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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) 1996-2020, 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 "miscadmin.h"
#include "storage/predicate.h"
#include "utils/datum.h"
#include "utils/memutils.h"
#include "utils/rel.h"
/* GUC parameter */
int GinFuzzySearchLimit = 0;
typedef struct pendingPosition
{
Buffer pendingBuffer;
OffsetNumber firstOffset;
OffsetNumber lastOffset;
ItemPointerData item;
bool *hasMatchKey;
} pendingPosition;
/*
* Goes to the next page if current offset is outside of bounds
*/
static bool
moveRightIfItNeeded(GinBtreeData *btree, GinBtreeStack *stack, Snapshot snapshot)
{
Page page = BufferGetPage(stack->buffer);
if (stack->off > PageGetMaxOffsetNumber(page))
{
/*
* We scanned the whole page, so we should take right page
*/
if (GinPageRightMost(page))
return false; /* no more pages */
stack->buffer = ginStepRight(stack->buffer, btree->index, GIN_SHARE);
stack->blkno = BufferGetBlockNumber(stack->buffer);
stack->off = FirstOffsetNumber;
PredicateLockPage(btree->index, stack->blkno, snapshot);
}
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, Snapshot snapshot)
{
GinBtreeData btree;
GinBtreeStack *stack;
Buffer buffer;
Page page;
/* Descend to the leftmost leaf page */
stack = ginScanBeginPostingTree(&btree, index, rootPostingTree, snapshot);
buffer = stack->buffer;
IncrBufferRefCount(buffer); /* prevent unpin in freeGinBtreeStack */
freeGinBtreeStack(stack);
/*
* Loop iterates through all leaf pages of posting tree
*/
for (;;)
{
page = BufferGetPage(buffer);
if ((GinPageGetOpaque(page)->flags & GIN_DELETED) == 0)
{
int n = GinDataLeafPageGetItemsToTbm(page, scanEntry->matchBitmap);
scanEntry->predictNumberResult += n;
}
if (GinPageRightMost(page))
break; /* no more pages */
buffer = ginStepRight(buffer, index, 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, Snapshot snapshot)
{
OffsetNumber attnum;
Form_pg_attribute attr;
/* Initialize empty bitmap result */
scanEntry->matchBitmap = tbm_create(work_mem * 1024L, NULL);
/* 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 = TupleDescAttr(btree->ginstate->origTupdesc, attnum - 1);
/*
* Predicate lock entry leaf page, following pages will be locked by
* moveRightIfItNeeded()
*/
PredicateLockPage(btree->index, stack->buffer, snapshot);
for (;;)
{
Page page;
IndexTuple itup;
Datum idatum;
GinNullCategory icategory;
/*
* stack->off points to the interested entry, buffer is already locked
*/
if (moveRightIfItNeeded(btree, stack, snapshot) == false)
return true;
page = BufferGetPage(stack->buffer);
TestForOldSnapshot(snapshot, btree->index, page);
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(FunctionCall4Coll(&btree->ginstate->comparePartialFn[attnum - 1],
btree->ginstate->supportCollation[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);
/*
* Acquire predicate lock on the posting tree. We already hold a
* lock on the entry page, but insertions to the posting tree
* don't check for conflicts on that level.
*/
PredicateLockPage(btree->index, rootPostingTree, snapshot);
/* Collect all the TIDs in this entry's posting tree */
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);
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, snapshot) == 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
{
ItemPointer ipd;
int nipd;
ipd = ginReadTuple(btree->ginstate, scanEntry->attnum, itup, &nipd);
tbm_add_tuples(scanEntry->matchBitmap, ipd, nipd, false);
scanEntry->predictNumberResult += GinGetNPosting(itup);
pfree(ipd);
}
/*
* Done with this entry, go to the next
*/
stack->off++;
}
}
/*
* Start* functions setup beginning state of searches: finds correct buffer and pins it.
*/
static void
startScanEntry(GinState *ginstate, GinScanEntry entry, Snapshot snapshot)
{
GinBtreeData btreeEntry;
GinBtreeStack *stackEntry;
Page page;
bool needUnlock;
restartScanEntry:
entry->buffer = InvalidBuffer;
ItemPointerSetMin(&entry->curItem);
entry->offset = InvalidOffsetNumber;
if (entry->list)
pfree(entry->list);
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);
stackEntry = ginFindLeafPage(&btreeEntry, true, false, snapshot);
page = BufferGetPage(stackEntry->buffer);
/* ginFindLeafPage() will have already checked snapshot age. */
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, snapshot)
== 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);
GinBtreeStack *stack;
Page page;
ItemPointerData minItem;
/*
* This is an equality scan, so lock the root of the posting tree.
* It represents a lock on the exact key value, and covers all the
* items in the posting tree.
*/
PredicateLockPage(ginstate->index, rootPostingTree, snapshot);
/*
* 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;
stack = ginScanBeginPostingTree(&entry->btree, ginstate->index,
rootPostingTree, snapshot);
entry->buffer = stack->buffer;
/*
* 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);
/*
* Load the first page into memory.
*/
ItemPointerSetMin(&minItem);
entry->list = GinDataLeafPageGetItems(page, &entry->nlist, minItem);
entry->predictNumberResult = stack->predictNumber * entry->nlist;
LockBuffer(entry->buffer, GIN_UNLOCK);
freeGinBtreeStack(stack);
entry->isFinished = false;
}
else
{
/*
* Lock the entry leaf page. This is more coarse-grained than
* necessary, because it will conflict with any insertions that
* land on the same leaf page, not only the exact key we searched
* for. But locking an individual tuple would require updating
* that lock whenever it moves because of insertions or vacuums,
* which seems too complicated.
*/
PredicateLockPage(ginstate->index,
BufferGetBlockNumber(stackEntry->buffer),
snapshot);
if (GinGetNPosting(itup) > 0)
{
entry->list = ginReadTuple(ginstate, entry->attnum, itup,
&entry->nlist);
entry->predictNumberResult = entry->nlist;
entry->isFinished = false;
}
}
}
else
{
/*
* No entry found. Predicate lock the leaf page, to lock the place
* where the entry would've been, had there been one.
*/
PredicateLockPage(ginstate->index,
BufferGetBlockNumber(stackEntry->buffer), snapshot);
}
if (needUnlock)
LockBuffer(stackEntry->buffer, GIN_UNLOCK);
freeGinBtreeStack(stackEntry);
}
/*
* Comparison function for scan entry indexes. Sorts by predictNumberResult,
* least frequent items first.
*/
static int
entryIndexByFrequencyCmp(const void *a1, const void *a2, void *arg)
{
const GinScanKey key = (const GinScanKey) arg;
int i1 = *(const int *) a1;
int i2 = *(const int *) a2;
uint32 n1 = key->scanEntry[i1]->predictNumberResult;
uint32 n2 = key->scanEntry[i2]->predictNumberResult;
if (n1 < n2)
return -1;
else if (n1 == n2)
return 0;
else
return 1;
}
static void
startScanKey(GinState *ginstate, GinScanOpaque so, GinScanKey key)
{
MemoryContext oldCtx = CurrentMemoryContext;
int i;
int j;
int *entryIndexes;
ItemPointerSetMin(&key->curItem);
key->curItemMatches = false;
key->recheckCurItem = false;
key->isFinished = false;
/*
* Divide the entries into two distinct sets: required and additional.
* Additional entries are not enough for a match alone, without any items
* from the required set, but are needed by the consistent function to
* decide if an item matches. When scanning, we can skip over items from
* additional entries that have no corresponding matches in any of the
* required entries. That speeds up queries like "frequent & rare"
* considerably, if the frequent term can be put in the additional set.
*
* There can be many legal ways to divide them entries into these two
* sets. A conservative division is to just put everything in the required
* set, but the more you can put in the additional set, the more you can
* skip during the scan. To maximize skipping, we try to put as many
* frequent items as possible into additional, and less frequent ones into
* required. To do that, sort the entries by frequency
* (predictNumberResult), and put entries into the required set in that
* order, until the consistent function says that none of the remaining
* entries can form a match, without any items from the required set. The
* rest go to the additional set.
*/
if (key->nentries > 1)
{
MemoryContextSwitchTo(so->tempCtx);
entryIndexes = (int *) palloc(sizeof(int) * key->nentries);
for (i = 0; i < key->nentries; i++)
entryIndexes[i] = i;
qsort_arg(entryIndexes, key->nentries, sizeof(int),
entryIndexByFrequencyCmp, key);
for (i = 0; i < key->nentries - 1; i++)
{
/* Pass all entries <= i as FALSE, and the rest as MAYBE */
for (j = 0; j <= i; j++)
key->entryRes[entryIndexes[j]] = GIN_FALSE;
for (j = i + 1; j < key->nentries; j++)
key->entryRes[entryIndexes[j]] = GIN_MAYBE;
if (key->triConsistentFn(key) == GIN_FALSE)
break;
}
/* i is now the last required entry. */
MemoryContextSwitchTo(so->keyCtx);
key->nrequired = i + 1;
key->nadditional = key->nentries - key->nrequired;
key->requiredEntries = palloc(key->nrequired * sizeof(GinScanEntry));
key->additionalEntries = palloc(key->nadditional * sizeof(GinScanEntry));
j = 0;
for (i = 0; i < key->nrequired; i++)
key->requiredEntries[i] = key->scanEntry[entryIndexes[j++]];
for (i = 0; i < key->nadditional; i++)
key->additionalEntries[i] = key->scanEntry[entryIndexes[j++]];
/* clean up after consistentFn calls (also frees entryIndexes) */
MemoryContextReset(so->tempCtx);
}
else
{
MemoryContextSwitchTo(so->keyCtx);
key->nrequired = 1;
key->nadditional = 0;
key->requiredEntries = palloc(1 * sizeof(GinScanEntry));
key->requiredEntries[0] = key->scanEntry[0];
}
MemoryContextSwitchTo(oldCtx);
}
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], scan->xs_snapshot);
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.
*/
bool reduce = true;
for (i = 0; i < so->totalentries; i++)
{
if (so->entries[i]->predictNumberResult <= so->totalentries * GinFuzzySearchLimit)
{
reduce = false;
break;
}
}
if (reduce)
{
for (i = 0; i < so->totalentries; i++)
{
so->entries[i]->predictNumberResult /= so->totalentries;
so->entries[i]->reduceResult = true;
}
}
}
/*
* Now that we have the estimates for the entry frequencies, finish
* initializing the scan keys.
*/
for (i = 0; i < so->nkeys; i++)
startScanKey(ginstate, so, so->keys + i);
}
/*
* Load the next batch of item pointers from a posting tree.
*
* Note that we copy the page into GinScanEntry->list array and unlock it, but
* keep it pinned to prevent interference with vacuum.
*/
static void
entryLoadMoreItems(GinState *ginstate, GinScanEntry entry,
ItemPointerData advancePast, Snapshot snapshot)
{
Page page;
int i;
bool stepright;
if (!BufferIsValid(entry->buffer))
{
entry->isFinished = true;
return;
}
/*
* We have two strategies for finding the correct page: step right from
* the current page, or descend the tree again from the root. If
* advancePast equals the current item, the next matching item should be
* on the next page, so we step right. Otherwise, descend from root.
*/
if (ginCompareItemPointers(&entry->curItem, &advancePast) == 0)
{
stepright = true;
LockBuffer(entry->buffer, GIN_SHARE);
}
else
{
GinBtreeStack *stack;
ReleaseBuffer(entry->buffer);
/*
* Set the search key, and find the correct leaf page.
*/
if (ItemPointerIsLossyPage(&advancePast))
{
ItemPointerSet(&entry->btree.itemptr,
GinItemPointerGetBlockNumber(&advancePast) + 1,
FirstOffsetNumber);
}
else
{
ItemPointerSet(&entry->btree.itemptr,
GinItemPointerGetBlockNumber(&advancePast),
OffsetNumberNext(GinItemPointerGetOffsetNumber(&advancePast)));
}
entry->btree.fullScan = false;
stack = ginFindLeafPage(&entry->btree, true, false, snapshot);
/* we don't need the stack, just the buffer. */
entry->buffer = stack->buffer;
IncrBufferRefCount(entry->buffer);
freeGinBtreeStack(stack);
stepright = false;
}
elog(DEBUG2, "entryLoadMoreItems, %u/%u, skip: %d",
GinItemPointerGetBlockNumber(&advancePast),
GinItemPointerGetOffsetNumber(&advancePast),
!stepright);
page = BufferGetPage(entry->buffer);
for (;;)
{
entry->offset = InvalidOffsetNumber;
if (entry->list)
{
pfree(entry->list);
entry->list = NULL;
entry->nlist = 0;
}
if (stepright)
{
/*
* We've processed all the entries on this page. If it was the
* last page in the tree, we're done.
*/
if (GinPageRightMost(page))
{
UnlockReleaseBuffer(entry->buffer);
entry->buffer = InvalidBuffer;
entry->isFinished = true;
return;
}
/*
* Step to next page, following the right link. then find the
* first ItemPointer greater than advancePast.
*/
entry->buffer = ginStepRight(entry->buffer,
ginstate->index,
GIN_SHARE);
page = BufferGetPage(entry->buffer);
}
stepright = true;
if (GinPageGetOpaque(page)->flags & GIN_DELETED)
continue; /* page was deleted by concurrent vacuum */
/*
* The first item > advancePast might not be on this page, but
* somewhere to the right, if the page was split, or a non-match from
* another key in the query allowed us to skip some items from this
* entry. Keep following the right-links until we re-find the correct
* page.
*/
if (!GinPageRightMost(page) &&
ginCompareItemPointers(&advancePast, GinDataPageGetRightBound(page)) >= 0)
{
/*
* the item we're looking is > the right bound of the page, so it
* can't be on this page.
*/
continue;
}
entry->list = GinDataLeafPageGetItems(page, &entry->nlist, advancePast);
for (i = 0; i < entry->nlist; i++)
{
if (ginCompareItemPointers(&advancePast, &entry->list[i]) < 0)
{
entry->offset = i;
if (GinPageRightMost(page))
{
/* after processing the copied items, we're done. */
UnlockReleaseBuffer(entry->buffer);
entry->buffer = InvalidBuffer;
}
else
LockBuffer(entry->buffer, GIN_UNLOCK);
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 > advancePast, for one entry
* of one scan key, or sets entry->isFinished to true if there are no more.
*
* Item pointers are 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,
ItemPointerData advancePast, Snapshot snapshot)
{
Assert(!entry->isFinished);
Assert(!ItemPointerIsValid(&entry->curItem) ||
ginCompareItemPointers(&entry->curItem, &advancePast) <= 0);
if (entry->matchBitmap)
{
/* A bitmap result */
BlockNumber advancePastBlk = GinItemPointerGetBlockNumber(&advancePast);
OffsetNumber advancePastOff = GinItemPointerGetOffsetNumber(&advancePast);
bool gotitem = false;
do
{
/*
* If we've exhausted all items on this block, move to next block
* in the bitmap.
*/
while (entry->matchResult == NULL ||
(entry->matchResult->ntuples >= 0 &&
entry->offset >= entry->matchResult->ntuples) ||
entry->matchResult->blockno < advancePastBlk ||
(ItemPointerIsLossyPage(&advancePast) &&
entry->matchResult->blockno == advancePastBlk))
{
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->isFinished)
break;
/*
* 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)
{
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.
*/
gotitem = true;
break;
}
/*
* Not a lossy page. Skip over any offsets <= advancePast, and
* return that.
*/
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.
*/
if (entry->matchResult->offsets[entry->matchResult->ntuples - 1] <= advancePastOff)
{
entry->offset = entry->matchResult->ntuples;
continue;
}
/* Otherwise scan to find the first item > advancePast */
while (entry->matchResult->offsets[entry->offset] <= advancePastOff)
entry->offset++;
}
ItemPointerSet(&entry->curItem,
entry->matchResult->blockno,
entry->matchResult->offsets[entry->offset]);
entry->offset++;
gotitem = true;
} while (!gotitem || (entry->reduceResult == true && dropItem(entry)));
}
else if (!BufferIsValid(entry->buffer))
{
/*
* A posting list from an entry tuple, or the last page of a posting
* tree.
*/
do
{
if (entry->offset >= entry->nlist)
{
ItemPointerSetInvalid(&entry->curItem);
entry->isFinished = true;
break;
}
entry->curItem = entry->list[entry->offset++];
} while (ginCompareItemPointers(&entry->curItem, &advancePast) <= 0);
/* XXX: shouldn't we apply the fuzzy search limit here? */
}
else
{
/* A posting tree */
do
{
/* If we've processed the current batch, load more items */
while (entry->offset >= entry->nlist)
{
entryLoadMoreItems(ginstate, entry, advancePast, snapshot);
if (entry->isFinished)
{
ItemPointerSetInvalid(&entry->curItem);
return;
}
}
entry->curItem = entry->list[entry->offset++];
} while (ginCompareItemPointers(&entry->curItem, &advancePast) <= 0 ||
(entry->reduceResult == true && dropItem(entry)));
}
}
/*
* Identify the "current" item among the input entry streams for this scan key
* that is greater than advancePast, 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 advancePast, Snapshot snapshot)
{
ItemPointerData minItem;
ItemPointerData curPageLossy;
uint32 i;
bool haveLossyEntry;
GinScanEntry entry;
GinTernaryValue res;
MemoryContext oldCtx;
bool allFinished;
Assert(!key->isFinished);
/*
* We might have already tested this item; if so, no need to repeat work.
* (Note: the ">" case can happen, if advancePast is exact but we
* previously had to set curItem to a lossy-page pointer.)
*/
if (ginCompareItemPointers(&key->curItem, &advancePast) > 0)
return;
/*
* Find the minimum item > advancePast among the active entry streams.
*
* 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);
allFinished = true;
for (i = 0; i < key->nrequired; i++)
{
entry = key->requiredEntries[i];
if (entry->isFinished)
continue;
/*
* Advance this stream if necessary.
*
* In particular, since entry->curItem was initialized with
* ItemPointerSetMin, this ensures we fetch the first item for each
* entry on the first call.
*/
if (ginCompareItemPointers(&entry->curItem, &advancePast) <= 0)
{
entryGetItem(ginstate, entry, advancePast, snapshot);
if (entry->isFinished)
continue;
}
allFinished = false;
if (ginCompareItemPointers(&entry->curItem, &minItem) < 0)
minItem = entry->curItem;
}
if (allFinished)
{
/* all entries are finished */
key->isFinished = true;
return;
}
/*
* Ok, we now know that there are no matches < minItem.
*
* If minItem is lossy, it means that there were no exact items on the
* page among requiredEntries, because lossy pointers sort after exact
* items. However, there might be exact items for the same page among
* additionalEntries, so we mustn't advance past them.
*/
if (ItemPointerIsLossyPage(&minItem))
{
if (GinItemPointerGetBlockNumber(&advancePast) <
GinItemPointerGetBlockNumber(&minItem))
{
ItemPointerSet(&advancePast,
GinItemPointerGetBlockNumber(&minItem),
InvalidOffsetNumber);
}
}
else
{
Assert(GinItemPointerGetOffsetNumber(&minItem) > 0);
ItemPointerSet(&advancePast,
GinItemPointerGetBlockNumber(&minItem),
OffsetNumberPrev(GinItemPointerGetOffsetNumber(&minItem)));
}
/*
* We might not have loaded all the entry streams for this TID yet. We
* could call the consistent function, passing MAYBE for those entries, to
* see if it can decide if this TID matches based on the information we
* have. But if the consistent-function is expensive, and cannot in fact
* decide with partial information, that could be a big loss. So, load all
* the additional entries, before calling the consistent function.
*/
for (i = 0; i < key->nadditional; i++)
{
entry = key->additionalEntries[i];
if (entry->isFinished)
continue;
if (ginCompareItemPointers(&entry->curItem, &advancePast) <= 0)
{
entryGetItem(ginstate, entry, advancePast, snapshot);
if (entry->isFinished)
continue;
}
/*
* Normally, none of the items in additionalEntries can have a curItem
* larger than minItem. But if minItem is a lossy page, then there
* might be exact items on the same page among additionalEntries.
*/
if (ginCompareItemPointers(&entry->curItem, &minItem) < 0)
{
Assert(ItemPointerIsLossyPage(&minItem));
minItem = entry->curItem;
}
}
/*
* Ok, we've advanced all the entries up to minItem now. Set key->curItem,
* and perform consistentFn test.
*
* 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.
*
* Our strategy is to call the tri-state consistent function, with the
* lossy-page entries set to MAYBE, and all the other entries FALSE. If it
* returns FALSE, none of the lossy items alone are enough for a match, so
* we don't need to return a lossy-page pointer. Otherwise, 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.)
*
* An exception is that it doesn't matter what we pass for lossy pointers
* in "hidden" entries, because the consistentFn's result can't depend on
* them. We could pass them as MAYBE as well, but if we're using the
* "shim" implementation of a tri-state consistent function (see
* ginlogic.c), it's better to pass as few MAYBEs as possible. So pass
* them as true.
*
* 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.
*/
key->curItem = minItem;
ItemPointerSetLossyPage(&curPageLossy,
GinItemPointerGetBlockNumber(&key->curItem));
haveLossyEntry = false;
for (i = 0; i < key->nentries; i++)
{
entry = key->scanEntry[i];
if (entry->isFinished == false &&
ginCompareItemPointers(&entry->curItem, &curPageLossy) == 0)
{
if (i < key->nuserentries)
key->entryRes[i] = GIN_MAYBE;
else
key->entryRes[i] = GIN_TRUE;
haveLossyEntry = true;
}
else
key->entryRes[i] = GIN_FALSE;
}
/* prepare for calling consistentFn in temp context */
oldCtx = MemoryContextSwitchTo(tempCtx);
if (haveLossyEntry)
{
/* Have lossy-page entries, so see if whole page matches */
res = key->triConsistentFn(key);
if (res == GIN_TRUE || res == GIN_MAYBE)
{
/* 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. Pass lossy pointers as
* MAYBE to the ternary consistent function, to let it decide if this
* tuple satisfies the overall key, even though we don't know if the lossy
* entries match.
*
* Prepare entryRes array to be passed to consistentFn.
*/
for (i = 0; i < key->nentries; i++)
{
entry = key->scanEntry[i];
if (entry->isFinished)
key->entryRes[i] = GIN_FALSE;
#if 0
/*
* This case can't currently happen, because we loaded all the entries
* for this item earlier.
*/
else if (ginCompareItemPointers(&entry->curItem, &advancePast) <= 0)
key->entryRes[i] = GIN_MAYBE;
#endif
else if (ginCompareItemPointers(&entry->curItem, &curPageLossy) == 0)
key->entryRes[i] = GIN_MAYBE;
else if (ginCompareItemPointers(&entry->curItem, &minItem) == 0)
key->entryRes[i] = GIN_TRUE;
else
key->entryRes[i] = GIN_FALSE;
}
res = key->triConsistentFn(key);
switch (res)
{
case GIN_TRUE:
key->curItemMatches = true;
/* triConsistentFn set recheckCurItem */
break;
case GIN_FALSE:
key->curItemMatches = false;
break;
case GIN_MAYBE:
key->curItemMatches = true;
key->recheckCurItem = true;
break;
default:
/*
* the 'default' case shouldn't happen, but if the consistent
* function returns something bogus, this is the safe result
*/
key->curItemMatches = true;
key->recheckCurItem = true;
break;
}
/*
* We have a tuple, and we know if it matches or not. If it's a non-match,
* we could continue to find the next matching tuple, but let's break out
* and give scanGetItem a chance to advance the other keys. They might be
* able to skip past to a much higher TID, allowing us to save work.
*/
/* 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, ItemPointerData advancePast,
ItemPointerData *item, bool *recheck)
{
GinScanOpaque so = (GinScanOpaque) scan->opaque;
uint32 i;
bool match;
/*----------
* Advance the scan keys in lock-step, until we find an item that matches
* all the keys. If any key reports isFinished, meaning its subset of the
* entries is exhausted, we can stop. Otherwise, set *item to the next
* matching item.
*
* 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.)
*----------
*/
do
{
ItemPointerSetMin(item);
match = true;
for (i = 0; i < so->nkeys && match; i++)
{
GinScanKey key = so->keys + i;
/* Fetch the next item for this key that is > advancePast. */
keyGetItem(&so->ginstate, so->tempCtx, key, advancePast,
scan->xs_snapshot);
if (key->isFinished)
return false;
/*
* If it's not a match, we can immediately conclude that nothing
* <= this item matches, without checking the rest of the keys.
*/
if (!key->curItemMatches)
{
advancePast = key->curItem;
match = false;
break;
}
/*
* It's a match. We can conclude that nothing < matches, so the
* other key streams can skip to this item.
*
* Beware of lossy pointers, though; from a lossy pointer, we can
* only conclude that nothing smaller than this *block* matches.
*/
if (ItemPointerIsLossyPage(&key->curItem))
{
if (GinItemPointerGetBlockNumber(&advancePast) <
GinItemPointerGetBlockNumber(&key->curItem))
{
ItemPointerSet(&advancePast,
GinItemPointerGetBlockNumber(&key->curItem),
InvalidOffsetNumber);
}
}
else
{
Assert(GinItemPointerGetOffsetNumber(&key->curItem) > 0);
ItemPointerSet(&advancePast,
GinItemPointerGetBlockNumber(&key->curItem),
OffsetNumberPrev(GinItemPointerGetOffsetNumber(&key->curItem)));
}
/*
* If this is the first key, remember this location as a potential
* match, and proceed to check the rest of the keys.
*
* Otherwise, check if this is the same item that we checked the
* previous keys for (or a lossy pointer for the same page). If
* not, loop back to check the previous keys for this item (we
* will check this key again too, but keyGetItem returns quickly
* for that)
*/
if (i == 0)
{
*item = key->curItem;
}
else
{
if (ItemPointerIsLossyPage(&key->curItem) ||
ItemPointerIsLossyPage(item))
{
Assert(GinItemPointerGetBlockNumber(&key->curItem) >= GinItemPointerGetBlockNumber(item));
match = (GinItemPointerGetBlockNumber(&key->curItem) ==
GinItemPointerGetBlockNumber(item));
}
else
{
Assert(ginCompareItemPointers(&key->curItem, item) >= 0);
match = (ginCompareItemPointers(&key->curItem, item) == 0);
}
}
}
} while (!match);
Assert(!ItemPointerIsMin(item));
/*
* Now *item contains the first ItemPointer after previous result that
* satisfied all the keys for that exact TID, or a lossy reference to the
* same page.
*
* 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);
TestForOldSnapshot(scan->xs_snapshot, scan->indexRelation, page);
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(FunctionCall4Coll(&ginstate->comparePartialFn[entry->attnum - 1],
ginstate->supportCollation[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, GIN_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);
TestForOldSnapshot(scan->xs_snapshot, scan->indexRelation, page);
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);
Page page;
BlockNumber blkno;
*ntids = 0;
/*
* Acquire predicate lock on the metapage, to conflict with any fastupdate
* insertions.
*/
PredicateLockPage(scan->indexRelation, GIN_METAPAGE_BLKNO, scan->xs_snapshot);
LockBuffer(metabuffer, GIN_SHARE);
page = BufferGetPage(metabuffer);
TestForOldSnapshot(scan->xs_snapshot, scan->indexRelation, page);
blkno = GinPageGetMeta(page)->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 (!key->boolConsistentFn(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 GinIsVoidRes(s) ( ((GinScanOpaque) scan->opaque)->isVoidRes )
int64
gingetbitmap(IndexScanDesc scan, TIDBitmap *tbm)
{
GinScanOpaque so = (GinScanOpaque) scan->opaque;
int64 ntids;
ItemPointerData iptr;
bool recheck;
/*
* Set up the scan keys, and check for unsatisfiable query.
*/
ginFreeScanKeys(so); /* there should be no keys yet, but just to be
* sure */
ginNewScanKey(scan);
if (GinIsVoidRes(scan))
return 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++;
}
return ntids;
}
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