From 573555747f7c0637167d81dcea0f1cd551794040 Mon Sep 17 00:00:00 2001
From: Jeff Davis <jdavis@postgresql.org>
Date: Fri, 11 Sep 2020 16:28:57 -0700
Subject: [PATCH] address review comments

---
 cstore.h        | 6 +++++-
 cstore_reader.c | 5 ++---
 cstore_writer.c | 3 ++-
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/cstore.h b/cstore.h
index 9679fea9c..d0f959032 100644
--- a/cstore.h
+++ b/cstore.h
@@ -300,6 +300,10 @@ typedef struct SmgrAddr
 	uint32		offset;
 } SmgrAddr;
 
+/*
+ * Map logical offsets (as tracked in the metadata) to a physical page and
+ * offset where the data is kept.
+ */
 static inline SmgrAddr
 logical_to_smgr(uint64 logicalOffset)
 {
@@ -307,7 +311,7 @@ logical_to_smgr(uint64 logicalOffset)
 	SmgrAddr addr;
 
 	addr.blockno = logicalOffset / bytes_per_page;
-	addr.offset = logicalOffset % bytes_per_page;
+	addr.offset = SizeOfPageHeaderData + (logicalOffset % bytes_per_page);
 
 	return addr;
 }
diff --git a/cstore_reader.c b/cstore_reader.c
index 4cbe2a44f..654d74697 100644
--- a/cstore_reader.c
+++ b/cstore_reader.c
@@ -1175,14 +1175,13 @@ ReadFromSmgr(Relation rel, uint64 offset, uint32 size)
 		PageHeader	phdr;
 		uint32		to_read;
 		SmgrAddr	addr = logical_to_smgr(offset + read);
-		uint32		pageoffset = addr.offset + SizeOfPageHeaderData;
 
 		buffer = ReadBuffer(rel, addr.blockno);
 		page = BufferGetPage(buffer);
 		phdr = (PageHeader)page;
 
-		to_read = Min(size - read, phdr->pd_upper - pageoffset);
-		memcpy(resultBuffer->data + read, page + pageoffset, to_read);
+		to_read = Min(size - read, phdr->pd_upper - addr.offset);
+		memcpy(resultBuffer->data + read, page + addr.offset, to_read);
 		ReleaseBuffer(buffer);
 		read += to_read;
 	}
diff --git a/cstore_writer.c b/cstore_writer.c
index 76e3aa070..319136dc9 100644
--- a/cstore_writer.c
+++ b/cstore_writer.c
@@ -405,12 +405,13 @@ WriteToSmgr(TableWriteState *writeState, char *data, uint32 dataLength)
 			PageInit(page, BLCKSZ, 0);
 
 		/* always appending */
-		Assert(phdr->pd_lower == addr.offset + SizeOfPageHeaderData);
+		Assert(phdr->pd_lower == addr.offset);
 
 		to_write = Min(phdr->pd_upper - phdr->pd_lower, remaining);
 		memcpy(page + phdr->pd_lower, data, to_write);
 		phdr->pd_lower += to_write;
 
+		MarkBufferDirty(buffer);
 		UnlockReleaseBuffer(buffer);
 
 		data += to_write;