Split tuptoaster.c into three separate files.

detoast.c/h contain functions required to detoast a datum, partially
or completely, plus a few other utility functions for examining the
size of toasted datums.

toast_internals.c/h contain functions that are used internally to the
TOAST subsystem but which (mostly) do not need to be accessed from
outside.

heaptoast.c/h contains code that is intrinsically specific to the
heap AM, either because it operates on HeapTuples or is based on the
layout of a heap page.

detoast.c and toast_internals.c are placed in
src/backend/access/common rather than src/backend/access/heap.  At
present, both files still have dependencies on the heap, but that will
be improved in a future commit.

Patch by me, reviewed and tested by Prabhat Sabu, Thomas Munro,
Andres Freund, and Álvaro Herrera.

Discussion: http://postgr.es/m/CA+TgmoZv-=2iWM4jcw5ZhJeL18HF96+W1yJeYrnGMYdkFFnEpQ@mail.gmail.com

Author: robertmhaas

doc/src/sgml/storage.sgml

@@ -382,7 +382,7 @@ The oldest and most common type is a pointer to out-of-line data stored in
 a <firstterm><acronym>TOAST</acronym> table</firstterm> that is separate from, but
 associated with, the table containing the <acronym>TOAST</acronym> pointer datum
 itself.  These <firstterm>on-disk</firstterm> pointer datums are created by the
-<acronym>TOAST</acronym> management code (in <filename>access/heap/tuptoaster.c</filename>)
+<acronym>TOAST</acronym> management code (in <filename>access/common/toast_internals.c</filename>)
 when a tuple to be stored on disk is too large to be stored as-is.
 Further details appear in <xref linkend="storage-toast-ondisk"/>.
 Alternatively, a <acronym>TOAST</acronym> pointer datum can contain a pointer to

src/backend/access/common/Makefile

@@ -12,7 +12,8 @@ subdir = src/backend/access/common
 top_builddir = ../../../..
 include $(top_builddir)/src/Makefile.global
 
-OBJS = bufmask.o heaptuple.o indextuple.o printsimple.o printtup.o \
-	relation.o reloptions.o scankey.o session.o tupconvert.o tupdesc.o
+OBJS = bufmask.o detoast.o heaptuple.o indextuple.o printsimple.o \
+	printtup.o relation.o reloptions.o scankey.o session.o toast_internals.o \
+	tupconvert.o tupdesc.o
 
 include $(top_srcdir)/src/backend/common.mk