On Wed, Jul 12, 2017 at 1:29 PM, Claudio Freire <klaussfre...@gmail.com> wrote:
> On Wed, Jul 12, 2017 at 1:08 PM, Claudio Freire <klaussfre...@gmail.com>
> wrote:
>> On Wed, Jul 12, 2017 at 11:48 AM, Alexey Chernyshov
>> <a.chernys...@postgrespro.ru> wrote:
>>> Thank you for the patch and benchmark results, I have a couple remarks.
>>> Firstly, padding in DeadTuplesSegment
>>>
>>> typedef struct DeadTuplesSegment
>>>
>>> {
>>>
>>> ItemPointerData last_dead_tuple; /* Copy of the last dead tuple
>>> (unset
>>>
>>> * until the segment is fully
>>>
>>> * populated). Keep it first to
>>> simplify
>>>
>>> * binary searches */
>>>
>>> unsigned short padding; /* Align dt_tids to 32-bits,
>>>
>>> * sizeof(ItemPointerData) is aligned to
>>>
>>> * short, so add a padding short, to make
>>> the
>>>
>>> * size of DeadTuplesSegment a multiple of
>>>
>>> * 32-bits and align integer components for
>>>
>>> * better performance during lookups into
>>> the
>>>
>>> * multiarray */
>>>
>>> int num_dead_tuples; /* # of entries in the segment */
>>>
>>> int max_dead_tuples; /* # of entries allocated in the
>>> segment */
>>>
>>> ItemPointer dt_tids; /* Array of dead tuples */
>>>
>>> } DeadTuplesSegment;
>>>
>>> In the comments to ItemPointerData is written that it is 6 bytes long, but
>>> can be padded to 8 bytes by some compilers, so if we add padding in a
>>> current way, there is no guaranty that it will be done as it is expected.
>>> The other way to do it with pg_attribute_alligned. But in my opinion, there
>>> is no need to do it manually, because the compiler will do this optimization
>>> itself.
>>
>> I'll look into it. But my experience is that compilers won't align
>> struct size like this, only attributes, and this attribute is composed
>> of 16-bit attributes so it doesn't get aligned by default.
>
> Doing sizeof(DeadTuplesSegment) suggests you were indeed right, at
> least in GCC. I'll remove the padding.
>
> Seems I just got the wrong impression at some point.
Updated versions of the patches attached.
A few runs of the benchmark show no significant difference, as it
should (being all cosmetic changes).
The bigger benchmark will take longer.
From b2bf9a671c2c4d517d59628f12a7f564ccf152f6 Mon Sep 17 00:00:00 2001
From: Claudio Freire <klaussfre...@gmail.com>
Date: Mon, 12 Sep 2016 23:36:42 -0300
Subject: [PATCH 1/2] Vacuum: allow using more than 1GB work mem
Turn the dead_tuples array into a structure composed of several
exponentially bigger arrays, to enable usage of more than 1GB
of work mem during vacuum and thus reduce the number of full
index scans necessary to remove all dead tids when the memory is
available.
Improve test ability to spot vacuum errors
---
src/backend/commands/vacuumlazy.c | 402 ++++++++++++++++++++++++++++-------
src/test/regress/expected/vacuum.out | 26 +++
src/test/regress/sql/vacuum.sql | 19 ++
3 files changed, 373 insertions(+), 74 deletions(-)
diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c
index 30a0050..287accd 100644
--- a/src/backend/commands/vacuumlazy.c
+++ b/src/backend/commands/vacuumlazy.c
@@ -11,11 +11,24 @@
*
* We are willing to use at most maintenance_work_mem (or perhaps
* autovacuum_work_mem) memory space to keep track of dead tuples. We
- * initially allocate an array of TIDs of that size, with an upper limit that
+ * initially allocate an array of TIDs of 128MB, or an upper limit that
* depends on table size (this limit ensures we don't allocate a huge area
- * uselessly for vacuuming small tables). If the array threatens to overflow,
+ * uselessly for vacuuming small tables). Additional arrays of increasingly
+ * large sizes are allocated as they become necessary.
+ *
+ * The TID array is thus represented as a list of multiple segments of
+ * varying size, beginning with the initial size of up to 128MB, and growing
+ * exponentially until the whole budget of (autovacuum_)maintenance_work_mem
+ * is used up.
+ *
+ * Lookup in that structure happens with a binary search of segments, and then
+ * with a binary search within each segment. Since segment's size grows
+ * exponentially, this retains O(log N) lookup complexity.
+ *
+ * If the multiarray's total size threatens to grow beyond maintenance_work_mem,
* we suspend the heap scan phase and perform a pass of index cleanup and page
- * compaction, then resume the heap scan with an empty TID array.
+ * compaction, then resume the heap scan with an array of logically empty but
+ * already preallocated TID segments to be refilled with more dead tuple TIDs.
*
* If we're processing a table with no indexes, we can just vacuum each page
* as we go; there's no need to save up multiple tuples to minimize the number
@@ -92,6 +105,14 @@
#define LAZY_ALLOC_TUPLES MaxHeapTuplesPerPage
/*
+ * Minimum (starting) size of the dead_tuples array segments. Will allocate
+ * space for 128MB worth of tid pointers in the first segment, further segments
+ * will grow in size exponentially. Don't make it too small or the segment list
+ * will grow bigger than the sweetspot for search efficiency on big vacuums.
+ */
+#define LAZY_INIT_TUPLES Max(MaxHeapTuplesPerPage, (128<<20) / sizeof(ItemPointerData))
+
+/*
* Before we consider skipping a page that's marked as clean in
* visibility map, we must've seen at least this many clean pages.
*/
@@ -103,6 +124,27 @@
*/
#define PREFETCH_SIZE ((BlockNumber) 32)
+typedef struct DeadTuplesSegment
+{
+ ItemPointerData last_dead_tuple; /* Copy of the last dead tuple (unset
+ * until the segment is fully
+ * populated). Keep it first to simplify
+ * binary searches */
+ int num_dead_tuples; /* # of entries in the segment */
+ int max_dead_tuples; /* # of entries allocated in the segment */
+ ItemPointer dt_tids; /* Array of dead tuples */
+} DeadTuplesSegment;
+
+typedef struct DeadTuplesMultiArray
+{
+ int num_entries; /* current # of entries */
+ int max_entries; /* total # of slots that can be allocated in
+ * array */
+ int num_segs; /* number of dead tuple segments allocated */
+ int last_seg; /* last dead tuple segment with data (or 0) */
+ DeadTuplesSegment *dt_segments; /* array of num_segs segments */
+} DeadTuplesMultiArray;
+
typedef struct LVRelStats
{
/* hasindex = true means two-pass strategy; false means one-pass */
@@ -123,14 +165,20 @@ typedef struct LVRelStats
BlockNumber nonempty_pages; /* actually, last nonempty page + 1 */
/* List of TIDs of tuples we intend to delete */
/* NB: this list is ordered by TID address */
- int num_dead_tuples; /* current # of entries */
- int max_dead_tuples; /* # slots allocated in array */
- ItemPointer dead_tuples; /* array of ItemPointerData */
+ DeadTuplesMultiArray dead_tuples;
int num_index_scans;
TransactionId latestRemovedXid;
bool lock_waiter_detected;
} LVRelStats;
+#define GetNumDeadTuplesSegments(lvrelstats) \
+ ((lvrelstats)->dead_tuples.num_segs)
+
+#define GetDeadTuplesSegment(lvrelstats, seg) \
+ (&((lvrelstats)->dead_tuples.dt_segments[seg]))
+
+#define DeadTuplesCurrentSegment(lvrelstats) \
+ GetDeadTuplesSegment(lvrelstats, (lvrelstats)->dead_tuples.last_seg)
/* A few variables that don't seem worth passing around as parameters */
static int elevel = -1;
@@ -155,7 +203,7 @@ static void lazy_cleanup_index(Relation indrel,
IndexBulkDeleteResult *stats,
LVRelStats *vacrelstats);
static int lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
- int tupindex, LVRelStats *vacrelstats, Buffer *vmbuffer);
+ int tupindex, LVRelStats *vacrelstats, DeadTuplesSegment * seg, Buffer *vmbuffer);
static bool should_attempt_truncation(LVRelStats *vacrelstats);
static void lazy_truncate_heap(Relation onerel, LVRelStats *vacrelstats);
static BlockNumber count_nondeletable_pages(Relation onerel,
@@ -163,8 +211,8 @@ static BlockNumber count_nondeletable_pages(Relation onerel,
static void lazy_space_alloc(LVRelStats *vacrelstats, BlockNumber relblocks);
static void lazy_record_dead_tuple(LVRelStats *vacrelstats,
ItemPointer itemptr);
+static void lazy_clear_dead_tuples(LVRelStats *vacrelstats);
static bool lazy_tid_reaped(ItemPointer itemptr, void *state);
-static int vac_cmp_itemptr(const void *left, const void *right);
static bool heap_page_is_all_visible(Relation rel, Buffer buf,
TransactionId *visibility_cutoff_xid, bool *all_frozen);
@@ -510,7 +558,7 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
/* Report that we're scanning the heap, advertising total # of blocks */
initprog_val[0] = PROGRESS_VACUUM_PHASE_SCAN_HEAP;
initprog_val[1] = nblocks;
- initprog_val[2] = vacrelstats->max_dead_tuples;
+ initprog_val[2] = vacrelstats->dead_tuples.max_entries;
pgstat_progress_update_multi_param(3, initprog_index, initprog_val);
/*
@@ -689,8 +737,8 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
* If we are close to overrunning the available space for dead-tuple
* TIDs, pause and do a cycle of vacuuming before we tackle this page.
*/
- if ((vacrelstats->max_dead_tuples - vacrelstats->num_dead_tuples) < MaxHeapTuplesPerPage &&
- vacrelstats->num_dead_tuples > 0)
+ if ((vacrelstats->dead_tuples.max_entries - vacrelstats->dead_tuples.num_entries) < MaxHeapTuplesPerPage &&
+ vacrelstats->dead_tuples.num_entries > 0)
{
const int hvp_index[] = {
PROGRESS_VACUUM_PHASE,
@@ -741,7 +789,7 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
* not to reset latestRemovedXid since we want that value to be
* valid.
*/
- vacrelstats->num_dead_tuples = 0;
+ lazy_clear_dead_tuples(vacrelstats);
vacrelstats->num_index_scans++;
/* Report that we are once again scanning the heap */
@@ -924,7 +972,7 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
has_dead_tuples = false;
nfrozen = 0;
hastup = false;
- prev_dead_count = vacrelstats->num_dead_tuples;
+ prev_dead_count = vacrelstats->dead_tuples.num_entries;
maxoff = PageGetMaxOffsetNumber(page);
/*
@@ -1136,10 +1184,16 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
* instead of doing a second scan.
*/
if (nindexes == 0 &&
- vacrelstats->num_dead_tuples > 0)
+ vacrelstats->dead_tuples.num_entries > 0)
{
+ /* Should never need more than one segment per page */
+ Assert(vacrelstats->dead_tuples.last_seg == 0);
+
+ /* Should have been initialized */
+ Assert(GetNumDeadTuplesSegments(vacrelstats) > 0);
+
/* Remove tuples from heap */
- lazy_vacuum_page(onerel, blkno, buf, 0, vacrelstats, &vmbuffer);
+ lazy_vacuum_page(onerel, blkno, buf, 0, vacrelstats, DeadTuplesCurrentSegment(vacrelstats), &vmbuffer);
has_dead_tuples = false;
/*
@@ -1147,7 +1201,7 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
* not to reset latestRemovedXid since we want that value to be
* valid.
*/
- vacrelstats->num_dead_tuples = 0;
+ lazy_clear_dead_tuples(vacrelstats);
vacuumed_pages++;
}
@@ -1250,7 +1304,7 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
* page, so remember its free space as-is. (This path will always be
* taken if there are no indexes.)
*/
- if (vacrelstats->num_dead_tuples == prev_dead_count)
+ if (vacrelstats->dead_tuples.num_entries == prev_dead_count)
RecordPageWithFreeSpace(onerel, blkno, freespace);
}
@@ -1281,7 +1335,7 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
/* If any tuples need to be deleted, perform final vacuum cycle */
/* XXX put a threshold on min number of tuples here? */
- if (vacrelstats->num_dead_tuples > 0)
+ if (vacrelstats->dead_tuples.num_entries > 0)
{
const int hvp_index[] = {
PROGRESS_VACUUM_PHASE,
@@ -1378,43 +1432,56 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
static void
lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats)
{
- int tupindex;
+ int tottuples;
+ int segindex;
int npages;
PGRUsage ru0;
Buffer vmbuffer = InvalidBuffer;
+ if (GetNumDeadTuplesSegments(vacrelstats) == 0)
+ return;
+
pg_rusage_init(&ru0);
npages = 0;
- tupindex = 0;
- while (tupindex < vacrelstats->num_dead_tuples)
+ segindex = 0;
+ tottuples = 0;
+ for (segindex = 0; segindex <= vacrelstats->dead_tuples.last_seg; segindex++)
{
- BlockNumber tblk;
- Buffer buf;
- Page page;
- Size freespace;
+ DeadTuplesSegment *seg = GetDeadTuplesSegment(vacrelstats, segindex);
+ int num_dead_tuples = seg->num_dead_tuples;
+ int tupindex = 0;
- vacuum_delay_point();
-
- tblk = ItemPointerGetBlockNumber(&vacrelstats->dead_tuples[tupindex]);
- buf = ReadBufferExtended(onerel, MAIN_FORKNUM, tblk, RBM_NORMAL,
- vac_strategy);
- if (!ConditionalLockBufferForCleanup(buf))
+ while (tupindex < num_dead_tuples)
{
- ReleaseBuffer(buf);
- ++tupindex;
- continue;
- }
- tupindex = lazy_vacuum_page(onerel, tblk, buf, tupindex, vacrelstats,
- &vmbuffer);
+ BlockNumber tblk;
+ Buffer buf;
+ Page page;
+ Size freespace;
- /* Now that we've compacted the page, record its available space */
- page = BufferGetPage(buf);
- freespace = PageGetHeapFreeSpace(page);
+ vacuum_delay_point();
- UnlockReleaseBuffer(buf);
- RecordPageWithFreeSpace(onerel, tblk, freespace);
- npages++;
+ tblk = ItemPointerGetBlockNumber(&seg->dt_tids[tupindex]);
+ buf = ReadBufferExtended(onerel, MAIN_FORKNUM, tblk, RBM_NORMAL,
+ vac_strategy);
+ if (!ConditionalLockBufferForCleanup(buf))
+ {
+ ReleaseBuffer(buf);
+ ++tupindex;
+ continue;
+ }
+ tupindex = lazy_vacuum_page(onerel, tblk, buf, tupindex, vacrelstats,
+ seg, &vmbuffer);
+
+ /* Now that we've compacted the page, record its available space */
+ page = BufferGetPage(buf);
+ freespace = PageGetHeapFreeSpace(page);
+
+ UnlockReleaseBuffer(buf);
+ RecordPageWithFreeSpace(onerel, tblk, freespace);
+ npages++;
+ }
+ tottuples += tupindex;
}
if (BufferIsValid(vmbuffer))
@@ -1426,7 +1493,7 @@ lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats)
ereport(elevel,
(errmsg("\"%s\": removed %d row versions in %d pages",
RelationGetRelationName(onerel),
- tupindex, npages),
+ tottuples, npages),
errdetail_internal("%s", pg_rusage_show(&ru0))));
}
@@ -1436,34 +1503,36 @@ lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats)
*
* Caller must hold pin and buffer cleanup lock on the buffer.
*
- * tupindex is the index in vacrelstats->dead_tuples of the first dead
+ * tupindex is the index in seg->dt_tids of the first dead
* tuple for this page. We assume the rest follow sequentially.
* The return value is the first tupindex after the tuples of this page.
*/
static int
lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
- int tupindex, LVRelStats *vacrelstats, Buffer *vmbuffer)
+ int tupindex, LVRelStats *vacrelstats, DeadTuplesSegment * seg, Buffer *vmbuffer)
{
Page page = BufferGetPage(buffer);
OffsetNumber unused[MaxOffsetNumber];
int uncnt = 0;
TransactionId visibility_cutoff_xid;
bool all_frozen;
+ ItemPointer dead_tuples = seg->dt_tids;
+ int num_dead_tuples = seg->num_dead_tuples;
pgstat_progress_update_param(PROGRESS_VACUUM_HEAP_BLKS_VACUUMED, blkno);
START_CRIT_SECTION();
- for (; tupindex < vacrelstats->num_dead_tuples; tupindex++)
+ for (; tupindex < num_dead_tuples; tupindex++)
{
BlockNumber tblk;
OffsetNumber toff;
ItemId itemid;
- tblk = ItemPointerGetBlockNumber(&vacrelstats->dead_tuples[tupindex]);
+ tblk = ItemPointerGetBlockNumber(&dead_tuples[tupindex]);
if (tblk != blkno)
break; /* past end of tuples for this block */
- toff = ItemPointerGetOffsetNumber(&vacrelstats->dead_tuples[tupindex]);
+ toff = ItemPointerGetOffsetNumber(&dead_tuples[tupindex]);
itemid = PageGetItemId(page, toff);
ItemIdSetUnused(itemid);
unused[uncnt++] = toff;
@@ -1597,6 +1666,8 @@ lazy_vacuum_index(Relation indrel,
{
IndexVacuumInfo ivinfo;
PGRUsage ru0;
+ DeadTuplesSegment *seg;
+ int n;
pg_rusage_init(&ru0);
@@ -1607,6 +1678,20 @@ lazy_vacuum_index(Relation indrel,
ivinfo.num_heap_tuples = vacrelstats->old_rel_tuples;
ivinfo.strategy = vac_strategy;
+ /* If uninitialized, we have no tuples to delete from the indexes */
+ if (GetNumDeadTuplesSegments(vacrelstats) == 0)
+ {
+ return;
+ }
+
+ /* Finalize all segments by setting their upper bound dead tuple */
+ for (n = 0; n <= vacrelstats->dead_tuples.last_seg; n++)
+ {
+ seg = GetDeadTuplesSegment(vacrelstats, n);
+ if (seg->num_dead_tuples > 0)
+ seg->last_dead_tuple = seg->dt_tids[seg->num_dead_tuples - 1];
+ }
+
/* Do bulk deletion */
*stats = index_bulk_delete(&ivinfo, *stats,
lazy_tid_reaped, (void *) vacrelstats);
@@ -1614,7 +1699,7 @@ lazy_vacuum_index(Relation indrel,
ereport(elevel,
(errmsg("scanned index \"%s\" to remove %d row versions",
RelationGetRelationName(indrel),
- vacrelstats->num_dead_tuples),
+ vacrelstats->dead_tuples.num_entries),
errdetail_internal("%s", pg_rusage_show(&ru0))));
}
@@ -1991,7 +2076,6 @@ lazy_space_alloc(LVRelStats *vacrelstats, BlockNumber relblocks)
{
maxtuples = (vac_work_mem * 1024L) / sizeof(ItemPointerData);
maxtuples = Min(maxtuples, INT_MAX);
- maxtuples = Min(maxtuples, MaxAllocSize / sizeof(ItemPointerData));
/* curious coding here to ensure the multiplication can't overflow */
if ((BlockNumber) (maxtuples / LAZY_ALLOC_TUPLES) > relblocks)
@@ -2005,10 +2089,11 @@ lazy_space_alloc(LVRelStats *vacrelstats, BlockNumber relblocks)
maxtuples = MaxHeapTuplesPerPage;
}
- vacrelstats->num_dead_tuples = 0;
- vacrelstats->max_dead_tuples = (int) maxtuples;
- vacrelstats->dead_tuples = (ItemPointer)
- palloc(maxtuples * sizeof(ItemPointerData));
+ vacrelstats->dead_tuples.num_entries = 0;
+ vacrelstats->dead_tuples.max_entries = (int) maxtuples;
+ vacrelstats->dead_tuples.num_segs = 0;
+ vacrelstats->dead_tuples.last_seg = 0;
+ vacrelstats->dead_tuples.dt_segments = NULL;
}
/*
@@ -2018,46 +2103,165 @@ static void
lazy_record_dead_tuple(LVRelStats *vacrelstats,
ItemPointer itemptr)
{
+ int mintuples;
+
+ /* Initialize multiarray if needed */
+ if (GetNumDeadTuplesSegments(vacrelstats) == 0)
+ {
+ mintuples = Min(LAZY_INIT_TUPLES, vacrelstats->dead_tuples.max_entries);
+
+ vacrelstats->dead_tuples.num_segs = 1;
+ vacrelstats->dead_tuples.dt_segments = (DeadTuplesSegment *)
+ palloc(sizeof(DeadTuplesSegment));
+ vacrelstats->dead_tuples.dt_segments[0].dt_tids = (ItemPointer)
+ palloc(mintuples * sizeof(ItemPointerData));
+ vacrelstats->dead_tuples.dt_segments[0].max_dead_tuples = mintuples;
+ vacrelstats->dead_tuples.dt_segments[0].num_dead_tuples = 0;
+ }
+
/*
* The array shouldn't overflow under normal behavior, but perhaps it
* could if we are given a really small maintenance_work_mem. In that
* case, just forget the last few tuples (we'll get 'em next time).
*/
- if (vacrelstats->num_dead_tuples < vacrelstats->max_dead_tuples)
+ if (vacrelstats->dead_tuples.num_entries < vacrelstats->dead_tuples.max_entries)
{
- vacrelstats->dead_tuples[vacrelstats->num_dead_tuples] = *itemptr;
- vacrelstats->num_dead_tuples++;
+ DeadTuplesSegment *seg = DeadTuplesCurrentSegment(vacrelstats);
+
+ if (seg->num_dead_tuples >= seg->max_dead_tuples)
+ {
+ DeadTuplesMultiArray *dt = &vacrelstats->dead_tuples;
+
+ /*
+ * The segment is overflowing, so we must allocate a new segment.
+ * We could have a preallocated segment descriptor already, in
+ * which case we just reinitialize it, or we may need to repalloc
+ * the vacrelstats->dead_tuples array. In that case, seg will no
+ * longer be valid, so we must be careful about that.
+ */
+ Assert(seg->num_dead_tuples == seg->max_dead_tuples);
+ if (dt->last_seg + 1 >= dt->num_segs)
+ {
+ int new_num_segs = dt->num_segs * 2;
+ int new_segs_size = new_num_segs * sizeof(DeadTuplesSegment);
+
+ dt->dt_segments = (DeadTuplesSegment *) repalloc((void *) dt->dt_segments, new_segs_size);
+ while (dt->num_segs < new_num_segs)
+ {
+ /* Initialize as "unallocated" */
+ DeadTuplesSegment *nseg = &(dt->dt_segments[dt->num_segs]);
+
+ nseg->num_dead_tuples = 0;
+ nseg->max_dead_tuples = 0;
+ nseg->dt_tids = NULL;
+ dt->num_segs++;
+ }
+ }
+ dt->last_seg++;
+ seg = DeadTuplesCurrentSegment(vacrelstats);
+ if (seg->dt_tids == NULL)
+ {
+ /*
+ * If unallocated, allocate up to twice the amount of the
+ * previous segment
+ */
+ DeadTuplesSegment *pseg = seg - 1;
+ int numtuples = dt->max_entries - dt->num_entries;
+
+ numtuples = Max(numtuples, MaxHeapTuplesPerPage);
+ numtuples = Min(numtuples, INT_MAX / 2);
+ numtuples = Min(numtuples, 2 * pseg->max_dead_tuples);
+ numtuples = Min(numtuples, MaxAllocSize / sizeof(ItemPointerData));
+ seg->dt_tids = (ItemPointer) palloc(sizeof(ItemPointerData) * numtuples);
+ seg->max_dead_tuples = numtuples;
+ }
+ seg->num_dead_tuples = 0;
+ }
+ seg->dt_tids[seg->num_dead_tuples] = *itemptr;
+ vacrelstats->dead_tuples.num_entries++;
+ seg->num_dead_tuples++;
pgstat_progress_update_param(PROGRESS_VACUUM_NUM_DEAD_TUPLES,
- vacrelstats->num_dead_tuples);
+ vacrelstats->dead_tuples.num_entries);
}
}
/*
- * lazy_tid_reaped() -- is a particular tid deletable?
+ * lazy_clear_dead_tuples - reset all dead tuples segments
+ */
+static void
+lazy_clear_dead_tuples(LVRelStats *vacrelstats)
+{
+ int nseg;
+
+ for (nseg = 0; nseg < GetNumDeadTuplesSegments(vacrelstats); nseg++)
+ GetDeadTuplesSegment(vacrelstats, nseg)->num_dead_tuples = 0;
+ vacrelstats->dead_tuples.last_seg = 0;
+ vacrelstats->dead_tuples.num_entries = 0;
+}
+
+/*
+ * vac_itemptr_binsrch() -- search a sorted array of item pointers
*
- * This has the right signature to be an IndexBulkDeleteCallback.
+ * Returns the offset of the first item pointer greater than or
+ * equal to refvalue, or arr_elems if there is no such item pointer
*
- * Assumes dead_tuples array is in sorted order.
+ * All item pointers in the array are assumed to be valid
+ *
+ * Within, vac_cmp_itemptr has been inlined to remove redundant
+ * validity checking (the dead tuples array contains only valid
+ * item pointers) and ItemPointerGetX invocations (the refvalue
+ * never changes). This makes the code easier to optimize for
+ * the compiler, and should improve performance
*/
-static bool
-lazy_tid_reaped(ItemPointer itemptr, void *state)
+static inline size_t vac_itemptr_binsrch(ItemPointer refvalue, void *arr,
+ size_t arr_elems, size_t arr_stride)
{
- LVRelStats *vacrelstats = (LVRelStats *) state;
- ItemPointer res;
+ BlockNumber refblk, blk;
+ OffsetNumber refoff, off;
+ ItemPointer value;
+ size_t left, right, mid;
- res = (ItemPointer) bsearch((void *) itemptr,
- (void *) vacrelstats->dead_tuples,
- vacrelstats->num_dead_tuples,
- sizeof(ItemPointerData),
- vac_cmp_itemptr);
+ if (arr_elems == 0 || !ItemPointerIsValid(refvalue))
+ return arr_elems;
+
+ refblk = ItemPointerGetBlockNumberNoCheck(refvalue);
+ refoff = ItemPointerGetOffsetNumberNoCheck(refvalue);
+
+ left = 0;
+ right = arr_elems - 1;
+ while (right > left)
+ {
+ mid = left + ((right - left) / 2);
+ value = (ItemPointer)((char*) arr + mid * arr_stride);
- return (res != NULL);
+ blk = ItemPointerGetBlockNumberNoCheck(value);
+ if (refblk < blk)
+ {
+ right = mid;
+ }
+ else if (refblk == blk)
+ {
+ off = ItemPointerGetOffsetNumberNoCheck(value);
+ if (refoff < off)
+ right = mid;
+ else if (refoff == off)
+ return mid;
+ else
+ left = mid + 1;
+ }
+ else
+ {
+ left = mid + 1;
+ }
+ }
+
+ return left;
}
/*
- * Comparator routines for use with qsort() and bsearch().
+ * Comparator routine for use within lazy_tid_reaped
*/
-static int
+static inline int
vac_cmp_itemptr(const void *left, const void *right)
{
BlockNumber lblk,
@@ -2085,6 +2289,56 @@ vac_cmp_itemptr(const void *left, const void *right)
}
/*
+ * lazy_tid_reaped() -- is a particular tid deletable?
+ *
+ * This has the right signature to be an IndexBulkDeleteCallback.
+ *
+ * Assumes the dead_tuples multiarray is in sorted order, both
+ * the segment list and each segment itself, and that all segments'
+ * last_dead_tuple fields up to date
+ */
+static bool
+lazy_tid_reaped(ItemPointer itemptr, void *state)
+{
+ LVRelStats *vacrelstats = (LVRelStats *) state;
+ DeadTuplesSegment *seg;
+ size_t iseg, itup;
+
+ if (GetNumDeadTuplesSegments(vacrelstats) == 0)
+ return false;
+
+ /* Quickly rule out by lower bound (should happen a lot) */
+ seg = vacrelstats->dead_tuples.dt_segments;
+ if (0 > vac_cmp_itemptr((void *) itemptr, (void *) seg->dt_tids))
+ return false;
+
+ /* Search for the segment likely to contain the item pointer */
+ iseg = vac_itemptr_binsrch(
+ (void *) itemptr,
+ (void *) &(seg->last_dead_tuple),
+ vacrelstats->dead_tuples.last_seg + 1,
+ sizeof(DeadTuplesSegment));
+
+ if (iseg > vacrelstats->dead_tuples.last_seg)
+ return false;
+
+ seg = GetDeadTuplesSegment(vacrelstats, iseg);
+ if (seg->num_dead_tuples == 0)
+ return false;
+
+ /* Search within the segment for the right item pointer */
+ itup = vac_itemptr_binsrch((void *) itemptr,
+ (void *) seg->dt_tids,
+ seg->num_dead_tuples,
+ sizeof(ItemPointerData));
+ if (itup >= seg->num_dead_tuples)
+ return false;
+ else
+ return 0 == vac_cmp_itemptr((void *) itemptr,
+ (void *) (&seg->dt_tids[itup]));
+}
+
+/*
* Check if every tuple in the given page is visible to all current and future
* transactions. Also return the visibility_cutoff_xid which is the highest
* xmin amongst the visible tuples. Set *all_frozen to true if every tuple
diff --git a/src/test/regress/expected/vacuum.out b/src/test/regress/expected/vacuum.out
index 6f68663..c4ebec5 100644
--- a/src/test/regress/expected/vacuum.out
+++ b/src/test/regress/expected/vacuum.out
@@ -81,6 +81,32 @@ SQL function "wrap_do_analyze" statement 1
VACUUM FULL vactst;
VACUUM (DISABLE_PAGE_SKIPPING) vaccluster;
DROP TABLE vaccluster;
+INSERT INTO vactst SELECT * from generate_series(1,400000);
+CREATE INDEX ix_vactst ON vactst (i);
+DELETE FROM vactst WHERE i in (SELECT i FROM vactst ORDER BY random() LIMIT 300000);
+SET maintenance_work_mem = 1024;
+VACUUM vactst;
+SET maintenance_work_mem TO DEFAULT;
+DROP INDEX ix_vactst;
+TRUNCATE TABLE vactst;
+INSERT INTO vactst SELECT * from generate_series(1,40);
+CREATE INDEX ix_vactst ON vactst (i);
+DELETE FROM vactst;
+VACUUM vactst;
+SELECT pg_relation_size('vactst', 'main');
+ pg_relation_size
+------------------
+ 0
+(1 row)
+
+SELECT count(*) FROM vactst;
+ count
+-------
+ 0
+(1 row)
+
+DROP INDEX ix_vactst;
+TRUNCATE TABLE vactst;
DROP TABLE vactst;
-- partitioned table
CREATE TABLE vacparted (a int, b char) PARTITION BY LIST (a);
diff --git a/src/test/regress/sql/vacuum.sql b/src/test/regress/sql/vacuum.sql
index 7c5fb04..85f4f9b 100644
--- a/src/test/regress/sql/vacuum.sql
+++ b/src/test/regress/sql/vacuum.sql
@@ -63,6 +63,25 @@ VACUUM FULL vactst;
VACUUM (DISABLE_PAGE_SKIPPING) vaccluster;
DROP TABLE vaccluster;
+
+INSERT INTO vactst SELECT * from generate_series(1,400000);
+CREATE INDEX ix_vactst ON vactst (i);
+DELETE FROM vactst WHERE i in (SELECT i FROM vactst ORDER BY random() LIMIT 300000);
+SET maintenance_work_mem = 1024;
+VACUUM vactst;
+SET maintenance_work_mem TO DEFAULT;
+DROP INDEX ix_vactst;
+TRUNCATE TABLE vactst;
+
+INSERT INTO vactst SELECT * from generate_series(1,40);
+CREATE INDEX ix_vactst ON vactst (i);
+DELETE FROM vactst;
+VACUUM vactst;
+SELECT pg_relation_size('vactst', 'main');
+SELECT count(*) FROM vactst;
+DROP INDEX ix_vactst;
+TRUNCATE TABLE vactst;
+
DROP TABLE vactst;
-- partitioned table
--
1.8.4.5
From 227cdaa3910fac015a3d395a01c2eeb13e346072 Mon Sep 17 00:00:00 2001
From: Claudio Freire <klaussfre...@gmail.com>
Date: Tue, 28 Mar 2017 22:40:39 -0300
Subject: [PATCH 2/2] Vacuum: free dead tuples array as early as possible
Allow other parts of the system to benefit from the possibly
large amount of memory reserved for dead tuples after they're
no longer necessary.
While the memory would be freed when the command finishes, it
can sometimes be some considerable time between the time vacuum
is done with the array until the command finishes - mostly due
to truncate taking a long time.
---
src/backend/commands/vacuumlazy.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c
index 287accd..1d2b18f 100644
--- a/src/backend/commands/vacuumlazy.c
+++ b/src/backend/commands/vacuumlazy.c
@@ -212,6 +212,7 @@ static void lazy_space_alloc(LVRelStats *vacrelstats, BlockNumber relblocks);
static void lazy_record_dead_tuple(LVRelStats *vacrelstats,
ItemPointer itemptr);
static void lazy_clear_dead_tuples(LVRelStats *vacrelstats);
+static void lazy_free_dead_tuples(LVRelStats *vacrelstats);
static bool lazy_tid_reaped(ItemPointer itemptr, void *state);
static bool heap_page_is_all_visible(Relation rel, Buffer buf,
TransactionId *visibility_cutoff_xid, bool *all_frozen);
@@ -1373,6 +1374,9 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
pgstat_progress_update_param(PROGRESS_VACUUM_PHASE,
PROGRESS_VACUUM_PHASE_INDEX_CLEANUP);
+ /* dead tuples no longer needed past this point */
+ lazy_free_dead_tuples(vacrelstats);
+
/* Do post-vacuum cleanup and statistics update for each index */
for (i = 0; i < nindexes; i++)
lazy_cleanup_index(Irel[i], indstats[i], vacrelstats);
@@ -2200,6 +2204,27 @@ lazy_clear_dead_tuples(LVRelStats *vacrelstats)
}
/*
+ * lazy_free_dead_tuples - reset all dead tuples segments
+ * and free all allocated memory
+ */
+static void
+lazy_free_dead_tuples(LVRelStats *vacrelstats)
+{
+ int nseg;
+
+ for (nseg = 0; nseg < GetNumDeadTuplesSegments(vacrelstats); nseg++)
+ if (GetDeadTuplesSegment(vacrelstats, nseg)->dt_tids != NULL)
+ pfree(GetDeadTuplesSegment(vacrelstats, nseg)->dt_tids);
+ if (vacrelstats->dead_tuples.dt_segments != NULL)
+ if (vacrelstats->dead_tuples.dt_segments != NULL)
+ pfree(vacrelstats->dead_tuples.dt_segments);
+ vacrelstats->dead_tuples.last_seg = 0;
+ vacrelstats->dead_tuples.num_segs = 0;
+ vacrelstats->dead_tuples.num_entries = 0;
+ vacrelstats->dead_tuples.dt_segments = NULL;
+}
+
+/*
* vac_itemptr_binsrch() -- search a sorted array of item pointers
*
* Returns the offset of the first item pointer greater than or
--
1.8.4.5
--
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