/*
* Return the offset of the next matching index entry. We begin the
* search at offset "n" and search for matches in the direction
* "dir". If no more matching entries are found on the page,
* InvalidOffsetNumber is returned.
*/
static OffsetNumber
findnext(IndexScanDesc s, OffsetNumber n, ScanDirection dir)
{
OffsetNumber maxoff;
IndexTuple it;
RTreePageOpaque po;
RTreeScanOpaque so;
Page p;
so = (RTreeScanOpaque) s->opaque;
p = BufferGetPage(so->curbuf);
maxoff = PageGetMaxOffsetNumber(p);
po = (RTreePageOpaque) PageGetSpecialPointer(p);
/*
* If we modified the index during the scan, we may have a pointer to a
* ghost tuple, before the scan. If this is the case, back up one.
*/
if (so->s_flags & RTS_CURBEFORE)
{
so->s_flags &= ~RTS_CURBEFORE;
n = OffsetNumberPrev(n);
}
while (n >= FirstOffsetNumber && n <= maxoff)
{
it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
if (po->flags & F_LEAF)
{
if (index_keytest(it,
RelationGetDescr(s->indexRelation),
s->numberOfKeys, s->keyData))
break;
}
else
{
if (index_keytest(it,
RelationGetDescr(s->indexRelation),
so->s_internalNKey, so->s_internalKey))
break;
}
if (ScanDirectionIsBackward(dir))
n = OffsetNumberPrev(n);
else
n = OffsetNumberNext(n);
}
if (n >= FirstOffsetNumber && n <= maxoff)
return n; /* found a match on this page */
else
return InvalidOffsetNumber; /* no match, go to next page */
}
/*
* Return the offset of the first index entry that is consistent with
* the search key after offset 'n' in the current page. If there are
* no more consistent entries, return InvalidOffsetNumber.
* Page should be locked....
*/
static OffsetNumber
gistfindnext(IndexScanDesc scan, OffsetNumber n, ScanDirection dir)
{
OffsetNumber maxoff;
IndexTuple it;
GISTScanOpaque so;
MemoryContext oldcxt;
Page p;
so = (GISTScanOpaque) scan->opaque;
p = BufferGetPage(so->curbuf);
maxoff = PageGetMaxOffsetNumber(p);
/*
* Make sure we're in a short-lived memory context when we invoke a
* user-supplied GiST method in gistindex_keytest(), so we don't leak
* memory
*/
oldcxt = MemoryContextSwitchTo(so->tempCxt);
/*
* If we modified the index during the scan, we may have a pointer to a
* ghost tuple, before the scan. If this is the case, back up one.
*/
if (so->flags & GS_CURBEFORE)
{
so->flags &= ~GS_CURBEFORE;
n = OffsetNumberPrev(n);
}
while (n >= FirstOffsetNumber && n <= maxoff)
{
it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
if (gistindex_keytest(it, scan, n))
break;
if (ScanDirectionIsBackward(dir))
n = OffsetNumberPrev(n);
else
n = OffsetNumberNext(n);
}
MemoryContextSwitchTo(oldcxt);
MemoryContextReset(so->tempCxt);
/*
* If we found a matching entry, return its offset; otherwise return
* InvalidOffsetNumber to inform the caller to go to the next page.
*/
if (n >= FirstOffsetNumber && n <= maxoff)
return n;
else
return InvalidOffsetNumber;
}
/*
* adjustiptr() -- adjust current and marked item pointers in the scan
*
* Depending on the type of update and the place it happened, we
* need to do nothing, to back up one record, or to start over on
* the same page.
*/
static void
adjustiptr(IndexScanDesc s,
ItemPointer iptr,
int op,
BlockNumber blkno,
OffsetNumber offnum)
{
OffsetNumber curoff;
RTreeScanOpaque so;
if (ItemPointerIsValid(iptr))
{
if (ItemPointerGetBlockNumber(iptr) == blkno)
{
curoff = ItemPointerGetOffsetNumber(iptr);
so = (RTreeScanOpaque) s->opaque;
switch (op)
{
case RTOP_DEL:
/* back up one if we need to */
if (curoff >= offnum)
{
if (curoff > FirstOffsetNumber)
{
/* just adjust the item pointer */
ItemPointerSet(iptr, blkno, OffsetNumberPrev(curoff));
}
else
{
/*
* remember that we're before the current
* tuple
*/
ItemPointerSet(iptr, blkno, FirstOffsetNumber);
if (iptr == &(s->currentItemData))
so->s_flags |= RTS_CURBEFORE;
else
so->s_flags |= RTS_MRKBEFORE;
}
}
break;
case RTOP_SPLIT:
/* back to start of page on split */
ItemPointerSet(iptr, blkno, FirstOffsetNumber);
if (iptr == &(s->currentItemData))
so->s_flags &= ~RTS_CURBEFORE;
else
so->s_flags &= ~RTS_MRKBEFORE;
break;
default:
elog(ERROR, "unrecognized operation in rtree scan adjust: %d", op);
}
}
}
}
/*
* _bt_first() -- Find the first item in a scan.
*
* We need to be clever about the direction of scan, the search
* conditions, and the tree ordering. We find the first item (or,
* if backwards scan, the last item) in the tree that satisfies the
* qualifications in the scan key. On success exit, the page containing
* the current index tuple is pinned but not locked, and data about
* the matching tuple(s) on the page has been loaded into so->currPos.
* scan->xs_ctup.t_self is set to the heap TID of the current tuple,
* and if requested, scan->xs_itup points to a copy of the index tuple.
*
* If there are no matching items in the index, we return FALSE, with no
* pins or locks held.
*
* Note that scan->keyData[], and the so->keyData[] scankey built from it,
* are both search-type scankeys (see nbtree/README for more about this).
* Within this routine, we build a temporary insertion-type scankey to use
* in locating the scan start position.
*/
bool
_bt_first(IndexScanDesc scan, ScanDirection dir)
{
Relation rel = scan->indexRelation;
BTScanOpaque so = (BTScanOpaque) scan->opaque;
Buffer buf;
BTStack stack;
OffsetNumber offnum;
StrategyNumber strat;
bool nextkey;
bool goback;
ScanKey startKeys[INDEX_MAX_KEYS];
ScanKeyData scankeys[INDEX_MAX_KEYS];
ScanKeyData notnullkeys[INDEX_MAX_KEYS];
int keysCount = 0;
int i;
StrategyNumber strat_total;
BTScanPosItem *currItem;
pgstat_count_index_scan(rel);
/*
* Examine the scan keys and eliminate any redundant keys; also mark the
* keys that must be matched to continue the scan.
*/
_bt_preprocess_keys(scan);
/*
* Quit now if _bt_preprocess_keys() discovered that the scan keys can
* never be satisfied (eg, x == 1 AND x > 2).
*/
if (!so->qual_ok)
return false;
/*----------
* Examine the scan keys to discover where we need to start the scan.
*
* We want to identify the keys that can be used as starting boundaries;
* these are =, >, or >= keys for a forward scan or =, <, <= keys for
* a backwards scan. We can use keys for multiple attributes so long as
* the prior attributes had only =, >= (resp. =, <=) keys. Once we accept
* a > or < boundary or find an attribute with no boundary (which can be
* thought of as the same as "> -infinity"), we can't use keys for any
* attributes to its right, because it would break our simplistic notion
* of what initial positioning strategy to use.
*
* When the scan keys include cross-type operators, _bt_preprocess_keys
* may not be able to eliminate redundant keys; in such cases we will
* arbitrarily pick a usable one for each attribute. This is correct
* but possibly not optimal behavior. (For example, with keys like
* "x >= 4 AND x >= 5" we would elect to scan starting at x=4 when
* x=5 would be more efficient.) Since the situation only arises given
* a poorly-worded query plus an incomplete opfamily, live with it.
*
* When both equality and inequality keys appear for a single attribute
* (again, only possible when cross-type operators appear), we *must*
* select one of the equality keys for the starting point, because
* _bt_checkkeys() will stop the scan as soon as an equality qual fails.
* For example, if we have keys like "x >= 4 AND x = 10" and we elect to
* start at x=4, we will fail and stop before reaching x=10. If multiple
* equality quals survive preprocessing, however, it doesn't matter which
* one we use --- by definition, they are either redundant or
* contradictory.
*
* Any regular (not SK_SEARCHNULL) key implies a NOT NULL qualifier.
* If the index stores nulls at the end of the index we'll be starting
* from, and we have no boundary key for the column (which means the key
* we deduced NOT NULL from is an inequality key that constrains the other
* end of the index), then we cons up an explicit SK_SEARCHNOTNULL key to
* use as a boundary key. If we didn't do this, we might find ourselves
* traversing a lot of null entries at the start of the scan.
*
* In this loop, row-comparison keys are treated the same as keys on their
* first (leftmost) columns. We'll add on lower-order columns of the row
* comparison below, if possible.
*
* The selected scan keys (at most one per index column) are remembered by
* storing their addresses into the local startKeys[] array.
*----------
*/
strat_total = BTEqualStrategyNumber;
if (so->numberOfKeys > 0)
{
AttrNumber curattr;
ScanKey chosen;
ScanKey impliesNN;
ScanKey cur;
/*
* chosen is the so-far-chosen key for the current attribute, if any.
* We don't cast the decision in stone until we reach keys for the
* next attribute.
*/
curattr = 1;
chosen = NULL;
/* Also remember any scankey that implies a NOT NULL constraint */
impliesNN = NULL;
/*
* Loop iterates from 0 to numberOfKeys inclusive; we use the last
* pass to handle after-last-key processing. Actual exit from the
* loop is at one of the "break" statements below.
*/
for (cur = so->keyData, i = 0;; cur++, i++)
{
if (i >= so->numberOfKeys || cur->sk_attno != curattr)
{
/*
* Done looking at keys for curattr. If we didn't find a
* usable boundary key, see if we can deduce a NOT NULL key.
*/
if (chosen == NULL && impliesNN != NULL &&
((impliesNN->sk_flags & SK_BT_NULLS_FIRST) ?
ScanDirectionIsForward(dir) :
ScanDirectionIsBackward(dir)))
{
/* Yes, so build the key in notnullkeys[keysCount] */
chosen = ¬nullkeys[keysCount];
ScanKeyEntryInitialize(chosen,
(SK_SEARCHNOTNULL | SK_ISNULL |
(impliesNN->sk_flags &
(SK_BT_DESC | SK_BT_NULLS_FIRST))),
curattr,
((impliesNN->sk_flags & SK_BT_NULLS_FIRST) ?
BTGreaterStrategyNumber :
BTLessStrategyNumber),
InvalidOid,
InvalidOid,
InvalidOid,
(Datum) 0);
}
/*
* If we still didn't find a usable boundary key, quit; else
* save the boundary key pointer in startKeys.
*/
if (chosen == NULL)
break;
startKeys[keysCount++] = chosen;
/*
* Adjust strat_total, and quit if we have stored a > or <
* key.
*/
strat = chosen->sk_strategy;
if (strat != BTEqualStrategyNumber)
{
strat_total = strat;
if (strat == BTGreaterStrategyNumber ||
strat == BTLessStrategyNumber)
break;
}
/*
* Done if that was the last attribute, or if next key is not
* in sequence (implying no boundary key is available for the
* next attribute).
*/
if (i >= so->numberOfKeys ||
cur->sk_attno != curattr + 1)
break;
/*
* Reset for next attr.
*/
curattr = cur->sk_attno;
chosen = NULL;
impliesNN = NULL;
}
/*
* Can we use this key as a starting boundary for this attr?
*
* If not, does it imply a NOT NULL constraint? (Because
* SK_SEARCHNULL keys are always assigned BTEqualStrategyNumber,
* *any* inequality key works for that; we need not test.)
*/
switch (cur->sk_strategy)
{
case BTLessStrategyNumber:
case BTLessEqualStrategyNumber:
if (chosen == NULL)
{
if (ScanDirectionIsBackward(dir))
chosen = cur;
else
impliesNN = cur;
}
break;
case BTEqualStrategyNumber:
/* override any non-equality choice */
chosen = cur;
break;
case BTGreaterEqualStrategyNumber:
case BTGreaterStrategyNumber:
if (chosen == NULL)
{
if (ScanDirectionIsForward(dir))
chosen = cur;
else
impliesNN = cur;
}
break;
}
}
}
/*
* If we found no usable boundary keys, we have to start from one end of
* the tree. Walk down that edge to the first or last key, and scan from
* there.
*/
if (keysCount == 0)
return _bt_endpoint(scan, dir);
/*
* We want to start the scan somewhere within the index. Set up an
* insertion scankey we can use to search for the boundary point we
* identified above. The insertion scankey is built in the local
* scankeys[] array, using the keys identified by startKeys[].
*/
Assert(keysCount <= INDEX_MAX_KEYS);
for (i = 0; i < keysCount; i++)
{
ScanKey cur = startKeys[i];
Assert(cur->sk_attno == i + 1);
if (cur->sk_flags & SK_ROW_HEADER)
{
/*
* Row comparison header: look to the first row member instead.
*
* The member scankeys are already in insertion format (ie, they
* have sk_func = 3-way-comparison function), but we have to watch
* out for nulls, which _bt_preprocess_keys didn't check. A null
* in the first row member makes the condition unmatchable, just
* like qual_ok = false.
*/
ScanKey subkey = (ScanKey) DatumGetPointer(cur->sk_argument);
Assert(subkey->sk_flags & SK_ROW_MEMBER);
if (subkey->sk_flags & SK_ISNULL)
return false;
memcpy(scankeys + i, subkey, sizeof(ScanKeyData));
/*
* If the row comparison is the last positioning key we accepted,
* try to add additional keys from the lower-order row members.
* (If we accepted independent conditions on additional index
* columns, we use those instead --- doesn't seem worth trying to
* determine which is more restrictive.) Note that this is OK
* even if the row comparison is of ">" or "<" type, because the
* condition applied to all but the last row member is effectively
* ">=" or "<=", and so the extra keys don't break the positioning
* scheme. But, by the same token, if we aren't able to use all
* the row members, then the part of the row comparison that we
* did use has to be treated as just a ">=" or "<=" condition, and
* so we'd better adjust strat_total accordingly.
*/
if (i == keysCount - 1)
{
bool used_all_subkeys = false;
Assert(!(subkey->sk_flags & SK_ROW_END));
for (;;)
{
subkey++;
Assert(subkey->sk_flags & SK_ROW_MEMBER);
if (subkey->sk_attno != keysCount + 1)
break; /* out-of-sequence, can't use it */
if (subkey->sk_strategy != cur->sk_strategy)
break; /* wrong direction, can't use it */
if (subkey->sk_flags & SK_ISNULL)
break; /* can't use null keys */
Assert(keysCount < INDEX_MAX_KEYS);
memcpy(scankeys + keysCount, subkey, sizeof(ScanKeyData));
keysCount++;
if (subkey->sk_flags & SK_ROW_END)
{
used_all_subkeys = true;
break;
}
}
if (!used_all_subkeys)
{
switch (strat_total)
{
case BTLessStrategyNumber:
strat_total = BTLessEqualStrategyNumber;
break;
case BTGreaterStrategyNumber:
strat_total = BTGreaterEqualStrategyNumber;
break;
}
}
break; /* done with outer loop */
}
}
else
{
/*
* Ordinary comparison key. Transform the search-style scan key
* to an insertion scan key by replacing the sk_func with the
* appropriate btree comparison function.
*
* If scankey operator is not a cross-type comparison, we can use
* the cached comparison function; otherwise gotta look it up in
* the catalogs. (That can't lead to infinite recursion, since no
* indexscan initiated by syscache lookup will use cross-data-type
* operators.)
*
* We support the convention that sk_subtype == InvalidOid means
* the opclass input type; this is a hack to simplify life for
* ScanKeyInit().
*/
if (cur->sk_subtype == rel->rd_opcintype[i] ||
cur->sk_subtype == InvalidOid)
{
FmgrInfo *procinfo;
procinfo = index_getprocinfo(rel, cur->sk_attno, BTORDER_PROC);
ScanKeyEntryInitializeWithInfo(scankeys + i,
cur->sk_flags,
cur->sk_attno,
InvalidStrategy,
cur->sk_subtype,
cur->sk_collation,
procinfo,
cur->sk_argument);
}
else
{
RegProcedure cmp_proc;
cmp_proc = get_opfamily_proc(rel->rd_opfamily[i],
rel->rd_opcintype[i],
cur->sk_subtype,
BTORDER_PROC);
if (!RegProcedureIsValid(cmp_proc))
elog(ERROR, "missing support function %d(%u,%u) for attribute %d of index \"%s\"",
BTORDER_PROC, rel->rd_opcintype[i], cur->sk_subtype,
cur->sk_attno, RelationGetRelationName(rel));
ScanKeyEntryInitialize(scankeys + i,
cur->sk_flags,
cur->sk_attno,
InvalidStrategy,
cur->sk_subtype,
cur->sk_collation,
cmp_proc,
cur->sk_argument);
}
}
}
/*----------
* Examine the selected initial-positioning strategy to determine exactly
* where we need to start the scan, and set flag variables to control the
* code below.
*
* If nextkey = false, _bt_search and _bt_binsrch will locate the first
* item >= scan key. If nextkey = true, they will locate the first
* item > scan key.
*
* If goback = true, we will then step back one item, while if
* goback = false, we will start the scan on the located item.
*----------
*/
switch (strat_total)
{
case BTLessStrategyNumber:
/*
* Find first item >= scankey, then back up one to arrive at last
* item < scankey. (Note: this positioning strategy is only used
* for a backward scan, so that is always the correct starting
* position.)
*/
nextkey = false;
goback = true;
break;
case BTLessEqualStrategyNumber:
/*
* Find first item > scankey, then back up one to arrive at last
* item <= scankey. (Note: this positioning strategy is only used
* for a backward scan, so that is always the correct starting
* position.)
*/
nextkey = true;
goback = true;
break;
case BTEqualStrategyNumber:
/*
* If a backward scan was specified, need to start with last equal
* item not first one.
*/
if (ScanDirectionIsBackward(dir))
{
/*
* This is the same as the <= strategy. We will check at the
* end whether the found item is actually =.
*/
nextkey = true;
goback = true;
}
else
{
/*
* This is the same as the >= strategy. We will check at the
* end whether the found item is actually =.
*/
nextkey = false;
goback = false;
}
break;
case BTGreaterEqualStrategyNumber:
/*
* Find first item >= scankey. (This is only used for forward
* scans.)
*/
nextkey = false;
goback = false;
break;
case BTGreaterStrategyNumber:
/*
* Find first item > scankey. (This is only used for forward
* scans.)
*/
nextkey = true;
goback = false;
break;
default:
/* can't get here, but keep compiler quiet */
elog(ERROR, "unrecognized strat_total: %d", (int) strat_total);
return false;
}
/*
* Use the manufactured insertion scan key to descend the tree and
* position ourselves on the target leaf page.
*/
stack = _bt_search(rel, keysCount, scankeys, nextkey, &buf, BT_READ);
/* don't need to keep the stack around... */
_bt_freestack(stack);
/* remember which buffer we have pinned, if any */
so->currPos.buf = buf;
if (!BufferIsValid(buf))
{
/*
* We only get here if the index is completely empty. Lock relation
* because nothing finer to lock exists.
*/
PredicateLockRelation(rel, scan->xs_snapshot);
return false;
}
else
PredicateLockPage(rel, BufferGetBlockNumber(buf),
scan->xs_snapshot);
/* initialize moreLeft/moreRight appropriately for scan direction */
if (ScanDirectionIsForward(dir))
{
so->currPos.moreLeft = false;
so->currPos.moreRight = true;
}
else
{
so->currPos.moreLeft = true;
so->currPos.moreRight = false;
}
so->numKilled = 0; /* just paranoia */
so->markItemIndex = -1; /* ditto */
/* position to the precise item on the page */
offnum = _bt_binsrch(rel, buf, keysCount, scankeys, nextkey);
/*
* If nextkey = false, we are positioned at the first item >= scan key, or
* possibly at the end of a page on which all the existing items are less
* than the scan key and we know that everything on later pages is greater
* than or equal to scan key.
*
* If nextkey = true, we are positioned at the first item > scan key, or
* possibly at the end of a page on which all the existing items are less
* than or equal to the scan key and we know that everything on later
* pages is greater than scan key.
*
* The actually desired starting point is either this item or the prior
* one, or in the end-of-page case it's the first item on the next page or
* the last item on this page. Adjust the starting offset if needed. (If
* this results in an offset before the first item or after the last one,
* _bt_readpage will report no items found, and then we'll step to the
* next page as needed.)
*/
if (goback)
offnum = OffsetNumberPrev(offnum);
/*
* Now load data from the first page of the scan.
*/
if (!_bt_readpage(scan, dir, offnum))
{
/*
* There's no actually-matching data on this page. Try to advance to
* the next page. Return false if there's no matching data at all.
*/
if (!_bt_steppage(scan, dir))
return false;
}
/* Drop the lock, but not pin, on the current page */
LockBuffer(so->currPos.buf, BUFFER_LOCK_UNLOCK);
/* OK, itemIndex says what to return */
currItem = &so->currPos.items[so->currPos.itemIndex];
scan->xs_ctup.t_self = currItem->heapTid;
if (scan->xs_want_itup)
scan->xs_itup = (IndexTuple) (so->currTuples + currItem->tupleOffset);
return true;
}
/*
* _bt_binsrch() -- Do a binary search for a key on a particular page.
*
* The passed scankey must be an insertion-type scankey (see nbtree/README),
* but it can omit the rightmost column(s) of the index.
*
* When nextkey is false (the usual case), we are looking for the first
* item >= scankey. When nextkey is true, we are looking for the first
* item strictly greater than scankey.
*
* On a leaf page, _bt_binsrch() returns the OffsetNumber of the first
* key >= given scankey, or > scankey if nextkey is true. (NOTE: in
* particular, this means it is possible to return a value 1 greater than the
* number of keys on the page, if the scankey is > all keys on the page.)
*
* On an internal (non-leaf) page, _bt_binsrch() returns the OffsetNumber
* of the last key < given scankey, or last key <= given scankey if nextkey
* is true. (Since _bt_compare treats the first data key of such a page as
* minus infinity, there will be at least one key < scankey, so the result
* always points at one of the keys on the page.) This key indicates the
* right place to descend to be sure we find all leaf keys >= given scankey
* (or leaf keys > given scankey when nextkey is true).
*
* This procedure is not responsible for walking right, it just examines
* the given page. _bt_binsrch() has no lock or refcount side effects
* on the buffer.
*/
OffsetNumber
_bt_binsrch(Relation rel,
Buffer buf,
int keysz,
ScanKey scankey,
bool nextkey)
{
Page page;
BTPageOpaque opaque;
OffsetNumber low,
high;
int32 result,
cmpval;
page = BufferGetPage(buf);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
low = P_FIRSTDATAKEY(opaque);
high = PageGetMaxOffsetNumber(page);
/*
* If there are no keys on the page, return the first available slot. Note
* this covers two cases: the page is really empty (no keys), or it
* contains only a high key. The latter case is possible after vacuuming.
* This can never happen on an internal page, however, since they are
* never empty (an internal page must have children).
*/
if (high < low)
return low;
/*
* Binary search to find the first key on the page >= scan key, or first
* key > scankey when nextkey is true.
*
* For nextkey=false (cmpval=1), the loop invariant is: all slots before
* 'low' are < scan key, all slots at or after 'high' are >= scan key.
*
* For nextkey=true (cmpval=0), the loop invariant is: all slots before
* 'low' are <= scan key, all slots at or after 'high' are > scan key.
*
* We can fall out when high == low.
*/
high++; /* establish the loop invariant for high */
cmpval = nextkey ? 0 : 1; /* select comparison value */
while (high > low)
{
OffsetNumber mid = low + ((high - low) / 2);
/* We have low <= mid < high, so mid points at a real slot */
result = _bt_compare(rel, keysz, scankey, page, mid);
if (result >= cmpval)
low = mid + 1;
else
high = mid;
}
/*
* At this point we have high == low, but be careful: they could point
* past the last slot on the page.
*
* On a leaf page, we always return the first key >= scan key (resp. >
* scan key), which could be the last slot + 1.
*/
if (P_ISLEAF(opaque))
return low;
/*
* On a non-leaf page, return the last key < scan key (resp. <= scan key).
* There must be one if _bt_compare() is playing by the rules.
*/
Assert(low > P_FIRSTDATAKEY(opaque));
return OffsetNumberPrev(low);
}
/*
* _bt_readpage() -- Load data from current index page into so->currPos
*
* Caller must have pinned and read-locked so->currPos.buf; the buffer's state
* is not changed here. Also, currPos.moreLeft and moreRight must be valid;
* they are updated as appropriate. All other fields of so->currPos are
* initialized from scratch here.
*
* We scan the current page starting at offnum and moving in the indicated
* direction. All items matching the scan keys are loaded into currPos.items.
* moreLeft or moreRight (as appropriate) is cleared if _bt_checkkeys reports
* that there can be no more matching tuples in the current scan direction.
*
* Returns true if any matching items found on the page, false if none.
*/
static bool
_bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum)
{
BTScanOpaque so = (BTScanOpaque) scan->opaque;
Page page;
BTPageOpaque opaque;
OffsetNumber minoff;
OffsetNumber maxoff;
int itemIndex;
IndexTuple itup;
bool continuescan;
/* we must have the buffer pinned and locked */
Assert(BufferIsValid(so->currPos.buf));
page = BufferGetPage(so->currPos.buf);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
minoff = P_FIRSTDATAKEY(opaque);
maxoff = PageGetMaxOffsetNumber(page);
/*
* we must save the page's right-link while scanning it; this tells us
* where to step right to after we're done with these items. There is no
* corresponding need for the left-link, since splits always go right.
*/
so->currPos.nextPage = opaque->btpo_next;
/* initialize tuple workspace to empty */
so->currPos.nextTupleOffset = 0;
if (ScanDirectionIsForward(dir))
{
/* load items[] in ascending order */
itemIndex = 0;
offnum = Max(offnum, minoff);
while (offnum <= maxoff)
{
itup = _bt_checkkeys(scan, page, offnum, dir, &continuescan);
if (itup != NULL)
{
/* tuple passes all scan key conditions, so remember it */
_bt_saveitem(so, itemIndex, offnum, itup);
itemIndex++;
}
if (!continuescan)
{
/* there can't be any more matches, so stop */
so->currPos.moreRight = false;
break;
}
offnum = OffsetNumberNext(offnum);
}
Assert(itemIndex <= MaxIndexTuplesPerPage);
so->currPos.firstItem = 0;
so->currPos.lastItem = itemIndex - 1;
so->currPos.itemIndex = 0;
}
else
{
/* load items[] in descending order */
itemIndex = MaxIndexTuplesPerPage;
offnum = Min(offnum, maxoff);
while (offnum >= minoff)
{
itup = _bt_checkkeys(scan, page, offnum, dir, &continuescan);
if (itup != NULL)
{
/* tuple passes all scan key conditions, so remember it */
itemIndex--;
_bt_saveitem(so, itemIndex, offnum, itup);
}
if (!continuescan)
{
/* there can't be any more matches, so stop */
so->currPos.moreLeft = false;
break;
}
offnum = OffsetNumberPrev(offnum);
}
Assert(itemIndex >= 0);
so->currPos.firstItem = itemIndex;
so->currPos.lastItem = MaxIndexTuplesPerPage - 1;
so->currPos.itemIndex = MaxIndexTuplesPerPage - 1;
}
return (so->currPos.firstItem <= so->currPos.lastItem);
}
/*
* _bt_step() -- Step one item in the requested direction in a scan on
* the tree.
*
* *bufP is the current buffer (read-locked and pinned). If we change
* pages, it's updated appropriately.
*
* If successful, update scan's currentItemData and return true.
* If no adjacent record exists in the requested direction,
* release buffer pin/locks and return false.
*/
bool
_bt_step(IndexScanDesc scan, Buffer *bufP, ScanDirection dir)
{
Relation rel = scan->indexRelation;
ItemPointer current = &(scan->currentItemData);
BTScanOpaque so = (BTScanOpaque) scan->opaque;
Page page;
BTPageOpaque opaque;
OffsetNumber offnum,
maxoff;
BlockNumber blkno;
/*
* Don't use ItemPointerGetOffsetNumber or you risk to get assertion
* due to ability of ip_posid to be equal 0.
*/
offnum = current->ip_posid;
page = BufferGetPage(*bufP);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
maxoff = PageGetMaxOffsetNumber(page);
if (ScanDirectionIsForward(dir))
{
if (!PageIsEmpty(page) && offnum < maxoff)
offnum = OffsetNumberNext(offnum);
else
{
/* Walk right to the next page with data */
for (;;)
{
/* if we're at end of scan, release the buffer and return */
if (P_RIGHTMOST(opaque))
{
_bt_relbuf(rel, *bufP);
ItemPointerSetInvalid(current);
*bufP = so->btso_curbuf = InvalidBuffer;
return false;
}
/* step right one page */
blkno = opaque->btpo_next;
_bt_relbuf(rel, *bufP);
*bufP = _bt_getbuf(rel, blkno, BT_READ);
page = BufferGetPage(*bufP);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
if (!P_IGNORE(opaque))
{
maxoff = PageGetMaxOffsetNumber(page);
/* done if it's not empty */
offnum = P_FIRSTDATAKEY(opaque);
if (!PageIsEmpty(page) && offnum <= maxoff)
break;
}
}
}
}
else
/* backwards scan */
{
if (offnum > P_FIRSTDATAKEY(opaque))
offnum = OffsetNumberPrev(offnum);
else
{
/*
* Walk left to the next page with data. This is much more
* complex than the walk-right case because of the possibility
* that the page to our left splits while we are in flight to
* it, plus the possibility that the page we were on gets
* deleted after we leave it. See nbtree/README for details.
*/
for (;;)
{
*bufP = _bt_walk_left(rel, *bufP);
/* if we're at end of scan, return failure */
if (*bufP == InvalidBuffer)
{
ItemPointerSetInvalid(current);
so->btso_curbuf = InvalidBuffer;
return false;
}
page = BufferGetPage(*bufP);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
/*
* Okay, we managed to move left to a non-deleted page.
* Done if it's not half-dead and not empty. Else loop
* back and do it all again.
*/
if (!P_IGNORE(opaque))
{
maxoff = PageGetMaxOffsetNumber(page);
offnum = maxoff;
if (!PageIsEmpty(page) &&
maxoff >= P_FIRSTDATAKEY(opaque))
break;
}
}
}
}
/* Update scan state */
so->btso_curbuf = *bufP;
blkno = BufferGetBlockNumber(*bufP);
ItemPointerSet(current, blkno, offnum);
return true;
}
/*
* _bt_binsrch() -- Do a binary search for a key on a particular page.
*
* The scankey we get has the compare function stored in the procedure
* entry of each data struct. We invoke this regproc to do the
* comparison for every key in the scankey.
*
* On a leaf page, _bt_binsrch() returns the OffsetNumber of the first
* key >= given scankey. (NOTE: in particular, this means it is possible
* to return a value 1 greater than the number of keys on the page,
* if the scankey is > all keys on the page.)
*
* On an internal (non-leaf) page, _bt_binsrch() returns the OffsetNumber
* of the last key < given scankey. (Since _bt_compare treats the first
* data key of such a page as minus infinity, there will be at least one
* key < scankey, so the result always points at one of the keys on the
* page.) This key indicates the right place to descend to be sure we
* find all leaf keys >= given scankey.
*
* This procedure is not responsible for walking right, it just examines
* the given page. _bt_binsrch() has no lock or refcount side effects
* on the buffer.
*/
OffsetNumber
_bt_binsrch(Relation rel,
Buffer buf,
int keysz,
ScanKey scankey)
{
TupleDesc itupdesc;
Page page;
BTPageOpaque opaque;
OffsetNumber low,
high;
int32 result;
itupdesc = RelationGetDescr(rel);
page = BufferGetPage(buf);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
low = P_FIRSTDATAKEY(opaque);
high = PageGetMaxOffsetNumber(page);
/*
* If there are no keys on the page, return the first available slot.
* Note this covers two cases: the page is really empty (no keys), or
* it contains only a high key. The latter case is possible after
* vacuuming. This can never happen on an internal page, however,
* since they are never empty (an internal page must have children).
*/
if (high < low)
return low;
/*
* Binary search to find the first key on the page >= scan key. Loop
* invariant: all slots before 'low' are < scan key, all slots at or
* after 'high' are >= scan key. We can fall out when high == low.
*/
high++; /* establish the loop invariant for high */
while (high > low)
{
OffsetNumber mid = low + ((high - low) / 2);
/* We have low <= mid < high, so mid points at a real slot */
result = _bt_compare(rel, keysz, scankey, page, mid);
if (result > 0)
low = mid + 1;
else
high = mid;
}
/*
* At this point we have high == low, but be careful: they could point
* past the last slot on the page.
*
* On a leaf page, we always return the first key >= scan key (which
* could be the last slot + 1).
*/
if (P_ISLEAF(opaque))
return low;
/*
* On a non-leaf page, return the last key < scan key. There must be
* one if _bt_compare() is playing by the rules.
*/
Assert(low > P_FIRSTDATAKEY(opaque));
return OffsetNumberPrev(low);
}
/*
* _hash_step() -- step to the next valid item in a scan in the bucket.
*
* If no valid record exists in the requested direction, return
* false. Else, return true and set the CurrentItemData for the
* scan to the right thing.
*
* 'bufP' points to the current buffer, which is pinned and read-locked.
* On success exit, we have pin and read-lock on whichever page
* contains the right item; on failure, we have released all buffers.
*/
bool
_hash_step(IndexScanDesc scan, Buffer *bufP, ScanDirection dir)
{
Relation rel = scan->indexRelation;
HashScanOpaque so = (HashScanOpaque) scan->opaque;
ItemPointer current;
Buffer buf;
Page page;
HashPageOpaque opaque;
OffsetNumber maxoff;
OffsetNumber offnum;
BlockNumber blkno;
IndexTuple itup;
current = &(scan->currentItemData);
buf = *bufP;
_hash_checkpage(rel, buf, LH_BUCKET_PAGE | LH_OVERFLOW_PAGE);
page = BufferGetPage(buf);
opaque = (HashPageOpaque) PageGetSpecialPointer(page);
/*
* If _hash_step is called from _hash_first, current will not be valid, so
* we can't dereference it. However, in that case, we presumably want to
* start at the beginning/end of the page...
*/
maxoff = PageGetMaxOffsetNumber(page);
if (ItemPointerIsValid(current))
offnum = ItemPointerGetOffsetNumber(current);
else
offnum = InvalidOffsetNumber;
/*
* 'offnum' now points to the last tuple we examined (if any).
*
* continue to step through tuples until: 1) we get to the end of the
* bucket chain or 2) we find a valid tuple.
*/
do
{
switch (dir)
{
case ForwardScanDirection:
if (offnum != InvalidOffsetNumber)
offnum = OffsetNumberNext(offnum); /* move forward */
else
offnum = FirstOffsetNumber; /* new page */
while (offnum > maxoff)
{
/*
* either this page is empty (maxoff ==
* InvalidOffsetNumber) or we ran off the end.
*/
_hash_readnext(rel, &buf, &page, &opaque);
if (BufferIsValid(buf))
{
maxoff = PageGetMaxOffsetNumber(page);
offnum = FirstOffsetNumber;
}
else
{
/* end of bucket */
maxoff = offnum = InvalidOffsetNumber;
break; /* exit while */
}
}
break;
case BackwardScanDirection:
if (offnum != InvalidOffsetNumber)
offnum = OffsetNumberPrev(offnum); /* move back */
else
offnum = maxoff; /* new page */
while (offnum < FirstOffsetNumber)
{
/*
* either this page is empty (offnum ==
* InvalidOffsetNumber) or we ran off the end.
*/
_hash_readprev(rel, &buf, &page, &opaque);
if (BufferIsValid(buf))
maxoff = offnum = PageGetMaxOffsetNumber(page);
else
{
/* end of bucket */
maxoff = offnum = InvalidOffsetNumber;
break; /* exit while */
}
}
break;
default:
/* NoMovementScanDirection */
/* this should not be reached */
break;
}
/* we ran off the end of the world without finding a match */
if (offnum == InvalidOffsetNumber)
{
/* we ran off the end of the bucket without finding a match */
*bufP = so->hashso_curbuf = InvalidBuffer;
ItemPointerSetInvalid(current);
return false;
}
/* get ready to check this tuple */
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
} while (!_hash_checkqual(scan, itup));
/* if we made it to here, we've found a valid tuple */
blkno = BufferGetBlockNumber(buf);
*bufP = so->hashso_curbuf = buf;
ItemPointerSet(current, blkno, offnum);
return true;
}
/*
* _hash_step() -- step to the next valid item in a scan in the bucket.
*
* If no valid record exists in the requested direction, return
* false. Else, return true and set the hashso_curpos for the
* scan to the right thing.
*
* 'bufP' points to the current buffer, which is pinned and read-locked.
* On success exit, we have pin and read-lock on whichever page
* contains the right item; on failure, we have released all buffers.
*/
bool
_hash_step(IndexScanDesc scan, Buffer *bufP, ScanDirection dir)
{
Relation rel = scan->indexRelation;
HashScanOpaque so = (HashScanOpaque) scan->opaque;
ItemPointer current;
Buffer buf;
Page page;
HashPageOpaque opaque;
OffsetNumber maxoff;
OffsetNumber offnum;
BlockNumber blkno;
IndexTuple itup;
current = &(so->hashso_curpos);
buf = *bufP;
_hash_checkpage(rel, buf, LH_BUCKET_PAGE | LH_OVERFLOW_PAGE);
page = BufferGetPage(buf);
opaque = (HashPageOpaque) PageGetSpecialPointer(page);
/*
* If _hash_step is called from _hash_first, current will not be valid, so
* we can't dereference it. However, in that case, we presumably want to
* start at the beginning/end of the page...
*/
maxoff = PageGetMaxOffsetNumber(page);
if (ItemPointerIsValid(current))
offnum = ItemPointerGetOffsetNumber(current);
else
offnum = InvalidOffsetNumber;
/*
* 'offnum' now points to the last tuple we examined (if any).
*
* continue to step through tuples until: 1) we get to the end of the
* bucket chain or 2) we find a valid tuple.
*/
do
{
switch (dir)
{
case ForwardScanDirection:
if (offnum != InvalidOffsetNumber)
offnum = OffsetNumberNext(offnum); /* move forward */
else
{
/* new page, locate starting position by binary search */
offnum = _hash_binsearch(page, so->hashso_sk_hash);
}
for (;;)
{
/*
* check if we're still in the range of items with the
* target hash key
*/
if (offnum <= maxoff)
{
Assert(offnum >= FirstOffsetNumber);
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
if (so->hashso_sk_hash == _hash_get_indextuple_hashkey(itup))
break; /* yes, so exit for-loop */
}
/*
* ran off the end of this page, try the next
*/
_hash_readnext(rel, &buf, &page, &opaque);
if (BufferIsValid(buf))
{
maxoff = PageGetMaxOffsetNumber(page);
offnum = _hash_binsearch(page, so->hashso_sk_hash);
}
else
{
/* end of bucket */
itup = NULL;
break; /* exit for-loop */
}
}
break;
case BackwardScanDirection:
if (offnum != InvalidOffsetNumber)
offnum = OffsetNumberPrev(offnum); /* move back */
else
{
/* new page, locate starting position by binary search */
offnum = _hash_binsearch_last(page, so->hashso_sk_hash);
}
for (;;)
{
/*
* check if we're still in the range of items with the
* target hash key
*/
if (offnum >= FirstOffsetNumber)
{
Assert(offnum <= maxoff);
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
if (so->hashso_sk_hash == _hash_get_indextuple_hashkey(itup))
break; /* yes, so exit for-loop */
}
/*
* ran off the end of this page, try the next
*/
_hash_readprev(rel, &buf, &page, &opaque);
if (BufferIsValid(buf))
{
maxoff = PageGetMaxOffsetNumber(page);
offnum = _hash_binsearch_last(page, so->hashso_sk_hash);
}
else
{
/* end of bucket */
itup = NULL;
break; /* exit for-loop */
}
}
break;
default:
/* NoMovementScanDirection */
/* this should not be reached */
itup = NULL;
break;
}
if (itup == NULL)
{
/* we ran off the end of the bucket without finding a match */
*bufP = so->hashso_curbuf = InvalidBuffer;
ItemPointerSetInvalid(current);
return false;
}
/* check the tuple quals, loop around if not met */
} while (!_hash_checkqual(scan, itup));
/* if we made it to here, we've found a valid tuple */
blkno = BufferGetBlockNumber(buf);
*bufP = so->hashso_curbuf = buf;
ItemPointerSet(current, blkno, offnum);
return true;
}
/*
* _hash_splitbucket -- split 'obucket' into 'obucket' and 'nbucket'
*
* We are splitting a bucket that consists of a base bucket page and zero
* or more overflow (bucket chain) pages. We must relocate tuples that
* belong in the new bucket, and compress out any free space in the old
* bucket.
*
* The caller must hold exclusive locks on both buckets to ensure that
* no one else is trying to access them (see README).
*
* The caller must hold a pin, but no lock, on the metapage buffer.
* The buffer is returned in the same state. (The metapage is only
* touched if it becomes necessary to add or remove overflow pages.)
*/
static void
_hash_splitbucket(Relation rel,
Buffer metabuf,
Bucket obucket,
Bucket nbucket,
BlockNumber start_oblkno,
BlockNumber start_nblkno,
uint32 maxbucket,
uint32 highmask,
uint32 lowmask)
{
Bucket bucket;
Buffer obuf;
Buffer nbuf;
BlockNumber oblkno;
BlockNumber nblkno;
bool null;
Datum datum;
HashItem hitem;
HashPageOpaque oopaque;
HashPageOpaque nopaque;
IndexTuple itup;
Size itemsz;
OffsetNumber ooffnum;
OffsetNumber noffnum;
OffsetNumber omaxoffnum;
Page opage;
Page npage;
TupleDesc itupdesc = RelationGetDescr(rel);
/*
* It should be okay to simultaneously write-lock pages from each
* bucket, since no one else can be trying to acquire buffer lock
* on pages of either bucket.
*/
oblkno = start_oblkno;
nblkno = start_nblkno;
obuf = _hash_getbuf(rel, oblkno, HASH_WRITE);
nbuf = _hash_getbuf(rel, nblkno, HASH_WRITE);
opage = BufferGetPage(obuf);
npage = BufferGetPage(nbuf);
_hash_checkpage(rel, opage, LH_BUCKET_PAGE);
oopaque = (HashPageOpaque) PageGetSpecialPointer(opage);
/* initialize the new bucket's primary page */
_hash_pageinit(npage, BufferGetPageSize(nbuf));
nopaque = (HashPageOpaque) PageGetSpecialPointer(npage);
nopaque->hasho_prevblkno = InvalidBlockNumber;
nopaque->hasho_nextblkno = InvalidBlockNumber;
nopaque->hasho_bucket = nbucket;
nopaque->hasho_flag = LH_BUCKET_PAGE;
nopaque->hasho_filler = HASHO_FILL;
/*
* Partition the tuples in the old bucket between the old bucket and the
* new bucket, advancing along the old bucket's overflow bucket chain
* and adding overflow pages to the new bucket as needed.
*/
ooffnum = FirstOffsetNumber;
omaxoffnum = PageGetMaxOffsetNumber(opage);
for (;;)
{
/*
* at each iteration through this loop, each of these variables
* should be up-to-date: obuf opage oopaque ooffnum omaxoffnum
*/
/* check if we're at the end of the page */
if (ooffnum > omaxoffnum)
{
/* at end of page, but check for an(other) overflow page */
oblkno = oopaque->hasho_nextblkno;
if (!BlockNumberIsValid(oblkno))
break;
/*
* we ran out of tuples on this particular page, but we
* have more overflow pages; advance to next page.
*/
_hash_wrtbuf(rel, obuf);
obuf = _hash_getbuf(rel, oblkno, HASH_WRITE);
opage = BufferGetPage(obuf);
_hash_checkpage(rel, opage, LH_OVERFLOW_PAGE);
oopaque = (HashPageOpaque) PageGetSpecialPointer(opage);
ooffnum = FirstOffsetNumber;
omaxoffnum = PageGetMaxOffsetNumber(opage);
continue;
}
/*
* Re-hash the tuple to determine which bucket it now belongs in.
*
* It is annoying to call the hash function while holding locks,
* but releasing and relocking the page for each tuple is unappealing
* too.
*/
hitem = (HashItem) PageGetItem(opage, PageGetItemId(opage, ooffnum));
itup = &(hitem->hash_itup);
datum = index_getattr(itup, 1, itupdesc, &null);
Assert(!null);
bucket = _hash_hashkey2bucket(_hash_datum2hashkey(rel, datum),
maxbucket, highmask, lowmask);
if (bucket == nbucket)
{
/*
* insert the tuple into the new bucket. if it doesn't fit on
* the current page in the new bucket, we must allocate a new
* overflow page and place the tuple on that page instead.
*/
itemsz = IndexTupleDSize(hitem->hash_itup)
+ (sizeof(HashItemData) - sizeof(IndexTupleData));
itemsz = MAXALIGN(itemsz);
if (PageGetFreeSpace(npage) < itemsz)
{
/* write out nbuf and drop lock, but keep pin */
_hash_chgbufaccess(rel, nbuf, HASH_WRITE, HASH_NOLOCK);
/* chain to a new overflow page */
nbuf = _hash_addovflpage(rel, metabuf, nbuf);
npage = BufferGetPage(nbuf);
_hash_checkpage(rel, npage, LH_OVERFLOW_PAGE);
/* we don't need nopaque within the loop */
}
noffnum = OffsetNumberNext(PageGetMaxOffsetNumber(npage));
if (PageAddItem(npage, (Item) hitem, itemsz, noffnum, LP_USED)
== InvalidOffsetNumber)
elog(ERROR, "failed to add index item to \"%s\"",
RelationGetRelationName(rel));
/*
* now delete the tuple from the old bucket. after this
* section of code, 'ooffnum' will actually point to the
* ItemId to which we would point if we had advanced it before
* the deletion (PageIndexTupleDelete repacks the ItemId
* array). this also means that 'omaxoffnum' is exactly one
* less than it used to be, so we really can just decrement it
* instead of calling PageGetMaxOffsetNumber.
*/
PageIndexTupleDelete(opage, ooffnum);
omaxoffnum = OffsetNumberPrev(omaxoffnum);
}
else
{
/*
* the tuple stays on this page. we didn't move anything, so
* we didn't delete anything and therefore we don't have to
* change 'omaxoffnum'.
*/
Assert(bucket == obucket);
ooffnum = OffsetNumberNext(ooffnum);
}
}
/*
* We're at the end of the old bucket chain, so we're done partitioning
* the tuples. Before quitting, call _hash_squeezebucket to ensure the
* tuples remaining in the old bucket (including the overflow pages) are
* packed as tightly as possible. The new bucket is already tight.
*/
_hash_wrtbuf(rel, obuf);
_hash_wrtbuf(rel, nbuf);
_hash_squeezebucket(rel, obucket, start_oblkno);
}
/*
* Bulk deletion of all index entries pointing to a set of heap tuples.
* The set of target tuples is specified via a callback routine that tells
* whether any given heap tuple (identified by ItemPointer) is being deleted.
*
* Result: a palloc'd struct containing statistical info for VACUUM displays.
*/
Datum
hashbulkdelete(PG_FUNCTION_ARGS)
{
IndexVacuumInfo *info = (IndexVacuumInfo *) PG_GETARG_POINTER(0);
IndexBulkDeleteResult *stats = (IndexBulkDeleteResult *) PG_GETARG_POINTER(1);
IndexBulkDeleteCallback callback = (IndexBulkDeleteCallback) PG_GETARG_POINTER(2);
void *callback_state = (void *) PG_GETARG_POINTER(3);
Relation rel = info->index;
double tuples_removed;
double num_index_tuples;
double orig_ntuples;
Bucket orig_maxbucket;
Bucket cur_maxbucket;
Bucket cur_bucket;
Buffer metabuf;
HashMetaPage metap;
HashMetaPageData local_metapage;
tuples_removed = 0;
num_index_tuples = 0;
/*
* Read the metapage to fetch original bucket and tuple counts. Also, we
* keep a copy of the last-seen metapage so that we can use its
* hashm_spares[] values to compute bucket page addresses. This is a bit
* hokey but perfectly safe, since the interesting entries in the spares
* array cannot change under us; and it beats rereading the metapage for
* each bucket.
*/
metabuf = _hash_getbuf(rel, HASH_METAPAGE, HASH_READ);
_hash_checkpage(rel, metabuf, LH_META_PAGE);
metap = (HashMetaPage) BufferGetPage(metabuf);
orig_maxbucket = metap->hashm_maxbucket;
orig_ntuples = metap->hashm_ntuples;
memcpy(&local_metapage, metap, sizeof(local_metapage));
_hash_relbuf(rel, metabuf);
/* Scan the buckets that we know exist */
cur_bucket = 0;
cur_maxbucket = orig_maxbucket;
loop_top:
while (cur_bucket <= cur_maxbucket)
{
BlockNumber bucket_blkno;
BlockNumber blkno;
bool bucket_dirty = false;
/* Get address of bucket's start page */
bucket_blkno = BUCKET_TO_BLKNO(&local_metapage, cur_bucket);
/* Exclusive-lock the bucket so we can shrink it */
_hash_getlock(rel, bucket_blkno, HASH_EXCLUSIVE);
/* Shouldn't have any active scans locally, either */
if (_hash_has_active_scan(rel, cur_bucket))
elog(ERROR, "hash index has active scan during VACUUM");
/* Scan each page in bucket */
blkno = bucket_blkno;
while (BlockNumberIsValid(blkno))
{
Buffer buf;
Page page;
HashPageOpaque opaque;
OffsetNumber offno;
OffsetNumber maxoffno;
bool page_dirty = false;
vacuum_delay_point();
buf = _hash_getbuf(rel, blkno, HASH_WRITE);
_hash_checkpage(rel, buf, LH_BUCKET_PAGE | LH_OVERFLOW_PAGE);
page = BufferGetPage(buf);
opaque = (HashPageOpaque) PageGetSpecialPointer(page);
Assert(opaque->hasho_bucket == cur_bucket);
/* Scan each tuple in page */
offno = FirstOffsetNumber;
maxoffno = PageGetMaxOffsetNumber(page);
while (offno <= maxoffno)
{
IndexTuple itup;
ItemPointer htup;
itup = (IndexTuple) PageGetItem(page,
PageGetItemId(page, offno));
htup = &(itup->t_tid);
if (callback(htup, callback_state))
{
/* delete the item from the page */
PageIndexTupleDelete(page, offno);
bucket_dirty = page_dirty = true;
/* don't increment offno, instead decrement maxoffno */
maxoffno = OffsetNumberPrev(maxoffno);
tuples_removed += 1;
}
else
{
offno = OffsetNumberNext(offno);
num_index_tuples += 1;
}
}
/*
* Write page if needed, advance to next page.
*/
blkno = opaque->hasho_nextblkno;
if (page_dirty)
_hash_wrtbuf(rel, buf);
else
_hash_relbuf(rel, buf);
}
/* If we deleted anything, try to compact free space */
if (bucket_dirty)
_hash_squeezebucket(rel, cur_bucket, bucket_blkno);
/* Release bucket lock */
_hash_droplock(rel, bucket_blkno, HASH_EXCLUSIVE);
/* Advance to next bucket */
cur_bucket++;
}
/* Write-lock metapage and check for split since we started */
metabuf = _hash_getbuf(rel, HASH_METAPAGE, HASH_WRITE);
_hash_checkpage(rel, metabuf, LH_META_PAGE);
metap = (HashMetaPage) BufferGetPage(metabuf);
if (cur_maxbucket != metap->hashm_maxbucket)
{
/* There's been a split, so process the additional bucket(s) */
cur_maxbucket = metap->hashm_maxbucket;
memcpy(&local_metapage, metap, sizeof(local_metapage));
_hash_relbuf(rel, metabuf);
goto loop_top;
}
/* Okay, we're really done. Update tuple count in metapage. */
if (orig_maxbucket == metap->hashm_maxbucket &&
orig_ntuples == metap->hashm_ntuples)
{
/*
* No one has split or inserted anything since start of scan, so
* believe our count as gospel.
*/
metap->hashm_ntuples = num_index_tuples;
}
else
{
/*
* Otherwise, our count is untrustworthy since we may have
* double-scanned tuples in split buckets. Proceed by dead-reckoning.
*/
if (metap->hashm_ntuples > tuples_removed)
metap->hashm_ntuples -= tuples_removed;
else
metap->hashm_ntuples = 0;
num_index_tuples = metap->hashm_ntuples;
}
_hash_wrtbuf(rel, metabuf);
/* return statistics */
if (stats == NULL)
stats = (IndexBulkDeleteResult *) palloc0(sizeof(IndexBulkDeleteResult));
stats->num_index_tuples = num_index_tuples;
stats->tuples_removed += tuples_removed;
/* hashvacuumcleanup will fill in num_pages */
PG_RETURN_POINTER(stats);
}
static bool
rtnext(IndexScanDesc s, ScanDirection dir)
{
Page p;
OffsetNumber n;
RTreePageOpaque po;
RTreeScanOpaque so;
so = (RTreeScanOpaque) s->opaque;
if (!ItemPointerIsValid(&(s->currentItemData)))
{
/* first call: start at the root */
Assert(BufferIsValid(so->curbuf) == false);
so->curbuf = ReadBuffer(s->indexRelation, P_ROOT);
pgstat_count_index_scan(&s->xs_pgstat_info);
}
p = BufferGetPage(so->curbuf);
po = (RTreePageOpaque) PageGetSpecialPointer(p);
if (!ItemPointerIsValid(&(s->currentItemData)))
{
/* first call: start at first/last offset */
if (ScanDirectionIsForward(dir))
n = FirstOffsetNumber;
else
n = PageGetMaxOffsetNumber(p);
}
else
{
/* go on to the next offset */
n = ItemPointerGetOffsetNumber(&(s->currentItemData));
if (ScanDirectionIsForward(dir))
n = OffsetNumberNext(n);
else
n = OffsetNumberPrev(n);
}
for (;;)
{
IndexTuple it;
RTSTACK *stk;
n = findnext(s, n, dir);
/* no match on this page, so read in the next stack entry */
if (n == InvalidOffsetNumber)
{
/* if out of stack entries, we're done */
if (so->s_stack == NULL)
{
ReleaseBuffer(so->curbuf);
so->curbuf = InvalidBuffer;
return false;
}
stk = so->s_stack;
so->curbuf = ReleaseAndReadBuffer(so->curbuf, s->indexRelation,
stk->rts_blk);
p = BufferGetPage(so->curbuf);
po = (RTreePageOpaque) PageGetSpecialPointer(p);
if (ScanDirectionIsBackward(dir))
n = OffsetNumberPrev(stk->rts_child);
else
n = OffsetNumberNext(stk->rts_child);
so->s_stack = stk->rts_parent;
pfree(stk);
continue;
}
if (po->flags & F_LEAF)
{
ItemPointerSet(&(s->currentItemData),
BufferGetBlockNumber(so->curbuf),
n);
it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
s->xs_ctup.t_self = it->t_tid;
return true;
}
else
{
BlockNumber blk;
stk = (RTSTACK *) palloc(sizeof(RTSTACK));
stk->rts_child = n;
stk->rts_blk = BufferGetBlockNumber(so->curbuf);
stk->rts_parent = so->s_stack;
so->s_stack = stk;
it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
blk = ItemPointerGetBlockNumber(&(it->t_tid));
/*
* Note that we release the pin on the page as we descend down the
* tree, even though there's a good chance we'll eventually need
* to re-read the buffer later in this scan. This may or may not
* be optimal, but it doesn't seem likely to make a huge
* performance difference either way.
*/
so->curbuf = ReleaseAndReadBuffer(so->curbuf, s->indexRelation, blk);
p = BufferGetPage(so->curbuf);
po = (RTreePageOpaque) PageGetSpecialPointer(p);
if (ScanDirectionIsBackward(dir))
n = PageGetMaxOffsetNumber(p);
else
n = FirstOffsetNumber;
}
}
}
/*
* Fetch a tuples that matchs the search key; this can be invoked
* either to fetch the first such tuple or subsequent matching
* tuples. Returns true iff a matching tuple was found.
*/
static int
gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids,
int maxtids, bool ignore_killed_tuples)
{
MIRROREDLOCK_BUFMGR_DECLARE;
Page p;
OffsetNumber n;
GISTScanOpaque so;
GISTSearchStack *stk;
IndexTuple it;
GISTPageOpaque opaque;
int ntids = 0;
so = (GISTScanOpaque) scan->opaque;
// -------- MirroredLock ----------
MIRROREDLOCK_BUFMGR_LOCK;
if ( so->qual_ok == false )
return 0;
if (ItemPointerIsValid(&so->curpos) == false)
{
/* Being asked to fetch the first entry, so start at the root */
Assert(so->curbuf == InvalidBuffer);
Assert(so->stack == NULL);
so->curbuf = ReadBuffer(scan->indexRelation, GIST_ROOT_BLKNO);
stk = so->stack = (GISTSearchStack *) palloc0(sizeof(GISTSearchStack));
stk->next = NULL;
stk->block = GIST_ROOT_BLKNO;
pgstat_count_index_scan(scan->indexRelation);
}
else if (so->curbuf == InvalidBuffer)
{
MIRROREDLOCK_BUFMGR_UNLOCK;
// -------- MirroredLock ----------
return 0;
}
/*
* check stored pointers from last visit
*/
if ( so->nPageData > 0 )
{
while( ntids < maxtids && so->curPageData < so->nPageData )
{
tids[ ntids ] = scan->xs_ctup.t_self = so->pageData[ so->curPageData ].heapPtr;
ItemPointerSet(&(so->curpos),
BufferGetBlockNumber(so->curbuf),
so->pageData[ so->curPageData ].pageOffset);
so->curPageData ++;
ntids++;
}
if ( ntids == maxtids )
{
MIRROREDLOCK_BUFMGR_UNLOCK;
// -------- MirroredLock ----------
return ntids;
}
/*
* Go to the next page
*/
stk = so->stack->next;
pfree(so->stack);
so->stack = stk;
/* If we're out of stack entries, we're done */
if (so->stack == NULL)
{
ReleaseBuffer(so->curbuf);
so->curbuf = InvalidBuffer;
MIRROREDLOCK_BUFMGR_UNLOCK;
// -------- MirroredLock ----------
return ntids;
}
so->curbuf = ReleaseAndReadBuffer(so->curbuf,
scan->indexRelation,
stk->block);
}
for (;;)
{
/* First of all, we need lock buffer */
Assert(so->curbuf != InvalidBuffer);
LockBuffer(so->curbuf, GIST_SHARE);
gistcheckpage(scan->indexRelation, so->curbuf);
p = BufferGetPage(so->curbuf);
opaque = GistPageGetOpaque(p);
/* remember lsn to identify page changed for tuple's killing */
so->stack->lsn = PageGetLSN(p);
/* check page split, occured from last visit or visit to parent */
if (!XLogRecPtrIsInvalid(so->stack->parentlsn) &&
XLByteLT(so->stack->parentlsn, opaque->nsn) &&
opaque->rightlink != InvalidBlockNumber /* sanity check */ &&
(so->stack->next == NULL || so->stack->next->block != opaque->rightlink) /* check if already
added */ )
{
/* detect page split, follow right link to add pages */
stk = (GISTSearchStack *) palloc(sizeof(GISTSearchStack));
stk->next = so->stack->next;
stk->block = opaque->rightlink;
stk->parentlsn = so->stack->parentlsn;
memset(&(stk->lsn), 0, sizeof(GistNSN));
so->stack->next = stk;
}
/* if page is empty, then just skip it */
if (PageIsEmpty(p))
{
LockBuffer(so->curbuf, GIST_UNLOCK);
stk = so->stack->next;
pfree(so->stack);
so->stack = stk;
if (so->stack == NULL)
{
ReleaseBuffer(so->curbuf);
so->curbuf = InvalidBuffer;
MIRROREDLOCK_BUFMGR_UNLOCK;
// -------- MirroredLock ----------
return ntids;
}
so->curbuf = ReleaseAndReadBuffer(so->curbuf, scan->indexRelation,
stk->block);
continue;
}
if (ScanDirectionIsBackward(dir))
n = PageGetMaxOffsetNumber(p);
else
n = FirstOffsetNumber;
/* wonderful, we can look at page */
so->nPageData = so->curPageData = 0;
for (;;)
{
n = gistfindnext(scan, n, dir);
if (!OffsetNumberIsValid(n))
{
while( ntids < maxtids && so->curPageData < so->nPageData )
{
tids[ ntids ] = scan->xs_ctup.t_self =
so->pageData[ so->curPageData ].heapPtr;
ItemPointerSet(&(so->curpos),
BufferGetBlockNumber(so->curbuf),
so->pageData[ so->curPageData ].pageOffset);
so->curPageData ++;
ntids++;
}
if ( ntids == maxtids )
{
LockBuffer(so->curbuf, GIST_UNLOCK);
MIRROREDLOCK_BUFMGR_UNLOCK;
// -------- MirroredLock ----------
return ntids;
}
/*
* We ran out of matching index entries on the current page,
* so pop the top stack entry and use it to continue the
* search.
*/
LockBuffer(so->curbuf, GIST_UNLOCK);
stk = so->stack->next;
pfree(so->stack);
so->stack = stk;
/* If we're out of stack entries, we're done */
if (so->stack == NULL)
{
ReleaseBuffer(so->curbuf);
so->curbuf = InvalidBuffer;
MIRROREDLOCK_BUFMGR_UNLOCK;
// -------- MirroredLock ----------
return ntids;
}
so->curbuf = ReleaseAndReadBuffer(so->curbuf,
scan->indexRelation,
stk->block);
/* XXX go up */
break;
}
if (GistPageIsLeaf(p))
{
/*
* We've found a matching index entry in a leaf page, so
* return success. Note that we keep "curbuf" pinned so that
* we can efficiently resume the index scan later.
*/
if (!(ignore_killed_tuples && ItemIdIsDead(PageGetItemId(p, n))))
{
it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
so->pageData[ so->nPageData ].heapPtr = it->t_tid;
so->pageData[ so->nPageData ].pageOffset = n;
so->nPageData ++;
}
}
else
{
/*
* We've found an entry in an internal node whose key is
* consistent with the search key, so push it to stack
*/
stk = (GISTSearchStack *) palloc(sizeof(GISTSearchStack));
it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
stk->block = ItemPointerGetBlockNumber(&(it->t_tid));
memset(&(stk->lsn), 0, sizeof(GistNSN));
stk->parentlsn = so->stack->lsn;
stk->next = so->stack->next;
so->stack->next = stk;
}
if (ScanDirectionIsBackward(dir))
n = OffsetNumberPrev(n);
else
n = OffsetNumberNext(n);
}
}
MIRROREDLOCK_BUFMGR_UNLOCK;
// -------- MirroredLock ----------
return ntids;
}
