0001-Allow-raw-block-numbers-to-be-read-from-ReadStream.patch

From db05a33e742cb292b1a2d44665582042fcd05d2f Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Tue, 10 Sep 2024 10:15:33 +1200
Subject: [PATCH] Allow raw block numbers to be read from ReadStream.

---
 src/backend/storage/aio/read_stream.c | 14 ++++++++++++++
 src/include/storage/read_stream.h     |  3 +++
 2 files changed, 17 insertions(+)

diff --git a/src/backend/storage/aio/read_stream.c b/src/backend/storage/aio/read_stream.c
index 7f0e07d9586..cf914a7712f 100644
--- a/src/backend/storage/aio/read_stream.c
+++ b/src/backend/storage/aio/read_stream.c
@@ -835,3 +835,17 @@ read_stream_end(ReadStream *stream)
 	read_stream_reset(stream);
 	pfree(stream);
 }
+
+/*
+ * Transitional support for code that would like to perform a read directly,
+ * without using the stream.  Returns, and skips, the next block number that
+ * would be read by the stream's look-ahead algorithm, or InvalidBlockNumber
+ * if the end of the stream is reached.  Also reports the strategy that would
+ * be used to read it.
+ */
+BlockNumber
+read_stream_next_block(ReadStream *stream, BufferAccessStrategy *strategy)
+{
+	*strategy = stream->ios[0].op.strategy;
+	return read_stream_get_block(stream, NULL);
+}
diff --git a/src/include/storage/read_stream.h b/src/include/storage/read_stream.h
index 2f94ee744b9..37b51934f8d 100644
--- a/src/include/storage/read_stream.h
+++ b/src/include/storage/read_stream.h
@@ -68,6 +68,9 @@ extern ReadStream *read_stream_begin_relation(int flags,
 											  void *callback_private_data,
 											  size_t per_buffer_data_size);
 extern Buffer read_stream_next_buffer(ReadStream *stream, void **per_buffer_data);
+extern BlockNumber read_stream_next_block(ReadStream *stream,
+										  BufferAccessStrategy *strategy);
+
 extern ReadStream *read_stream_begin_smgr_relation(int flags,
 												   BufferAccessStrategy strategy,
 												   SMgrRelation smgr,
-- 
2.46.0