From c91a9b5a285e20e54cf90f3660ce51ce3a5c2ef4 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Mon, 19 May 2014 13:16:24 +0300 Subject: [PATCH] Fix backup-block numbering in redo of b-tree split. I got the backup block numbers off-by-one in the commit that changed the way incomplete-splits are handled. I blame the comments, which said "backup block 1" and "backup block 2", even though the backup blocks are numbered starting from 0, in the macros and functions used in replay. Fix the comments and the code. Per Jeff Janes' bug report about corruption caused by torn page writes. The incorrect code is new in git master, but backpatch the comment change down to 9.0, where the numbering in the redo-side macros was changed. --- src/backend/access/nbtree/nbtinsert.c | 12 ++++++------ src/backend/access/nbtree/nbtxlog.c | 8 ++++---- 2 files changed, 10 insertions(+), 10 deletions(-) diff --git a/src/backend/access/nbtree/nbtinsert.c b/src/backend/access/nbtree/nbtinsert.c index d64cbd9822..ecee5ac7f6 100644 --- a/src/backend/access/nbtree/nbtinsert.c +++ b/src/backend/access/nbtree/nbtinsert.c @@ -1299,7 +1299,7 @@ _bt_split(Relation rel, Buffer buf, Buffer cbuf, OffsetNumber firstright, lastrdata->data = (char *) newitem; lastrdata->len = MAXALIGN(newitemsz); - lastrdata->buffer = buf; /* backup block 1 */ + lastrdata->buffer = buf; /* backup block 0 */ lastrdata->buffer_std = true; } @@ -1320,7 +1320,7 @@ _bt_split(Relation rel, Buffer buf, Buffer cbuf, OffsetNumber firstright, item = (IndexTuple) PageGetItem(origpage, itemid); lastrdata->data = (char *) item; lastrdata->len = MAXALIGN(IndexTupleSize(item)); - lastrdata->buffer = buf; /* backup block 1 */ + lastrdata->buffer = buf; /* backup block 0 */ lastrdata->buffer_std = true; } @@ -1333,11 +1333,11 @@ _bt_split(Relation rel, Buffer buf, Buffer cbuf, OffsetNumber firstright, * Although we don't need to WAL-log anything on the left page, we * still need XLogInsert to consider storing a full-page image of * the left page, so make an empty entry referencing that buffer. - * This also ensures that the left page is always backup block 1. + * This also ensures that the left page is always backup block 0. */ lastrdata->data = NULL; lastrdata->len = 0; - lastrdata->buffer = buf; /* backup block 1 */ + lastrdata->buffer = buf; /* backup block 0 */ lastrdata->buffer_std = true; } @@ -1353,7 +1353,7 @@ _bt_split(Relation rel, Buffer buf, Buffer cbuf, OffsetNumber firstright, cblkno = BufferGetBlockNumber(cbuf); lastrdata->data = (char *) &cblkno; lastrdata->len = sizeof(BlockNumber); - lastrdata->buffer = cbuf; /* backup block 2 */ + lastrdata->buffer = cbuf; /* backup block 1 */ lastrdata->buffer_std = true; } @@ -1386,7 +1386,7 @@ _bt_split(Relation rel, Buffer buf, Buffer cbuf, OffsetNumber firstright, lastrdata->data = NULL; lastrdata->len = 0; - lastrdata->buffer = sbuf; /* bkp block 2 (leaf) or 3 (non-leaf) */ + lastrdata->buffer = sbuf; /* bkp block 1 (leaf) or 2 (non-leaf) */ lastrdata->buffer_std = true; } diff --git a/src/backend/access/nbtree/nbtxlog.c b/src/backend/access/nbtree/nbtxlog.c index 640639c175..5f9fc49e78 100644 --- a/src/backend/access/nbtree/nbtxlog.c +++ b/src/backend/access/nbtree/nbtxlog.c @@ -300,8 +300,8 @@ btree_xlog_split(bool onleft, bool isroot, */ if (!isleaf) { - if (record->xl_info & XLR_BKP_BLOCK(2)) - (void) RestoreBackupBlock(lsn, record, 2, false, false); + if (record->xl_info & XLR_BKP_BLOCK(1)) + (void) RestoreBackupBlock(lsn, record, 1, false, false); else _bt_clear_incomplete_split(lsn, record, xlrec->node, cblkno); } @@ -439,10 +439,10 @@ btree_xlog_split(bool onleft, bool isroot, if (xlrec->rnext != P_NONE) { /* - * the backup block containing right sibling is 2 or 3, depending + * the backup block containing right sibling is 1 or 2, depending * whether this was a leaf or internal page. */ - int rnext_index = isleaf ? 2 : 3; + int rnext_index = isleaf ? 1 : 2; if (record->xl_info & XLR_BKP_BLOCK(rnext_index)) (void) RestoreBackupBlock(lsn, record, rnext_index, false, false);