On Mon, Feb 10, 2025 at 4:22 PM Melanie Plageman
<melanieplage...@gmail.com> wrote:
>
> I don't really know what to do about this. The behavior of master
> parallel bitmap heap scan can be emulated with the patch by increasing
> effective_io_concurrency. But, IIRC we didn't want to do that for some
> reason?
> Not only does effective_io_concurrency == 1 negatively affect read
> ahead, but it also prevents read combining regardless of the
> io_combine_limit.
Would a sensible default be something like 4?
I did some self-review on the patches and cleaned up the commit
messages etc. Attached is v29.
- Melanie
From f98a2255fdb1441ac6b4a6c8df42eced771c5125 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplage...@gmail.com>
Date: Fri, 17 Jan 2025 17:20:28 -0500
Subject: [PATCH v29 2/4] Separate TBM[Shared|Private]Iterator and
TBMIterateResult
Remove the TBMIterateResult member from the TBMPrivateIterator and
TBMSharedIterator and make tbm_[shared|private_]iterate() take a
TBMIterateResult as a parameter.
This allows tidbitmap API users to manage multiple TBMIterateResults per
scan, instead of only one per iterator. This is required for
asynchronous I/O to use the TIDBitmap -- as there may be multiple I/Os
in flight at once.
Because GIN only needs a single TBMIterateResult, we inline the
matchResult in the GinScanEntry to avoid having to separately manage
memory for the TBMIterateResult.
---
src/backend/access/gin/ginget.c | 39 +++++------
src/backend/access/gin/ginscan.c | 2 +-
src/backend/access/heap/heapam_handler.c | 30 ++++-----
src/backend/executor/nodeBitmapHeapscan.c | 40 ++++++------
src/backend/nodes/tidbitmap.c | 79 +++++++++++------------
src/include/access/gin_private.h | 7 +-
src/include/nodes/tidbitmap.h | 6 +-
7 files changed, 104 insertions(+), 99 deletions(-)
diff --git a/src/backend/access/gin/ginget.c b/src/backend/access/gin/ginget.c
index 63dd1f3679f..ac1b749ed98 100644
--- a/src/backend/access/gin/ginget.c
+++ b/src/backend/access/gin/ginget.c
@@ -332,10 +332,11 @@ restartScanEntry:
entry->list = NULL;
entry->nlist = 0;
entry->matchBitmap = NULL;
- entry->matchResult = NULL;
+ entry->matchResult.blockno = InvalidBlockNumber;
entry->reduceResult = false;
entry->predictNumberResult = 0;
+
/*
* we should find entry, and begin scan of posting tree or just store
* posting list in memory
@@ -824,19 +825,19 @@ entryGetItem(GinState *ginstate, GinScanEntry entry,
{
/*
* If we've exhausted all items on this block, move to next block
- * in the bitmap.
+ * in the bitmap. tbm_private_iterate() sets matchResult->blockno
+ * to InvalidBlockNumber when the bitmap is exhausted.
*/
- while (entry->matchResult == NULL ||
- (entry->matchResult->ntuples >= 0 &&
- entry->offset >= entry->matchResult->ntuples) ||
- entry->matchResult->blockno < advancePastBlk ||
+ while ((!BlockNumberIsValid(entry->matchResult.blockno)) ||
+ (entry->matchResult.ntuples >= 0 &&
+ entry->offset >= entry->matchResult.ntuples) ||
+ entry->matchResult.blockno < advancePastBlk ||
(ItemPointerIsLossyPage(&advancePast) &&
- entry->matchResult->blockno == advancePastBlk))
+ entry->matchResult.blockno == advancePastBlk))
{
- entry->matchResult =
- tbm_private_iterate(entry->matchIterator);
+ tbm_private_iterate(entry->matchIterator, &entry->matchResult);
- if (entry->matchResult == NULL)
+ if (!BlockNumberIsValid(entry->matchResult.blockno))
{
ItemPointerSetInvalid(&entry->curItem);
tbm_end_private_iterate(entry->matchIterator);
@@ -847,7 +848,7 @@ entryGetItem(GinState *ginstate, GinScanEntry entry,
/*
* Reset counter to the beginning of entry->matchResult. Note:
- * entry->offset is still greater than matchResult->ntuples if
+ * entry->offset is still greater than matchResult.ntuples if
* matchResult is lossy. So, on next call we will get next
* result from TIDBitmap.
*/
@@ -860,10 +861,10 @@ entryGetItem(GinState *ginstate, GinScanEntry entry,
* We're now on the first page after advancePast which has any
* items on it. If it's a lossy result, return that.
*/
- if (entry->matchResult->ntuples < 0)
+ if (entry->matchResult.ntuples < 0)
{
ItemPointerSetLossyPage(&entry->curItem,
- entry->matchResult->blockno);
+ entry->matchResult.blockno);
/*
* We might as well fall out of the loop; we could not
@@ -877,27 +878,27 @@ entryGetItem(GinState *ginstate, GinScanEntry entry,
* Not a lossy page. Skip over any offsets <= advancePast, and
* return that.
*/
- if (entry->matchResult->blockno == advancePastBlk)
+ if (entry->matchResult.blockno == advancePastBlk)
{
/*
* First, do a quick check against the last offset on the
* page. If that's > advancePast, so are all the other
* offsets, so just go back to the top to get the next page.
*/
- if (entry->matchResult->offsets[entry->matchResult->ntuples - 1] <= advancePastOff)
+ if (entry->matchResult.offsets[entry->matchResult.ntuples - 1] <= advancePastOff)
{
- entry->offset = entry->matchResult->ntuples;
+ entry->offset = entry->matchResult.ntuples;
continue;
}
/* Otherwise scan to find the first item > advancePast */
- while (entry->matchResult->offsets[entry->offset] <= advancePastOff)
+ while (entry->matchResult.offsets[entry->offset] <= advancePastOff)
entry->offset++;
}
ItemPointerSet(&entry->curItem,
- entry->matchResult->blockno,
- entry->matchResult->offsets[entry->offset]);
+ entry->matchResult.blockno,
+ entry->matchResult.offsets[entry->offset]);
entry->offset++;
/* Done unless we need to reduce the result */
diff --git a/src/backend/access/gin/ginscan.c b/src/backend/access/gin/ginscan.c
index 7d1e6615260..625140fdf25 100644
--- a/src/backend/access/gin/ginscan.c
+++ b/src/backend/access/gin/ginscan.c
@@ -106,7 +106,7 @@ ginFillScanEntry(GinScanOpaque so, OffsetNumber attnum,
ItemPointerSetMin(&scanEntry->curItem);
scanEntry->matchBitmap = NULL;
scanEntry->matchIterator = NULL;
- scanEntry->matchResult = NULL;
+ scanEntry->matchResult.blockno = InvalidBlockNumber;
scanEntry->list = NULL;
scanEntry->nlist = 0;
scanEntry->offset = InvalidOffsetNumber;
diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c
index c0bec014154..39d10849c65 100644
--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -2126,7 +2126,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
Buffer buffer;
Snapshot snapshot;
int ntup;
- TBMIterateResult *tbmres;
+ TBMIterateResult tbmres;
Assert(scan->rs_flags & SO_TYPE_BITMAPSCAN);
@@ -2140,9 +2140,9 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
{
CHECK_FOR_INTERRUPTS();
- tbmres = tbm_iterate(&scan->st.rs_tbmiterator);
+ tbm_iterate(&scan->st.rs_tbmiterator, &tbmres);
- if (tbmres == NULL)
+ if (!BlockNumberIsValid(tbmres.blockno))
return false;
/*
@@ -2154,11 +2154,11 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
* reachable by the index.
*/
} while (!IsolationIsSerializable() &&
- tbmres->blockno >= hscan->rs_nblocks);
+ tbmres.blockno >= hscan->rs_nblocks);
/* Got a valid block */
- *blockno = tbmres->blockno;
- *recheck = tbmres->recheck;
+ *blockno = tbmres.blockno;
+ *recheck = tbmres.recheck;
/*
* We can skip fetching the heap page if we don't need any fields from the
@@ -2166,19 +2166,19 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
* page are visible to our transaction.
*/
if (!(scan->rs_flags & SO_NEED_TUPLES) &&
- !tbmres->recheck &&
- VM_ALL_VISIBLE(scan->rs_rd, tbmres->blockno, &bscan->rs_vmbuffer))
+ !tbmres.recheck &&
+ VM_ALL_VISIBLE(scan->rs_rd, tbmres.blockno, &bscan->rs_vmbuffer))
{
/* can't be lossy in the skip_fetch case */
- Assert(tbmres->ntuples >= 0);
+ Assert(tbmres.ntuples >= 0);
Assert(bscan->rs_empty_tuples_pending >= 0);
- bscan->rs_empty_tuples_pending += tbmres->ntuples;
+ bscan->rs_empty_tuples_pending += tbmres.ntuples;
return true;
}
- block = tbmres->blockno;
+ block = tbmres.blockno;
/*
* Acquire pin on the target heap page, trading in any pin we held before.
@@ -2207,7 +2207,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
/*
* We need two separate strategies for lossy and non-lossy cases.
*/
- if (tbmres->ntuples >= 0)
+ if (tbmres.ntuples >= 0)
{
/*
* Bitmap is non-lossy, so we just look through the offsets listed in
@@ -2216,9 +2216,9 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
*/
int curslot;
- for (curslot = 0; curslot < tbmres->ntuples; curslot++)
+ for (curslot = 0; curslot < tbmres.ntuples; curslot++)
{
- OffsetNumber offnum = tbmres->offsets[curslot];
+ OffsetNumber offnum = tbmres.offsets[curslot];
ItemPointerData tid;
HeapTupleData heapTuple;
@@ -2268,7 +2268,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
Assert(ntup <= MaxHeapTuplesPerPage);
hscan->rs_ntuples = ntup;
- if (tbmres->ntuples >= 0)
+ if (tbmres.ntuples >= 0)
(*exact_pages)++;
else
(*lossy_pages)++;
diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c
index be0d24d901b..32dea13cb86 100644
--- a/src/backend/executor/nodeBitmapHeapscan.c
+++ b/src/backend/executor/nodeBitmapHeapscan.c
@@ -317,7 +317,7 @@ BitmapAdjustPrefetchIterator(BitmapHeapScanState *node)
{
#ifdef USE_PREFETCH
ParallelBitmapHeapState *pstate = node->pstate;
- TBMIterateResult *tbmpre;
+ TBMIterateResult tbmpre;
if (pstate == NULL)
{
@@ -330,9 +330,8 @@ BitmapAdjustPrefetchIterator(BitmapHeapScanState *node)
}
else if (!tbm_exhausted(prefetch_iterator))
{
- tbmpre = tbm_iterate(prefetch_iterator);
- node->prefetch_blockno = tbmpre ? tbmpre->blockno :
- InvalidBlockNumber;
+ tbm_iterate(prefetch_iterator, &tbmpre);
+ node->prefetch_blockno = tbmpre.blockno;
}
return;
}
@@ -371,9 +370,8 @@ BitmapAdjustPrefetchIterator(BitmapHeapScanState *node)
*/
if (!tbm_exhausted(prefetch_iterator))
{
- tbmpre = tbm_iterate(prefetch_iterator);
- node->prefetch_blockno = tbmpre ? tbmpre->blockno :
- InvalidBlockNumber;
+ tbm_iterate(prefetch_iterator, &tbmpre);
+ node->prefetch_blockno = tbmpre.blockno;
}
}
}
@@ -441,17 +439,19 @@ BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan)
{
while (node->prefetch_pages < node->prefetch_target)
{
- TBMIterateResult *tbmpre = tbm_iterate(prefetch_iterator);
+ TBMIterateResult tbmpre;
bool skip_fetch;
- if (tbmpre == NULL)
+ tbm_iterate(prefetch_iterator, &tbmpre);
+
+ if (!BlockNumberIsValid(tbmpre.blockno))
{
/* No more pages to prefetch */
tbm_end_iterate(prefetch_iterator);
break;
}
node->prefetch_pages++;
- node->prefetch_blockno = tbmpre->blockno;
+ node->prefetch_blockno = tbmpre.blockno;
/*
* If we expect not to have to actually read this heap page,
@@ -460,13 +460,13 @@ BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan)
* prefetch_pages?)
*/
skip_fetch = (!(scan->rs_flags & SO_NEED_TUPLES) &&
- !tbmpre->recheck &&
+ !tbmpre.recheck &&
VM_ALL_VISIBLE(node->ss.ss_currentRelation,
- tbmpre->blockno,
+ tbmpre.blockno,
&node->pvmbuffer));
if (!skip_fetch)
- PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre->blockno);
+ PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre.blockno);
}
}
@@ -481,7 +481,7 @@ BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan)
{
while (1)
{
- TBMIterateResult *tbmpre;
+ TBMIterateResult tbmpre;
bool do_prefetch = false;
bool skip_fetch;
@@ -500,25 +500,25 @@ BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan)
if (!do_prefetch)
return;
- tbmpre = tbm_iterate(prefetch_iterator);
- if (tbmpre == NULL)
+ tbm_iterate(prefetch_iterator, &tbmpre);
+ if (!BlockNumberIsValid(tbmpre.blockno))
{
/* No more pages to prefetch */
tbm_end_iterate(prefetch_iterator);
break;
}
- node->prefetch_blockno = tbmpre->blockno;
+ node->prefetch_blockno = tbmpre.blockno;
/* As above, skip prefetch if we expect not to need page */
skip_fetch = (!(scan->rs_flags & SO_NEED_TUPLES) &&
- !tbmpre->recheck &&
+ !tbmpre.recheck &&
VM_ALL_VISIBLE(node->ss.ss_currentRelation,
- tbmpre->blockno,
+ tbmpre.blockno,
&node->pvmbuffer));
if (!skip_fetch)
- PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre->blockno);
+ PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre.blockno);
}
}
}
diff --git a/src/backend/nodes/tidbitmap.c b/src/backend/nodes/tidbitmap.c
index c573086453e..b7e4b4d9e1c 100644
--- a/src/backend/nodes/tidbitmap.c
+++ b/src/backend/nodes/tidbitmap.c
@@ -172,7 +172,6 @@ struct TBMPrivateIterator
int spageptr; /* next spages index */
int schunkptr; /* next schunks index */
int schunkbit; /* next bit to check in current schunk */
- TBMIterateResult output;
};
/*
@@ -213,7 +212,6 @@ struct TBMSharedIterator
PTEntryArray *ptbase; /* pagetable element array */
PTIterationArray *ptpages; /* sorted exact page index list */
PTIterationArray *ptchunks; /* sorted lossy page index list */
- TBMIterateResult output;
};
/* Local function prototypes */
@@ -948,20 +946,21 @@ tbm_advance_schunkbit(PagetableEntry *chunk, int *schunkbitp)
/*
* tbm_private_iterate - scan through next page of a TIDBitmap
*
- * Returns a TBMIterateResult representing one page, or NULL if there are
- * no more pages to scan. Pages are guaranteed to be delivered in numerical
- * order. If result->ntuples < 0, then the bitmap is "lossy" and failed to
- * remember the exact tuples to look at on this page --- the caller must
- * examine all tuples on the page and check if they meet the intended
- * condition. If result->recheck is true, only the indicated tuples need
- * be examined, but the condition must be rechecked anyway. (For ease of
- * testing, recheck is always set true when ntuples < 0.)
+ * Caller must pass in a TBMIterateResult to be filled.
+ *
+ * Pages are guaranteed to be delivered in numerical order. tbmres->blockno is
+ * set to InvalidBlockNumber when there are no more pages to scan. If
+ * tbmres->ntuples < 0, then the bitmap is "lossy" and failed to remember the
+ * exact tuples to look at on this page --- the caller must examine all tuples
+ * on the page and check if they meet the intended condition. If
+ * tbmres->recheck is true, only the indicated tuples need be examined, but the
+ * condition must be rechecked anyway. (For ease of testing, recheck is always
+ * set true when ntuples < 0.)
*/
-TBMIterateResult *
-tbm_private_iterate(TBMPrivateIterator *iterator)
+void
+tbm_private_iterate(TBMPrivateIterator *iterator, TBMIterateResult *tbmres)
{
TIDBitmap *tbm = iterator->tbm;
- TBMIterateResult *output = &(iterator->output);
Assert(tbm->iterating == TBM_ITERATING_PRIVATE);
@@ -999,11 +998,11 @@ tbm_private_iterate(TBMPrivateIterator *iterator)
chunk_blockno < tbm->spages[iterator->spageptr]->blockno)
{
/* Return a lossy page indicator from the chunk */
- output->blockno = chunk_blockno;
- output->ntuples = -1;
- output->recheck = true;
+ tbmres->blockno = chunk_blockno;
+ tbmres->ntuples = -1;
+ tbmres->recheck = true;
iterator->schunkbit++;
- return output;
+ return;
}
}
@@ -1019,16 +1018,16 @@ tbm_private_iterate(TBMPrivateIterator *iterator)
page = tbm->spages[iterator->spageptr];
/* scan bitmap to extract individual offset numbers */
- ntuples = tbm_extract_page_tuple(page, output);
- output->blockno = page->blockno;
- output->ntuples = ntuples;
- output->recheck = page->recheck;
+ ntuples = tbm_extract_page_tuple(page, tbmres);
+ tbmres->blockno = page->blockno;
+ tbmres->ntuples = ntuples;
+ tbmres->recheck = page->recheck;
iterator->spageptr++;
- return output;
+ return;
}
/* Nothing more in the bitmap */
- return NULL;
+ tbmres->blockno = InvalidBlockNumber;
}
/*
@@ -1038,10 +1037,9 @@ tbm_private_iterate(TBMPrivateIterator *iterator)
* across multiple processes. We need to acquire the iterator LWLock,
* before accessing the shared members.
*/
-TBMIterateResult *
-tbm_shared_iterate(TBMSharedIterator *iterator)
+void
+tbm_shared_iterate(TBMSharedIterator *iterator, TBMIterateResult *tbmres)
{
- TBMIterateResult *output = &iterator->output;
TBMSharedIteratorState *istate = iterator->state;
PagetableEntry *ptbase = NULL;
int *idxpages = NULL;
@@ -1092,13 +1090,13 @@ tbm_shared_iterate(TBMSharedIterator *iterator)
chunk_blockno < ptbase[idxpages[istate->spageptr]].blockno)
{
/* Return a lossy page indicator from the chunk */
- output->blockno = chunk_blockno;
- output->ntuples = -1;
- output->recheck = true;
+ tbmres->blockno = chunk_blockno;
+ tbmres->ntuples = -1;
+ tbmres->recheck = true;
istate->schunkbit++;
LWLockRelease(&istate->lock);
- return output;
+ return;
}
}
@@ -1108,21 +1106,21 @@ tbm_shared_iterate(TBMSharedIterator *iterator)
int ntuples;
/* scan bitmap to extract individual offset numbers */
- ntuples = tbm_extract_page_tuple(page, output);
- output->blockno = page->blockno;
- output->ntuples = ntuples;
- output->recheck = page->recheck;
+ ntuples = tbm_extract_page_tuple(page, tbmres);
+ tbmres->blockno = page->blockno;
+ tbmres->ntuples = ntuples;
+ tbmres->recheck = page->recheck;
istate->spageptr++;
LWLockRelease(&istate->lock);
- return output;
+ return;
}
LWLockRelease(&istate->lock);
/* Nothing more in the bitmap */
- return NULL;
+ tbmres->blockno = InvalidBlockNumber;
}
/*
@@ -1598,13 +1596,14 @@ tbm_end_iterate(TBMIterator *iterator)
/*
* Get the next TBMIterateResult from the shared or private bitmap iterator.
*/
-TBMIterateResult *
-tbm_iterate(TBMIterator *iterator)
+void
+tbm_iterate(TBMIterator *iterator, TBMIterateResult *tbmres)
{
Assert(iterator);
+ Assert(tbmres);
if (iterator->shared)
- return tbm_shared_iterate(iterator->i.shared_iterator);
+ return tbm_shared_iterate(iterator->i.shared_iterator, tbmres);
else
- return tbm_private_iterate(iterator->i.private_iterator);
+ return tbm_private_iterate(iterator->i.private_iterator, tbmres);
}
diff --git a/src/include/access/gin_private.h b/src/include/access/gin_private.h
index dcd1ae3fc34..478e2a8a377 100644
--- a/src/include/access/gin_private.h
+++ b/src/include/access/gin_private.h
@@ -353,7 +353,12 @@ typedef struct GinScanEntryData
/* for a partial-match or full-scan query, we accumulate all TIDs here */
TIDBitmap *matchBitmap;
TBMPrivateIterator *matchIterator;
- TBMIterateResult *matchResult;
+
+ /*
+ * If blockno is InvalidBlockNumber, all of the other fields in the
+ * matchResult are meaningless.
+ */
+ TBMIterateResult matchResult;
/* used for Posting list and one page in Posting tree */
ItemPointerData *list;
diff --git a/src/include/nodes/tidbitmap.h b/src/include/nodes/tidbitmap.h
index 661a52b4fe3..bc4adca3809 100644
--- a/src/include/nodes/tidbitmap.h
+++ b/src/include/nodes/tidbitmap.h
@@ -86,8 +86,8 @@ extern bool tbm_is_empty(const TIDBitmap *tbm);
extern TBMPrivateIterator *tbm_begin_private_iterate(TIDBitmap *tbm);
extern dsa_pointer tbm_prepare_shared_iterate(TIDBitmap *tbm);
-extern TBMIterateResult *tbm_private_iterate(TBMPrivateIterator *iterator);
-extern TBMIterateResult *tbm_shared_iterate(TBMSharedIterator *iterator);
+extern void tbm_private_iterate(TBMPrivateIterator *iterator, TBMIterateResult *tbmres);
+extern void tbm_shared_iterate(TBMSharedIterator *iterator, TBMIterateResult *tbmres);
extern void tbm_end_private_iterate(TBMPrivateIterator *iterator);
extern void tbm_end_shared_iterate(TBMSharedIterator *iterator);
extern TBMSharedIterator *tbm_attach_shared_iterate(dsa_area *dsa,
@@ -98,7 +98,7 @@ extern TBMIterator tbm_begin_iterate(TIDBitmap *tbm,
dsa_area *dsa, dsa_pointer dsp);
extern void tbm_end_iterate(TBMIterator *iterator);
-extern TBMIterateResult *tbm_iterate(TBMIterator *iterator);
+extern void tbm_iterate(TBMIterator *iterator, TBMIterateResult *tbmres);
static inline bool
tbm_exhausted(TBMIterator *iterator)
--
2.34.1
From 084ad01eb4456385ca193a3a3a0feb12c9d1f7bf Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplage...@gmail.com>
Date: Fri, 17 Jan 2025 16:42:25 -0500
Subject: [PATCH v29 1/4] Hard-code TBMIterateResult offsets array size
TIDBitmap's TBMIterateResult had a flexible sized array of tuple offsets
but the API always allocated MaxHeapTuplesPerPage OffsetNumbers.
Creating a fixed-size aray of size MaxHeapTuplesPerPage is more clear
for the tidbitmap API user. Doing so also allows us to nest inline
TBMIterateResults in other structs.
---
src/backend/nodes/tidbitmap.c | 26 +++++++-------------------
src/include/nodes/tidbitmap.h | 12 ++++++++++--
2 files changed, 17 insertions(+), 21 deletions(-)
diff --git a/src/backend/nodes/tidbitmap.c b/src/backend/nodes/tidbitmap.c
index 66b3c387d53..c573086453e 100644
--- a/src/backend/nodes/tidbitmap.c
+++ b/src/backend/nodes/tidbitmap.c
@@ -40,7 +40,6 @@
#include <limits.h>
-#include "access/htup_details.h"
#include "common/hashfn.h"
#include "common/int.h"
#include "nodes/bitmapset.h"
@@ -48,14 +47,6 @@
#include "storage/lwlock.h"
#include "utils/dsa.h"
-/*
- * The maximum number of tuples per page is not large (typically 256 with
- * 8K pages, or 1024 with 32K pages). So there's not much point in making
- * the per-page bitmaps variable size. We just legislate that the size
- * is this:
- */
-#define MAX_TUPLES_PER_PAGE MaxHeapTuplesPerPage
-
/*
* When we have to switch over to lossy storage, we use a data structure
* with one bit per page, where all pages having the same number DIV
@@ -67,7 +58,7 @@
* table, using identical data structures. (This is because the memory
* management for hashtables doesn't easily/efficiently allow space to be
* transferred easily from one hashtable to another.) Therefore it's best
- * if PAGES_PER_CHUNK is the same as MAX_TUPLES_PER_PAGE, or at least not
+ * if PAGES_PER_CHUNK is the same as MaxHeapTuplesPerPage, or at least not
* too different. But we also want PAGES_PER_CHUNK to be a power of 2 to
* avoid expensive integer remainder operations. So, define it like this:
*/
@@ -79,7 +70,7 @@
#define BITNUM(x) ((x) % BITS_PER_BITMAPWORD)
/* number of active words for an exact page: */
-#define WORDS_PER_PAGE ((MAX_TUPLES_PER_PAGE - 1) / BITS_PER_BITMAPWORD + 1)
+#define WORDS_PER_PAGE ((MaxHeapTuplesPerPage - 1) / BITS_PER_BITMAPWORD + 1)
/* number of active words for a lossy chunk: */
#define WORDS_PER_CHUNK ((PAGES_PER_CHUNK - 1) / BITS_PER_BITMAPWORD + 1)
@@ -181,7 +172,7 @@ struct TBMPrivateIterator
int spageptr; /* next spages index */
int schunkptr; /* next schunks index */
int schunkbit; /* next bit to check in current schunk */
- TBMIterateResult output; /* MUST BE LAST (because variable-size) */
+ TBMIterateResult output;
};
/*
@@ -222,7 +213,7 @@ struct TBMSharedIterator
PTEntryArray *ptbase; /* pagetable element array */
PTIterationArray *ptpages; /* sorted exact page index list */
PTIterationArray *ptchunks; /* sorted lossy page index list */
- TBMIterateResult output; /* MUST BE LAST (because variable-size) */
+ TBMIterateResult output;
};
/* Local function prototypes */
@@ -390,7 +381,7 @@ tbm_add_tuples(TIDBitmap *tbm, const ItemPointer tids, int ntids,
bitnum;
/* safety check to ensure we don't overrun bit array bounds */
- if (off < 1 || off > MAX_TUPLES_PER_PAGE)
+ if (off < 1 || off > MaxHeapTuplesPerPage)
elog(ERROR, "tuple offset out of range: %u", off);
/*
@@ -696,9 +687,7 @@ tbm_begin_private_iterate(TIDBitmap *tbm)
* Create the TBMPrivateIterator struct, with enough trailing space to
* serve the needs of the TBMIterateResult sub-struct.
*/
- iterator = (TBMPrivateIterator *) palloc(sizeof(TBMPrivateIterator) +
- MAX_TUPLES_PER_PAGE *
- sizeof(OffsetNumber));
+ iterator = (TBMPrivateIterator *) palloc(sizeof(TBMPrivateIterator));
iterator->tbm = tbm;
/*
@@ -1468,8 +1457,7 @@ tbm_attach_shared_iterate(dsa_area *dsa, dsa_pointer dp)
* Create the TBMSharedIterator struct, with enough trailing space to
* serve the needs of the TBMIterateResult sub-struct.
*/
- iterator = (TBMSharedIterator *) palloc0(sizeof(TBMSharedIterator) +
- MAX_TUPLES_PER_PAGE * sizeof(OffsetNumber));
+ iterator = (TBMSharedIterator *) palloc0(sizeof(TBMSharedIterator));
istate = (TBMSharedIteratorState *) dsa_get_address(dsa, dp);
diff --git a/src/include/nodes/tidbitmap.h b/src/include/nodes/tidbitmap.h
index a6ffeac90be..661a52b4fe3 100644
--- a/src/include/nodes/tidbitmap.h
+++ b/src/include/nodes/tidbitmap.h
@@ -22,6 +22,7 @@
#ifndef TIDBITMAP_H
#define TIDBITMAP_H
+#include "access/htup_details.h"
#include "storage/itemptr.h"
#include "utils/dsa.h"
@@ -55,9 +56,16 @@ typedef struct TBMIterateResult
{
BlockNumber blockno; /* page number containing tuples */
int ntuples; /* -1 indicates lossy result */
- bool recheck; /* should the tuples be rechecked? */
/* Note: recheck is always true if ntuples < 0 */
- OffsetNumber offsets[FLEXIBLE_ARRAY_MEMBER];
+ bool recheck; /* should the tuples be rechecked? */
+
+ /*
+ * The maximum number of tuples per page is not large (typically 256 with
+ * 8K pages, or 1024 with 32K pages). So there's not much point in making
+ * the per-page bitmaps variable size. We just legislate that the size is
+ * this:
+ */
+ OffsetNumber offsets[MaxHeapTuplesPerPage];
} TBMIterateResult;
/* function prototypes in nodes/tidbitmap.c */
--
2.34.1
From 20f02a1780ee8a135e360c455651372b92e926d2 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplage...@gmail.com>
Date: Wed, 22 Jan 2025 15:35:17 -0500
Subject: [PATCH v29 4/4] Remove table AM callback scan_bitmap_next_block
After pushing the bitmap iterator into table-AM specific code (as part
of making bitmap heap scan use the read stream API),
scan_bitmap_next_block() no longer returns the current block number.
Since scan_bitmap_next_block() isn't returning any relevant information
to bitmap table scan code, it makes more sense to get rid of it.
Now, bitmap table scan code only calls table_scan_bitmap_next_tuple(),
and the heap AM implementation of scan_bitmap_next_block() is a local
helper in heapam_handler.c.
---
src/backend/access/heap/heapam_handler.c | 354 ++++++++++++----------
src/backend/access/table/tableamapi.c | 2 -
src/backend/executor/nodeBitmapHeapscan.c | 71 ++---
src/backend/optimizer/util/plancat.c | 2 +-
src/include/access/tableam.h | 90 ++----
5 files changed, 235 insertions(+), 284 deletions(-)
diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c
index dcebac66534..f6387f60e3e 100644
--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -56,6 +56,11 @@ static bool SampleHeapTupleVisible(TableScanDesc scan, Buffer buffer,
static BlockNumber heapam_scan_get_blocks_done(HeapScanDesc hscan);
+static bool BitmapHeapScanNextBlock(TableScanDesc scan,
+ bool *recheck,
+ uint64 *lossy_pages, uint64 *exact_pages);
+
+
/* ------------------------------------------------------------------------
* Slot related callbacks for heap AM
@@ -2116,189 +2121,44 @@ heapam_estimate_rel_size(Relation rel, int32 *attr_widths,
*/
static bool
-heapam_scan_bitmap_next_block(TableScanDesc scan,
+heapam_scan_bitmap_next_tuple(TableScanDesc scan,
+ TupleTableSlot *slot,
bool *recheck,
- uint64 *lossy_pages, uint64 *exact_pages)
+ uint64 *lossy_pages,
+ uint64 *exact_pages)
{
BitmapHeapScanDesc bscan = (BitmapHeapScanDesc) scan;
HeapScanDesc hscan = (HeapScanDesc) bscan;
- BlockNumber block;
- void *per_buffer_data;
- Buffer buffer;
- Snapshot snapshot;
- int ntup;
- TBMIterateResult *tbmres;
-
- Assert(scan->rs_flags & SO_TYPE_BITMAPSCAN);
- Assert(hscan->rs_read_stream);
-
- hscan->rs_cindex = 0;
- hscan->rs_ntuples = 0;
-
- /* Release buffer containing previous block. */
- if (BufferIsValid(hscan->rs_cbuf))
- {
- ReleaseBuffer(hscan->rs_cbuf);
- hscan->rs_cbuf = InvalidBuffer;
- }
-
- hscan->rs_cbuf = read_stream_next_buffer(hscan->rs_read_stream, &per_buffer_data);
-
- if (BufferIsInvalid(hscan->rs_cbuf))
- {
- if (BufferIsValid(bscan->rs_vmbuffer))
- {
- ReleaseBuffer(bscan->rs_vmbuffer);
- bscan->rs_vmbuffer = InvalidBuffer;
- }
-
- /*
- * Bitmap is exhausted. Time to emit empty tuples if relevant. We emit
- * all empty tuples at the end instead of emitting them per block we
- * skip fetching. This is necessary because the streaming read API
- * will only return TBMIterateResults for blocks actually fetched.
- * When we skip fetching a block, we keep track of how many empty
- * tuples to emit at the end of the BitmapHeapScan. We do not recheck
- * all NULL tuples.
- */
- *recheck = false;
- return bscan->rs_empty_tuples_pending > 0;
- }
-
- Assert(per_buffer_data);
-
- tbmres = per_buffer_data;
-
- Assert(BufferGetBlockNumber(hscan->rs_cbuf) == tbmres->blockno);
-
- *recheck = tbmres->recheck;
-
- hscan->rs_cblock = tbmres->blockno;
- hscan->rs_ntuples = tbmres->ntuples;
-
- block = tbmres->blockno;
- buffer = hscan->rs_cbuf;
- snapshot = scan->rs_snapshot;
-
- ntup = 0;
-
- /*
- * Prune and repair fragmentation for the whole page, if possible.
- */
- heap_page_prune_opt(scan->rs_rd, buffer);
-
- /*
- * We must hold share lock on the buffer content while examining tuple
- * visibility. Afterwards, however, the tuples we have found to be
- * visible are guaranteed good as long as we hold the buffer pin.
- */
- LockBuffer(buffer, BUFFER_LOCK_SHARE);
+ OffsetNumber targoffset;
+ Page page;
+ ItemId lp;
/*
- * We need two separate strategies for lossy and non-lossy cases.
+ * Out of range? If so, nothing more to look at on this page
*/
- if (tbmres->ntuples >= 0)
+ while (hscan->rs_cindex >= hscan->rs_ntuples)
{
/*
- * Bitmap is non-lossy, so we just look through the offsets listed in
- * tbmres; but we have to follow any HOT chain starting at each such
- * offset.
- */
- int curslot;
-
- for (curslot = 0; curslot < tbmres->ntuples; curslot++)
- {
- OffsetNumber offnum = tbmres->offsets[curslot];
- ItemPointerData tid;
- HeapTupleData heapTuple;
-
- ItemPointerSet(&tid, block, offnum);
- if (heap_hot_search_buffer(&tid, scan->rs_rd, buffer, snapshot,
- &heapTuple, NULL, true))
- hscan->rs_vistuples[ntup++] = ItemPointerGetOffsetNumber(&tid);
- }
- }
- else
- {
- /*
- * Bitmap is lossy, so we must examine each line pointer on the page.
- * But we can ignore HOT chains, since we'll check each tuple anyway.
+ * Emit empty tuples before advancing to the next block
*/
- Page page = BufferGetPage(buffer);
- OffsetNumber maxoff = PageGetMaxOffsetNumber(page);
- OffsetNumber offnum;
-
- for (offnum = FirstOffsetNumber; offnum <= maxoff; offnum = OffsetNumberNext(offnum))
+ if (bscan->rs_empty_tuples_pending > 0)
{
- ItemId lp;
- HeapTupleData loctup;
- bool valid;
-
- lp = PageGetItemId(page, offnum);
- if (!ItemIdIsNormal(lp))
- continue;
- loctup.t_data = (HeapTupleHeader) PageGetItem(page, lp);
- loctup.t_len = ItemIdGetLength(lp);
- loctup.t_tableOid = scan->rs_rd->rd_id;
- ItemPointerSet(&loctup.t_self, block, offnum);
- valid = HeapTupleSatisfiesVisibility(&loctup, snapshot, buffer);
- if (valid)
- {
- hscan->rs_vistuples[ntup++] = offnum;
- PredicateLockTID(scan->rs_rd, &loctup.t_self, snapshot,
- HeapTupleHeaderGetXmin(loctup.t_data));
- }
- HeapCheckForSerializableConflictOut(valid, scan->rs_rd, &loctup,
- buffer, snapshot);
+ /*
+ * If we don't have to fetch the tuple, just return nulls.
+ */
+ ExecStoreAllNullTuple(slot);
+ bscan->rs_empty_tuples_pending--;
+ return true;
}
- }
-
- LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
-
- Assert(ntup <= MaxHeapTuplesPerPage);
- hscan->rs_ntuples = ntup;
-
- if (tbmres->ntuples >= 0)
- (*exact_pages)++;
- else
- (*lossy_pages)++;
-
- /*
- * Return true to indicate that a valid block was found and the bitmap is
- * not exhausted. If there are no visible tuples on this page,
- * hscan->rs_ntuples will be 0 and heapam_scan_bitmap_next_tuple() will
- * return false returning control to this function to advance to the next
- * block in the bitmap.
- */
- return true;
-}
-
-static bool
-heapam_scan_bitmap_next_tuple(TableScanDesc scan,
- TupleTableSlot *slot)
-{
- BitmapHeapScanDesc bscan = (BitmapHeapScanDesc) scan;
- HeapScanDesc hscan = (HeapScanDesc) bscan;
- OffsetNumber targoffset;
- Page page;
- ItemId lp;
- if (bscan->rs_empty_tuples_pending > 0)
- {
/*
- * If we don't have to fetch the tuple, just return nulls.
+ * Returns false if the bitmap is exhausted and there are no further
+ * blocks we need to scan.
*/
- ExecStoreAllNullTuple(slot);
- bscan->rs_empty_tuples_pending--;
- return true;
+ if (!BitmapHeapScanNextBlock(scan, recheck, lossy_pages, exact_pages))
+ return false;
}
- /*
- * Out of range? If so, nothing more to look at on this page
- */
- if (hscan->rs_cindex >= hscan->rs_ntuples)
- return false;
-
targoffset = hscan->rs_vistuples[hscan->rs_cindex];
page = BufferGetPage(hscan->rs_cbuf);
lp = PageGetItemId(page, targoffset);
@@ -2605,6 +2465,167 @@ SampleHeapTupleVisible(TableScanDesc scan, Buffer buffer,
}
}
+/*
+ * Helper function get the next block of a bitmap heap scan. Returns true when
+ * it got the next block and saved it in the scan descriptor and false when
+ * the bitmap and or relation are exhausted.
+ */
+static bool
+BitmapHeapScanNextBlock(TableScanDesc scan,
+ bool *recheck,
+ uint64 *lossy_pages, uint64 *exact_pages)
+{
+ BitmapHeapScanDesc bscan = (BitmapHeapScanDesc) scan;
+ HeapScanDesc hscan = (HeapScanDesc) bscan;
+ BlockNumber block;
+ void *per_buffer_data;
+ Buffer buffer;
+ Snapshot snapshot;
+ int ntup;
+ TBMIterateResult *tbmres;
+
+ Assert(scan->rs_flags & SO_TYPE_BITMAPSCAN);
+ Assert(hscan->rs_read_stream);
+
+ hscan->rs_cindex = 0;
+ hscan->rs_ntuples = 0;
+
+ /* Release buffer containing previous block. */
+ if (BufferIsValid(hscan->rs_cbuf))
+ {
+ ReleaseBuffer(hscan->rs_cbuf);
+ hscan->rs_cbuf = InvalidBuffer;
+ }
+
+ hscan->rs_cbuf = read_stream_next_buffer(hscan->rs_read_stream, &per_buffer_data);
+
+ if (BufferIsInvalid(hscan->rs_cbuf))
+ {
+ if (BufferIsValid(bscan->rs_vmbuffer))
+ {
+ ReleaseBuffer(bscan->rs_vmbuffer);
+ bscan->rs_vmbuffer = InvalidBuffer;
+ }
+
+ /*
+ * Bitmap is exhausted. Time to emit empty tuples if relevant. We emit
+ * all empty tuples at the end instead of emitting them per block we
+ * skip fetching. This is necessary because the streaming read API
+ * will only return TBMIterateResults for blocks actually fetched.
+ * When we skip fetching a block, we keep track of how many empty
+ * tuples to emit at the end of the BitmapHeapScan. We do not recheck
+ * all NULL tuples.
+ */
+ *recheck = false;
+ return bscan->rs_empty_tuples_pending > 0;
+ }
+
+ Assert(per_buffer_data);
+
+ tbmres = per_buffer_data;
+
+ Assert(BufferGetBlockNumber(hscan->rs_cbuf) == tbmres->blockno);
+
+ *recheck = tbmres->recheck;
+
+ hscan->rs_cblock = tbmres->blockno;
+ hscan->rs_ntuples = tbmres->ntuples;
+
+ block = tbmres->blockno;
+ buffer = hscan->rs_cbuf;
+ snapshot = scan->rs_snapshot;
+
+ ntup = 0;
+
+ /*
+ * Prune and repair fragmentation for the whole page, if possible.
+ */
+ heap_page_prune_opt(scan->rs_rd, buffer);
+
+ /*
+ * We must hold share lock on the buffer content while examining tuple
+ * visibility. Afterwards, however, the tuples we have found to be
+ * visible are guaranteed good as long as we hold the buffer pin.
+ */
+ LockBuffer(buffer, BUFFER_LOCK_SHARE);
+
+ /*
+ * We need two separate strategies for lossy and non-lossy cases.
+ */
+ if (tbmres->ntuples >= 0)
+ {
+ /*
+ * Bitmap is non-lossy, so we just look through the offsets listed in
+ * tbmres; but we have to follow any HOT chain starting at each such
+ * offset.
+ */
+ int curslot;
+
+ for (curslot = 0; curslot < tbmres->ntuples; curslot++)
+ {
+ OffsetNumber offnum = tbmres->offsets[curslot];
+ ItemPointerData tid;
+ HeapTupleData heapTuple;
+
+ ItemPointerSet(&tid, block, offnum);
+ if (heap_hot_search_buffer(&tid, scan->rs_rd, buffer, snapshot,
+ &heapTuple, NULL, true))
+ hscan->rs_vistuples[ntup++] = ItemPointerGetOffsetNumber(&tid);
+ }
+ }
+ else
+ {
+ /*
+ * Bitmap is lossy, so we must examine each line pointer on the page.
+ * But we can ignore HOT chains, since we'll check each tuple anyway.
+ */
+ Page page = BufferGetPage(buffer);
+ OffsetNumber maxoff = PageGetMaxOffsetNumber(page);
+ OffsetNumber offnum;
+
+ for (offnum = FirstOffsetNumber; offnum <= maxoff; offnum = OffsetNumberNext(offnum))
+ {
+ ItemId lp;
+ HeapTupleData loctup;
+ bool valid;
+
+ lp = PageGetItemId(page, offnum);
+ if (!ItemIdIsNormal(lp))
+ continue;
+ loctup.t_data = (HeapTupleHeader) PageGetItem(page, lp);
+ loctup.t_len = ItemIdGetLength(lp);
+ loctup.t_tableOid = scan->rs_rd->rd_id;
+ ItemPointerSet(&loctup.t_self, block, offnum);
+ valid = HeapTupleSatisfiesVisibility(&loctup, snapshot, buffer);
+ if (valid)
+ {
+ hscan->rs_vistuples[ntup++] = offnum;
+ PredicateLockTID(scan->rs_rd, &loctup.t_self, snapshot,
+ HeapTupleHeaderGetXmin(loctup.t_data));
+ }
+ HeapCheckForSerializableConflictOut(valid, scan->rs_rd, &loctup,
+ buffer, snapshot);
+ }
+ }
+
+ LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+
+ Assert(ntup <= MaxHeapTuplesPerPage);
+ hscan->rs_ntuples = ntup;
+
+ if (tbmres->ntuples >= 0)
+ (*exact_pages)++;
+ else
+ (*lossy_pages)++;
+
+ /*
+ * Return true to indicate that a valid block was found and the bitmap is
+ * not exhausted. If there are no visible tuples on this page,
+ * hscan->rs_ntuples will be 0 and heapam_scan_bitmap_next_tuple() will
+ * invoke this function again.
+ */
+ return true;
+}
/* ------------------------------------------------------------------------
* Definition of the heap table access method.
@@ -2664,7 +2685,6 @@ static const TableAmRoutine heapam_methods = {
.relation_estimate_size = heapam_estimate_rel_size,
- .scan_bitmap_next_block = heapam_scan_bitmap_next_block,
.scan_bitmap_next_tuple = heapam_scan_bitmap_next_tuple,
.scan_sample_next_block = heapam_scan_sample_next_block,
.scan_sample_next_tuple = heapam_scan_sample_next_tuple
diff --git a/src/backend/access/table/tableamapi.c b/src/backend/access/table/tableamapi.c
index 760a36fd2a1..56378007a81 100644
--- a/src/backend/access/table/tableamapi.c
+++ b/src/backend/access/table/tableamapi.c
@@ -92,8 +92,6 @@ GetTableAmRoutine(Oid amhandler)
Assert(routine->relation_estimate_size != NULL);
/* optional, but one callback implies presence of the other */
- Assert((routine->scan_bitmap_next_block == NULL) ==
- (routine->scan_bitmap_next_tuple == NULL));
Assert(routine->scan_sample_next_block != NULL);
Assert(routine->scan_sample_next_tuple != NULL);
diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c
index 46721e091ab..68499e3aa45 100644
--- a/src/backend/executor/nodeBitmapHeapscan.c
+++ b/src/backend/executor/nodeBitmapHeapscan.c
@@ -139,67 +139,44 @@ BitmapTableScanSetup(BitmapHeapScanState *node)
static TupleTableSlot *
BitmapHeapNext(BitmapHeapScanState *node)
{
- ExprContext *econtext;
- TableScanDesc scan;
- TupleTableSlot *slot;
-
- /*
- * extract necessary information from index scan node
- */
- econtext = node->ss.ps.ps_ExprContext;
- slot = node->ss.ss_ScanTupleSlot;
- scan = node->ss.ss_currentScanDesc;
+ ExprContext *econtext = node->ss.ps.ps_ExprContext;
+ TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
/*
* If we haven't yet performed the underlying index scan, do it, and begin
* the iteration over the bitmap.
*/
if (!node->initialized)
- {
BitmapTableScanSetup(node);
- scan = node->ss.ss_currentScanDesc;
- goto new_page;
- }
- for (;;)
+ while (table_scan_bitmap_next_tuple(node->ss.ss_currentScanDesc,
+ slot, &node->recheck,
+ &node->stats.lossy_pages,
+ &node->stats.exact_pages))
{
- while (table_scan_bitmap_next_tuple(scan, slot))
+ /*
+ * Continuing in previously obtained page.
+ */
+ CHECK_FOR_INTERRUPTS();
+
+ /*
+ * If we are using lossy info, we have to recheck the qual conditions
+ * at every tuple.
+ */
+ if (node->recheck)
{
- /*
- * Continuing in previously obtained page.
- */
- CHECK_FOR_INTERRUPTS();
-
- /*
- * If we are using lossy info, we have to recheck the qual
- * conditions at every tuple.
- */
- if (node->recheck)
+ econtext->ecxt_scantuple = slot;
+ if (!ExecQualAndReset(node->bitmapqualorig, econtext))
{
- econtext->ecxt_scantuple = slot;
- if (!ExecQualAndReset(node->bitmapqualorig, econtext))
- {
- /* Fails recheck, so drop it and loop back for another */
- InstrCountFiltered2(node, 1);
- ExecClearTuple(slot);
- continue;
- }
+ /* Fails recheck, so drop it and loop back for another */
+ InstrCountFiltered2(node, 1);
+ ExecClearTuple(slot);
+ continue;
}
-
- /* OK to return this tuple */
- return slot;
}
-new_page:
- /*
- * Returns false if the bitmap is exhausted and there are no further
- * blocks we need to scan.
- */
- if (!table_scan_bitmap_next_block(scan,
- &node->recheck,
- &node->stats.lossy_pages,
- &node->stats.exact_pages))
- break;
+ /* OK to return this tuple */
+ return slot;
}
/*
diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index 71abb01f655..0489ad36644 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -325,7 +325,7 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
info->amcanparallel = amroutine->amcanparallel;
info->amhasgettuple = (amroutine->amgettuple != NULL);
info->amhasgetbitmap = amroutine->amgetbitmap != NULL &&
- relation->rd_tableam->scan_bitmap_next_block != NULL;
+ relation->rd_tableam->scan_bitmap_next_tuple != NULL;
info->amcanmarkpos = (amroutine->ammarkpos != NULL &&
amroutine->amrestrpos != NULL);
info->amcostestimate = amroutine->amcostestimate;
diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h
index b5675b47dcc..4206a6d0ab1 100644
--- a/src/include/access/tableam.h
+++ b/src/include/access/tableam.h
@@ -780,43 +780,23 @@ typedef struct TableAmRoutine
*/
/*
- * Prepare to fetch / check / return tuples from `blockno` as part of a
- * bitmap table scan. `scan` was started via table_beginscan_bm(). Return
- * false if the bitmap is exhausted and true otherwise.
- *
- * This will typically read and pin the target block, and do the necessary
- * work to allow scan_bitmap_next_tuple() to return tuples (e.g. it might
- * make sense to perform tuple visibility checks at this time).
- *
- * `lossy_pages` and `exact_pages` are EXPLAIN counters that can be
- * incremented by the table AM to indicate whether or not the block's
- * representation in the bitmap is lossy.
+ * Fetch the next tuple of a bitmap table scan into `slot` and return true
+ * if a visible tuple was found, false otherwise.
*
- * `recheck` is set by the table AM to indicate whether or not the tuples
- * from this block should be rechecked. Tuples from lossy pages will
- * always need to be rechecked, but some non-lossy pages' tuples may also
- * require recheck.
+ * `lossy_pages` is incremented if the bitmap is lossy for the selected
+ * page; otherwise, `exact_pages` is incremented. This is tracked for
+ * display in EXPLAIN ANALYZE output.
*
* Prefetching additional data from the bitmap is left to the table AM.
*
- * Optional callback, but either both scan_bitmap_next_block and
- * scan_bitmap_next_tuple need to exist, or neither.
+ * This is an optional callback.
*/
- bool (*scan_bitmap_next_block) (TableScanDesc scan,
+ bool (*scan_bitmap_next_tuple) (TableScanDesc scan,
+ TupleTableSlot *slot,
bool *recheck,
uint64 *lossy_pages,
uint64 *exact_pages);
- /*
- * Fetch the next tuple of a bitmap table scan into `slot` and return true
- * if a visible tuple was found, false otherwise.
- *
- * Optional callback, but either both scan_bitmap_next_block and
- * scan_bitmap_next_tuple need to exist, or neither.
- */
- bool (*scan_bitmap_next_tuple) (TableScanDesc scan,
- TupleTableSlot *slot);
-
/*
* Prepare to fetch tuples from the next block in a sample scan. Return
* false if the sample scan is finished, true otherwise. `scan` was
@@ -1943,51 +1923,24 @@ table_relation_estimate_size(Relation rel, int32 *attr_widths,
*/
/*
- * Prepare to fetch / check / return tuples as part of a bitmap table scan.
- * `scan` needs to have been started via table_beginscan_bm(). Returns false
- * if there are no more blocks in the bitmap, true otherwise.
- *
- * `lossy_pages` and `exact_pages` are EXPLAIN counters that can be
- * incremented by the table AM to indicate whether or not the block's
- * representation in the bitmap is lossy.
+ * Fetch / check / return tuples as part of a bitmap table scan. `scan` needs
+ * to have been started via table_beginscan_bm(). Fetch the next tuple of a
+ * bitmap table scan into `slot` and return true if a visible tuple was found,
+ * false otherwise.
*
- * `recheck` is set by the table AM to indicate whether or not the tuples
- * from this block should be rechecked.
+ * `recheck` is set by the table AM to indicate whether or not the tuple in
+ * `slot` should be rechecked. Tuples from lossy pages will always need to be
+ * rechecked, but some non-lossy pages' tuples may also require recheck.
*
- * Note, this is an optionally implemented function, therefore should only be
- * used after verifying the presence (at plan time or such).
+ * `lossy_pages` is incremented if the block's representation in the bitmap is
+ * lossy; otherwise, `exact_pages` is incremented.
*/
static inline bool
-table_scan_bitmap_next_block(TableScanDesc scan,
+table_scan_bitmap_next_tuple(TableScanDesc scan,
+ TupleTableSlot *slot,
bool *recheck,
uint64 *lossy_pages,
uint64 *exact_pages)
-{
- /*
- * We don't expect direct calls to table_scan_bitmap_next_block with valid
- * CheckXidAlive for catalog or regular tables. See detailed comments in
- * xact.c where these variables are declared.
- */
- if (unlikely(TransactionIdIsValid(CheckXidAlive) && !bsysscan))
- elog(ERROR, "unexpected table_scan_bitmap_next_block call during logical decoding");
-
- return scan->rs_rd->rd_tableam->scan_bitmap_next_block(scan,
- recheck,
- lossy_pages,
- exact_pages);
-}
-
-/*
- * Fetch the next tuple of a bitmap table scan into `slot` and return true if
- * a visible tuple was found, false otherwise.
- * table_scan_bitmap_next_block() needs to previously have selected a
- * block (i.e. returned true), and no previous
- * table_scan_bitmap_next_tuple() for the same block may have
- * returned false.
- */
-static inline bool
-table_scan_bitmap_next_tuple(TableScanDesc scan,
- TupleTableSlot *slot)
{
/*
* We don't expect direct calls to table_scan_bitmap_next_tuple with valid
@@ -1998,7 +1951,10 @@ table_scan_bitmap_next_tuple(TableScanDesc scan,
elog(ERROR, "unexpected table_scan_bitmap_next_tuple call during logical decoding");
return scan->rs_rd->rd_tableam->scan_bitmap_next_tuple(scan,
- slot);
+ slot,
+ recheck,
+ lossy_pages,
+ exact_pages);
}
/*
--
2.34.1
From 71efb544d59ce8a11b71b447d96b6d8a9b4bbcb5 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplage...@gmail.com>
Date: Wed, 22 Jan 2025 15:00:12 -0500
Subject: [PATCH v29 3/4] BitmapHeapScan uses read stream API
Make Bitmap Heap Scan use the read stream API instead of invoking
ReadBuffer() for each block indicated by the bitmap.
The read stream API handles prefetching, so remove all of the explicit
prefetching from bitmap heap scan code.
Now, heap table AM implements a read stream callback which uses the
bitmap iterator to return the next required block to the read stream
code.
---
src/backend/access/heap/heapam.c | 70 +++++
src/backend/access/heap/heapam_handler.c | 86 +++---
src/backend/executor/nodeBitmapHeapscan.c | 355 +---------------------
src/include/access/relscan.h | 8 +-
src/include/access/tableam.h | 33 +-
src/include/nodes/execnodes.h | 23 +-
6 files changed, 130 insertions(+), 445 deletions(-)
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index ea0a12b39af..45f419f849f 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -279,6 +279,62 @@ heap_scan_stream_read_next_serial(ReadStream *stream,
return scan->rs_prefetch_block;
}
+/*
+ * Read stream API callback for bitmap heap scans.
+ * Returns the next block the caller wants from the read stream or
+ * InvalidBlockNumber when done.
+ */
+static BlockNumber
+bitmapheap_stream_read_next(ReadStream *pgsr, void *private_data,
+ void *per_buffer_data)
+{
+ TBMIterateResult *tbmres = per_buffer_data;
+ BitmapHeapScanDesc bscan = (BitmapHeapScanDesc) private_data;
+ HeapScanDesc hscan = (HeapScanDesc) bscan;
+ TableScanDesc sscan = &hscan->rs_base;
+
+ for (;;)
+ {
+ CHECK_FOR_INTERRUPTS();
+
+ tbm_iterate(&sscan->st.bitmap.rs_iterator, tbmres);
+
+ /* no more entries in the bitmap */
+ if (!BlockNumberIsValid(tbmres->blockno))
+ return InvalidBlockNumber;
+
+ /*
+ * Ignore any claimed entries past what we think is the end of the
+ * relation. It may have been extended after the start of our scan (we
+ * only hold an AccessShareLock, and it could be inserts from this
+ * backend). We don't take this optimization in SERIALIZABLE
+ * isolation though, as we need to examine all invisible tuples
+ * reachable by the index.
+ */
+ if (!IsolationIsSerializable() &&
+ tbmres->blockno >= hscan->rs_nblocks)
+ continue;
+
+ /*
+ * We can skip fetching the heap page if we don't need any fields from
+ * the heap, the bitmap entries don't need rechecking, and all tuples
+ * on the page are visible to our transaction.
+ */
+ if (!(sscan->rs_flags & SO_NEED_TUPLES) &&
+ !tbmres->recheck &&
+ VM_ALL_VISIBLE(sscan->rs_rd, tbmres->blockno, &bscan->rs_vmbuffer))
+ {
+ bscan->rs_empty_tuples_pending += tbmres->ntuples;
+ continue;
+ }
+
+ return tbmres->blockno;
+ }
+
+ /* not reachable */
+ Assert(false);
+}
+
/* ----------------
* initscan - scan code common to heap_beginscan and heap_rescan
* ----------------
@@ -1067,6 +1123,7 @@ heap_beginscan(Relation relation, Snapshot snapshot,
scan->rs_base.rs_flags = flags;
scan->rs_base.rs_parallel = parallel_scan;
scan->rs_strategy = NULL; /* set in initscan */
+ scan->rs_cbuf = InvalidBuffer;
/*
* Disable page-at-a-time mode if it's not a MVCC-safe snapshot.
@@ -1146,6 +1203,16 @@ heap_beginscan(Relation relation, Snapshot snapshot,
scan,
0);
}
+ else if (scan->rs_base.rs_flags & SO_TYPE_BITMAPSCAN)
+ {
+ scan->rs_read_stream = read_stream_begin_relation(READ_STREAM_DEFAULT,
+ scan->rs_strategy,
+ scan->rs_base.rs_rd,
+ MAIN_FORKNUM,
+ bitmapheap_stream_read_next,
+ scan,
+ sizeof(TBMIterateResult));
+ }
return (TableScanDesc) scan;
@@ -1180,7 +1247,10 @@ heap_rescan(TableScanDesc sscan, ScanKey key, bool set_params,
* unpin scan buffers
*/
if (BufferIsValid(scan->rs_cbuf))
+ {
ReleaseBuffer(scan->rs_cbuf);
+ scan->rs_cbuf = InvalidBuffer;
+ }
if (scan->rs_base.rs_flags & SO_TYPE_BITMAPSCAN)
{
diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c
index 39d10849c65..dcebac66534 100644
--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -2117,76 +2117,66 @@ heapam_estimate_rel_size(Relation rel, int32 *attr_widths,
static bool
heapam_scan_bitmap_next_block(TableScanDesc scan,
- BlockNumber *blockno, bool *recheck,
+ bool *recheck,
uint64 *lossy_pages, uint64 *exact_pages)
{
BitmapHeapScanDesc bscan = (BitmapHeapScanDesc) scan;
HeapScanDesc hscan = (HeapScanDesc) bscan;
BlockNumber block;
+ void *per_buffer_data;
Buffer buffer;
Snapshot snapshot;
int ntup;
- TBMIterateResult tbmres;
+ TBMIterateResult *tbmres;
Assert(scan->rs_flags & SO_TYPE_BITMAPSCAN);
+ Assert(hscan->rs_read_stream);
hscan->rs_cindex = 0;
hscan->rs_ntuples = 0;
- *blockno = InvalidBlockNumber;
- *recheck = true;
-
- do
+ /* Release buffer containing previous block. */
+ if (BufferIsValid(hscan->rs_cbuf))
{
- CHECK_FOR_INTERRUPTS();
+ ReleaseBuffer(hscan->rs_cbuf);
+ hscan->rs_cbuf = InvalidBuffer;
+ }
- tbm_iterate(&scan->st.rs_tbmiterator, &tbmres);
+ hscan->rs_cbuf = read_stream_next_buffer(hscan->rs_read_stream, &per_buffer_data);
- if (!BlockNumberIsValid(tbmres.blockno))
- return false;
+ if (BufferIsInvalid(hscan->rs_cbuf))
+ {
+ if (BufferIsValid(bscan->rs_vmbuffer))
+ {
+ ReleaseBuffer(bscan->rs_vmbuffer);
+ bscan->rs_vmbuffer = InvalidBuffer;
+ }
/*
- * Ignore any claimed entries past what we think is the end of the
- * relation. It may have been extended after the start of our scan (we
- * only hold an AccessShareLock, and it could be inserts from this
- * backend). We don't take this optimization in SERIALIZABLE
- * isolation though, as we need to examine all invisible tuples
- * reachable by the index.
+ * Bitmap is exhausted. Time to emit empty tuples if relevant. We emit
+ * all empty tuples at the end instead of emitting them per block we
+ * skip fetching. This is necessary because the streaming read API
+ * will only return TBMIterateResults for blocks actually fetched.
+ * When we skip fetching a block, we keep track of how many empty
+ * tuples to emit at the end of the BitmapHeapScan. We do not recheck
+ * all NULL tuples.
*/
- } while (!IsolationIsSerializable() &&
- tbmres.blockno >= hscan->rs_nblocks);
+ *recheck = false;
+ return bscan->rs_empty_tuples_pending > 0;
+ }
- /* Got a valid block */
- *blockno = tbmres.blockno;
- *recheck = tbmres.recheck;
+ Assert(per_buffer_data);
- /*
- * We can skip fetching the heap page if we don't need any fields from the
- * heap, the bitmap entries don't need rechecking, and all tuples on the
- * page are visible to our transaction.
- */
- if (!(scan->rs_flags & SO_NEED_TUPLES) &&
- !tbmres.recheck &&
- VM_ALL_VISIBLE(scan->rs_rd, tbmres.blockno, &bscan->rs_vmbuffer))
- {
- /* can't be lossy in the skip_fetch case */
- Assert(tbmres.ntuples >= 0);
- Assert(bscan->rs_empty_tuples_pending >= 0);
+ tbmres = per_buffer_data;
- bscan->rs_empty_tuples_pending += tbmres.ntuples;
+ Assert(BufferGetBlockNumber(hscan->rs_cbuf) == tbmres->blockno);
- return true;
- }
+ *recheck = tbmres->recheck;
- block = tbmres.blockno;
+ hscan->rs_cblock = tbmres->blockno;
+ hscan->rs_ntuples = tbmres->ntuples;
- /*
- * Acquire pin on the target heap page, trading in any pin we held before.
- */
- hscan->rs_cbuf = ReleaseAndReadBuffer(hscan->rs_cbuf,
- scan->rs_rd,
- block);
- hscan->rs_cblock = block;
+ block = tbmres->blockno;
buffer = hscan->rs_cbuf;
snapshot = scan->rs_snapshot;
@@ -2207,7 +2197,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
/*
* We need two separate strategies for lossy and non-lossy cases.
*/
- if (tbmres.ntuples >= 0)
+ if (tbmres->ntuples >= 0)
{
/*
* Bitmap is non-lossy, so we just look through the offsets listed in
@@ -2216,9 +2206,9 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
*/
int curslot;
- for (curslot = 0; curslot < tbmres.ntuples; curslot++)
+ for (curslot = 0; curslot < tbmres->ntuples; curslot++)
{
- OffsetNumber offnum = tbmres.offsets[curslot];
+ OffsetNumber offnum = tbmres->offsets[curslot];
ItemPointerData tid;
HeapTupleData heapTuple;
@@ -2268,7 +2258,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
Assert(ntup <= MaxHeapTuplesPerPage);
hscan->rs_ntuples = ntup;
- if (tbmres.ntuples >= 0)
+ if (tbmres->ntuples >= 0)
(*exact_pages)++;
else
(*lossy_pages)++;
diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c
index 32dea13cb86..46721e091ab 100644
--- a/src/backend/executor/nodeBitmapHeapscan.c
+++ b/src/backend/executor/nodeBitmapHeapscan.c
@@ -51,10 +51,6 @@
static void BitmapTableScanSetup(BitmapHeapScanState *node);
static TupleTableSlot *BitmapHeapNext(BitmapHeapScanState *node);
static inline void BitmapDoneInitializingSharedState(ParallelBitmapHeapState *pstate);
-static inline void BitmapAdjustPrefetchIterator(BitmapHeapScanState *node);
-static inline void BitmapAdjustPrefetchTarget(BitmapHeapScanState *node);
-static inline void BitmapPrefetch(BitmapHeapScanState *node,
- TableScanDesc scan);
static bool BitmapShouldInitializeSharedState(ParallelBitmapHeapState *pstate);
@@ -62,14 +58,6 @@ static bool BitmapShouldInitializeSharedState(ParallelBitmapHeapState *pstate);
* Do the underlying index scan, build the bitmap, set up the parallel state
* needed for parallel workers to iterate through the bitmap, and set up the
* underlying table scan descriptor.
- *
- * For prefetching, we use *two* iterators, one for the pages we are actually
- * scanning and another that runs ahead of the first for prefetching.
- * node->prefetch_pages tracks exactly how many pages ahead the prefetch
- * iterator is. Also, node->prefetch_target tracks the desired prefetch
- * distance, which starts small and increases up to the
- * node->prefetch_maximum. This is to avoid doing a lot of prefetching in a
- * scan that stops after a few tuples because of a LIMIT.
*/
static void
BitmapTableScanSetup(BitmapHeapScanState *node)
@@ -102,14 +90,6 @@ BitmapTableScanSetup(BitmapHeapScanState *node)
*/
pstate->tbmiterator = tbm_prepare_shared_iterate(node->tbm);
-#ifdef USE_PREFETCH
- if (node->prefetch_maximum > 0)
- {
- pstate->prefetch_iterator =
- tbm_prepare_shared_iterate(node->tbm);
- }
-#endif /* USE_PREFETCH */
-
/* We have initialized the shared state so wake up others. */
BitmapDoneInitializingSharedState(pstate);
}
@@ -119,15 +99,6 @@ BitmapTableScanSetup(BitmapHeapScanState *node)
pstate->tbmiterator :
InvalidDsaPointer);
-#ifdef USE_PREFETCH
- if (node->prefetch_maximum > 0)
- node->prefetch_iterator =
- tbm_begin_iterate(node->tbm, dsa,
- pstate ?
- pstate->prefetch_iterator :
- InvalidDsaPointer);
-#endif /* USE_PREFETCH */
-
/*
* If this is the first scan of the underlying table, create the table
* scan descriptor and begin the scan.
@@ -149,16 +120,16 @@ BitmapTableScanSetup(BitmapHeapScanState *node)
node->ss.ss_currentScanDesc =
table_beginscan_bm(node->ss.ss_currentRelation,
node->ss.ps.state->es_snapshot,
+ pstate,
0,
NULL,
need_tuples);
}
- node->ss.ss_currentScanDesc->st.rs_tbmiterator = tbmiterator;
+ node->ss.ss_currentScanDesc->st.bitmap.rs_iterator = tbmiterator;
node->initialized = true;
}
-
/* ----------------------------------------------------------------
* BitmapHeapNext
*
@@ -172,10 +143,6 @@ BitmapHeapNext(BitmapHeapScanState *node)
TableScanDesc scan;
TupleTableSlot *slot;
-#ifdef USE_PREFETCH
- ParallelBitmapHeapState *pstate = node->pstate;
-#endif
-
/*
* extract necessary information from index scan node
*/
@@ -201,40 +168,8 @@ BitmapHeapNext(BitmapHeapScanState *node)
/*
* Continuing in previously obtained page.
*/
-
CHECK_FOR_INTERRUPTS();
-#ifdef USE_PREFETCH
-
- /*
- * Try to prefetch at least a few pages even before we get to the
- * second page if we don't stop reading after the first tuple.
- */
- if (!pstate)
- {
- if (node->prefetch_target < node->prefetch_maximum)
- node->prefetch_target++;
- }
- else if (pstate->prefetch_target < node->prefetch_maximum)
- {
- /* take spinlock while updating shared state */
- SpinLockAcquire(&pstate->mutex);
- if (pstate->prefetch_target < node->prefetch_maximum)
- pstate->prefetch_target++;
- SpinLockRelease(&pstate->mutex);
- }
-#endif /* USE_PREFETCH */
-
- /*
- * We issue prefetch requests *after* fetching the current page to
- * try to avoid having prefetching interfere with the main I/O.
- * Also, this should happen only when we have determined there is
- * still something to do on the current page, else we may
- * uselessly prefetch the same page we are just about to request
- * for real.
- */
- BitmapPrefetch(node, scan);
-
/*
* If we are using lossy info, we have to recheck the qual
* conditions at every tuple.
@@ -254,34 +189,17 @@ BitmapHeapNext(BitmapHeapScanState *node)
/* OK to return this tuple */
return slot;
}
-
new_page:
- BitmapAdjustPrefetchIterator(node);
-
/*
* Returns false if the bitmap is exhausted and there are no further
* blocks we need to scan.
*/
- if (!table_scan_bitmap_next_block(scan, &node->blockno,
+ if (!table_scan_bitmap_next_block(scan,
&node->recheck,
&node->stats.lossy_pages,
&node->stats.exact_pages))
break;
-
- /*
- * If serial, we can error out if the prefetch block doesn't stay
- * ahead of the current block.
- */
- if (node->pstate == NULL &&
- !tbm_exhausted(&node->prefetch_iterator) &&
- node->prefetch_blockno < node->blockno)
- elog(ERROR,
- "prefetch and main iterators are out of sync. pfblockno: %d. blockno: %d",
- node->prefetch_blockno, node->blockno);
-
- /* Adjust the prefetch target */
- BitmapAdjustPrefetchTarget(node);
}
/*
@@ -305,226 +223,6 @@ BitmapDoneInitializingSharedState(ParallelBitmapHeapState *pstate)
ConditionVariableBroadcast(&pstate->cv);
}
-/*
- * BitmapAdjustPrefetchIterator - Adjust the prefetch iterator
- *
- * We keep track of how far the prefetch iterator is ahead of the main
- * iterator in prefetch_pages. For each block the main iterator returns, we
- * decrement prefetch_pages.
- */
-static inline void
-BitmapAdjustPrefetchIterator(BitmapHeapScanState *node)
-{
-#ifdef USE_PREFETCH
- ParallelBitmapHeapState *pstate = node->pstate;
- TBMIterateResult tbmpre;
-
- if (pstate == NULL)
- {
- TBMIterator *prefetch_iterator = &node->prefetch_iterator;
-
- if (node->prefetch_pages > 0)
- {
- /* The main iterator has closed the distance by one page */
- node->prefetch_pages--;
- }
- else if (!tbm_exhausted(prefetch_iterator))
- {
- tbm_iterate(prefetch_iterator, &tbmpre);
- node->prefetch_blockno = tbmpre.blockno;
- }
- return;
- }
-
- /*
- * XXX: There is a known issue with keeping the prefetch and current block
- * iterators in sync for parallel bitmap table scans. This can lead to
- * prefetching blocks that have already been read. See the discussion
- * here:
- * https://postgr.es/m/20240315211449.en2jcmdqxv5o6tlz%40alap3.anarazel.de
- * Note that moving the call site of BitmapAdjustPrefetchIterator()
- * exacerbates the effects of this bug.
- */
- if (node->prefetch_maximum > 0)
- {
- TBMIterator *prefetch_iterator = &node->prefetch_iterator;
-
- SpinLockAcquire(&pstate->mutex);
- if (pstate->prefetch_pages > 0)
- {
- pstate->prefetch_pages--;
- SpinLockRelease(&pstate->mutex);
- }
- else
- {
- /* Release the mutex before iterating */
- SpinLockRelease(&pstate->mutex);
-
- /*
- * In case of shared mode, we can not ensure that the current
- * blockno of the main iterator and that of the prefetch iterator
- * are same. It's possible that whatever blockno we are
- * prefetching will be processed by another process. Therefore,
- * we don't validate the blockno here as we do in non-parallel
- * case.
- */
- if (!tbm_exhausted(prefetch_iterator))
- {
- tbm_iterate(prefetch_iterator, &tbmpre);
- node->prefetch_blockno = tbmpre.blockno;
- }
- }
- }
-#endif /* USE_PREFETCH */
-}
-
-/*
- * BitmapAdjustPrefetchTarget - Adjust the prefetch target
- *
- * Increase prefetch target if it's not yet at the max. Note that
- * we will increase it to zero after fetching the very first
- * page/tuple, then to one after the second tuple is fetched, then
- * it doubles as later pages are fetched.
- */
-static inline void
-BitmapAdjustPrefetchTarget(BitmapHeapScanState *node)
-{
-#ifdef USE_PREFETCH
- ParallelBitmapHeapState *pstate = node->pstate;
-
- if (pstate == NULL)
- {
- if (node->prefetch_target >= node->prefetch_maximum)
- /* don't increase any further */ ;
- else if (node->prefetch_target >= node->prefetch_maximum / 2)
- node->prefetch_target = node->prefetch_maximum;
- else if (node->prefetch_target > 0)
- node->prefetch_target *= 2;
- else
- node->prefetch_target++;
- return;
- }
-
- /* Do an unlocked check first to save spinlock acquisitions. */
- if (pstate->prefetch_target < node->prefetch_maximum)
- {
- SpinLockAcquire(&pstate->mutex);
- if (pstate->prefetch_target >= node->prefetch_maximum)
- /* don't increase any further */ ;
- else if (pstate->prefetch_target >= node->prefetch_maximum / 2)
- pstate->prefetch_target = node->prefetch_maximum;
- else if (pstate->prefetch_target > 0)
- pstate->prefetch_target *= 2;
- else
- pstate->prefetch_target++;
- SpinLockRelease(&pstate->mutex);
- }
-#endif /* USE_PREFETCH */
-}
-
-/*
- * BitmapPrefetch - Prefetch, if prefetch_pages are behind prefetch_target
- */
-static inline void
-BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan)
-{
-#ifdef USE_PREFETCH
- ParallelBitmapHeapState *pstate = node->pstate;
-
- if (pstate == NULL)
- {
- TBMIterator *prefetch_iterator = &node->prefetch_iterator;
-
- if (!tbm_exhausted(prefetch_iterator))
- {
- while (node->prefetch_pages < node->prefetch_target)
- {
- TBMIterateResult tbmpre;
- bool skip_fetch;
-
- tbm_iterate(prefetch_iterator, &tbmpre);
-
- if (!BlockNumberIsValid(tbmpre.blockno))
- {
- /* No more pages to prefetch */
- tbm_end_iterate(prefetch_iterator);
- break;
- }
- node->prefetch_pages++;
- node->prefetch_blockno = tbmpre.blockno;
-
- /*
- * If we expect not to have to actually read this heap page,
- * skip this prefetch call, but continue to run the prefetch
- * logic normally. (Would it be better not to increment
- * prefetch_pages?)
- */
- skip_fetch = (!(scan->rs_flags & SO_NEED_TUPLES) &&
- !tbmpre.recheck &&
- VM_ALL_VISIBLE(node->ss.ss_currentRelation,
- tbmpre.blockno,
- &node->pvmbuffer));
-
- if (!skip_fetch)
- PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre.blockno);
- }
- }
-
- return;
- }
-
- if (pstate->prefetch_pages < pstate->prefetch_target)
- {
- TBMIterator *prefetch_iterator = &node->prefetch_iterator;
-
- if (!tbm_exhausted(prefetch_iterator))
- {
- while (1)
- {
- TBMIterateResult tbmpre;
- bool do_prefetch = false;
- bool skip_fetch;
-
- /*
- * Recheck under the mutex. If some other process has already
- * done enough prefetching then we need not to do anything.
- */
- SpinLockAcquire(&pstate->mutex);
- if (pstate->prefetch_pages < pstate->prefetch_target)
- {
- pstate->prefetch_pages++;
- do_prefetch = true;
- }
- SpinLockRelease(&pstate->mutex);
-
- if (!do_prefetch)
- return;
-
- tbm_iterate(prefetch_iterator, &tbmpre);
- if (!BlockNumberIsValid(tbmpre.blockno))
- {
- /* No more pages to prefetch */
- tbm_end_iterate(prefetch_iterator);
- break;
- }
-
- node->prefetch_blockno = tbmpre.blockno;
-
- /* As above, skip prefetch if we expect not to need page */
- skip_fetch = (!(scan->rs_flags & SO_NEED_TUPLES) &&
- !tbmpre.recheck &&
- VM_ALL_VISIBLE(node->ss.ss_currentRelation,
- tbmpre.blockno,
- &node->pvmbuffer));
-
- if (!skip_fetch)
- PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre.blockno);
- }
- }
- }
-#endif /* USE_PREFETCH */
-}
-
/*
* BitmapHeapRecheck -- access method routine to recheck a tuple in EvalPlanQual
*/
@@ -574,31 +272,19 @@ ExecReScanBitmapHeapScan(BitmapHeapScanState *node)
* End iteration on iterators saved in scan descriptor if they have
* not already been cleaned up.
*/
- if (!tbm_exhausted(&scan->st.rs_tbmiterator))
- tbm_end_iterate(&scan->st.rs_tbmiterator);
+ if (!tbm_exhausted(&scan->st.bitmap.rs_iterator))
+ tbm_end_iterate(&scan->st.bitmap.rs_iterator);
/* rescan to release any page pin */
table_rescan(node->ss.ss_currentScanDesc, NULL);
}
- /* If we did not already clean up the prefetch iterator, do so now. */
- if (!tbm_exhausted(&node->prefetch_iterator))
- tbm_end_iterate(&node->prefetch_iterator);
-
/* release bitmaps and buffers if any */
if (node->tbm)
tbm_free(node->tbm);
- if (node->pvmbuffer != InvalidBuffer)
- ReleaseBuffer(node->pvmbuffer);
node->tbm = NULL;
node->initialized = false;
- node->pvmbuffer = InvalidBuffer;
node->recheck = true;
- /* Only used for serial BHS */
- node->blockno = InvalidBlockNumber;
- node->prefetch_blockno = InvalidBlockNumber;
- node->prefetch_pages = 0;
- node->prefetch_target = -1;
ExecScanReScan(&node->ss);
@@ -658,8 +344,8 @@ ExecEndBitmapHeapScan(BitmapHeapScanState *node)
* End iteration on iterators saved in scan descriptor if they have
* not already been cleaned up.
*/
- if (!tbm_exhausted(&scanDesc->st.rs_tbmiterator))
- tbm_end_iterate(&scanDesc->st.rs_tbmiterator);
+ if (!tbm_exhausted(&scanDesc->st.bitmap.rs_iterator))
+ tbm_end_iterate(&scanDesc->st.bitmap.rs_iterator);
/*
* close table scan
@@ -667,17 +353,11 @@ ExecEndBitmapHeapScan(BitmapHeapScanState *node)
table_endscan(scanDesc);
}
- /* If we did not already clean up the prefetch iterator, do so now. */
- if (!tbm_exhausted(&node->prefetch_iterator))
- tbm_end_iterate(&node->prefetch_iterator);
-
/*
* release bitmaps and buffers if any
*/
if (node->tbm)
tbm_free(node->tbm);
- if (node->pvmbuffer != InvalidBuffer)
- ReleaseBuffer(node->pvmbuffer);
}
/* ----------------------------------------------------------------
@@ -710,18 +390,13 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
scanstate->ss.ps.ExecProcNode = ExecBitmapHeapScan;
scanstate->tbm = NULL;
- scanstate->pvmbuffer = InvalidBuffer;
/* Zero the statistics counters */
memset(&scanstate->stats, 0, sizeof(BitmapHeapScanInstrumentation));
- scanstate->prefetch_pages = 0;
- scanstate->prefetch_target = -1;
scanstate->initialized = false;
scanstate->pstate = NULL;
scanstate->recheck = true;
- scanstate->blockno = InvalidBlockNumber;
- scanstate->prefetch_blockno = InvalidBlockNumber;
/*
* Miscellaneous initialization
@@ -761,13 +436,6 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
scanstate->bitmapqualorig =
ExecInitQual(node->bitmapqualorig, (PlanState *) scanstate);
- /*
- * Maximum number of prefetches for the tablespace if configured,
- * otherwise the current value of the effective_io_concurrency GUC.
- */
- scanstate->prefetch_maximum =
- get_tablespace_io_concurrency(currentRelation->rd_rel->reltablespace);
-
scanstate->ss.ss_currentRelation = currentRelation;
/*
@@ -871,12 +539,9 @@ ExecBitmapHeapInitializeDSM(BitmapHeapScanState *node,
sinstrument = (SharedBitmapHeapInstrumentation *) ptr;
pstate->tbmiterator = 0;
- pstate->prefetch_iterator = 0;
/* Initialize the mutex */
SpinLockInit(&pstate->mutex);
- pstate->prefetch_pages = 0;
- pstate->prefetch_target = -1;
pstate->state = BM_INITIAL;
ConditionVariableInit(&pstate->cv);
@@ -913,17 +578,11 @@ ExecBitmapHeapReInitializeDSM(BitmapHeapScanState *node,
return;
pstate->state = BM_INITIAL;
- pstate->prefetch_pages = 0;
- pstate->prefetch_target = -1;
if (DsaPointerIsValid(pstate->tbmiterator))
tbm_free_shared_area(dsa, pstate->tbmiterator);
- if (DsaPointerIsValid(pstate->prefetch_iterator))
- tbm_free_shared_area(dsa, pstate->prefetch_iterator);
-
pstate->tbmiterator = InvalidDsaPointer;
- pstate->prefetch_iterator = InvalidDsaPointer;
}
/* ----------------------------------------------------------------
diff --git a/src/include/access/relscan.h b/src/include/access/relscan.h
index dc6e0184284..934b667ad78 100644
--- a/src/include/access/relscan.h
+++ b/src/include/access/relscan.h
@@ -43,8 +43,12 @@ typedef struct TableScanDescData
*/
union
{
- /* Iterator for Bitmap Table Scans */
- TBMIterator rs_tbmiterator;
+ /* State for Bitmap Table Scans */
+ struct
+ {
+ struct ParallelBitmapHeapState *rs_pstate;
+ TBMIterator rs_iterator;
+ } bitmap;
/*
* Range of ItemPointers for table_scan_getnextslot_tidrange() to
diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h
index 131c050c15f..b5675b47dcc 100644
--- a/src/include/access/tableam.h
+++ b/src/include/access/tableam.h
@@ -797,28 +797,12 @@ typedef struct TableAmRoutine
* always need to be rechecked, but some non-lossy pages' tuples may also
* require recheck.
*
- * `blockno` is the current block and is set by the table AM. The table AM
- * is responsible for advancing the main iterator, but the bitmap table
- * scan code still advances the prefetch iterator. `blockno` is used by
- * bitmap table scan code to validate that the prefetch block stays ahead
- * of the current block.
- *
- * XXX: Currently this may only be implemented if the AM uses md.c as its
- * storage manager, and uses ItemPointer->ip_blkid in a manner that maps
- * blockids directly to the underlying storage. nodeBitmapHeapscan.c
- * performs prefetching directly using that interface. This probably
- * needs to be rectified at a later point.
- *
- * XXX: Currently this may only be implemented if the AM uses the
- * visibilitymap, as nodeBitmapHeapscan.c unconditionally accesses it to
- * perform prefetching. This probably needs to be rectified at a later
- * point.
+ * Prefetching additional data from the bitmap is left to the table AM.
*
* Optional callback, but either both scan_bitmap_next_block and
* scan_bitmap_next_tuple need to exist, or neither.
*/
bool (*scan_bitmap_next_block) (TableScanDesc scan,
- BlockNumber *blockno,
bool *recheck,
uint64 *lossy_pages,
uint64 *exact_pages);
@@ -956,15 +940,19 @@ table_beginscan_strat(Relation rel, Snapshot snapshot,
*/
static inline TableScanDesc
table_beginscan_bm(Relation rel, Snapshot snapshot,
+ struct ParallelBitmapHeapState *pstate,
int nkeys, struct ScanKeyData *key, bool need_tuple)
{
+ TableScanDesc result;
uint32 flags = SO_TYPE_BITMAPSCAN | SO_ALLOW_PAGEMODE;
if (need_tuple)
flags |= SO_NEED_TUPLES;
- return rel->rd_tableam->scan_begin(rel, snapshot, nkeys, key,
- NULL, flags);
+ result = rel->rd_tableam->scan_begin(rel, snapshot, nkeys,
+ key, NULL, flags);
+ result->st.bitmap.rs_pstate = pstate;
+ return result;
}
/*
@@ -1966,16 +1954,11 @@ table_relation_estimate_size(Relation rel, int32 *attr_widths,
* `recheck` is set by the table AM to indicate whether or not the tuples
* from this block should be rechecked.
*
- * `blockno` is the current block and is set by the table AM and is used by
- * bitmap table scan code to validate that the prefetch block stays ahead of
- * the current block.
- *
* Note, this is an optionally implemented function, therefore should only be
* used after verifying the presence (at plan time or such).
*/
static inline bool
table_scan_bitmap_next_block(TableScanDesc scan,
- BlockNumber *blockno,
bool *recheck,
uint64 *lossy_pages,
uint64 *exact_pages)
@@ -1989,7 +1972,7 @@ table_scan_bitmap_next_block(TableScanDesc scan,
elog(ERROR, "unexpected table_scan_bitmap_next_block call during logical decoding");
return scan->rs_rd->rd_tableam->scan_bitmap_next_block(scan,
- blockno, recheck,
+ recheck,
lossy_pages,
exact_pages);
}
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index e2d1dc1e067..c08fa33ad83 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1822,11 +1822,7 @@ typedef enum
/* ----------------
* ParallelBitmapHeapState information
* tbmiterator iterator for scanning current pages
- * prefetch_iterator iterator for prefetching ahead of current page
- * mutex mutual exclusion for the prefetching variable
- * and state
- * prefetch_pages # pages prefetch iterator is ahead of current
- * prefetch_target current target prefetch distance
+ * mutex mutual exclusion for state
* state current state of the TIDBitmap
* cv conditional wait variable
* ----------------
@@ -1834,10 +1830,7 @@ typedef enum
typedef struct ParallelBitmapHeapState
{
dsa_pointer tbmiterator;
- dsa_pointer prefetch_iterator;
slock_t mutex;
- int prefetch_pages;
- int prefetch_target;
SharedBitmapState state;
ConditionVariable cv;
} ParallelBitmapHeapState;
@@ -1861,18 +1854,11 @@ typedef struct SharedBitmapHeapInstrumentation
*
* bitmapqualorig execution state for bitmapqualorig expressions
* tbm bitmap obtained from child index scan(s)
- * pvmbuffer buffer for visibility-map lookups of prefetched pages
* stats execution statistics
- * prefetch_iterator iterator for prefetching ahead of current page
- * prefetch_pages # pages prefetch iterator is ahead of current
- * prefetch_target current target prefetch distance
- * prefetch_maximum maximum value for prefetch_target
* initialized is node is ready to iterate
* pstate shared state for parallel bitmap scan
* sinstrument statistics for parallel workers
* recheck do current page's tuples need recheck
- * blockno used to validate pf and current block stay in sync
- * prefetch_blockno used to validate pf stays ahead of current block
* ----------------
*/
typedef struct BitmapHeapScanState
@@ -1880,18 +1866,11 @@ typedef struct BitmapHeapScanState
ScanState ss; /* its first field is NodeTag */
ExprState *bitmapqualorig;
TIDBitmap *tbm;
- Buffer pvmbuffer;
BitmapHeapScanInstrumentation stats;
- TBMIterator prefetch_iterator;
- int prefetch_pages;
- int prefetch_target;
- int prefetch_maximum;
bool initialized;
ParallelBitmapHeapState *pstate;
SharedBitmapHeapInstrumentation *sinstrument;
bool recheck;
- BlockNumber blockno;
- BlockNumber prefetch_blockno;
} BitmapHeapScanState;
/* ----------------
--
2.34.1
