commit 179285fb5175d715c20fc95eca3087b6a1899ed9
Author: Anastasia <a.lubennikova@postgrespro.ru>
Date:   Wed Feb 28 17:45:54 2018 +0300

    add function generate_xlog_for_rel()

diff --git a/src/backend/access/transam/generic_xlog.c b/src/backend/access/transam/generic_xlog.c
index ce02354..dd2c041 100644
--- a/src/backend/access/transam/generic_xlog.c
+++ b/src/backend/access/transam/generic_xlog.c
@@ -545,3 +545,34 @@ generic_mask(char *page, BlockNumber blkno)
 
 	mask_unused_space(page);
 }
+
+/*
+ * Function to write generic xlog for every existing block of a relation.
+ * Caller is responsible for locking the relation exclusively.
+ */
+void
+generate_xlog_for_rel(Relation rel)
+{
+	BlockNumber blkno;
+	BlockNumber nblocks;
+
+	nblocks = RelationGetNumberOfBlocks(rel);
+
+	elog(DEBUG2, "generate_xlog_for_rel '%s', nblocks %u BEGIN.",
+		 RelationGetRelationName(rel), nblocks);
+
+	for (blkno = 0; blkno < nblocks; blkno++)
+	{
+		Buffer	buffer;
+		GenericXLogState *state;
+
+		CHECK_FOR_INTERRUPTS();
+
+		buffer = ReadBuffer(rel, blkno);
+		LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+
+		state = GenericXLogStart(rel);
+		GenericXLogRegisterBuffer(state, buffer, GENERIC_XLOG_FULL_IMAGE);
+		GenericXLogFinish(state);
+
+		UnlockReleaseBuffer(buffer);
+	}
+	elog(DEBUG2, "generate_xlog_for_rel '%s' END.", RelationGetRelationName(rel));
+}
diff --git a/src/include/access/generic_xlog.h b/src/include/access/generic_xlog.h
index b23e1f6..33be157 100644
--- a/src/include/access/generic_xlog.h
+++ b/src/include/access/generic_xlog.h
@@ -42,4 +42,7 @@ extern const char *generic_identify(uint8 info);
 extern void generic_desc(StringInfo buf, XLogReaderState *record);
 extern void generic_mask(char *pagedata, BlockNumber blkno);
 
+/* other utils */
+void generate_xlog_for_rel(Relation rel);
+
 #endif							/* GENERIC_XLOG_H */