From 197111e1c31aff66335eaf05de0189ae8d17f48d Mon Sep 17 00:00:00 2001
From: Dilip Kumar <dilipkumar@localhost.localdomain>
Date: Fri, 24 Sep 2021 18:13:25 +0530
Subject: [PATCH v3 3/6] Refactor index_copy_data

Make separate interface for copying relation storage, this will
be used by later patch for copying the database relations.
---
 src/backend/commands/tablecmds.c | 59 +++++++++++++++++++-------------
 src/include/commands/tablecmds.h |  5 +++
 2 files changed, 40 insertions(+), 24 deletions(-)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index dbee6ae199..c3e5aee8a4 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -14189,21 +14189,13 @@ AlterTableMoveAll(AlterTableMoveAllStmt *stmt)
 	return new_tablespaceoid;
 }
 
-static void
-index_copy_data(Relation rel, RelFileNode newrnode)
+/*
+ * Copy source smgr all fork's data to the destination smgr.
+ */
+void
+RelationCopyAllFork(SMgrRelation src_smgr, SMgrRelation	dst_smgr,
+					char relpersistence, copy_relation_storage copy_storage)
 {
-	SMgrRelation dstrel;
-
-	dstrel = smgropen(newrnode, rel->rd_backend);
-
-	/*
-	 * Since we copy the file directly without looking at the shared buffers,
-	 * we'd better first flush out any pages of the source relation that are
-	 * in shared buffers.  We assume no new changes will be made while we are
-	 * holding exclusive lock on the rel.
-	 */
-	FlushRelationBuffers(rel);
-
 	/*
 	 * Create and copy all forks of the relation, and schedule unlinking of
 	 * old physical files.
@@ -14211,32 +14203,51 @@ index_copy_data(Relation rel, RelFileNode newrnode)
 	 * NOTE: any conflict in relfilenode value will be caught in
 	 * RelationCreateStorage().
 	 */
-	RelationCreateStorage(newrnode, rel->rd_rel->relpersistence);
+	RelationCreateStorage(dst_smgr->smgr_rnode.node, relpersistence);
 
 	/* copy main fork */
-	RelationCopyStorage(RelationGetSmgr(rel), dstrel, MAIN_FORKNUM,
-						rel->rd_rel->relpersistence);
+	copy_storage(src_smgr, dst_smgr, MAIN_FORKNUM, relpersistence);
 
 	/* copy those extra forks that exist */
 	for (ForkNumber forkNum = MAIN_FORKNUM + 1;
 		 forkNum <= MAX_FORKNUM; forkNum++)
 	{
-		if (smgrexists(RelationGetSmgr(rel), forkNum))
+		if (smgrexists(src_smgr, forkNum))
 		{
-			smgrcreate(dstrel, forkNum, false);
+			smgrcreate(dst_smgr, forkNum, false);
 
 			/*
 			 * WAL log creation if the relation is persistent, or this is the
 			 * init fork of an unlogged relation.
 			 */
-			if (RelationIsPermanent(rel) ||
-				(rel->rd_rel->relpersistence == RELPERSISTENCE_UNLOGGED &&
+			if (relpersistence == RELPERSISTENCE_PERMANENT ||
+				(relpersistence == RELPERSISTENCE_UNLOGGED &&
 				 forkNum == INIT_FORKNUM))
-				log_smgrcreate(&newrnode, forkNum);
-			RelationCopyStorage(RelationGetSmgr(rel), dstrel, forkNum,
-								rel->rd_rel->relpersistence);
+				log_smgrcreate(&dst_smgr->smgr_rnode.node, forkNum);
+
+			/* Copy a fork's data, block by block. */
+			copy_storage(src_smgr, dst_smgr, forkNum, relpersistence);
 		}
 	}
+}
+
+static void
+index_copy_data(Relation rel, RelFileNode newrnode)
+{
+	SMgrRelation dstrel;
+
+	dstrel = smgropen(newrnode, rel->rd_backend);
+
+	/*
+	 * Since we copy the file directly without looking at the shared buffers,
+	 * we'd better first flush out any pages of the source relation that are
+	 * in shared buffers.  We assume no new changes will be made while we are
+	 * holding exclusive lock on the rel.
+	 */
+	FlushRelationBuffers(rel);
+
+	RelationCopyAllFork(RelationGetSmgr(rel), dstrel,
+						rel->rd_rel->relpersistence, RelationCopyStorage);
 
 	/* drop old relation, and close new one */
 	RelationDropStorage(rel);
diff --git a/src/include/commands/tablecmds.h b/src/include/commands/tablecmds.h
index 336549cc5f..e0e0aa5aa0 100644
--- a/src/include/commands/tablecmds.h
+++ b/src/include/commands/tablecmds.h
@@ -19,10 +19,13 @@
 #include "catalog/objectaddress.h"
 #include "nodes/parsenodes.h"
 #include "storage/lock.h"
+#include "storage/smgr.h"
 #include "utils/relcache.h"
 
 struct AlterTableUtilityContext;	/* avoid including tcop/utility.h here */
 
+typedef void (*copy_relation_storage) (SMgrRelation src, SMgrRelation dst,
+									  ForkNumber forkNum, char relpersistence);
 
 extern ObjectAddress DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId,
 									ObjectAddress *typaddress, const char *queryString);
@@ -42,6 +45,8 @@ extern void AlterTableInternal(Oid relid, List *cmds, bool recurse);
 
 extern Oid	AlterTableMoveAll(AlterTableMoveAllStmt *stmt);
 
+extern void RelationCopyAllFork(SMgrRelation src_smgr, SMgrRelation	dst_smgr,
+								char relpersistence, copy_relation_storage copy_storage);
 extern ObjectAddress AlterTableNamespace(AlterObjectSchemaStmt *stmt,
 										 Oid *oldschema);
 
-- 
2.23.0