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postgresql/src/backend/access/gin/ginget.c

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/*-------------------------------------------------------------------------
*
* ginget.c
* fetch tuples from a GIN scan.
*
*
* Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/backend/access/gin/ginget.c
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/gin_private.h"
#include "access/relscan.h"
#include "catalog/index.h"
#include "miscadmin.h"
#include "storage/bufmgr.h"
#include "utils/datum.h"
#include "utils/memutils.h"
typedef struct pendingPosition
{
Buffer pendingBuffer;
OffsetNumber firstOffset;
OffsetNumber lastOffset;
ItemPointerData item;
bool *hasMatchKey;
} pendingPosition;
/*
* Convenience function for invoking a key's consistentFn
*/
static bool
callConsistentFn(GinState *ginstate, GinScanKey key)
{
/*
* If we're dealing with a dummy EVERYTHING key, we don't want to call the
* consistentFn; just claim it matches.
*/
if (key->searchMode == GIN_SEARCH_MODE_EVERYTHING)
{
key->recheckCurItem = false;
return true;
}
/*
* Initialize recheckCurItem in case the consistentFn doesn't know it
* should set it. The safe assumption in that case is to force recheck.
*/
key->recheckCurItem = true;
return DatumGetBool(FunctionCall8(&ginstate->consistentFn[key->attnum - 1],
PointerGetDatum(key->entryRes),
UInt16GetDatum(key->strategy),
key->query,
UInt32GetDatum(key->nuserentries),
PointerGetDatum(key->extra_data),
PointerGetDatum(&key->recheckCurItem),
PointerGetDatum(key->queryValues),
PointerGetDatum(key->queryCategories)));
}
/*
* Tries to refind previously taken ItemPointer on a posting page.
*/
static bool
findItemInPostingPage(Page page, ItemPointer item, OffsetNumber *off)
{
OffsetNumber maxoff = GinPageGetOpaque(page)->maxoff;
int res;
if (GinPageGetOpaque(page)->flags & GIN_DELETED)
/* page was deleted by concurrent vacuum */
return false;
/*
* scan page to find equal or first greater value
*/
for (*off = FirstOffsetNumber; *off <= maxoff; (*off)++)
{
res = ginCompareItemPointers(item, (ItemPointer) GinDataPageGetItem(page, *off));
if (res <= 0)
return true;
}
return false;
}
/*
* Goes to the next page if current offset is outside of bounds
*/
static bool
moveRightIfItNeeded(GinBtreeData *btree, GinBtreeStack *stack)
{
Page page = BufferGetPage(stack->buffer);
if (stack->off > PageGetMaxOffsetNumber(page))
{
/*
* We scanned the whole page, so we should take right page
*/
stack->blkno = GinPageGetOpaque(page)->rightlink;
if (GinPageRightMost(page))
return false; /* no more pages */
LockBuffer(stack->buffer, GIN_UNLOCK);
stack->buffer = ReleaseAndReadBuffer(stack->buffer,
btree->index,
stack->blkno);
LockBuffer(stack->buffer, GIN_SHARE);
stack->off = FirstOffsetNumber;
}
return true;
}
/*
* Scan all pages of a posting tree and save all its heap ItemPointers
* in scanEntry->matchBitmap
*/
static void
scanPostingTree(Relation index, GinScanEntry scanEntry,
BlockNumber rootPostingTree)
{
GinPostingTreeScan *gdi;
Buffer buffer;
Page page;
BlockNumber blkno;
/* Descend to the leftmost leaf page */
gdi = ginPrepareScanPostingTree(index, rootPostingTree, TRUE);
buffer = ginScanBeginPostingTree(gdi);
IncrBufferRefCount(buffer); /* prevent unpin in freeGinBtreeStack */
freeGinBtreeStack(gdi->stack);
pfree(gdi);
/*
* Loop iterates through all leaf pages of posting tree
*/
for (;;)
{
page = BufferGetPage(buffer);
if ((GinPageGetOpaque(page)->flags & GIN_DELETED) == 0 &&
GinPageGetOpaque(page)->maxoff >= FirstOffsetNumber)
{
tbm_add_tuples(scanEntry->matchBitmap,
(ItemPointer) GinDataPageGetItem(page, FirstOffsetNumber),
GinPageGetOpaque(page)->maxoff, false);
scanEntry->predictNumberResult += GinPageGetOpaque(page)->maxoff;
}
if (GinPageRightMost(page))
break; /* no more pages */
blkno = GinPageGetOpaque(page)->rightlink;
LockBuffer(buffer, GIN_UNLOCK);
buffer = ReleaseAndReadBuffer(buffer, index, blkno);
LockBuffer(buffer, GIN_SHARE);
}
UnlockReleaseBuffer(buffer);
}
/*
* Collects TIDs into scanEntry->matchBitmap for all heap tuples that
* match the search entry. This supports three different match modes:
*
* 1. Partial-match support: scan from current point until the
* comparePartialFn says we're done.
* 2. SEARCH_MODE_ALL: scan from current point (which should be first
* key for the current attnum) until we hit null items or end of attnum
* 3. SEARCH_MODE_EVERYTHING: scan from current point (which should be first
* key for the current attnum) until we hit end of attnum
*
* Returns true if done, false if it's necessary to restart scan from scratch
*/
static bool
collectMatchBitmap(GinBtreeData *btree, GinBtreeStack *stack,
GinScanEntry scanEntry)
{
OffsetNumber attnum;
Form_pg_attribute attr;
/* Initialize empty bitmap result */
scanEntry->matchBitmap = tbm_create(work_mem * 1024L);
/* Null query cannot partial-match anything */
if (scanEntry->isPartialMatch &&
scanEntry->queryCategory != GIN_CAT_NORM_KEY)
return true;
/* Locate tupdesc entry for key column (for attbyval/attlen data) */
attnum = scanEntry->attnum;
attr = btree->ginstate->origTupdesc->attrs[attnum - 1];
for (;;)
{
Page page;
IndexTuple itup;
Datum idatum;
GinNullCategory icategory;
/*
* stack->off points to the interested entry, buffer is already locked
*/
if (moveRightIfItNeeded(btree, stack) == false)
return true;
page = BufferGetPage(stack->buffer);
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, stack->off));
/*
* If tuple stores another attribute then stop scan
*/
if (gintuple_get_attrnum(btree->ginstate, itup) != attnum)
return true;
/* Safe to fetch attribute value */
idatum = gintuple_get_key(btree->ginstate, itup, &icategory);
/*
* Check for appropriate scan stop conditions
*/
if (scanEntry->isPartialMatch)
{
int32 cmp;
/*
* In partial match, stop scan at any null (including
* placeholders); partial matches never match nulls
*/
if (icategory != GIN_CAT_NORM_KEY)
return true;
/*----------
* Check of partial match.
* case cmp == 0 => match
* case cmp > 0 => not match and finish scan
* case cmp < 0 => not match and continue scan
*----------
*/
cmp = DatumGetInt32(FunctionCall4(&btree->ginstate->comparePartialFn[attnum - 1],
scanEntry->queryKey,
idatum,
UInt16GetDatum(scanEntry->strategy),
PointerGetDatum(scanEntry->extra_data)));
if (cmp > 0)
return true;
else if (cmp < 0)
{
stack->off++;
continue;
}
}
else if (scanEntry->searchMode == GIN_SEARCH_MODE_ALL)
{
/*
* In ALL mode, we are not interested in null items, so we can
* stop if we get to a null-item placeholder (which will be the
* last entry for a given attnum). We do want to include NULL_KEY
* and EMPTY_ITEM entries, though.
*/
if (icategory == GIN_CAT_NULL_ITEM)
return true;
}
/*
* OK, we want to return the TIDs listed in this entry.
*/
if (GinIsPostingTree(itup))
{
BlockNumber rootPostingTree = GinGetPostingTree(itup);
/*
* We should unlock current page (but not unpin) during tree scan
* to prevent deadlock with vacuum processes.
*
* We save current entry value (idatum) to be able to re-find our
* tuple after re-locking
*/
if (icategory == GIN_CAT_NORM_KEY)
idatum = datumCopy(idatum, attr->attbyval, attr->attlen);
LockBuffer(stack->buffer, GIN_UNLOCK);
/* Collect all the TIDs in this entry's posting tree */
scanPostingTree(btree->index, scanEntry, rootPostingTree);
/*
* 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);
if (!GinPageIsLeaf(page))
{
/*
* Root page becomes non-leaf while we unlock it. We will
* start again, this situation doesn't occur often - root can
* became a non-leaf only once per life of index.
*/
return false;
}
/* Search forward to re-find idatum */
for (;;)
{
Datum newDatum;
GinNullCategory newCategory;
if (moveRightIfItNeeded(btree, stack) == false)
elog(ERROR, "lost saved point in index"); /* must not happen !!! */
page = BufferGetPage(stack->buffer);
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, stack->off));
if (gintuple_get_attrnum(btree->ginstate, itup) != attnum)
elog(ERROR, "lost saved point in index"); /* must not happen !!! */
newDatum = gintuple_get_key(btree->ginstate, itup,
&newCategory);
if (ginCompareEntries(btree->ginstate, attnum,
newDatum, newCategory,
idatum, icategory) == 0)
break; /* Found! */
stack->off++;
}
if (icategory == GIN_CAT_NORM_KEY && !attr->attbyval)
pfree(DatumGetPointer(idatum));
}
else
{
tbm_add_tuples(scanEntry->matchBitmap,
GinGetPosting(itup), GinGetNPosting(itup), false);
scanEntry->predictNumberResult += GinGetNPosting(itup);
}
/*
* Done with this entry, go to the next
*/
stack->off++;
}
return true;
}
/*
* Start* functions setup beginning state of searches: finds correct buffer and pins it.
*/
static void
startScanEntry(GinState *ginstate, GinScanEntry entry)
{
GinBtreeData btreeEntry;
GinBtreeStack *stackEntry;
Page page;
bool needUnlock;
restartScanEntry:
entry->buffer = InvalidBuffer;
ItemPointerSetMin(&entry->curItem);
entry->offset = InvalidOffsetNumber;
entry->list = NULL;
entry->nlist = 0;
entry->matchBitmap = NULL;
entry->matchResult = NULL;
entry->reduceResult = FALSE;
entry->predictNumberResult = 0;
/*
* we should find entry, and begin scan of posting tree or just store
* posting list in memory
*/
ginPrepareEntryScan(&btreeEntry, entry->attnum,
entry->queryKey, entry->queryCategory,
ginstate);
btreeEntry.searchMode = TRUE;
stackEntry = ginFindLeafPage(&btreeEntry, NULL);
page = BufferGetPage(stackEntry->buffer);
needUnlock = TRUE;
entry->isFinished = TRUE;
if (entry->isPartialMatch ||
entry->queryCategory == GIN_CAT_EMPTY_QUERY)
{
/*
* btreeEntry.findItem locates the first item >= given search key.
* (For GIN_CAT_EMPTY_QUERY, it will find the leftmost index item
* because of the way the GIN_CAT_EMPTY_QUERY category code is
* assigned.) We scan forward from there and collect all TIDs needed
* for the entry type.
*/
btreeEntry.findItem(&btreeEntry, stackEntry);
if (collectMatchBitmap(&btreeEntry, stackEntry, entry) == false)
{
/*
* GIN tree was seriously restructured, so we will cleanup all
* found data and rescan. See comments near 'return false' in
* collectMatchBitmap()
*/
if (entry->matchBitmap)
{
if (entry->matchIterator)
tbm_end_iterate(entry->matchIterator);
entry->matchIterator = NULL;
tbm_free(entry->matchBitmap);
entry->matchBitmap = NULL;
}
LockBuffer(stackEntry->buffer, GIN_UNLOCK);
freeGinBtreeStack(stackEntry);
goto restartScanEntry;
}
if (entry->matchBitmap && !tbm_is_empty(entry->matchBitmap))
{
entry->matchIterator = tbm_begin_iterate(entry->matchBitmap);
entry->isFinished = FALSE;
}
}
else if (btreeEntry.findItem(&btreeEntry, stackEntry))
{
IndexTuple itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, stackEntry->off));
if (GinIsPostingTree(itup))
{
BlockNumber rootPostingTree = GinGetPostingTree(itup);
GinPostingTreeScan *gdi;
Page page;
/*
* We should unlock entry page before touching posting tree to
* prevent deadlocks with vacuum processes. Because entry is never
* deleted from page and posting tree is never reduced to the
* posting list, we can unlock page after getting BlockNumber of
* root of posting tree.
*/
LockBuffer(stackEntry->buffer, GIN_UNLOCK);
needUnlock = FALSE;
gdi = ginPrepareScanPostingTree(ginstate->index, rootPostingTree, TRUE);
entry->buffer = ginScanBeginPostingTree(gdi);
/*
* We keep buffer pinned because we need to prevent deletion of
* page during scan. See GIN's vacuum implementation. RefCount is
* increased to keep buffer pinned after freeGinBtreeStack() call.
*/
IncrBufferRefCount(entry->buffer);
page = BufferGetPage(entry->buffer);
entry->predictNumberResult = gdi->stack->predictNumber * GinPageGetOpaque(page)->maxoff;
/*
* Keep page content in memory to prevent durable page locking
*/
entry->list = (ItemPointerData *) palloc(BLCKSZ);
entry->nlist = GinPageGetOpaque(page)->maxoff;
memcpy(entry->list, GinDataPageGetItem(page, FirstOffsetNumber),
GinPageGetOpaque(page)->maxoff * sizeof(ItemPointerData));
LockBuffer(entry->buffer, GIN_UNLOCK);
freeGinBtreeStack(gdi->stack);
pfree(gdi);
entry->isFinished = FALSE;
}
else if (GinGetNPosting(itup) > 0)
{
entry->nlist = GinGetNPosting(itup);
entry->list = (ItemPointerData *) palloc(sizeof(ItemPointerData) * entry->nlist);
memcpy(entry->list, GinGetPosting(itup), sizeof(ItemPointerData) * entry->nlist);
entry->isFinished = FALSE;
}
}
if (needUnlock)
LockBuffer(stackEntry->buffer, GIN_UNLOCK);
freeGinBtreeStack(stackEntry);
}
static void
startScanKey(GinState *ginstate, GinScanKey key)
{
ItemPointerSetMin(&key->curItem);
key->curItemMatches = false;
key->recheckCurItem = false;
key->isFinished = false;
}
static void
startScan(IndexScanDesc scan)
{
GinScanOpaque so = (GinScanOpaque) scan->opaque;
GinState *ginstate = &so->ginstate;
uint32 i;
for (i = 0; i < so->totalentries; i++)
startScanEntry(ginstate, so->entries[i]);
if (GinFuzzySearchLimit > 0)
{
/*
* If all of keys more than threshold we will try to reduce result, we
* hope (and only hope, for intersection operation of array our
* supposition isn't true), that total result will not more than
* minimal predictNumberResult.
*/
for (i = 0; i < so->totalentries; i++)
if (so->entries[i]->predictNumberResult <= so->totalentries * GinFuzzySearchLimit)
return;
for (i = 0; i < so->totalentries; i++)
if (so->entries[i]->predictNumberResult > so->totalentries * GinFuzzySearchLimit)
{
so->entries[i]->predictNumberResult /= so->totalentries;
so->entries[i]->reduceResult = TRUE;
}
}
for (i = 0; i < so->nkeys; i++)
startScanKey(ginstate, so->keys + i);
}
/*
* Gets next ItemPointer from PostingTree. Note, that we copy
* page into GinScanEntry->list array and unlock page, but keep it pinned
* to prevent interference with vacuum
*/
static void
entryGetNextItem(GinState *ginstate, GinScanEntry entry)
{
Page page;
BlockNumber blkno;
for (;;)
{
if (entry->offset < entry->nlist)
{
entry->curItem = entry->list[entry->offset++];
return;
}
LockBuffer(entry->buffer, GIN_SHARE);
page = BufferGetPage(entry->buffer);
for (;;)
{
/*
* It's needed to go by right link. During that we should refind
* first ItemPointer greater that stored
*/
blkno = GinPageGetOpaque(page)->rightlink;
LockBuffer(entry->buffer, GIN_UNLOCK);
if (blkno == InvalidBlockNumber)
{
ReleaseBuffer(entry->buffer);
ItemPointerSetInvalid(&entry->curItem);
entry->buffer = InvalidBuffer;
entry->isFinished = TRUE;
return;
}
entry->buffer = ReleaseAndReadBuffer(entry->buffer,
ginstate->index,
blkno);
LockBuffer(entry->buffer, GIN_SHARE);
page = BufferGetPage(entry->buffer);
entry->offset = InvalidOffsetNumber;
if (!ItemPointerIsValid(&entry->curItem) ||
findItemInPostingPage(page, &entry->curItem, &entry->offset))
{
/*
* Found position equal to or greater than stored
*/
entry->nlist = GinPageGetOpaque(page)->maxoff;
memcpy(entry->list, GinDataPageGetItem(page, FirstOffsetNumber),
GinPageGetOpaque(page)->maxoff * sizeof(ItemPointerData));
LockBuffer(entry->buffer, GIN_UNLOCK);
if (!ItemPointerIsValid(&entry->curItem) ||
ginCompareItemPointers(&entry->curItem,
entry->list + entry->offset - 1) == 0)
{
/*
* First pages are deleted or empty, or we found exact
* position, so break inner loop and continue outer one.
*/
break;
}
/*
* Find greater than entry->curItem position, store it.
*/
entry->curItem = entry->list[entry->offset - 1];
return;
}
}
}
}
#define gin_rand() (((double) random()) / ((double) MAX_RANDOM_VALUE))
#define dropItem(e) ( gin_rand() > ((double)GinFuzzySearchLimit)/((double)((e)->predictNumberResult)) )
/*
* Sets entry->curItem to next heap item pointer for one entry of one scan key,
* or sets entry->isFinished to TRUE if there are no more.
*
* Item pointers must be returned in ascending order.
*
* Note: this can return a "lossy page" item pointer, indicating that the
* entry potentially matches all items on that heap page. However, it is
* not allowed to return both a lossy page pointer and exact (regular)
* item pointers for the same page. (Doing so would break the key-combination
* logic in keyGetItem and scanGetItem; see comment in scanGetItem.) In the
* current implementation this is guaranteed by the behavior of tidbitmaps.
*/
static void
entryGetItem(GinState *ginstate, GinScanEntry entry)
{
Assert(!entry->isFinished);
if (entry->matchBitmap)
{
do
{
if (entry->matchResult == NULL ||
entry->offset >= entry->matchResult->ntuples)
{
entry->matchResult = tbm_iterate(entry->matchIterator);
if (entry->matchResult == NULL)
{
ItemPointerSetInvalid(&entry->curItem);
tbm_end_iterate(entry->matchIterator);
entry->matchIterator = NULL;
entry->isFinished = TRUE;
break;
}
/*
* Reset counter to the beginning of entry->matchResult. Note:
* entry->offset is still greater than matchResult->ntuples if
* matchResult is lossy. So, on next call we will get next
* result from TIDBitmap.
*/
entry->offset = 0;
}
if (entry->matchResult->ntuples < 0)
{
/*
* lossy result, so we need to check the whole page
*/
ItemPointerSetLossyPage(&entry->curItem,
entry->matchResult->blockno);
/*
* We might as well fall out of the loop; we could not
* estimate number of results on this page to support correct
* reducing of result even if it's enabled
*/
break;
}
ItemPointerSet(&entry->curItem,
entry->matchResult->blockno,
entry->matchResult->offsets[entry->offset]);
entry->offset++;
} while (entry->reduceResult == TRUE && dropItem(entry));
}
else if (!BufferIsValid(entry->buffer))
{
entry->offset++;
if (entry->offset <= entry->nlist)
entry->curItem = entry->list[entry->offset - 1];
else
{
ItemPointerSetInvalid(&entry->curItem);
entry->isFinished = TRUE;
}
}
else
{
do
{
entryGetNextItem(ginstate, entry);
} while (entry->isFinished == FALSE &&
entry->reduceResult == TRUE &&
dropItem(entry));
}
}
/*
* Identify the "current" item among the input entry streams for this scan key,
* and test whether it passes the scan key qual condition.
*
* The current item is the smallest curItem among the inputs. key->curItem
* is set to that value. key->curItemMatches is set to indicate whether that
* TID passes the consistentFn test. If so, key->recheckCurItem is set true
* iff recheck is needed for this item pointer (including the case where the
* item pointer is a lossy page pointer).
*
* If all entry streams are exhausted, sets key->isFinished to TRUE.
*
* Item pointers must be returned in ascending order.
*
* Note: this can return a "lossy page" item pointer, indicating that the
* key potentially matches all items on that heap page. However, it is
* not allowed to return both a lossy page pointer and exact (regular)
* item pointers for the same page. (Doing so would break the key-combination
* logic in scanGetItem.)
*/
static void
keyGetItem(GinState *ginstate, MemoryContext tempCtx, GinScanKey key)
{
ItemPointerData minItem;
ItemPointerData curPageLossy;
uint32 i;
uint32 lossyEntry;
bool haveLossyEntry;
GinScanEntry entry;
bool res;
MemoryContext oldCtx;
Assert(!key->isFinished);
/*
* Find the minimum of the active entry curItems.
*
* Note: a lossy-page entry is encoded by a ItemPointer with max value for
* offset (0xffff), so that it will sort after any exact entries for the
* same page. So we'll prefer to return exact pointers not lossy
* pointers, which is good.
*/
ItemPointerSetMax(&minItem);
for (i = 0; i < key->nentries; i++)
{
entry = key->scanEntry[i];
if (entry->isFinished == FALSE &&
ginCompareItemPointers(&entry->curItem, &minItem) < 0)
minItem = entry->curItem;
}
if (ItemPointerIsMax(&minItem))
{
/* all entries are finished */
key->isFinished = TRUE;
return;
}
/*
* We might have already tested this item; if so, no need to repeat work.
* (Note: the ">" case can happen, if minItem is exact but we previously
* had to set curItem to a lossy-page pointer.)
*/
if (ginCompareItemPointers(&key->curItem, &minItem) >= 0)
return;
/*
* OK, advance key->curItem and perform consistentFn test.
*/
key->curItem = minItem;
/*
* Lossy-page entries pose a problem, since we don't know the correct
* entryRes state to pass to the consistentFn, and we also don't know what
* its combining logic will be (could be AND, OR, or even NOT). If the
* logic is OR then the consistentFn might succeed for all items in the
* lossy page even when none of the other entries match.
*
* If we have a single lossy-page entry then we check to see if the
* consistentFn will succeed with only that entry TRUE. If so, we return
* a lossy-page pointer to indicate that the whole heap page must be
* checked. (On subsequent calls, we'll do nothing until minItem is past
* the page altogether, thus ensuring that we never return both regular
* and lossy pointers for the same page.)
*
* This idea could be generalized to more than one lossy-page entry, but
* ideally lossy-page entries should be infrequent so it would seldom be
* the case that we have more than one at once. So it doesn't seem worth
* the extra complexity to optimize that case. If we do find more than
* one, we just punt and return a lossy-page pointer always.
*
* Note that only lossy-page entries pointing to the current item's page
* should trigger this processing; we might have future lossy pages in the
* entry array, but they aren't relevant yet.
*/
ItemPointerSetLossyPage(&curPageLossy,
GinItemPointerGetBlockNumber(&key->curItem));
lossyEntry = 0;
haveLossyEntry = false;
for (i = 0; i < key->nentries; i++)
{
entry = key->scanEntry[i];
if (entry->isFinished == FALSE &&
ginCompareItemPointers(&entry->curItem, &curPageLossy) == 0)
{
if (haveLossyEntry)
{
/* Multiple lossy entries, punt */
key->curItem = curPageLossy;
key->curItemMatches = true;
key->recheckCurItem = true;
return;
}
lossyEntry = i;
haveLossyEntry = true;
}
}
/* prepare for calling consistentFn in temp context */
oldCtx = MemoryContextSwitchTo(tempCtx);
if (haveLossyEntry)
{
/* Single lossy-page entry, so see if whole page matches */
memset(key->entryRes, FALSE, key->nentries);
key->entryRes[lossyEntry] = TRUE;
if (callConsistentFn(ginstate, key))
{
/* Yes, so clean up ... */
MemoryContextSwitchTo(oldCtx);
MemoryContextReset(tempCtx);
/* and return lossy pointer for whole page */
key->curItem = curPageLossy;
key->curItemMatches = true;
key->recheckCurItem = true;
return;
}
}
/*
* At this point we know that we don't need to return a lossy whole-page
* pointer, but we might have matches for individual exact item pointers,
* possibly in combination with a lossy pointer. Our strategy if there's
* a lossy pointer is to try the consistentFn both ways and return a hit
* if it accepts either one (forcing the hit to be marked lossy so it will
* be rechecked). An exception is that we don't need to try it both ways
* if the lossy pointer is in a "hidden" entry, because the consistentFn's
* result can't depend on that.
*
* Prepare entryRes array to be passed to consistentFn.
*/
for (i = 0; i < key->nentries; i++)
{
entry = key->scanEntry[i];
if (entry->isFinished == FALSE &&
ginCompareItemPointers(&entry->curItem, &key->curItem) == 0)
key->entryRes[i] = TRUE;
else
key->entryRes[i] = FALSE;
}
if (haveLossyEntry)
key->entryRes[lossyEntry] = TRUE;
res = callConsistentFn(ginstate, key);
if (!res && haveLossyEntry && lossyEntry < key->nuserentries)
{
/* try the other way for the lossy item */
key->entryRes[lossyEntry] = FALSE;
res = callConsistentFn(ginstate, key);
}
key->curItemMatches = res;
/* If we matched a lossy entry, force recheckCurItem = true */
if (haveLossyEntry)
key->recheckCurItem = true;
/* clean up after consistentFn calls */
MemoryContextSwitchTo(oldCtx);
MemoryContextReset(tempCtx);
}
/*
* Get next heap item pointer (after advancePast) from scan.
* Returns true if anything found.
* On success, *item and *recheck are set.
*
* Note: this is very nearly the same logic as in keyGetItem(), except
* that we know the keys are to be combined with AND logic, whereas in
* keyGetItem() the combination logic is known only to the consistentFn.
*/
static bool
scanGetItem(IndexScanDesc scan, ItemPointer advancePast,
ItemPointerData *item, bool *recheck)
{
GinScanOpaque so = (GinScanOpaque) scan->opaque;
GinState *ginstate = &so->ginstate;
ItemPointerData myAdvancePast = *advancePast;
uint32 i;
bool allFinished;
bool match;
for (;;)
{
/*
* Advance any entries that are <= myAdvancePast. In particular,
* since entry->curItem was initialized with ItemPointerSetMin, this
* ensures we fetch the first item for each entry on the first call.
*/
allFinished = TRUE;
for (i = 0; i < so->totalentries; i++)
{
GinScanEntry entry = so->entries[i];
while (entry->isFinished == FALSE &&
ginCompareItemPointers(&entry->curItem,
&myAdvancePast) <= 0)
entryGetItem(ginstate, entry);
if (entry->isFinished == FALSE)
allFinished = FALSE;
}
if (allFinished)
{
/* all entries exhausted, so we're done */
return false;
}
/*
* Perform the consistentFn test for each scan key. If any key
* reports isFinished, meaning its subset of the entries is exhausted,
* we can stop. Otherwise, set *item to the minimum of the key
* curItems.
*/
ItemPointerSetMax(item);
for (i = 0; i < so->nkeys; i++)
{
GinScanKey key = so->keys + i;
keyGetItem(&so->ginstate, so->tempCtx, key);
if (key->isFinished)
return false; /* finished one of keys */
if (ginCompareItemPointers(&key->curItem, item) < 0)
*item = key->curItem;
}
Assert(!ItemPointerIsMax(item));
/*----------
* Now *item contains first ItemPointer after previous result.
*
* The item is a valid hit only if all the keys succeeded for either
* that exact TID, or a lossy reference to the same page.
*
* This logic works only if a keyGetItem stream can never contain both
* exact and lossy pointers for the same page. Else we could have a
* case like
*
* stream 1 stream 2
* ... ...
* 42/6 42/7
* 50/1 42/0xffff
* ... ...
*
* We would conclude that 42/6 is not a match and advance stream 1,
* thus never detecting the match to the lossy pointer in stream 2.
* (keyGetItem has a similar problem versus entryGetItem.)
*----------
*/
match = true;
for (i = 0; i < so->nkeys; i++)
{
GinScanKey key = so->keys + i;
if (key->curItemMatches)
{
if (ginCompareItemPointers(item, &key->curItem) == 0)
continue;
if (ItemPointerIsLossyPage(&key->curItem) &&
GinItemPointerGetBlockNumber(&key->curItem) ==
GinItemPointerGetBlockNumber(item))
continue;
}
match = false;
break;
}
if (match)
break;
/*
* No hit. Update myAdvancePast to this TID, so that on the next pass
* we'll move to the next possible entry.
*/
myAdvancePast = *item;
}
/*
* We must return recheck = true if any of the keys are marked recheck.
*/
*recheck = false;
for (i = 0; i < so->nkeys; i++)
{
GinScanKey key = so->keys + i;
if (key->recheckCurItem)
{
*recheck = true;
break;
}
}
return TRUE;
}
/*
* Functions for scanning the pending list
*/
/*
* Get ItemPointer of next heap row to be checked from pending list.
* Returns false if there are no more. On pages with several heap rows
* it returns each row separately, on page with part of heap row returns
* per page data. pos->firstOffset and pos->lastOffset are set to identify
* the range of pending-list tuples belonging to this heap row.
*
* The pendingBuffer is presumed pinned and share-locked on entry, and is
* pinned and share-locked on success exit. On failure exit it's released.
*/
static bool
scanGetCandidate(IndexScanDesc scan, pendingPosition *pos)
{
OffsetNumber maxoff;
Page page;
IndexTuple itup;
ItemPointerSetInvalid(&pos->item);
for (;;)
{
page = BufferGetPage(pos->pendingBuffer);
maxoff = PageGetMaxOffsetNumber(page);
if (pos->firstOffset > maxoff)
{
BlockNumber blkno = GinPageGetOpaque(page)->rightlink;
if (blkno == InvalidBlockNumber)
{
UnlockReleaseBuffer(pos->pendingBuffer);
pos->pendingBuffer = InvalidBuffer;
return false;
}
else
{
/*
* Here we must prevent deletion of next page by insertcleanup
* process, which may be trying to obtain exclusive lock on
* current page. So, we lock next page before releasing the
* current one
*/
Buffer tmpbuf = ReadBuffer(scan->indexRelation, blkno);
LockBuffer(tmpbuf, GIN_SHARE);
UnlockReleaseBuffer(pos->pendingBuffer);
pos->pendingBuffer = tmpbuf;
pos->firstOffset = FirstOffsetNumber;
}
}
else
{
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, pos->firstOffset));
pos->item = itup->t_tid;
if (GinPageHasFullRow(page))
{
/*
* find itempointer to the next row
*/
for (pos->lastOffset = pos->firstOffset + 1; pos->lastOffset <= maxoff; pos->lastOffset++)
{
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, pos->lastOffset));
if (!ItemPointerEquals(&pos->item, &itup->t_tid))
break;
}
}
else
{
/*
* All itempointers are the same on this page
*/
pos->lastOffset = maxoff + 1;
}
/*
* Now pos->firstOffset points to the first tuple of current heap
* row, pos->lastOffset points to the first tuple of next heap row
* (or to the end of page)
*/
break;
}
}
return true;
}
/*
* Scan pending-list page from current tuple (off) up till the first of:
* - match is found (then returns true)
* - no later match is possible
* - tuple's attribute number is not equal to entry's attrnum
* - reach end of page
*
* datum[]/category[]/datumExtracted[] arrays are used to cache the results
* of gintuple_get_key() on the current page.
*/
static bool
matchPartialInPendingList(GinState *ginstate, Page page,
OffsetNumber off, OffsetNumber maxoff,
GinScanEntry entry,
Datum *datum, GinNullCategory *category,
bool *datumExtracted)
{
IndexTuple itup;
int32 cmp;
/* Partial match to a null is not possible */
if (entry->queryCategory != GIN_CAT_NORM_KEY)
return false;
while (off < maxoff)
{
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, off));
if (gintuple_get_attrnum(ginstate, itup) != entry->attnum)
return false;
if (datumExtracted[off - 1] == false)
{
datum[off - 1] = gintuple_get_key(ginstate, itup,
&category[off - 1]);
datumExtracted[off - 1] = true;
}
/* Once we hit nulls, no further match is possible */
if (category[off - 1] != GIN_CAT_NORM_KEY)
return false;
/*----------
* Check partial match.
* case cmp == 0 => match
* case cmp > 0 => not match and end scan (no later match possible)
* case cmp < 0 => not match and continue scan
*----------
*/
cmp = DatumGetInt32(FunctionCall4(&ginstate->comparePartialFn[entry->attnum - 1],
entry->queryKey,
datum[off - 1],
UInt16GetDatum(entry->strategy),
PointerGetDatum(entry->extra_data)));
if (cmp == 0)
return true;
else if (cmp > 0)
return false;
off++;
}
return false;
}
/*
* Set up the entryRes array for each key by looking at
* every entry for current heap row in pending list.
*
* Returns true if each scan key has at least one entryRes match.
* This corresponds to the situations where the normal index search will
* try to apply the key's consistentFn. (A tuple not meeting that requirement
* cannot be returned by the normal search since no entry stream will
* source its TID.)
*
* The pendingBuffer is presumed pinned and share-locked on entry.
*/
static bool
collectMatchesForHeapRow(IndexScanDesc scan, pendingPosition *pos)
{
GinScanOpaque so = (GinScanOpaque) scan->opaque;
OffsetNumber attrnum;
Page page;
IndexTuple itup;
int i,
j;
/*
* Reset all entryRes and hasMatchKey flags
*/
for (i = 0; i < so->nkeys; i++)
{
GinScanKey key = so->keys + i;
memset(key->entryRes, FALSE, key->nentries);
}
memset(pos->hasMatchKey, FALSE, so->nkeys);
/*
* Outer loop iterates over multiple pending-list pages when a single heap
* row has entries spanning those pages.
*/
for (;;)
{
Datum datum[BLCKSZ / sizeof(IndexTupleData)];
GinNullCategory category[BLCKSZ / sizeof(IndexTupleData)];
bool datumExtracted[BLCKSZ / sizeof(IndexTupleData)];
Assert(pos->lastOffset > pos->firstOffset);
memset(datumExtracted + pos->firstOffset - 1, 0,
sizeof(bool) * (pos->lastOffset - pos->firstOffset));
page = BufferGetPage(pos->pendingBuffer);
for (i = 0; i < so->nkeys; i++)
{
GinScanKey key = so->keys + i;
for (j = 0; j < key->nentries; j++)
{
GinScanEntry entry = key->scanEntry[j];
OffsetNumber StopLow = pos->firstOffset,
StopHigh = pos->lastOffset,
StopMiddle;
/* If already matched on earlier page, do no extra work */
if (key->entryRes[j])
continue;
/*
* Interesting tuples are from pos->firstOffset to
* pos->lastOffset and they are ordered by (attnum, Datum) as
* it's done in entry tree. So we can use binary search to
* avoid linear scanning.
*/
while (StopLow < StopHigh)
{
int res;
StopMiddle = StopLow + ((StopHigh - StopLow) >> 1);
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, StopMiddle));
attrnum = gintuple_get_attrnum(&so->ginstate, itup);
if (key->attnum < attrnum)
{
StopHigh = StopMiddle;
continue;
}
if (key->attnum > attrnum)
{
StopLow = StopMiddle + 1;
continue;
}
if (datumExtracted[StopMiddle - 1] == false)
{
datum[StopMiddle - 1] =
gintuple_get_key(&so->ginstate, itup,
&category[StopMiddle - 1]);
datumExtracted[StopMiddle - 1] = true;
}
if (entry->queryCategory == GIN_CAT_EMPTY_QUERY)
{
/* special behavior depending on searchMode */
if (entry->searchMode == GIN_SEARCH_MODE_ALL)
{
/* match anything except NULL_ITEM */
if (category[StopMiddle - 1] == GIN_CAT_NULL_ITEM)
res = -1;
else
res = 0;
}
else
{
/* match everything */
res = 0;
}
}
else
{
res = ginCompareEntries(&so->ginstate,
entry->attnum,
entry->queryKey,
entry->queryCategory,
datum[StopMiddle - 1],
category[StopMiddle - 1]);
}
if (res == 0)
{
/*
* Found exact match (there can be only one, except in
* EMPTY_QUERY mode).
*
* If doing partial match, scan forward from here to
* end of page to check for matches.
*
* See comment above about tuple's ordering.
*/
if (entry->isPartialMatch)
key->entryRes[j] =
matchPartialInPendingList(&so->ginstate,
page,
StopMiddle,
pos->lastOffset,
entry,
datum,
category,
datumExtracted);
else
key->entryRes[j] = true;
/* done with binary search */
break;
}
else if (res < 0)
StopHigh = StopMiddle;
else
StopLow = StopMiddle + 1;
}
if (StopLow >= StopHigh && entry->isPartialMatch)
{
/*
* No exact match on this page. If doing partial match,
* scan from the first tuple greater than target value to
* end of page. Note that since we don't remember whether
* the comparePartialFn told us to stop early on a
* previous page, we will uselessly apply comparePartialFn
* to the first tuple on each subsequent page.
*/
key->entryRes[j] =
matchPartialInPendingList(&so->ginstate,
page,
StopHigh,
pos->lastOffset,
entry,
datum,
category,
datumExtracted);
}
pos->hasMatchKey[i] |= key->entryRes[j];
}
}
/* Advance firstOffset over the scanned tuples */
pos->firstOffset = pos->lastOffset;
if (GinPageHasFullRow(page))
{
/*
* We have examined all pending entries for the current heap row.
* Break out of loop over pages.
*/
break;
}
else
{
/*
* Advance to next page of pending entries for the current heap
* row. Complain if there isn't one.
*/
ItemPointerData item = pos->item;
if (scanGetCandidate(scan, pos) == false ||
!ItemPointerEquals(&pos->item, &item))
elog(ERROR, "could not find additional pending pages for same heap tuple");
}
}
/*
* Now return "true" if all scan keys have at least one matching datum
*/
for (i = 0; i < so->nkeys; i++)
{
if (pos->hasMatchKey[i] == false)
return false;
}
return true;
}
/*
* Collect all matched rows from pending list into bitmap
*/
static void
scanPendingInsert(IndexScanDesc scan, TIDBitmap *tbm, int64 *ntids)
{
GinScanOpaque so = (GinScanOpaque) scan->opaque;
MemoryContext oldCtx;
bool recheck,
match;
int i;
pendingPosition pos;
Buffer metabuffer = ReadBuffer(scan->indexRelation, GIN_METAPAGE_BLKNO);
BlockNumber blkno;
*ntids = 0;
LockBuffer(metabuffer, GIN_SHARE);
blkno = GinPageGetMeta(BufferGetPage(metabuffer))->head;
/*
* fetch head of list before unlocking metapage. head page must be pinned
* to prevent deletion by vacuum process
*/
if (blkno == InvalidBlockNumber)
{
/* No pending list, so proceed with normal scan */
UnlockReleaseBuffer(metabuffer);
return;
}
pos.pendingBuffer = ReadBuffer(scan->indexRelation, blkno);
LockBuffer(pos.pendingBuffer, GIN_SHARE);
pos.firstOffset = FirstOffsetNumber;
UnlockReleaseBuffer(metabuffer);
pos.hasMatchKey = palloc(sizeof(bool) * so->nkeys);
/*
* loop for each heap row. scanGetCandidate returns full row or row's
* tuples from first page.
*/
while (scanGetCandidate(scan, &pos))
{
/*
* Check entries in tuple and set up entryRes array.
*
* If pending tuples belonging to the current heap row are spread
* across several pages, collectMatchesForHeapRow will read all of
* those pages.
*/
if (!collectMatchesForHeapRow(scan, &pos))
continue;
/*
* Matching of entries of one row is finished, so check row using
* consistent functions.
*/
oldCtx = MemoryContextSwitchTo(so->tempCtx);
recheck = false;
match = true;
for (i = 0; i < so->nkeys; i++)
{
GinScanKey key = so->keys + i;
if (!callConsistentFn(&so->ginstate, key))
{
match = false;
break;
}
recheck |= key->recheckCurItem;
}
MemoryContextSwitchTo(oldCtx);
MemoryContextReset(so->tempCtx);
if (match)
{
tbm_add_tuples(tbm, &pos.item, 1, recheck);
(*ntids)++;
}
}
pfree(pos.hasMatchKey);
}
#define GinIsNewKey(s) ( ((GinScanOpaque) scan->opaque)->keys == NULL )
#define GinIsVoidRes(s) ( ((GinScanOpaque) scan->opaque)->isVoidRes )
Datum
gingetbitmap(PG_FUNCTION_ARGS)
{
IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
TIDBitmap *tbm = (TIDBitmap *) PG_GETARG_POINTER(1);
int64 ntids;
ItemPointerData iptr;
bool recheck;
/*
* Set up the scan keys, and check for unsatisfiable query.
*/
if (GinIsNewKey(scan))
ginNewScanKey(scan);
if (GinIsVoidRes(scan))
PG_RETURN_INT64(0);
ntids = 0;
/*
* First, scan the pending list and collect any matching entries into the
* bitmap. After we scan a pending item, some other backend could post it
* into the main index, and so we might visit it a second time during the
* main scan. This is okay because we'll just re-set the same bit in the
* bitmap. (The possibility of duplicate visits is a major reason why GIN
* can't support the amgettuple API, however.) Note that it would not do
* to scan the main index before the pending list, since concurrent
* cleanup could then make us miss entries entirely.
*/
scanPendingInsert(scan, tbm, &ntids);
/*
* Now scan the main index.
*/
startScan(scan);
ItemPointerSetMin(&iptr);
for (;;)
{
CHECK_FOR_INTERRUPTS();
if (!scanGetItem(scan, &iptr, &iptr, &recheck))
break;
if (ItemPointerIsLossyPage(&iptr))
tbm_add_page(tbm, ItemPointerGetBlockNumber(&iptr));
else
tbm_add_tuples(tbm, &iptr, 1, recheck);
ntids++;
}
PG_RETURN_INT64(ntids);
}
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