From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 14 Dec 2021 20:09:01 +0000 (-0500)
Subject: avoid stepping on memory that's still needed
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=refs%2Fheads%2Fconveyor_old;p=users%2Frhaas%2Fpostgres.git

avoid stepping on memory that's still needed
---

diff --git a/src/backend/access/conveyor/cbmetapage.c b/src/backend/access/conveyor/cbmetapage.c
index 2abf7cc650..15021e092b 100644
--- a/src/backend/access/conveyor/cbmetapage.c
+++ b/src/backend/access/conveyor/cbmetapage.c
@@ -403,12 +403,16 @@ cb_metapage_remove_index_entries(CBMetapageData *meta, unsigned count,
 }
 
 /*
- * Return a pointer to the in-metapage index entries.
+ * Copy the indicated number of index entries out of the metapage.
  */
-CBSegNo *
-cb_metapage_get_index_entry_pointer(CBMetapageData *meta)
+void
+cb_metapage_get_index_entries(CBMetapageData *meta, unsigned num_index_entries,
+							  CBSegNo *index_entries)
 {
-	return meta->cbm_index;
+	Assert(num_index_entries <= cb_metapage_get_index_entries_used(meta));
+
+	memcpy(index_entries, meta->cbm_index,
+		   num_index_entries * sizeof(CBSegNo));
 }
 
 /*
diff --git a/src/backend/access/conveyor/conveyor.c b/src/backend/access/conveyor/conveyor.c
index 431a01c9f8..12a188884d 100644
--- a/src/backend/access/conveyor/conveyor.c
+++ b/src/backend/access/conveyor/conveyor.c
@@ -450,7 +450,7 @@ ConveyorBeltGetNewPage(ConveyorBelt *cb, CBPageNo *pageno)
 		{
 			unsigned	pageoffset;
 			unsigned	num_index_entries;
-			CBSegNo	   *index_entries;
+			CBSegNo	    index_entries[CB_METAPAGE_INDEX_ENTRIES];
 			CBPageNo	index_page_start;
 			unsigned	logical_pages_in_index_segments;
 			unsigned	index_entries_in_index_segments;
@@ -468,7 +468,8 @@ ConveyorBeltGetNewPage(ConveyorBelt *cb, CBPageNo *pageno)
 
 			num_index_entries = Min(CB_METAPAGE_INDEX_ENTRIES,
 									CB_INDEXPAGE_INDEX_ENTRIES - pageoffset);
-			index_entries = cb_metapage_get_index_entry_pointer(meta);
+			cb_metapage_get_index_entries(meta, num_index_entries,
+										  index_entries);
 			index_page_start = index_metapage_start -
 				pageoffset * cb->cb_pages_per_segment;
 			cb_relocate_index_entries(cb->cb_insert_relfilenode, cb->cb_fork,
diff --git a/src/include/access/cbmetapage.h b/src/include/access/cbmetapage.h
index 490130c339..b7a65187bb 100644
--- a/src/include/access/cbmetapage.h
+++ b/src/include/access/cbmetapage.h
@@ -142,7 +142,9 @@ extern void cb_metapage_add_index_entry(CBMetapageData *meta, CBSegNo segno);
 extern void cb_metapage_remove_index_entries(CBMetapageData *meta,
 											 unsigned count,
 											 bool relocating);
-extern CBSegNo *cb_metapage_get_index_entry_pointer(CBMetapageData *meta);
+extern void cb_metapage_get_index_entries(CBMetapageData *meta,
+										  unsigned num_index_entries,
+										  CBSegNo *index_entries);
 extern void cb_metapage_get_critical_info(CBMetapageData *meta,
 										  uint16 *pages_per_segment,
 										  uint64 *index_segments_moved);