Convert Assert checking for empty page into a regular test and elog.

The consequences of overwriting a non-empty page are bad enough that
we should not omit this test in production builds.

diff --git a/src/backend/access/heap/hio.c b/src/backend/access/heap/hio.c
index 116dcb71d3322149d0f1f43a80778f07dee34c05..6481493f3a45127f13ae5a169ceb26c17fd7a35b 100644 (file)
--- a/src/backend/access/heap/hio.c
+++ b/src/backend/access/heap/hio.c
@@ -281,10 +281,17 @@ RelationGetBufferForTuple(Relation relation, Size len,
                UnlockRelationForExtension(relation, ExclusiveLock);
 
        /*
-        * We need to initialize the empty new page.
+        * We need to initialize the empty new page.  Double-check that it really
+        * is empty (this should never happen, but if it does we don't want to
+        * risk wiping out valid data).
         */
        pageHeader = (Page) BufferGetPage(buffer);
-       Assert(PageIsNew((PageHeader) pageHeader));
+
+       if (!PageIsNew((PageHeader) pageHeader))
+               elog(ERROR, "page %u of relation \"%s\" should be empty but is not",
+                        BufferGetBlockNumber(buffer),
+                        RelationGetRelationName(relation));
+
        PageInit(pageHeader, BufferGetPageSize(buffer), 0);
 
        if (len > PageGetFreeSpace(pageHeader))