Hi,
It's a bit odd that syncscan.c is used by both heapam.c and tableam.c,
and provides a generic block-synchronization mechanism that other
table AMs might want to use too, but it lives under
src/backend/access/heap. It doesn't actually do anything heap
specific (beyond being block-oriented), and it's weird that tableam.c
has to include heapam.h.
Perhaps we should move the .c file under src/backend/access/table, as attached.
I suppose it's remotely possible that someone might invent
physical-order index scans, and once you have those you might sync
scans of those too, and then even table would be too specific, but
that may be a bit far fetched.
From c80c24572e8f42121aa9d75c2fdd8c6b127f8ae9 Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.mu...@gmail.com>
Date: Tue, 23 Jun 2020 10:49:51 +1200
Subject: [PATCH] Move syncscan.c to src/backend/access/table.
Since the tableam.c code needs to make use of the syncscan.c routines
itself, and since other block-oriented table AMs might also need to do
that, it didn't make sense for syncscan.c to be under
src/backend/access/heap.
---
src/backend/access/heap/Makefile | 1 -
src/backend/access/heap/heapam.c | 1 +
src/backend/access/heap/heapam_handler.c | 1 +
src/backend/access/table/Makefile | 1 +
src/backend/access/{heap => table}/syncscan.c | 6 ++---
src/backend/access/table/tableam.c | 2 +-
src/backend/storage/ipc/ipci.c | 1 +
src/include/access/heapam.h | 6 -----
src/include/access/syncscan.h | 25 +++++++++++++++++++
9 files changed, 33 insertions(+), 11 deletions(-)
rename src/backend/access/{heap => table}/syncscan.c (98%)
create mode 100644 src/include/access/syncscan.h
diff --git a/src/backend/access/heap/Makefile b/src/backend/access/heap/Makefile
index 51a7f5e0d0..af0bd1888e 100644
--- a/src/backend/access/heap/Makefile
+++ b/src/backend/access/heap/Makefile
@@ -20,7 +20,6 @@ OBJS = \
hio.o \
pruneheap.o \
rewriteheap.o \
- syncscan.o \
vacuumlazy.o \
visibilitymap.o
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 537913d1bb..d91722cfa5 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -41,6 +41,7 @@
#include "access/parallel.h"
#include "access/relscan.h"
#include "access/subtrans.h"
+#include "access/syncscan.h"
#include "access/sysattr.h"
#include "access/tableam.h"
#include "access/transam.h"
diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c
index 56b35622f1..ac71c2352f 100644
--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -24,6 +24,7 @@
#include "access/heaptoast.h"
#include "access/multixact.h"
#include "access/rewriteheap.h"
+#include "access/syncscan.h"
#include "access/tableam.h"
#include "access/tsmapi.h"
#include "access/xact.h"
diff --git a/src/backend/access/table/Makefile b/src/backend/access/table/Makefile
index 9aba3ff489..4c2c669828 100644
--- a/src/backend/access/table/Makefile
+++ b/src/backend/access/table/Makefile
@@ -13,6 +13,7 @@ top_builddir = ../../../..
include $(top_builddir)/src/Makefile.global
OBJS = \
+ syncscan.o \
table.o \
tableam.o \
tableamapi.o \
diff --git a/src/backend/access/heap/syncscan.c b/src/backend/access/table/syncscan.c
similarity index 98%
rename from src/backend/access/heap/syncscan.c
rename to src/backend/access/table/syncscan.c
index a32f6836f8..3f0e91c0cf 100644
--- a/src/backend/access/heap/syncscan.c
+++ b/src/backend/access/table/syncscan.c
@@ -1,7 +1,7 @@
/*-------------------------------------------------------------------------
*
* syncscan.c
- * heap scan synchronization support
+ * scan synchronization support for block-oriented table AMs
*
* When multiple backends run a sequential scan on the same table, we try
* to keep them synchronized to reduce the overall I/O needed. The goal is
@@ -40,13 +40,13 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * src/backend/access/heap/syncscan.c
+ * src/backend/access/table/syncscan.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
-#include "access/heapam.h"
+#include "access/syncscan.h"
#include "miscadmin.h"
#include "storage/lwlock.h"
#include "storage/shmem.h"
diff --git a/src/backend/access/table/tableam.c b/src/backend/access/table/tableam.c
index c814733b22..7e0cd895ac 100644
--- a/src/backend/access/table/tableam.c
+++ b/src/backend/access/table/tableam.c
@@ -21,7 +21,7 @@
#include <math.h>
-#include "access/heapam.h" /* for ss_* */
+#include "access/syncscan.h"
#include "access/tableam.h"
#include "access/xact.h"
#include "optimizer/plancat.h"
diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c
index 427b0d59cd..e850ebd131 100644
--- a/src/backend/storage/ipc/ipci.c
+++ b/src/backend/storage/ipc/ipci.c
@@ -20,6 +20,7 @@
#include "access/multixact.h"
#include "access/nbtree.h"
#include "access/subtrans.h"
+#include "access/syncscan.h"
#include "access/twophase.h"
#include "commands/async.h"
#include "miscadmin.h"
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index f279edc473..b31de38910 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -182,12 +182,6 @@ extern void heap_page_prune_execute(Buffer buffer,
OffsetNumber *nowunused, int nunused);
extern void heap_get_root_tuples(Page page, OffsetNumber *root_offsets);
-/* in heap/syncscan.c */
-extern void ss_report_location(Relation rel, BlockNumber location);
-extern BlockNumber ss_get_location(Relation rel, BlockNumber relnblocks);
-extern void SyncScanShmemInit(void);
-extern Size SyncScanShmemSize(void);
-
/* in heap/vacuumlazy.c */
struct VacuumParams;
extern void heap_vacuum_rel(Relation onerel,
diff --git a/src/include/access/syncscan.h b/src/include/access/syncscan.h
new file mode 100644
index 0000000000..7cbf63c399
--- /dev/null
+++ b/src/include/access/syncscan.h
@@ -0,0 +1,25 @@
+/*-------------------------------------------------------------------------
+ *
+ * syncscan.h
+ * POSTGRES synchronous scan support functions.
+ *
+ *
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/access/syncscan.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SYNCSCAN_H
+#define SYNCSCAN_H
+
+#include "storage/block.h"
+#include "utils/relcache.h"
+
+extern void ss_report_location(Relation rel, BlockNumber location);
+extern BlockNumber ss_get_location(Relation rel, BlockNumber relnblocks);
+extern void SyncScanShmemInit(void);
+extern Size SyncScanShmemSize(void);
+
+#endif
--
2.20.1
