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heapam: Pass number of required pages to RelationGetBufferForTuple() 

A future commit will use this information to determine how aggressively to
extend the relation by. In heap_multi_insert() we know accurately how many
pages we need once we need to extend the relation, providing an accurate lower
bound for how much to extend.

Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://postgr.es/m/20221029025420.eplyow6k7tgu6he3@awork3.anarazel.de
This commit is contained in:
Andres Freund 2023-04-06 14:18:24 -07:00
parent 7d71d3dd08
commit 5279e9db8e
3 changed files with 63 additions and 6 deletions
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58
src/backend/access/heap/heapam.c
View File

@ -1847,7 +1847,8 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
*/
buffer = RelationGetBufferForTuple(relation, heaptup->t_len,
InvalidBuffer, options, bistate,
&vmbuffer, NULL);
&vmbuffer, NULL,
0);
/*
* We're about to do the actual insert -- but check for conflict first, to
@ -2050,6 +2051,32 @@ heap_prepare_insert(Relation relation, HeapTuple tup, TransactionId xid,
return tup;
}
/*
* Helper for heap_multi_insert() that computes the number of entire pages
* that inserting the remaining heaptuples requires. Used to determine how
* much the relation needs to be extended by.
*/
static int
heap_multi_insert_pages(HeapTuple *heaptuples, int done, int ntuples, Size saveFreeSpace)
{
size_t page_avail = BLCKSZ - SizeOfPageHeaderData - saveFreeSpace;
int npages = 1;
for (int i = done; i < ntuples; i++)
{
size_t tup_sz = sizeof(ItemIdData) + MAXALIGN(heaptuples[i]->t_len);
if (page_avail < tup_sz)
{
npages++;
page_avail = BLCKSZ - SizeOfPageHeaderData - saveFreeSpace;
}
page_avail -= tup_sz;
}
return npages;
}
/*
* heap_multi_insert - insert multiple tuples into a heap
*
@ -2076,6 +2103,9 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
Size saveFreeSpace;
bool need_tuple_data = RelationIsLogicallyLogged(relation);
bool need_cids = RelationIsAccessibleInLogicalDecoding(relation);
bool starting_with_empty_page = false;
int npages = 0;
int npages_used = 0;
/* currently not needed (thus unsupported) for heap_multi_insert() */
Assert(!(options & HEAP_INSERT_NO_LOGICAL));
@ -2126,13 +2156,31 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
while (ndone < ntuples)
{
Buffer buffer;
bool starting_with_empty_page;
bool all_visible_cleared = false;
bool all_frozen_set = false;
int nthispage;
CHECK_FOR_INTERRUPTS();
/*
* Compute number of pages needed to fit the to-be-inserted tuples in
* the worst case. This will be used to determine how much to extend
* the relation by in RelationGetBufferForTuple(), if needed. If we
* filled a prior page from scratch, we can just update our last
* computation, but if we started with a partially filled page,
* recompute from scratch, the number of potentially required pages
* can vary due to tuples needing to fit onto the page, page headers
* etc.
*/
if (ndone == 0 || !starting_with_empty_page)
{
npages = heap_multi_insert_pages(heaptuples, ndone, ntuples,
saveFreeSpace);
npages_used = 0;
}
else
npages_used++;
/*
* Find buffer where at least the next tuple will fit. If the page is
* all-visible, this will also pin the requisite visibility map page.
@ -2142,7 +2190,8 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
*/
buffer = RelationGetBufferForTuple(relation, heaptuples[ndone]->t_len,
InvalidBuffer, options, bistate,
&vmbuffer, NULL);
&vmbuffer, NULL,
npages - npages_used);
page = BufferGetPage(buffer);
starting_with_empty_page = PageGetMaxOffsetNumber(page) == 0;
@ -3576,7 +3625,8 @@ l2:
/* It doesn't fit, must use RelationGetBufferForTuple. */
newbuf = RelationGetBufferForTuple(relation, heaptup->t_len,
buffer, 0, NULL,
&vmbuffer_new, &vmbuffer);
&vmbuffer_new, &vmbuffer,
0);
/* We're all done. */
break;
}

8
src/backend/access/heap/hio.c
View File

@ -301,6 +301,11 @@ RelationAddExtraBlocks(Relation relation, BulkInsertState bistate)
* Returns pinned and exclusive-locked buffer of a page in given relation
* with free space >= given len.
*
* If num_pages is > 1, we will try to extend the relation by at least that
* many pages when we decide to extend the relation. This is more efficient
* for callers that know they will need multiple pages
* (e.g. heap_multi_insert()).
*
* If otherBuffer is not InvalidBuffer, then it references a previously
* pinned buffer of another page in the same relation; on return, this
* buffer will also be exclusive-locked. (This case is used by heap_update;
@ -359,7 +364,8 @@ Buffer
RelationGetBufferForTuple(Relation relation, Size len,
Buffer otherBuffer, int options,
BulkInsertState bistate,
Buffer *vmbuffer, Buffer *vmbuffer_other)
Buffer *vmbuffer, Buffer *vmbuffer_other,
int num_pages)
{
bool use_fsm = !(options & HEAP_INSERT_SKIP_FSM);
Buffer buffer = InvalidBuffer;

3
src/include/access/hio.h
View File

@ -38,6 +38,7 @@ extern void RelationPutHeapTuple(Relation relation, Buffer buffer,
extern Buffer RelationGetBufferForTuple(Relation relation, Size len,
Buffer otherBuffer, int options,
BulkInsertStateData *bistate,
Buffer *vmbuffer, Buffer *vmbuffer_other);
Buffer *vmbuffer, Buffer *vmbuffer_other,
int num_pages);
#endif /* HIO_H */