v2-0004-Add-pg_streaming_read_reset.patch

From 38cc779724b92514a1b63ba27057fe438b06df29 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplageman@gmail.com>
Date: Mon, 26 Feb 2024 15:33:39 -0500
Subject: [PATCH v2 4/5] Add pg_streaming_read_reset

For rescan, we want to reuse the streaming read object and simply
release the buffers that were pinned by the streaming read
infrastructure.
---
 src/backend/storage/aio/streaming_read.c | 18 ++++++++++++++++++
 src/include/storage/streaming_read.h     |  1 +
 2 files changed, 19 insertions(+)

diff --git a/src/backend/storage/aio/streaming_read.c b/src/backend/storage/aio/streaming_read.c
index 19605090fea..4479f101abe 100644
--- a/src/backend/storage/aio/streaming_read.c
+++ b/src/backend/storage/aio/streaming_read.c
@@ -433,3 +433,21 @@ pg_streaming_read_free(PgStreamingRead *pgsr)
 		pfree(pgsr->per_buffer_data);
 	pfree(pgsr);
 }
+
+
+/*
+ * Reset a streaming read object by releasing all of the buffers. Note that
+ * max_ios is not recalculated, so any changes to maintenance_io_concurrency and
+ * effective_io_concurrency will have no effect.
+ */
+void
+pg_streaming_read_reset(PgStreamingRead *pgsr)
+{
+	Buffer		buffer;
+
+	/* Stop looking ahead, and unpin anything that wasn't consumed. */
+	pgsr->finished = true;
+	while ((buffer = pg_streaming_read_buffer_get_next(pgsr, NULL)) != InvalidBuffer)
+		ReleaseBuffer(buffer);
+	pgsr->finished = false;
+}
diff --git a/src/include/storage/streaming_read.h b/src/include/storage/streaming_read.h
index 40c3408c541..1acfab20ff5 100644
--- a/src/include/storage/streaming_read.h
+++ b/src/include/storage/streaming_read.h
@@ -41,5 +41,6 @@ extern PgStreamingRead *pg_streaming_read_buffer_alloc(int flags,
 extern void pg_streaming_read_prefetch(PgStreamingRead *pgsr);
 extern Buffer pg_streaming_read_buffer_get_next(PgStreamingRead *pgsr, void **per_buffer_private);
 extern void pg_streaming_read_free(PgStreamingRead *pgsr);
+extern void pg_streaming_read_reset(PgStreamingRead *pgsr);
 
 #endif
-- 
2.37.2