bytea_toaster	\
 		citext		\
 		cube		\
 		dblink		\

contrib/bytea_toaster/Makefile

@@ -0,0 +1,23 @@
+# contrib/bytea_toaster/Makefile
+
+MODULE_big = bytea_toaster
+OBJS = \
+	$(WIN32RES) \
+	bytea_toaster.o
+
+EXTENSION = bytea_toaster
+DATA = bytea_toaster--1.0.sql
+PGFILEDESC = "bytea_toaster - appendable bytea toaster"
+
+REGRESS = bytea_toaster
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/bytea_toaster
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif

contrib/bytea_toaster/bytea_toaster--1.0.sql

@@ -0,0 +1,13 @@
+/* contrib/bytea_toaster/bytea_toaster--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION bytea_toaster" to load this file. \quit
+
+CREATE FUNCTION bytea_toaster_handler(internal)
+RETURNS toaster_handler
+AS 'MODULE_PATHNAME'
+LANGUAGE C;
+
+CREATE TOASTER bytea_toaster  HANDLER bytea_toaster_handler;
+
+COMMENT ON TOASTER bytea_toaster IS 'bytea_toaster is a appendable bytea toaster';