diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/access/nbtree/nbtpage.c | 64 |
1 files changed, 38 insertions, 26 deletions
diff --git a/src/backend/access/nbtree/nbtpage.c b/src/backend/access/nbtree/nbtpage.c index 41dc3f8fdff..ac264a5952d 100644 --- a/src/backend/access/nbtree/nbtpage.c +++ b/src/backend/access/nbtree/nbtpage.c @@ -1978,9 +1978,6 @@ _bt_pagedel(Relation rel, Buffer leafbuf, TransactionId *oldestBtpoXact) * Then unlink it from its siblings. Each call to * _bt_unlink_halfdead_page unlinks the topmost page from the subtree, * making it shallower. Iterate until the leafbuf page is deleted. - * - * _bt_unlink_halfdead_page should never fail, since we established - * that deletion is generally safe in _bt_mark_page_halfdead. */ rightsib_empty = false; Assert(P_ISLEAF(opaque) && P_ISHALFDEAD(opaque)); @@ -1991,7 +1988,15 @@ _bt_pagedel(Relation rel, Buffer leafbuf, TransactionId *oldestBtpoXact) &rightsib_empty, oldestBtpoXact, &ndeleted)) { - /* _bt_unlink_halfdead_page failed, released buffer */ + /* + * _bt_unlink_halfdead_page should never fail, since we + * established that deletion is generally safe in + * _bt_mark_page_halfdead -- index must be corrupt. + * + * Note that _bt_unlink_halfdead_page already released the + * lock and pin on leafbuf for us. + */ + Assert(false); return ndeleted; } } @@ -2355,11 +2360,7 @@ _bt_unlink_halfdead_page(Relation rel, Buffer leafbuf, BlockNumber scanblkno, * So, first lock the leaf page, if it's not the target. Then find and * write-lock the current left sibling of the target page. The sibling * that was current a moment ago could have split, so we may have to move - * right. This search could fail if either the sibling or the target page - * was deleted by someone else meanwhile; if so, give up. (Right now, - * that should never happen, since page deletion is only done in VACUUM - * and there shouldn't be multiple VACUUMs concurrently on the same - * table.) + * right. */ if (target != leafblkno) _bt_lockbuf(rel, leafbuf, BT_WRITE); @@ -2370,23 +2371,26 @@ _bt_unlink_halfdead_page(Relation rel, Buffer leafbuf, BlockNumber scanblkno, opaque = (BTPageOpaque) PageGetSpecialPointer(page); while (P_ISDELETED(opaque) || opaque->btpo_next != target) { - /* step right one page */ - leftsib = opaque->btpo_next; - _bt_relbuf(rel, lbuf); + bool leftsibvalid = true; /* - * It'd be good to check for interrupts here, but it's not easy to - * do so because a lock is always held. This block isn't - * frequently reached, so hopefully the consequences of not - * checking interrupts aren't too bad. + * Before we follow the link from the page that was the left + * sibling mere moments ago, validate its right link. This + * reduces the opportunities for loop to fail to ever make any + * progress in the presence of index corruption. + * + * Note: we rely on the assumption that there can only be one + * vacuum process running at a time (against the same index). */ + if (P_RIGHTMOST(opaque) || P_ISDELETED(opaque) || + leftsib == opaque->btpo_next) + leftsibvalid = false; + + leftsib = opaque->btpo_next; + _bt_relbuf(rel, lbuf); - if (leftsib == P_NONE) + if (!leftsibvalid) { - ereport(LOG, - (errmsg("no left sibling (concurrent deletion?) of block %u in \"%s\"", - target, - RelationGetRelationName(rel)))); if (target != leafblkno) { /* we have only a pin on target, but pin+lock on leafbuf */ @@ -2398,8 +2402,20 @@ _bt_unlink_halfdead_page(Relation rel, Buffer leafbuf, BlockNumber scanblkno, /* we have only a pin on leafbuf */ ReleaseBuffer(leafbuf); } + + ereport(LOG, + (errcode(ERRCODE_INDEX_CORRUPTED), + errmsg_internal("valid left sibling for deletion target could not be located: " + "left sibling %u of target %u with leafblkno %u and scanblkno %u in index \"%s\"", + leftsib, target, leafblkno, scanblkno, + RelationGetRelationName(rel)))); + return false; } + + CHECK_FOR_INTERRUPTS(); + + /* step right one page */ lbuf = _bt_getbuf(rel, leftsib, BT_WRITE); page = BufferGetPage(lbuf); opaque = (BTPageOpaque) PageGetSpecialPointer(page); @@ -2408,11 +2424,7 @@ _bt_unlink_halfdead_page(Relation rel, Buffer leafbuf, BlockNumber scanblkno, else lbuf = InvalidBuffer; - /* - * Next write-lock the target page itself. It's okay to take a write lock - * rather than a superexclusive lock, since no scan will stop on an empty - * page. - */ + /* Next write-lock the target page itself */ _bt_lockbuf(rel, buf, BT_WRITE); page = BufferGetPage(buf); opaque = (BTPageOpaque) PageGetSpecialPointer(page); |