Fix two bugs in WAL-logging of GIN pending-list pages.

In writeListPage, never take a full-page image of the page, because we
have all the information required to re-initialize in the WAL record
anyway. Before this fix, a full-page image was always generated, unless
full_page_writes=off, because when the page is initialized its LSN is
always 0. In stable-branches, keep the code to restore the backup blocks
if they exist, in case that the WAL is generated with an older minor
version, but in master Assert that there are no full-page images.

In the redo routine, add missing "off++". Otherwise the tuples are added
to the page in reverse order. That happens to be harmless because we
always scan and remove all the tuples together, but it was clearly wrong.
Also, it was masked by the first bug unless full_page_writes=off, because
the page was always restored from a full-page image.

Backpatch to all supported versions.

diff --git a/src/backend/access/gin/ginfast.c b/src/backend/access/gin/ginfast.c
index fb6710e7e4966de02df3771ffed595407e4e37da..71f6cb3741e0140fb7d9f5915438925c0c5dfa82 100644 (file)
--- a/src/backend/access/gin/ginfast.c
+++ b/src/backend/access/gin/ginfast.c
@@ -119,8 +119,7 @@ writeListPage(Relation index, Buffer buffer,
                rdata[0].len = sizeof(ginxlogInsertListPage);
                rdata[0].next = rdata + 1;
 
-               rdata[1].buffer = buffer;
-               rdata[1].buffer_std = true;
+               rdata[1].buffer = InvalidBuffer;
                rdata[1].data = workspace;
                rdata[1].len = size;
                rdata[1].next = NULL;

diff --git a/src/backend/access/gin/ginxlog.c b/src/backend/access/gin/ginxlog.c
index f66938a130314862caa8a33bd981f3744b74fe86..2344ec25bcf538c818f917e6ff034455492aa5ea 100644 (file)
--- a/src/backend/access/gin/ginxlog.c
+++ b/src/backend/access/gin/ginxlog.c
@@ -587,6 +587,11 @@ ginRedoInsertListPage(XLogRecPtr lsn, XLogRecord *record)
                                tupsize;
        IndexTuple      tuples = (IndexTuple) (XLogRecGetData(record) + sizeof(ginxlogInsertListPage));
 
+       /*
+        * If we have a full-page image, we're done.  (As the code stands, we
+        * never create full-page images, but we used to.  Cope if we're
+        * reading WAL generated with an older minor version.)
+        */
        if (record->xl_info & XLR_BKP_BLOCK_1)
                return;
 
@@ -617,6 +622,7 @@ ginRedoInsertListPage(XLogRecPtr lsn, XLogRecord *record)
                        elog(ERROR, "failed to add item to index page");
 
                tuples = (IndexTuple) (((char *) tuples) + tupsize);
+               off++;
        }
 
        PageSetLSN(page, lsn);