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Refactor how heap_prune_chain() updates prunable_xid 

In preparation of freezing and counting tuples which are not
candidates for pruning, split heap_prune_record_unchanged() into
multiple functions, depending the kind of line pointer. That's not too
interesting right now, but makes the next commit smaller.

Recording the lowest soon-to-be prunable xid is one of the actions we
take for unchanged LP_NORMAL item pointers but not for others, so move
that to the new heap_prune_record_unchanged_lp_normal() function. The
next commit will add more actions to these functions.

Author: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://www.postgresql.org/message-id/20240330055710.kqg6ii2cdojsxgje@liskov
This commit is contained in:
Heikki Linnakangas 2024-04-03 19:32:21 +03:00
parent be2f073100
commit 26d138f644
1 changed files with 92 additions and 33 deletions
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125
src/backend/access/heap/pruneheap.c
View File

@ -78,7 +78,11 @@ static void heap_prune_record_redirect(PruneState *prstate,
static void heap_prune_record_dead(PruneState *prstate, OffsetNumber offnum, bool was_normal);
static void heap_prune_record_dead_or_unused(PruneState *prstate, OffsetNumber offnum, bool was_normal);
static void heap_prune_record_unused(PruneState *prstate, OffsetNumber offnum, bool was_normal);
static void heap_prune_record_unchanged(PruneState *prstate, OffsetNumber offnum);
static void heap_prune_record_unchanged_lp_unused(Page page, PruneState *prstate, OffsetNumber offnum);
static void heap_prune_record_unchanged_lp_normal(Page page, int8 *htsv, PruneState *prstate, OffsetNumber offnum);
static void heap_prune_record_unchanged_lp_dead(Page page, PruneState *prstate, OffsetNumber offnum);
static void heap_prune_record_unchanged_lp_redirect(PruneState *prstate, OffsetNumber offnum);
static void page_verify_redirects(Page page);
@ -311,7 +315,7 @@ heap_page_prune(Relation relation, Buffer buffer,
/* Nothing to do if slot doesn't contain a tuple */
if (!ItemIdIsUsed(itemid))
{
heap_prune_record_unchanged(&prstate, offnum);
heap_prune_record_unchanged_lp_unused(page, &prstate, offnum);
continue;
}
@ -324,7 +328,7 @@ heap_page_prune(Relation relation, Buffer buffer,
if (unlikely(prstate.mark_unused_now))
heap_prune_record_unused(&prstate, offnum, false);
else
heap_prune_record_unchanged(&prstate, offnum);
heap_prune_record_unchanged_lp_dead(page, &prstate, offnum);
continue;
}
@ -434,7 +438,7 @@ heap_page_prune(Relation relation, Buffer buffer,
}
}
else
heap_prune_record_unchanged(&prstate, offnum);
heap_prune_record_unchanged_lp_normal(page, presult->htsv, &prstate, offnum);
}
/* We should now have processed every tuple exactly once */
@ -652,9 +656,6 @@ heap_prune_chain(Page page, BlockNumber blockno, OffsetNumber maxoff,
*/
chainitems[nchain++] = offnum;
/*
* Check tuple's visibility status.
*/
switch (htsv_get_valid_status(htsv[offnum]))
{
case HEAPTUPLE_DEAD:
@ -670,9 +671,6 @@ heap_prune_chain(Page page, BlockNumber blockno, OffsetNumber maxoff,
case HEAPTUPLE_RECENTLY_DEAD:
/*
* This tuple may soon become DEAD. Update the hint field so
* that the page is reconsidered for pruning in future.
*
* We don't need to advance the conflict horizon for
* RECENTLY_DEAD tuples, even if we are removing them. This
* is because we only remove RECENTLY_DEAD tuples if they
@ -681,8 +679,6 @@ heap_prune_chain(Page page, BlockNumber blockno, OffsetNumber maxoff,
* tuple by virtue of being later in the chain. We will have
* advanced the conflict horizon for the DEAD tuple.
*/
heap_prune_record_prunable(prstate,
HeapTupleHeaderGetUpdateXid(htup));
/*
* Advance past RECENTLY_DEAD tuples just in case there's a
@ -693,24 +689,8 @@ heap_prune_chain(Page page, BlockNumber blockno, OffsetNumber maxoff,
break;
case HEAPTUPLE_DELETE_IN_PROGRESS:
/*
* This tuple may soon become DEAD. Update the hint field so
* that the page is reconsidered for pruning in future.
*/
heap_prune_record_prunable(prstate,
HeapTupleHeaderGetUpdateXid(htup));
goto process_chain;
case HEAPTUPLE_LIVE:
case HEAPTUPLE_INSERT_IN_PROGRESS:
/*
* If we wanted to optimize for aborts, we might consider
* marking the page prunable when we see INSERT_IN_PROGRESS.
* But we don't. See related decisions about when to mark the
* page prunable in heapam.c.
*/
goto process_chain;
default:
@ -757,8 +737,15 @@ process_chain:
* No DEAD tuple was found, so the chain is entirely composed of
* normal, unchanged tuples. Leave it alone.
*/
for (int i = 0; i < nchain; i++)
heap_prune_record_unchanged(prstate, chainitems[i]);
int i = 0;
if (ItemIdIsRedirected(rootlp))
{
heap_prune_record_unchanged_lp_redirect(prstate, rootoffnum);
i++;
}
for (; i < nchain; i++)
heap_prune_record_unchanged_lp_normal(page, htsv, prstate, chainitems[i]);
}
else if (ndeadchain == nchain)
{
@ -784,7 +771,7 @@ process_chain:
/* the rest of tuples in the chain are normal, unchanged tuples */
for (int i = ndeadchain; i < nchain; i++)
heap_prune_record_unchanged(prstate, chainitems[i]);
heap_prune_record_unchanged_lp_normal(page, htsv, prstate, chainitems[i]);
}
}
@ -894,9 +881,81 @@ heap_prune_record_unused(PruneState *prstate, OffsetNumber offnum, bool was_norm
prstate->ndeleted++;
}
/* Record a line pointer that is left unchanged */
/*
* Record an unused line pointer that is left unchanged.
*/
static void
heap_prune_record_unchanged(PruneState *prstate, OffsetNumber offnum)
heap_prune_record_unchanged_lp_unused(Page page, PruneState *prstate, OffsetNumber offnum)
{
Assert(!prstate->processed[offnum]);
prstate->processed[offnum] = true;
}
/*
* Record LP_NORMAL line pointer that is left unchanged.
*/
static void
heap_prune_record_unchanged_lp_normal(Page page, int8 *htsv, PruneState *prstate, OffsetNumber offnum)
{
HeapTupleHeader htup;
Assert(!prstate->processed[offnum]);
prstate->processed[offnum] = true;
switch (htsv[offnum])
{
case HEAPTUPLE_LIVE:
case HEAPTUPLE_INSERT_IN_PROGRESS:
/*
* If we wanted to optimize for aborts, we might consider marking
* the page prunable when we see INSERT_IN_PROGRESS. But we
* don't. See related decisions about when to mark the page
* prunable in heapam.c.
*/
break;
case HEAPTUPLE_RECENTLY_DEAD:
case HEAPTUPLE_DELETE_IN_PROGRESS:
htup = (HeapTupleHeader) PageGetItem(page, PageGetItemId(page, offnum));
/*
* This tuple may soon become DEAD. Update the hint field so that
* the page is reconsidered for pruning in future.
*/
heap_prune_record_prunable(prstate,
HeapTupleHeaderGetUpdateXid(htup));
break;
default:
/*
* DEAD tuples should've been passed to heap_prune_record_dead()
* or heap_prune_record_unused() instead.
*/
elog(ERROR, "unexpected HeapTupleSatisfiesVacuum result %d", htsv[offnum]);
break;
}
}
/*
* Record line pointer that was already LP_DEAD and is left unchanged.
*/
static void
heap_prune_record_unchanged_lp_dead(Page page, PruneState *prstate, OffsetNumber offnum)
{
Assert(!prstate->processed[offnum]);
prstate->processed[offnum] = true;
}
/*
* Record LP_REDIRECT that is left unchanged.
*/
static void
heap_prune_record_unchanged_lp_redirect(PruneState *prstate, OffsetNumber offnum)
{
Assert(!prstate->processed[offnum]);
prstate->processed[offnum] = true;