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Revert no-op changes to BufferGetPage()

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The reverted changes were intended to force a choice of whether any
newly-added BufferGetPage() calls needed to be accompanied by a
test of the snapshot age, to support the "snapshot too old"
feature.  Such an accompanying test is needed in about 7% of the
cases, where the page is being used as part of a scan rather than
positioning for other purposes (such as DML or vacuuming).  The
additional effort required for back-patching, and the doubt whether
the intended benefit would really be there, have indicated it is
best just to rely on developers to do the right thing based on
comments and existing usage, as we do with many other conventions.

This change should have little or no effect on generated executable
code.

Motivated by the back-patching pain of Tom Lane and Robert Haas
This commit is contained in:
Kevin Grittner
2016-04-20 08:31:19 -05:00
parent 4db0d2d2fe
commit a343e223a5
65 changed files with 550 additions and 736 deletions
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41
src/backend/access/gin/ginget.c
View File

@ -19,7 +19,6 @@
#include "miscadmin.h"
#include "utils/datum.h"
#include "utils/memutils.h"
#include "utils/rel.h"
/* GUC parameter */
int GinFuzzySearchLimit = 0;
@ -40,8 +39,7 @@ typedef struct pendingPosition
static bool
moveRightIfItNeeded(GinBtreeData *btree, GinBtreeStack *stack)
{
Page page = BufferGetPage(stack->buffer, NULL, NULL,
BGP_NO_SNAPSHOT_TEST);
Page page = BufferGetPage(stack->buffer);
if (stack->off > PageGetMaxOffsetNumber(page))
{
@ -84,7 +82,7 @@ scanPostingTree(Relation index, GinScanEntry scanEntry,
*/
for (;;)
{
page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
page = BufferGetPage(buffer);
if ((GinPageGetOpaque(page)->flags & GIN_DELETED) == 0)
{
int n = GinDataLeafPageGetItemsToTbm(page, scanEntry->matchBitmap);
@ -146,8 +144,8 @@ collectMatchBitmap(GinBtreeData *btree, GinBtreeStack *stack,
if (moveRightIfItNeeded(btree, stack) == false)
return true;
page = BufferGetPage(stack->buffer, snapshot, btree->index,
BGP_TEST_FOR_OLD_SNAPSHOT);
page = BufferGetPage(stack->buffer);
TestForOldSnapshot(snapshot, btree->index, page);
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, stack->off));
/*
@ -227,14 +225,15 @@ collectMatchBitmap(GinBtreeData *btree, GinBtreeStack *stack,
LockBuffer(stack->buffer, GIN_UNLOCK);
/* Collect all the TIDs in this entry's posting tree */
scanPostingTree(btree->index, scanEntry, rootPostingTree, snapshot);
scanPostingTree(btree->index, scanEntry, rootPostingTree,
snapshot);
/*
* We lock again the entry page and while it was unlocked insert
* might have occurred, so we need to re-find our position.
*/
LockBuffer(stack->buffer, GIN_SHARE);
page = BufferGetPage(stack->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
page = BufferGetPage(stack->buffer);
if (!GinPageIsLeaf(page))
{
/*
@ -254,7 +253,7 @@ collectMatchBitmap(GinBtreeData *btree, GinBtreeStack *stack,
if (moveRightIfItNeeded(btree, stack) == false)
elog(ERROR, "lost saved point in index"); /* must not happen !!! */
page = BufferGetPage(stack->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
page = BufferGetPage(stack->buffer);
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, stack->off));
if (gintuple_get_attrnum(btree->ginstate, itup) != attnum)
@ -323,7 +322,8 @@ restartScanEntry:
entry->queryKey, entry->queryCategory,
ginstate);
stackEntry = ginFindLeafPage(&btreeEntry, true, snapshot);
page = BufferGetPage(stackEntry->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
page = BufferGetPage(stackEntry->buffer);
/* ginFindLeafPage() will have already checked snapshot age. */
needUnlock = TRUE;
entry->isFinished = TRUE;
@ -339,7 +339,8 @@ restartScanEntry:
* for the entry type.
*/
btreeEntry.findItem(&btreeEntry, stackEntry);
if (!collectMatchBitmap(&btreeEntry, stackEntry, entry, snapshot))
if (collectMatchBitmap(&btreeEntry, stackEntry, entry, snapshot)
== false)
{
/*
* GIN tree was seriously restructured, so we will cleanup all
@ -397,7 +398,7 @@ restartScanEntry:
*/
IncrBufferRefCount(entry->buffer);
page = BufferGetPage(entry->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
page = BufferGetPage(entry->buffer);
/*
* Load the first page into memory.
@ -643,7 +644,7 @@ entryLoadMoreItems(GinState *ginstate, GinScanEntry entry,
GinItemPointerGetOffsetNumber(&advancePast),
!stepright);
page = BufferGetPage(entry->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
page = BufferGetPage(entry->buffer);
for (;;)
{
entry->offset = InvalidOffsetNumber;
@ -675,7 +676,7 @@ entryLoadMoreItems(GinState *ginstate, GinScanEntry entry,
entry->buffer = ginStepRight(entry->buffer,
ginstate->index,
GIN_SHARE);
page = BufferGetPage(entry->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
page = BufferGetPage(entry->buffer);
}
stepright = true;
@ -1337,8 +1338,8 @@ scanGetCandidate(IndexScanDesc scan, pendingPosition *pos)
ItemPointerSetInvalid(&pos->item);
for (;;)
{
page = BufferGetPage(pos->pendingBuffer, scan->xs_snapshot,
scan->indexRelation, BGP_TEST_FOR_OLD_SNAPSHOT);
page = BufferGetPage(pos->pendingBuffer);
TestForOldSnapshot(scan->xs_snapshot, scan->indexRelation, page);
maxoff = PageGetMaxOffsetNumber(page);
if (pos->firstOffset > maxoff)
@ -1518,8 +1519,8 @@ collectMatchesForHeapRow(IndexScanDesc scan, pendingPosition *pos)
memset(datumExtracted + pos->firstOffset - 1, 0,
sizeof(bool) * (pos->lastOffset - pos->firstOffset));
page = BufferGetPage(pos->pendingBuffer, scan->xs_snapshot,
scan->indexRelation, BGP_TEST_FOR_OLD_SNAPSHOT);
page = BufferGetPage(pos->pendingBuffer);
TestForOldSnapshot(scan->xs_snapshot, scan->indexRelation, page);
for (i = 0; i < so->nkeys; i++)
{
@ -1712,8 +1713,8 @@ scanPendingInsert(IndexScanDesc scan, TIDBitmap *tbm, int64 *ntids)
*ntids = 0;
LockBuffer(metabuffer, GIN_SHARE);
page = BufferGetPage(metabuffer, scan->xs_snapshot, scan->indexRelation,
BGP_TEST_FOR_OLD_SNAPSHOT);
page = BufferGetPage(metabuffer);
TestForOldSnapshot(scan->xs_snapshot, scan->indexRelation, page);
blkno = GinPageGetMeta(page)->head;
/*