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 55df02ace6ab120a35fc31891b19ca0ba61d7577..d6f2b69f14d8cddf5956962720bd429fa35f5433 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 bd4b0427f503daaffb3ccaf4d914e5d5a2502e01..2d524539286ec6bbb30528290f8c08c6e9302767 100644 (file)
--- a/src/backend/access/gin/ginxlog.c
+++ b/src/backend/access/gin/ginxlog.c
@@ -620,7 +620,11 @@ ginRedoInsertListPage(XLogRecPtr lsn, XLogRecord *record)
                                tupsize;
        IndexTuple      tuples = (IndexTuple) (XLogRecGetData(record) + sizeof(ginxlogInsertListPage));
 
-       /* If we have a full-page image, restore it and we're done */
+       /*
+        * If we have a full-page image, restore it and 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(0))
        {
                (void) RestoreBackupBlock(lsn, record, 0, false, false);
@@ -654,6 +658,7 @@ ginRedoInsertListPage(XLogRecPtr lsn, XLogRecord *record)
                        elog(ERROR, "failed to add item to index page");
 
                tuples = (IndexTuple) (((char *) tuples) + tupsize);
+               off++;
        }
 
        PageSetLSN(page, lsn);