pg_rewind: Fix thinko in parsing target WAL.

It's entirely possible to see WAL for a relation that doesn't exist in
the target anymore. That happens when the relation was dropped later.
The refactoring in commit eb00f1d4b broke that case, by sanity-checking
the file type in the target before checking the flag forwhether it
exists there at all.

I noticed this during manual testing. Modify the 001_basic.pl test so
that it covers this case.

1 files changed, 12 insertions, 9 deletions

diff --git a/src/bin/pg_rewind/filemap.c b/src/bin/pg_rewind/filemap.c
index 314b064b223..ba34dbac146 100644
--- a/src/bin/pg_rewind/filemap.c
+++ b/src/bin/pg_rewind/filemap.c
@@ -324,17 +324,20 @@ process_target_wal_block_change(ForkNumber forknum, RelFileNode rnode,
 	{
 		Assert(entry->isrelfile);
 
-		if (entry->target_type != FILE_TYPE_REGULAR)
-			pg_fatal("unexpected page modification for non-regular file \"%s\"",
-					 entry->path);
-
-		if (entry->target_exists && entry->source_exists)
+		if (entry->target_exists)
 		{
-			off_t		end_offset;
+			if (entry->target_type != FILE_TYPE_REGULAR)
+				pg_fatal("unexpected page modification for non-regular file \"%s\"",
+						 entry->path);
 
-			end_offset = (blkno_inseg + 1) * BLCKSZ;
-			if (end_offset <= entry->source_size && end_offset <= entry->target_size)
-				datapagemap_add(&entry->target_pages_to_overwrite, blkno_inseg);
+			if (entry->source_exists)
+			{
+				off_t		end_offset;
+
+				end_offset = (blkno_inseg + 1) * BLCKSZ;
+				if (end_offset <= entry->source_size && end_offset <= entry->target_size)
+					datapagemap_add(&entry->target_pages_to_overwrite, blkno_inseg);
+			}
 		}
 	}
 }