diff options
| -rw-r--r-- | src/backend/access/heap/pruneheap.c | 4 | ||||
| -rw-r--r-- | src/backend/access/heap/vacuumlazy.c | 11 | ||||
| -rw-r--r-- | src/backend/storage/page/bufpage.c | 35 |
3 files changed, 33 insertions, 17 deletions
diff --git a/src/backend/access/heap/pruneheap.c b/src/backend/access/heap/pruneheap.c index 4656f1b3db4..98d31de0031 100644 --- a/src/backend/access/heap/pruneheap.c +++ b/src/backend/access/heap/pruneheap.c @@ -244,7 +244,9 @@ heap_page_prune_opt(Relation relation, Buffer buffer) * Prune and repair fragmentation in the specified page. * * Caller must have pin and buffer cleanup lock on the page. Note that we - * don't update the FSM information for page on caller's behalf. + * don't update the FSM information for page on caller's behalf. Caller might + * also need to account for a reduction in the length of the line pointer + * array following array truncation by us. * * vistest is used to distinguish whether tuples are DEAD or RECENTLY_DEAD * (see heap_prune_satisfies_vacuum and diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c index 092b739dda9..e1cac74e620 100644 --- a/src/backend/access/heap/vacuumlazy.c +++ b/src/backend/access/heap/vacuumlazy.c @@ -223,7 +223,7 @@ typedef struct LVRelState */ typedef struct LVPagePruneState { - bool hastup; /* Page is truncatable? */ + bool hastup; /* Page prevents rel truncation? */ bool has_lpdead_items; /* includes existing LP_DEAD items */ /* @@ -1393,7 +1393,7 @@ lazy_scan_skip(LVRelState *vacrel, Buffer *vmbuffer, BlockNumber next_block, * * It's necessary to consider new pages as a special case, since the rules for * maintaining the visibility map and FSM with empty pages are a little - * different (though new pages can be truncated based on the usual rules). + * different (though new pages can be truncated away during rel truncation). * * Empty pages are not really a special case -- they're just heap pages that * have no allocated tuples (including even LP_UNUSED items). You might @@ -1561,6 +1561,11 @@ lazy_scan_prune(LVRelState *vacrel, Assert(BufferGetBlockNumber(buf) == blkno); + /* + * maxoff might be reduced following line pointer array truncation in + * heap_page_prune. That's safe for us to ignore, since the reclaimed + * space will continue to look like LP_UNUSED items below. + */ maxoff = PageGetMaxOffsetNumber(page); retry: @@ -1768,7 +1773,7 @@ retry: * Check tuple left behind after pruning to see if needs to be frozen * now. */ - prunestate->hastup = true; /* page won't be truncatable */ + prunestate->hastup = true; /* page makes rel truncation unsafe */ if (heap_prepare_freeze_tuple(tuple.t_data, vacrel->relfrozenxid, vacrel->relminmxid, diff --git a/src/backend/storage/page/bufpage.c b/src/backend/storage/page/bufpage.c index 147ba4d9232..366d57ea7ac 100644 --- a/src/backend/storage/page/bufpage.c +++ b/src/backend/storage/page/bufpage.c @@ -688,22 +688,14 @@ compactify_tuples(itemIdCompact itemidbase, int nitems, Page page, bool presorte * * This routine is usable for heap pages only, but see PageIndexMultiDelete. * - * Never removes unused line pointers. PageTruncateLinePointerArray can - * safely remove some unused line pointers. It ought to be safe for this - * routine to free unused line pointers in roughly the same way, but it's not - * clear that that would be beneficial. - * - * PageTruncateLinePointerArray is only called during VACUUM's second pass - * over the heap. Any unused line pointers that it sees are likely to have - * been set to LP_UNUSED (from LP_DEAD) immediately before the time it is - * called. On the other hand, many tables have the vast majority of all - * required pruning performed opportunistically (not during VACUUM). And so - * there is, in general, a good chance that even large groups of unused line - * pointers that we see here will be recycled quickly. + * This routine removes unused line pointers from the end of the line pointer + * array. This is possible when dead heap-only tuples get removed by pruning, + * especially when there were HOT chains with several tuples each beforehand. * * Caller had better have a full cleanup lock on page's buffer. As a side * effect the page's PD_HAS_FREE_LINES hint bit will be set or unset as - * needed. + * needed. Caller might also need to account for a reduction in the length of + * the line pointer array following array truncation. */ void PageRepairFragmentation(Page page) @@ -718,6 +710,7 @@ PageRepairFragmentation(Page page) int nline, nstorage, nunused; + OffsetNumber finalusedlp = InvalidOffsetNumber; int i; Size totallen; bool presorted = true; /* For now */ @@ -771,10 +764,13 @@ PageRepairFragmentation(Page page) totallen += itemidptr->alignedlen; itemidptr++; } + + finalusedlp = i; /* Could be the final non-LP_UNUSED item */ } else { /* Unused entries should have lp_len = 0, but make sure */ + Assert(!ItemIdHasStorage(lp)); ItemIdSetUnused(lp); nunused++; } @@ -798,6 +794,19 @@ PageRepairFragmentation(Page page) compactify_tuples(itemidbase, nstorage, page, presorted); } + if (finalusedlp != nline) + { + /* The last line pointer is not the last used line pointer */ + int nunusedend = nline - finalusedlp; + + Assert(nunused >= nunusedend && nunusedend > 0); + + /* remove trailing unused line pointers from the count */ + nunused -= nunusedend; + /* truncate the line pointer array */ + ((PageHeader) page)->pd_lower -= (sizeof(ItemIdData) * nunusedend); + } + /* Set hint bit for PageAddItemExtended */ if (nunused > 0) PageSetHasFreeLinePointers(page); |