greenplumn nbtinsert 源码
greenplumn nbtinsert 代码
文件路径：/src/backend/access/nbtree/nbtinsert.c
/*-------------------------------------------------------------------------
*
* nbtinsert.c
* Item insertion in Lehman and Yao btrees for Postgres.
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/access/nbtree/nbtinsert.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/nbtree.h"
#include "access/nbtxlog.h"
#include "access/tableam.h"
#include "access/transam.h"
#include "access/xloginsert.h"
#include "miscadmin.h"
#include "storage/lmgr.h"
#include "storage/predicate.h"
#include "storage/smgr.h"
#include "cdb/cdbappendonlyam.h"
#include "cdb/cdbaocsam.h"
/* Minimum tree height for application of fastpath optimization */
#define BTREE_FASTPATH_MIN_LEVEL 2
static Buffer _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf);
static TransactionId _bt_check_unique(Relation rel, BTInsertState insertstate,
Relation heapRel,
IndexUniqueCheck checkUnique, bool *is_unique,
uint32 *speculativeToken);
static OffsetNumber _bt_findinsertloc(Relation rel,
BTInsertState insertstate,
bool checkingunique,
BTStack stack,
Relation heapRel);
static void _bt_stepright(Relation rel, BTInsertState insertstate, BTStack stack);
static void _bt_insertonpg(Relation rel, BTScanInsert itup_key,
Buffer buf,
Buffer cbuf,
BTStack stack,
IndexTuple itup,
OffsetNumber newitemoff,
bool split_only_page);
static Buffer _bt_split(Relation rel, BTScanInsert itup_key, Buffer buf,
Buffer cbuf, OffsetNumber newitemoff, Size newitemsz,
IndexTuple newitem);
static void _bt_insert_parent(Relation rel, Buffer buf, Buffer rbuf,
BTStack stack, bool is_root, bool is_only);
static bool _bt_pgaddtup(Page page, Size itemsize, IndexTuple itup,
OffsetNumber itup_off);
static void _bt_vacuum_one_page(Relation rel, Buffer buffer, Relation heapRel);
/*
* _bt_doinsert() -- Handle insertion of a single index tuple in the tree.
*
* This routine is called by the public interface routine, btinsert.
* By here, itup is filled in, including the TID.
*
* If checkUnique is UNIQUE_CHECK_NO or UNIQUE_CHECK_PARTIAL, this
* will allow duplicates. Otherwise (UNIQUE_CHECK_YES or
* UNIQUE_CHECK_EXISTING) it will throw error for a duplicate.
* For UNIQUE_CHECK_EXISTING we merely run the duplicate check, and
* don't actually insert.
*
* The result value is only significant for UNIQUE_CHECK_PARTIAL:
* it must be true if the entry is known unique, else false.
* (In the current implementation we'll also return true after a
* successful UNIQUE_CHECK_YES or UNIQUE_CHECK_EXISTING call, but
* that's just a coding artifact.)
*/
bool
_bt_doinsert(Relation rel, IndexTuple itup,
IndexUniqueCheck checkUnique, Relation heapRel)
{
bool is_unique = false;
BTInsertStateData insertstate;
BTScanInsert itup_key;
BTStack stack = NULL;
Buffer buf;
bool fastpath;
bool checkingunique = (checkUnique != UNIQUE_CHECK_NO);
/* we need an insertion scan key to do our search, so build one */
itup_key = _bt_mkscankey(rel, itup);
if (checkingunique)
{
if (!itup_key->anynullkeys)
{
/* No (heapkeyspace) scantid until uniqueness established */
itup_key->scantid = NULL;
}
else
{
/*
* Scan key for new tuple contains NULL key values. Bypass
* checkingunique steps. They are unnecessary because core code
* considers NULL unequal to every value, including NULL.
*
* This optimization avoids O(N^2) behavior within the
* _bt_findinsertloc() heapkeyspace path when a unique index has a
* large number of "duplicates" with NULL key values.
*/
checkingunique = false;
/* Tuple is unique in the sense that core code cares about */
Assert(checkUnique != UNIQUE_CHECK_EXISTING);
is_unique = true;
}
}
/*
* Fill in the BTInsertState working area, to track the current page and
* position within the page to insert on
*/
insertstate.itup = itup;
/* PageAddItem will MAXALIGN(), but be consistent */
insertstate.itemsz = MAXALIGN(IndexTupleSize(itup));
insertstate.itup_key = itup_key;
insertstate.bounds_valid = false;
insertstate.buf = InvalidBuffer;
/*
* It's very common to have an index on an auto-incremented or
* monotonically increasing value. In such cases, every insertion happens
* towards the end of the index. We try to optimize that case by caching
* the right-most leaf of the index. If our cached block is still the
* rightmost leaf, has enough free space to accommodate a new entry and
* the insertion key is strictly greater than the first key in this page,
* then we can safely conclude that the new key will be inserted in the
* cached block. So we simply search within the cached block and insert
* the key at the appropriate location. We call it a fastpath.
*
* Testing has revealed, though, that the fastpath can result in increased
* contention on the exclusive-lock on the rightmost leaf page. So we
* conditionally check if the lock is available. If it's not available
* then we simply abandon the fastpath and take the regular path. This
* makes sense because unavailability of the lock also signals that some
* other backend might be concurrently inserting into the page, thus
* reducing our chances to finding an insertion place in this page.
*/
top:
fastpath = false;
if (RelationGetTargetBlock(rel) != InvalidBlockNumber)
{
Page page;
BTPageOpaque lpageop;
/*
* Conditionally acquire exclusive lock on the buffer before doing any
* checks. If we don't get the lock, we simply follow slowpath. If we
* do get the lock, this ensures that the index state cannot change,
* as far as the rightmost part of the index is concerned.
*/
buf = ReadBuffer(rel, RelationGetTargetBlock(rel));
if (ConditionalLockBuffer(buf))
{
_bt_checkpage(rel, buf);
page = BufferGetPage(buf);
lpageop = (BTPageOpaque) PageGetSpecialPointer(page);
/*
* Check if the page is still the rightmost leaf page, has enough
* free space to accommodate the new tuple, and the insertion scan
* key is strictly greater than the first key on the page.
*/
if (P_ISLEAF(lpageop) && P_RIGHTMOST(lpageop) &&
!P_IGNORE(lpageop) &&
(PageGetFreeSpace(page) > insertstate.itemsz) &&
PageGetMaxOffsetNumber(page) >= P_FIRSTDATAKEY(lpageop) &&
_bt_compare(rel, itup_key, page, P_FIRSTDATAKEY(lpageop)) > 0)
{
/*
* The right-most block should never have an incomplete split.
* But be paranoid and check for it anyway.
*/
Assert(!P_INCOMPLETE_SPLIT(lpageop));
fastpath = true;
}
else
{
_bt_relbuf(rel, buf);
/*
* Something did not work out. Just forget about the cached
* block and follow the normal path. It might be set again if
* the conditions are favourable.
*/
RelationSetTargetBlock(rel, InvalidBlockNumber);
}
}
else
{
ReleaseBuffer(buf);
/*
* If someone's holding a lock, it's likely to change anyway, so
* don't try again until we get an updated rightmost leaf.
*/
RelationSetTargetBlock(rel, InvalidBlockNumber);
}
}
if (!fastpath)
{
/*
* Find the first page containing this key. Buffer returned by
* _bt_search() is locked in exclusive mode.
*/
stack = _bt_search(rel, itup_key, &buf, BT_WRITE, NULL);
}
insertstate.buf = buf;
buf = InvalidBuffer; /* insertstate.buf now owns the buffer */
/*
* If we're not allowing duplicates, make sure the key isn't already in
* the index.
*
* NOTE: obviously, _bt_check_unique can only detect keys that are already
* in the index; so it cannot defend against concurrent insertions of the
* same key. We protect against that by means of holding a write lock on
* the first page the value could be on, with omitted/-inf value for the
* implicit heap TID tiebreaker attribute. Any other would-be inserter of
* the same key must acquire a write lock on the same page, so only one
* would-be inserter can be making the check at one time. Furthermore,
* once we are past the check we hold write locks continuously until we
* have performed our insertion, so no later inserter can fail to see our
* insertion. (This requires some care in _bt_findinsertloc.)
*
* If we must wait for another xact, we release the lock while waiting,
* and then must start over completely.
*
* For a partial uniqueness check, we don't wait for the other xact. Just
* let the tuple in and return false for possibly non-unique, or true for
* definitely unique.
*/
if (checkingunique)
{
TransactionId xwait;
uint32 speculativeToken;
xwait = _bt_check_unique(rel, &insertstate, heapRel, checkUnique,
&is_unique, &speculativeToken);
if (TransactionIdIsValid(xwait))
{
/* Have to wait for the other guy ... */
_bt_relbuf(rel, insertstate.buf);
insertstate.buf = InvalidBuffer;
/*
* If it's a speculative insertion, wait for it to finish (ie. to
* go ahead with the insertion, or kill the tuple). Otherwise
* wait for the transaction to finish as usual.
*/
if (speculativeToken)
SpeculativeInsertionWait(xwait, speculativeToken);
else
XactLockTableWait(xwait, rel, &itup->t_tid, XLTW_InsertIndex);
/* start over... */
if (stack)
_bt_freestack(stack);
goto top;
}
/* Uniqueness is established -- restore heap tid as scantid */
if (itup_key->heapkeyspace)
itup_key->scantid = &itup->t_tid;
}
if (checkUnique != UNIQUE_CHECK_EXISTING)
{
OffsetNumber newitemoff;
/*
* The only conflict predicate locking cares about for indexes is when
* an index tuple insert conflicts with an existing lock. We don't
* know the actual page we're going to insert on for sure just yet in
* checkingunique and !heapkeyspace cases, but it's okay to use the
* first page the value could be on (with scantid omitted) instead.
*/
CheckForSerializableConflictIn(rel, NULL, insertstate.buf);
/*
* Do the insertion. Note that insertstate contains cached binary
* search bounds established within _bt_check_unique when insertion is
* checkingunique.
*/
newitemoff = _bt_findinsertloc(rel, &insertstate, checkingunique,
stack, heapRel);
_bt_insertonpg(rel, itup_key, insertstate.buf, InvalidBuffer, stack,
itup, newitemoff, false);
}
else
{
/* just release the buffer */
_bt_relbuf(rel, insertstate.buf);
}
/* be tidy */
if (stack)
_bt_freestack(stack);
pfree(itup_key);
return is_unique;
}
/*
* _bt_check_unique() -- Check for violation of unique index constraint
*
* Returns InvalidTransactionId if there is no conflict, else an xact ID
* we must wait for to see if it commits a conflicting tuple. If an actual
* conflict is detected, no return --- just ereport(). If an xact ID is
* returned, and the conflicting tuple still has a speculative insertion in
* progress, *speculativeToken is set to non-zero, and the caller can wait for
* the verdict on the insertion using SpeculativeInsertionWait().
*
* However, if checkUnique == UNIQUE_CHECK_PARTIAL, we always return
* InvalidTransactionId because we don't want to wait. In this case we
* set *is_unique to false if there is a potential conflict, and the
* core code must redo the uniqueness check later.
*
* As a side-effect, sets state in insertstate that can later be used by
* _bt_findinsertloc() to reuse most of the binary search work we do
* here.
*
* Do not call here when there are NULL values in scan key. NULL should be
* considered unequal to NULL when checking for duplicates, but we are not
* prepared to handle that correctly.
*/
static TransactionId
_bt_check_unique(Relation rel, BTInsertState insertstate, Relation heapRel,
IndexUniqueCheck checkUnique, bool *is_unique,
uint32 *speculativeToken)
{
IndexTuple itup = insertstate->itup;
BTScanInsert itup_key = insertstate->itup_key;
SnapshotData SnapshotDirty;
OffsetNumber offset;
OffsetNumber maxoff;
Page page;
BTPageOpaque opaque;
Buffer nbuf = InvalidBuffer;
bool found = false;
/* Assume unique until we find a duplicate */
*is_unique = true;
InitDirtySnapshot(SnapshotDirty);
page = BufferGetPage(insertstate->buf);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
maxoff = PageGetMaxOffsetNumber(page);
/*
* Find the first tuple with the same key.
*
* This also saves the binary search bounds in insertstate. We use them
* in the fastpath below, but also in the _bt_findinsertloc() call later.
*/
Assert(!insertstate->bounds_valid);
offset = _bt_binsrch_insert(rel, insertstate);
/*
* Scan over all equal tuples, looking for live conflicts.
*/
Assert(!insertstate->bounds_valid || insertstate->low == offset);
Assert(!itup_key->anynullkeys);
Assert(itup_key->scantid == NULL);
for (;;)
{
ItemId curitemid;
IndexTuple curitup;
BlockNumber nblkno;
/*
* make sure the offset points to an actual item before trying to
* examine it...
*/
if (offset <= maxoff)
{
/*
* Fastpath: In most cases, we can use cached search bounds to
* limit our consideration to items that are definitely
* duplicates. This fastpath doesn't apply when the original page
* is empty, or when initial offset is past the end of the
* original page, which may indicate that we need to examine a
* second or subsequent page.
*
* Note that this optimization allows us to avoid calling
* _bt_compare() directly when there are no duplicates, as long as
* the offset where the key will go is not at the end of the page.
*/
if (nbuf == InvalidBuffer && offset == insertstate->stricthigh)
{
Assert(insertstate->bounds_valid);
Assert(insertstate->low >= P_FIRSTDATAKEY(opaque));
Assert(insertstate->low <= insertstate->stricthigh);
Assert(_bt_compare(rel, itup_key, page, offset) < 0);
break;
}
curitemid = PageGetItemId(page, offset);
/*
* We can skip items that are marked killed.
*
* In the presence of heavy update activity an index may contain
* many killed items with the same key; running _bt_compare() on
* each killed item gets expensive. Just advance over killed
* items as quickly as we can. We only apply _bt_compare() when
* we get to a non-killed item. Even those comparisons could be
* avoided (in the common case where there is only one page to
* visit) by reusing bounds, but just skipping dead items is fast
* enough.
*/
if (!ItemIdIsDead(curitemid))
{
ItemPointerData htid;
bool all_dead;
if (_bt_compare(rel, itup_key, page, offset) != 0)
break; /* we're past all the equal tuples */
/* okay, we gotta fetch the heap tuple ... */
curitup = (IndexTuple) PageGetItem(page, curitemid);
htid = curitup->t_tid;
/*
* If we are doing a recheck, we expect to find the tuple we
* are rechecking. It's not a duplicate, but we have to keep
* scanning.
*/
if (checkUnique == UNIQUE_CHECK_EXISTING &&
ItemPointerCompare(&htid, &itup->t_tid) == 0)
{
found = true;
}
/*
* Check if there's any table tuples for this index entry
* satisfying SnapshotDirty. This is necessary because for AMs
* with optimizations like heap's HOT, we have just a single
* index entry for the entire chain.
*/
else if (table_index_fetch_tuple_check(heapRel, &htid,
&SnapshotDirty,
&all_dead))
{
TransactionId xwait;
/*
* It is a duplicate. If we are only doing a partial
* check, then don't bother checking if the tuple is being
* updated in another transaction. Just return the fact
* that it is a potential conflict and leave the full
* check till later. Don't invalidate binary search
* bounds.
*/
if (checkUnique == UNIQUE_CHECK_PARTIAL)
{
if (nbuf != InvalidBuffer)
_bt_relbuf(rel, nbuf);
*is_unique = false;
return InvalidTransactionId;
}
/*
* If this tuple is being updated by other transaction
* then we have to wait for its commit/abort.
*/
xwait = (TransactionIdIsValid(SnapshotDirty.xmin)) ?
SnapshotDirty.xmin : SnapshotDirty.xmax;
if (TransactionIdIsValid(xwait))
{
if (nbuf != InvalidBuffer)
_bt_relbuf(rel, nbuf);
/* Tell _bt_doinsert to wait... */
*speculativeToken = SnapshotDirty.speculativeToken;
/* Caller releases lock on buf immediately */
insertstate->bounds_valid = false;
return xwait;
}
/*
* Otherwise we have a definite conflict. But before
* complaining, look to see if the tuple we want to insert
* is itself now committed dead --- if so, don't complain.
* This is a waste of time in normal scenarios but we must
* do it to support CREATE INDEX CONCURRENTLY.
*
* We must follow HOT-chains here because during
* concurrent index build, we insert the root TID though
* the actual tuple may be somewhere in the HOT-chain.
* While following the chain we might not stop at the
* exact tuple which triggered the insert, but that's OK
* because if we find a live tuple anywhere in this chain,
* we have a unique key conflict. The other live tuple is
* not part of this chain because it had a different index
* entry.
*/
htid = itup->t_tid;
if (table_index_fetch_tuple_check(heapRel, &htid,
SnapshotSelf, NULL))
{
/* Normal case --- it's still live */
}
else
{
/*
* It's been deleted, so no error, and no need to
* continue searching
*/
break;
}
/*
* Check for a conflict-in as we would if we were going to
* write to this page. We aren't actually going to write,
* but we want a chance to report SSI conflicts that would
* otherwise be masked by this unique constraint
* violation.
*/
CheckForSerializableConflictIn(rel, NULL, insertstate->buf);
/*
* This is a definite conflict. Break the tuple down into
* datums and report the error. But first, make sure we
* release the buffer locks we're holding ---
* BuildIndexValueDescription could make catalog accesses,
* which in the worst case might touch this same index and
* cause deadlocks.
*/
if (nbuf != InvalidBuffer)
_bt_relbuf(rel, nbuf);
_bt_relbuf(rel, insertstate->buf);
insertstate->buf = InvalidBuffer;
insertstate->bounds_valid = false;
{
Datum values[INDEX_MAX_KEYS];
bool isnull[INDEX_MAX_KEYS];
char *key_desc;
index_deform_tuple(itup, RelationGetDescr(rel),
values, isnull);
key_desc = BuildIndexValueDescription(rel, values,
isnull);
ereport(ERROR,
(errcode(ERRCODE_UNIQUE_VIOLATION),
errmsg("duplicate key value violates unique constraint \"%s\"",
RelationGetRelationName(rel)),
key_desc ? errdetail("Key %s already exists.",
key_desc) : 0,
errtableconstraint(heapRel,
RelationGetRelationName(rel))));
}
}
else if (all_dead)
{
/*
* The conflicting tuple (or whole HOT chain) is dead to
* everyone, so we may as well mark the index entry
* killed.
*/
ItemIdMarkDead(curitemid);
opaque->btpo_flags |= BTP_HAS_GARBAGE;
/*
* Mark buffer with a dirty hint, since state is not
* crucial. Be sure to mark the proper buffer dirty.
*/
if (nbuf != InvalidBuffer)
MarkBufferDirtyHint(nbuf, true);
else
MarkBufferDirtyHint(insertstate->buf, true);
}
}
}
/*
* Advance to next tuple to continue checking.
*/
if (offset < maxoff)
offset = OffsetNumberNext(offset);
else
{
int highkeycmp;
/* If scankey == hikey we gotta check the next page too */
if (P_RIGHTMOST(opaque))
break;
highkeycmp = _bt_compare(rel, itup_key, page, P_HIKEY);
Assert(highkeycmp <= 0);
if (highkeycmp != 0)
break;
/* Advance to next non-dead page --- there must be one */
for (;;)
{
nblkno = opaque->btpo_next;
nbuf = _bt_relandgetbuf(rel, nbuf, nblkno, BT_READ);
page = BufferGetPage(nbuf);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
if (!P_IGNORE(opaque))
break;
if (P_RIGHTMOST(opaque))
elog(ERROR, "fell off the end of index \"%s\"",
RelationGetRelationName(rel));
}
maxoff = PageGetMaxOffsetNumber(page);
offset = P_FIRSTDATAKEY(opaque);
/* Don't invalidate binary search bounds */
}
}
/*
* If we are doing a recheck then we should have found the tuple we are
* checking. Otherwise there's something very wrong --- probably, the
* index is on a non-immutable expression.
*/
if (checkUnique == UNIQUE_CHECK_EXISTING && !found)
ereport(ERROR,
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg("failed to re-find tuple within index \"%s\"",
RelationGetRelationName(rel)),
errhint("This may be because of a non-immutable index expression."),
errtableconstraint(heapRel,
RelationGetRelationName(rel))));
if (nbuf != InvalidBuffer)
_bt_relbuf(rel, nbuf);
return InvalidTransactionId;
}
/*
* _bt_findinsertloc() -- Finds an insert location for a tuple
*
* On entry, insertstate buffer contains the page the new tuple belongs
* on. It is exclusive-locked and pinned by the caller.
*
* If 'checkingunique' is true, the buffer on entry is the first page
* that contains duplicates of the new key. If there are duplicates on
* multiple pages, the correct insertion position might be some page to
* the right, rather than the first page. In that case, this function
* moves right to the correct target page.
*
* (In a !heapkeyspace index, there can be multiple pages with the same
* high key, where the new tuple could legitimately be placed on. In
* that case, the caller passes the first page containing duplicates,
* just like when checkingunique=true. If that page doesn't have enough
* room for the new tuple, this function moves right, trying to find a
* legal page that does.)
*
* On exit, insertstate buffer contains the chosen insertion page, and
* the offset within that page is returned. If _bt_findinsertloc needed
* to move right, the lock and pin on the original page are released, and
* the new buffer is exclusively locked and pinned instead.
*
* If insertstate contains cached binary search bounds, we will take
* advantage of them. This avoids repeating comparisons that we made in
* _bt_check_unique() already.
*
* If there is not enough room on the page for the new tuple, we try to
* make room by removing any LP_DEAD tuples.
*/
static OffsetNumber
_bt_findinsertloc(Relation rel,
BTInsertState insertstate,
bool checkingunique,
BTStack stack,
Relation heapRel)
{
BTScanInsert itup_key = insertstate->itup_key;
Page page = BufferGetPage(insertstate->buf);
BTPageOpaque lpageop;
lpageop = (BTPageOpaque) PageGetSpecialPointer(page);
/* Check 1/3 of a page restriction */
if (unlikely(insertstate->itemsz > BTMaxItemSize(page)))
_bt_check_third_page(rel, heapRel, itup_key->heapkeyspace, page,
insertstate->itup);
Assert(P_ISLEAF(lpageop) && !P_INCOMPLETE_SPLIT(lpageop));
Assert(!insertstate->bounds_valid || checkingunique);
Assert(!itup_key->heapkeyspace || itup_key->scantid != NULL);
Assert(itup_key->heapkeyspace || itup_key->scantid == NULL);
if (itup_key->heapkeyspace)
{
/*
* If we're inserting into a unique index, we may have to walk right
* through leaf pages to find the one leaf page that we must insert on
* to.
*
* This is needed for checkingunique callers because a scantid was not
* used when we called _bt_search(). scantid can only be set after
* _bt_check_unique() has checked for duplicates. The buffer
* initially stored in insertstate->buf has the page where the first
* duplicate key might be found, which isn't always the page that new
* tuple belongs on. The heap TID attribute for new tuple (scantid)
* could force us to insert on a sibling page, though that should be
* very rare in practice.
*/
if (checkingunique)
{
for (;;)
{
/*
* Does the new tuple belong on this page?
*
* The earlier _bt_check_unique() call may well have
* established a strict upper bound on the offset for the new
* item. If it's not the last item of the page (i.e. if there
* is at least one tuple on the page that goes after the tuple
* we're inserting) then we know that the tuple belongs on
* this page. We can skip the high key check.
*/
if (insertstate->bounds_valid &&
insertstate->low <= insertstate->stricthigh &&
insertstate->stricthigh <= PageGetMaxOffsetNumber(page))
break;
/* Test '<=', not '!=', since scantid is set now */
if (P_RIGHTMOST(lpageop) ||
_bt_compare(rel, itup_key, page, P_HIKEY) <= 0)
break;
_bt_stepright(rel, insertstate, stack);
/* Update local state after stepping right */
page = BufferGetPage(insertstate->buf);
lpageop = (BTPageOpaque) PageGetSpecialPointer(page);
}
}
/*
* If the target page is full, see if we can obtain enough space by
* erasing LP_DEAD items
*/
if (PageGetFreeSpace(page) < insertstate->itemsz &&
P_HAS_GARBAGE(lpageop))
{
_bt_vacuum_one_page(rel, insertstate->buf, heapRel);
insertstate->bounds_valid = false;
}
}
else
{
/*----------
* This is a !heapkeyspace (version 2 or 3) index. The current page
* is the first page that we could insert the new tuple to, but there
* may be other pages to the right that we could opt to use instead.
*
* If the new key is equal to one or more existing keys, we can
* legitimately place it anywhere in the series of equal keys. In
* fact, if the new key is equal to the page's "high key" we can place
* it on the next page. If it is equal to the high key, and there's
* not room to insert the new tuple on the current page without
* splitting, then we move right hoping to find more free space and
* avoid a split.
*
* Keep scanning right until we
* (a) find a page with enough free space,
* (b) reach the last page where the tuple can legally go, or
* (c) get tired of searching.
* (c) is not flippant; it is important because if there are many
* pages' worth of equal keys, it's better to split one of the early
* pages than to scan all the way to the end of the run of equal keys
* on every insert. We implement "get tired" as a random choice,
* since stopping after scanning a fixed number of pages wouldn't work
* well (we'd never reach the right-hand side of previously split
* pages). The probability of moving right is set at 0.99, which may
* seem too high to change the behavior much, but it does an excellent
* job of preventing O(N^2) behavior with many equal keys.
*----------
*/
while (PageGetFreeSpace(page) < insertstate->itemsz)
{
/*
* Before considering moving right, see if we can obtain enough
* space by erasing LP_DEAD items
*/
if (P_HAS_GARBAGE(lpageop))
{
_bt_vacuum_one_page(rel, insertstate->buf, heapRel);
insertstate->bounds_valid = false;
if (PageGetFreeSpace(page) >= insertstate->itemsz)
break; /* OK, now we have enough space */
}
/*
* Nope, so check conditions (b) and (c) enumerated above
*
* The earlier _bt_check_unique() call may well have established a
* strict upper bound on the offset for the new item. If it's not
* the last item of the page (i.e. if there is at least one tuple
* on the page that's greater than the tuple we're inserting to)
* then we know that the tuple belongs on this page. We can skip
* the high key check.
*/
if (insertstate->bounds_valid &&
insertstate->low <= insertstate->stricthigh &&
insertstate->stricthigh <= PageGetMaxOffsetNumber(page))
break;
if (P_RIGHTMOST(lpageop) ||
_bt_compare(rel, itup_key, page, P_HIKEY) != 0 ||
random() <= (MAX_RANDOM_VALUE / 100))
break;
_bt_stepright(rel, insertstate, stack);
/* Update local state after stepping right */
page = BufferGetPage(insertstate->buf);
lpageop = (BTPageOpaque) PageGetSpecialPointer(page);
}
}
/*
* We should now be on the correct page. Find the offset within the page
* for the new tuple. (Possibly reusing earlier search bounds.)
*/
Assert(P_RIGHTMOST(lpageop) ||
_bt_compare(rel, itup_key, page, P_HIKEY) <= 0);
return _bt_binsrch_insert(rel, insertstate);
}
/*
* Step right to next non-dead page, during insertion.
*
* This is a bit more complicated than moving right in a search. We must
* write-lock the target page before releasing write lock on current page;
* else someone else's _bt_check_unique scan could fail to see our insertion.
* Write locks on intermediate dead pages won't do because we don't know when
* they will get de-linked from the tree.
*
* This is more aggressive than it needs to be for non-unique !heapkeyspace
* indexes.
*/
static void
_bt_stepright(Relation rel, BTInsertState insertstate, BTStack stack)
{
Page page;
BTPageOpaque lpageop;
Buffer rbuf;
BlockNumber rblkno;
page = BufferGetPage(insertstate->buf);
lpageop = (BTPageOpaque) PageGetSpecialPointer(page);
rbuf = InvalidBuffer;
rblkno = lpageop->btpo_next;
for (;;)
{
rbuf = _bt_relandgetbuf(rel, rbuf, rblkno, BT_WRITE);
page = BufferGetPage(rbuf);
lpageop = (BTPageOpaque) PageGetSpecialPointer(page);
/*
* If this page was incompletely split, finish the split now. We do
* this while holding a lock on the left sibling, which is not good
* because finishing the split could be a fairly lengthy operation.
* But this should happen very seldom.
*/
if (P_INCOMPLETE_SPLIT(lpageop))
{
_bt_finish_split(rel, rbuf, stack);
rbuf = InvalidBuffer;
continue;
}
if (!P_IGNORE(lpageop))
break;
if (P_RIGHTMOST(lpageop))
elog(ERROR, "fell off the end of index \"%s\"",
RelationGetRelationName(rel));
rblkno = lpageop->btpo_next;
}
/* rbuf locked; unlock buf, update state for caller */
_bt_relbuf(rel, insertstate->buf);
insertstate->buf = rbuf;
insertstate->bounds_valid = false;
}
/*----------
* _bt_insertonpg() -- Insert a tuple on a particular page in the index.
*
* This recursive procedure does the following things:
*
* + if necessary, splits the target page, using 'itup_key' for
* suffix truncation on leaf pages (caller passes NULL for
* non-leaf pages).
* + inserts the tuple.
* + if the page was split, pops the parent stack, and finds the
* right place to insert the new child pointer (by walking
* right using information stored in the parent stack).
* + invokes itself with the appropriate tuple for the right
* child page on the parent.
* + updates the metapage if a true root or fast root is split.
*
* On entry, we must have the correct buffer in which to do the
* insertion, and the buffer must be pinned and write-locked. On return,
* we will have dropped both the pin and the lock on the buffer.
*
* This routine only performs retail tuple insertions. 'itup' should
* always be either a non-highkey leaf item, or a downlink (new high
* key items are created indirectly, when a page is split). When
* inserting to a non-leaf page, 'cbuf' is the left-sibling of the page
* we're inserting the downlink for. This function will clear the
* INCOMPLETE_SPLIT flag on it, and release the buffer.
*----------
*/
static void
_bt_insertonpg(Relation rel,
BTScanInsert itup_key,
Buffer buf,
Buffer cbuf,
BTStack stack,
IndexTuple itup,
OffsetNumber newitemoff,
bool split_only_page)
{
Page page;
BTPageOpaque lpageop;
Size itemsz;
page = BufferGetPage(buf);
lpageop = (BTPageOpaque) PageGetSpecialPointer(page);
/* child buffer must be given iff inserting on an internal page */
Assert(P_ISLEAF(lpageop) == !BufferIsValid(cbuf));
/* tuple must have appropriate number of attributes */
Assert(!P_ISLEAF(lpageop) ||
BTreeTupleGetNAtts(itup, rel) ==
IndexRelationGetNumberOfAttributes(rel));
Assert(P_ISLEAF(lpageop) ||
BTreeTupleGetNAtts(itup, rel) <=
IndexRelationGetNumberOfKeyAttributes(rel));
/* The caller should've finished any incomplete splits already. */
if (P_INCOMPLETE_SPLIT(lpageop))
elog(ERROR, "cannot insert to incompletely split page %u",
BufferGetBlockNumber(buf));
itemsz = IndexTupleSize(itup);
itemsz = MAXALIGN(itemsz); /* be safe, PageAddItem will do this but we
* need to be consistent */
/*
* Do we need to split the page to fit the item on it?
*
* Note: PageGetFreeSpace() subtracts sizeof(ItemIdData) from its result,
* so this comparison is correct even though we appear to be accounting
* only for the item and not for its line pointer.
*/
if (PageGetFreeSpace(page) < itemsz)
{
bool is_root = P_ISROOT(lpageop);
bool is_only = P_LEFTMOST(lpageop) && P_RIGHTMOST(lpageop);
Buffer rbuf;
/*
* If we're here then a pagesplit is needed. We should never reach
* here if we're using the fastpath since we should have checked for
* all the required conditions, including the fact that this page has
* enough freespace. Note that this routine can in theory deal with
* the situation where a NULL stack pointer is passed (that's what
* would happen if the fastpath is taken). But that path is much
* slower, defeating the very purpose of the optimization. The
* following assertion should protect us from any future code changes
* that invalidate those assumptions.
*
* Note that whenever we fail to take the fastpath, we clear the
* cached block. Checking for a valid cached block at this point is
* enough to decide whether we're in a fastpath or not.
*/
Assert(!(P_ISLEAF(lpageop) &&
BlockNumberIsValid(RelationGetTargetBlock(rel))));
/* split the buffer into left and right halves */
rbuf = _bt_split(rel, itup_key, buf, cbuf, newitemoff, itemsz, itup);
PredicateLockPageSplit(rel,
BufferGetBlockNumber(buf),
BufferGetBlockNumber(rbuf));
/*----------
* By here,
*
* + our target page has been split;
* + the original tuple has been inserted;
* + we have write locks on both the old (left half)
* and new (right half) buffers, after the split; and
* + we know the key we want to insert into the parent
* (it's the "high key" on the left child page).
*
* We're ready to do the parent insertion. We need to hold onto the
* locks for the child pages until we locate the parent, but we can
* at least release the lock on the right child before doing the
* actual insertion. The lock on the left child will be released
* last of all by parent insertion, where it is the 'cbuf' of parent
* page.
*----------
*/
_bt_insert_parent(rel, buf, rbuf, stack, is_root, is_only);
}
else
{
Buffer metabuf = InvalidBuffer;
Page metapg = NULL;
BTMetaPageData *metad = NULL;
OffsetNumber itup_off;
BlockNumber itup_blkno;
BlockNumber cachedBlock = InvalidBlockNumber;
itup_off = newitemoff;
itup_blkno = BufferGetBlockNumber(buf);
/*
* If we are doing this insert because we split a page that was the
* only one on its tree level, but was not the root, it may have been
* the "fast root". We need to ensure that the fast root link points
* at or above the current page. We can safely acquire a lock on the
* metapage here --- see comments for _bt_newroot().
*/
if (split_only_page)
{
Assert(!P_ISLEAF(lpageop));
metabuf = _bt_getbuf(rel, BTREE_METAPAGE, BT_WRITE);
metapg = BufferGetPage(metabuf);
metad = BTPageGetMeta(metapg);
if (metad->btm_fastlevel >= lpageop->btpo.level)
{
/* no update wanted */
_bt_relbuf(rel, metabuf);
metabuf = InvalidBuffer;
}
}
/*
* Every internal page should have exactly one negative infinity item
* at all times. Only _bt_split() and _bt_newroot() should add items
* that become negative infinity items through truncation, since
* they're the only routines that allocate new internal pages. Do not
* allow a retail insertion of a new item at the negative infinity
* offset.
*/
if (!P_ISLEAF(lpageop) && newitemoff == P_FIRSTDATAKEY(lpageop))
elog(ERROR, "cannot insert second negative infinity item in block %u of index \"%s\"",
itup_blkno, RelationGetRelationName(rel));
/* Do the update. No ereport(ERROR) until changes are logged */
START_CRIT_SECTION();
if (!_bt_pgaddtup(page, itemsz, itup, newitemoff))
elog(PANIC, "failed to add new item to block %u in index \"%s\"",
itup_blkno, RelationGetRelationName(rel));
MarkBufferDirty(buf);
if (BufferIsValid(metabuf))
{
/* upgrade meta-page if needed */
if (metad->btm_version < BTREE_NOVAC_VERSION)
_bt_upgrademetapage(metapg);
metad->btm_fastroot = itup_blkno;
metad->btm_fastlevel = lpageop->btpo.level;
MarkBufferDirty(metabuf);
}
/* clear INCOMPLETE_SPLIT flag on child if inserting a downlink */
if (BufferIsValid(cbuf))
{
Page cpage = BufferGetPage(cbuf);
BTPageOpaque cpageop = (BTPageOpaque) PageGetSpecialPointer(cpage);
Assert(P_INCOMPLETE_SPLIT(cpageop));
cpageop->btpo_flags &= ~BTP_INCOMPLETE_SPLIT;
MarkBufferDirty(cbuf);
}
/*
* Cache the block information if we just inserted into the rightmost
* leaf page of the index and it's not the root page. For very small
* index where root is also the leaf, there is no point trying for any
* optimization.
*/
if (P_RIGHTMOST(lpageop) && P_ISLEAF(lpageop) && !P_ISROOT(lpageop))
cachedBlock = BufferGetBlockNumber(buf);
/* XLOG stuff */
if (RelationNeedsWAL(rel))
{
xl_btree_insert xlrec;
xl_btree_metadata xlmeta;
uint8 xlinfo;
XLogRecPtr recptr;
xlrec.offnum = itup_off;
XLogBeginInsert();
XLogRegisterData((char *) &xlrec, SizeOfBtreeInsert);
if (P_ISLEAF(lpageop))
xlinfo = XLOG_BTREE_INSERT_LEAF;
else
{
/*
* Register the left child whose INCOMPLETE_SPLIT flag was
* cleared.
*/
XLogRegisterBuffer(1, cbuf, REGBUF_STANDARD);
xlinfo = XLOG_BTREE_INSERT_UPPER;
}
if (BufferIsValid(metabuf))
{
Assert(metad->btm_version >= BTREE_NOVAC_VERSION);
xlmeta.version = metad->btm_version;
xlmeta.root = metad->btm_root;
xlmeta.level = metad->btm_level;
xlmeta.fastroot = metad->btm_fastroot;
xlmeta.fastlevel = metad->btm_fastlevel;
xlmeta.oldest_btpo_xact = metad->btm_oldest_btpo_xact;
xlmeta.last_cleanup_num_heap_tuples =
metad->btm_last_cleanup_num_heap_tuples;
XLogRegisterBuffer(2, metabuf, REGBUF_WILL_INIT | REGBUF_STANDARD);
XLogRegisterBufData(2, (char *) &xlmeta, sizeof(xl_btree_metadata));
xlinfo = XLOG_BTREE_INSERT_META;
}
XLogRegisterBuffer(0, buf, REGBUF_STANDARD);
XLogRegisterBufData(0, (char *) itup, IndexTupleSize(itup));
recptr = XLogInsert(RM_BTREE_ID, xlinfo);
if (BufferIsValid(metabuf))
{
PageSetLSN(metapg, recptr);
}
if (BufferIsValid(cbuf))
{
PageSetLSN(BufferGetPage(cbuf), recptr);
}
PageSetLSN(page, recptr);
}
END_CRIT_SECTION();
/* release buffers */
if (BufferIsValid(metabuf))
_bt_relbuf(rel, metabuf);
if (BufferIsValid(cbuf))
_bt_relbuf(rel, cbuf);
_bt_relbuf(rel, buf);
/*
* If we decided to cache the insertion target block, then set it now.
* But before that, check for the height of the tree and don't go for
* the optimization for small indexes. We defer that check to this
* point to ensure that we don't call _bt_getrootheight while holding
* lock on any other block.
*
* We do this after dropping locks on all buffers. So the information
* about whether the insertion block is still the rightmost block or
* not may have changed in between. But we will deal with that during
* next insert operation. No special care is required while setting
* it.
*/
if (BlockNumberIsValid(cachedBlock) &&
_bt_getrootheight(rel) >= BTREE_FASTPATH_MIN_LEVEL)
RelationSetTargetBlock(rel, cachedBlock);
}
}
/*
* _bt_split() -- split a page in the btree.
*
* On entry, buf is the page to split, and is pinned and write-locked.
* newitemoff etc. tell us about the new item that must be inserted
* along with the data from the original page.
*
* itup_key is used for suffix truncation on leaf pages (internal
* page callers pass NULL). When splitting a non-leaf page, 'cbuf'
* is the left-sibling of the page we're inserting the downlink for.
* This function will clear the INCOMPLETE_SPLIT flag on it, and
* release the buffer.
*
* Returns the new right sibling of buf, pinned and write-locked.
* The pin and lock on buf are maintained.
*/
static Buffer
_bt_split(Relation rel, BTScanInsert itup_key, Buffer buf, Buffer cbuf,
OffsetNumber newitemoff, Size newitemsz, IndexTuple newitem)
{
Buffer rbuf;
Page origpage;
Page leftpage,
rightpage;
BlockNumber origpagenumber,
rightpagenumber;
BTPageOpaque ropaque,
lopaque,
oopaque;
Buffer sbuf = InvalidBuffer;
Page spage = NULL;
BTPageOpaque sopaque = NULL;
Size itemsz;
ItemId itemid;
IndexTuple item;
OffsetNumber leftoff,
rightoff;
OffsetNumber firstright;
OffsetNumber maxoff;
OffsetNumber i;
bool newitemonleft,
isleaf;
IndexTuple lefthikey;
int indnatts = IndexRelationGetNumberOfAttributes(rel);
int indnkeyatts = IndexRelationGetNumberOfKeyAttributes(rel);
/*
* origpage is the original page to be split. leftpage is a temporary
* buffer that receives the left-sibling data, which will be copied back
* into origpage on success. rightpage is the new page that will receive
* the right-sibling data.
*
* leftpage is allocated after choosing a split point. rightpage's new
* buffer isn't acquired until after leftpage is initialized and has new
* high key, the last point where splitting the page may fail (barring
* corruption). Failing before acquiring new buffer won't have lasting
* consequences, since origpage won't have been modified and leftpage is
* only workspace.
*/
origpage = BufferGetPage(buf);
oopaque = (BTPageOpaque) PageGetSpecialPointer(origpage);
origpagenumber = BufferGetBlockNumber(buf);
/*
* Choose a point to split origpage at.
*
* A split point can be thought of as a point _between_ two existing
* tuples on origpage (lastleft and firstright tuples), provided you
* pretend that the new item that didn't fit is already on origpage.
*
* Since origpage does not actually contain newitem, the representation of
* split points needs to work with two boundary cases: splits where
* newitem is lastleft, and splits where newitem is firstright.
* newitemonleft resolves the ambiguity that would otherwise exist when
* newitemoff == firstright. In all other cases it's clear which side of
* the split every tuple goes on from context. newitemonleft is usually
* (but not always) redundant information.
*/
firstright = _bt_findsplitloc(rel, origpage, newitemoff, newitemsz,
newitem, &newitemonleft);
/* Allocate temp buffer for leftpage */
leftpage = PageGetTempPage(origpage);
_bt_pageinit(leftpage, BufferGetPageSize(buf));
lopaque = (BTPageOpaque) PageGetSpecialPointer(leftpage);
/*
* leftpage won't be the root when we're done. Also, clear the SPLIT_END
* and HAS_GARBAGE flags.
*/
lopaque->btpo_flags = oopaque->btpo_flags;
lopaque->btpo_flags &= ~(BTP_ROOT | BTP_SPLIT_END | BTP_HAS_GARBAGE);
/* set flag in leftpage indicating that rightpage has no downlink yet */
lopaque->btpo_flags |= BTP_INCOMPLETE_SPLIT;
lopaque->btpo_prev = oopaque->btpo_prev;
/* handle btpo_next after rightpage buffer acquired */
lopaque->btpo.level = oopaque->btpo.level;
/* handle btpo_cycleid after rightpage buffer acquired */
/*
* Copy the original page's LSN into leftpage, which will become the
* updated version of the page. We need this because XLogInsert will
* examine the LSN and possibly dump it in a page image.
*/
PageSetLSN(leftpage, PageGetLSN(origpage));
isleaf = P_ISLEAF(oopaque);
/*
* The "high key" for the new left page will be the first key that's going
* to go into the new right page, or a truncated version if this is a leaf
* page split.
*
* The high key for the left page is formed using the first item on the
* right page, which may seem to be contrary to Lehman & Yao's approach of
* using the left page's last item as its new high key when splitting on
* the leaf level. It isn't, though: suffix truncation will leave the
* left page's high key fully equal to the last item on the left page when
* two tuples with equal key values (excluding heap TID) enclose the split
* point. It isn't actually necessary for a new leaf high key to be equal
* to the last item on the left for the L&Y "subtree" invariant to hold.
* It's sufficient to make sure that the new leaf high key is strictly
* less than the first item on the right leaf page, and greater than or
* equal to (not necessarily equal to) the last item on the left leaf
* page.
*
* In other words, when suffix truncation isn't possible, L&Y's exact
* approach to leaf splits is taken. (Actually, even that is slightly
* inaccurate. A tuple with all the keys from firstright but the heap TID
* from lastleft will be used as the new high key, since the last left
* tuple could be physically larger despite being opclass-equal in respect
* of all attributes prior to the heap TID attribute.)
*/
if (!newitemonleft && newitemoff == firstright)
{
/* incoming tuple will become first on right page */
itemsz = newitemsz;
item = newitem;
}
else
{
/* existing item at firstright will become first on right page */
itemid = PageGetItemId(origpage, firstright);
itemsz = ItemIdGetLength(itemid);
item = (IndexTuple) PageGetItem(origpage, itemid);
}
/*
* Truncate unneeded key and non-key attributes of the high key item
* before inserting it on the left page. This can only happen at the leaf
* level, since in general all pivot tuple values originate from leaf
* level high keys. A pivot tuple in a grandparent page must guide a
* search not only to the correct parent page, but also to the correct
* leaf page.
*/
if (isleaf && (itup_key->heapkeyspace || indnatts != indnkeyatts))
{
IndexTuple lastleft;
/*
* Determine which tuple will become the last on the left page. This
* is needed to decide how many attributes from the first item on the
* right page must remain in new high key for left page.
*/
if (newitemonleft && newitemoff == firstright)
{
/* incoming tuple will become last on left page */
lastleft = newitem;
}
else
{
OffsetNumber lastleftoff;
/* item just before firstright will become last on left page */
lastleftoff = OffsetNumberPrev(firstright);
Assert(lastleftoff >= P_FIRSTDATAKEY(oopaque));
itemid = PageGetItemId(origpage, lastleftoff);
lastleft = (IndexTuple) PageGetItem(origpage, itemid);
}
Assert(lastleft != item);
lefthikey = _bt_truncate(rel, lastleft, item, itup_key);
itemsz = IndexTupleSize(lefthikey);
itemsz = MAXALIGN(itemsz);
}
else
lefthikey = item;
/*
* Add new high key to leftpage
*/
leftoff = P_HIKEY;
Assert(BTreeTupleGetNAtts(lefthikey, rel) > 0);
Assert(BTreeTupleGetNAtts(lefthikey, rel) <= indnkeyatts);
if (PageAddItem(leftpage, (Item) lefthikey, itemsz, leftoff,
false, false) == InvalidOffsetNumber)
elog(ERROR, "failed to add hikey to the left sibling"
" while splitting block %u of index \"%s\"",
origpagenumber, RelationGetRelationName(rel));
leftoff = OffsetNumberNext(leftoff);
/* be tidy */
if (lefthikey != item)
pfree(lefthikey);
/*
* Acquire a new right page to split into, now that left page has a new
* high key. From here on, it's not okay to throw an error without
* zeroing rightpage first. This coding rule ensures that we won't
* confuse future VACUUM operations, which might otherwise try to re-find
* a downlink to a leftover junk page as the page undergoes deletion.
*
* It would be reasonable to start the critical section just after the new
* rightpage buffer is acquired instead; that would allow us to avoid
* leftover junk pages without bothering to zero rightpage. We do it this
* way because it avoids an unnecessary PANIC when either origpage or its
* existing sibling page are corrupt.
*/
rbuf = _bt_getbuf(rel, P_NEW, BT_WRITE);
rightpage = BufferGetPage(rbuf);
rightpagenumber = BufferGetBlockNumber(rbuf);
/* rightpage was initialized by _bt_getbuf */
ropaque = (BTPageOpaque) PageGetSpecialPointer(rightpage);
/*
* Finish off remaining leftpage special area fields. They cannot be set
* before both origpage (leftpage) and rightpage buffers are acquired and
* locked.
*/
lopaque->btpo_next = rightpagenumber;
lopaque->btpo_cycleid = _bt_vacuum_cycleid(rel);
/*
* rightpage won't be the root when we're done. Also, clear the SPLIT_END
* and HAS_GARBAGE flags.
*/
ropaque->btpo_flags = oopaque->btpo_flags;
ropaque->btpo_flags &= ~(BTP_ROOT | BTP_SPLIT_END | BTP_HAS_GARBAGE);
ropaque->btpo_prev = origpagenumber;
ropaque->btpo_next = oopaque->btpo_next;
ropaque->btpo.level = oopaque->btpo.level;
ropaque->btpo_cycleid = lopaque->btpo_cycleid;
/*
* Add new high key to rightpage where necessary.
*
* If the page we're splitting is not the rightmost page at its level in
* the tree, then the first entry on the page is the high key from
* origpage.
*/
rightoff = P_HIKEY;
if (!P_RIGHTMOST(oopaque))
{
itemid = PageGetItemId(origpage, P_HIKEY);
itemsz = ItemIdGetLength(itemid);
item = (IndexTuple) PageGetItem(origpage, itemid);
Assert(BTreeTupleGetNAtts(item, rel) > 0);
Assert(BTreeTupleGetNAtts(item, rel) <= indnkeyatts);
if (PageAddItem(rightpage, (Item) item, itemsz, rightoff,
false, false) == InvalidOffsetNumber)
{
memset(rightpage, 0, BufferGetPageSize(rbuf));
elog(ERROR, "failed to add hikey to the right sibling"
" while splitting block %u of index \"%s\"",
origpagenumber, RelationGetRelationName(rel));
}
rightoff = OffsetNumberNext(rightoff);
}
/*
* Now transfer all the data items (non-pivot tuples in isleaf case, or
* additional pivot tuples in !isleaf case) to the appropriate page.
*
* Note: we *must* insert at least the right page's items in item-number
* order, for the benefit of _bt_restore_page().
*/
maxoff = PageGetMaxOffsetNumber(origpage);
for (i = P_FIRSTDATAKEY(oopaque); i <= maxoff; i = OffsetNumberNext(i))
{
itemid = PageGetItemId(origpage, i);
itemsz = ItemIdGetLength(itemid);
item = (IndexTuple) PageGetItem(origpage, itemid);
/* does new item belong before this one? */
if (i == newitemoff)
{
if (newitemonleft)
{
Assert(newitemoff <= firstright);
if (!_bt_pgaddtup(leftpage, newitemsz, newitem, leftoff))
{
memset(rightpage, 0, BufferGetPageSize(rbuf));
elog(ERROR, "failed to add new item to the left sibling"
" while splitting block %u of index \"%s\"",
origpagenumber, RelationGetRelationName(rel));
}
leftoff = OffsetNumberNext(leftoff);
}
else
{
Assert(newitemoff >= firstright);
if (!_bt_pgaddtup(rightpage, newitemsz, newitem, rightoff))
{
memset(rightpage, 0, BufferGetPageSize(rbuf));
elog(ERROR, "failed to add new item to the right sibling"
" while splitting block %u of index \"%s\"",
origpagenumber, RelationGetRelationName(rel));
}
rightoff = OffsetNumberNext(rightoff);
}
}
/* decide which page to put it on */
if (i < firstright)
{
if (!_bt_pgaddtup(leftpage, itemsz, item, leftoff))
{
memset(rightpage, 0, BufferGetPageSize(rbuf));
elog(ERROR, "failed to add old item to the left sibling"
" while splitting block %u of index \"%s\"",
origpagenumber, RelationGetRelationName(rel));
}
leftoff = OffsetNumberNext(leftoff);
}
else
{
if (!_bt_pgaddtup(rightpage, itemsz, item, rightoff))
{
memset(rightpage, 0, BufferGetPageSize(rbuf));
elog(ERROR, "failed to add old item to the right sibling"
" while splitting block %u of index \"%s\"",
origpagenumber, RelationGetRelationName(rel));
}
rightoff = OffsetNumberNext(rightoff);
}
}
/* cope with possibility that newitem goes at the end */
if (i <= newitemoff)
{
/*
* Can't have newitemonleft here; that would imply we were told to put
* *everything* on the left page, which cannot fit (if it could, we'd
* not be splitting the page).
*/
Assert(!newitemonleft);
if (!_bt_pgaddtup(rightpage, newitemsz, newitem, rightoff))
{
memset(rightpage, 0, BufferGetPageSize(rbuf));
elog(ERROR, "failed to add new item to the right sibling"
" while splitting block %u of index \"%s\"",
origpagenumber, RelationGetRelationName(rel));
}
rightoff = OffsetNumberNext(rightoff);
}
/*
* We have to grab the right sibling (if any) and fix the prev pointer
* there. We are guaranteed that this is deadlock-free since no other
* writer will be holding a lock on that page and trying to move left, and
* all readers release locks on a page before trying to fetch its
* neighbors.
*/
if (!P_RIGHTMOST(oopaque))
{
sbuf = _bt_getbuf(rel, oopaque->btpo_next, BT_WRITE);
spage = BufferGetPage(sbuf);
sopaque = (BTPageOpaque) PageGetSpecialPointer(spage);
if (sopaque->btpo_prev != origpagenumber)
{
memset(rightpage, 0, BufferGetPageSize(rbuf));
elog(ERROR, "right sibling's left-link doesn't match: "
"block %u links to %u instead of expected %u in index \"%s\"",
oopaque->btpo_next, sopaque->btpo_prev, origpagenumber,
RelationGetRelationName(rel));
}
/*
* Check to see if we can set the SPLIT_END flag in the right-hand
* split page; this can save some I/O for vacuum since it need not
* proceed to the right sibling. We can set the flag if the right
* sibling has a different cycleid: that means it could not be part of
* a group of pages that were all split off from the same ancestor
* page. If you're confused, imagine that page A splits to A B and
* then again, yielding A C B, while vacuum is in progress. Tuples
* originally in A could now be in either B or C, hence vacuum must
* examine both pages. But if D, our right sibling, has a different
* cycleid then it could not contain any tuples that were in A when
* the vacuum started.
*/
if (sopaque->btpo_cycleid != ropaque->btpo_cycleid)
ropaque->btpo_flags |= BTP_SPLIT_END;
}
/*
* Right sibling is locked, new siblings are prepared, but original page
* is not updated yet.
*
* NO EREPORT(ERROR) till right sibling is updated. We can get away with
* not starting the critical section till here because we haven't been
* scribbling on the original page yet; see comments above.
*/
START_CRIT_SECTION();
/*
* By here, the original data page has been split into two new halves, and
* these are correct. The algorithm requires that the left page never
* move during a split, so we copy the new left page back on top of the
* original. Note that this is not a waste of time, since we also require
* (in the page management code) that the center of a page always be
* clean, and the most efficient way to guarantee this is just to compact
* the data by reinserting it into a new left page. (XXX the latter
* comment is probably obsolete; but in any case it's good to not scribble
* on the original page until we enter the critical section.)
*
* We need to do this before writing the WAL record, so that XLogInsert
* can WAL log an image of the page if necessary.
*/
PageRestoreTempPage(leftpage, origpage);
/* leftpage, lopaque must not be used below here */
MarkBufferDirty(buf);
MarkBufferDirty(rbuf);
if (!P_RIGHTMOST(ropaque))
{
sopaque->btpo_prev = rightpagenumber;
MarkBufferDirty(sbuf);
}
/*
* Clear INCOMPLETE_SPLIT flag on child if inserting the new item finishes
* a split.
*/
if (!isleaf)
{
Page cpage = BufferGetPage(cbuf);
BTPageOpaque cpageop = (BTPageOpaque) PageGetSpecialPointer(cpage);
cpageop->btpo_flags &= ~BTP_INCOMPLETE_SPLIT;
MarkBufferDirty(cbuf);
}
/* XLOG stuff */
if (RelationNeedsWAL(rel))
{
xl_btree_split xlrec;
uint8 xlinfo;
XLogRecPtr recptr;
xlrec.level = ropaque->btpo.level;
xlrec.firstright = firstright;
xlrec.newitemoff = newitemoff;
XLogBeginInsert();
XLogRegisterData((char *) &xlrec, SizeOfBtreeSplit);
XLogRegisterBuffer(0, buf, REGBUF_STANDARD);
XLogRegisterBuffer(1, rbuf, REGBUF_WILL_INIT);
/* Log the right sibling, because we've changed its prev-pointer. */
if (!P_RIGHTMOST(ropaque))
XLogRegisterBuffer(2, sbuf, REGBUF_STANDARD);
if (BufferIsValid(cbuf))
XLogRegisterBuffer(3, cbuf, REGBUF_STANDARD);
/*
* Log the new item, if it was inserted on the left page. (If it was
* put on the right page, we don't need to explicitly WAL log it
* because it's included with all the other items on the right page.)
* Show the new item as belonging to the left page buffer, so that it
* is not stored if XLogInsert decides it needs a full-page image of
* the left page. We store the offset anyway, though, to support
* archive compression of these records.
*/
if (newitemonleft)
XLogRegisterBufData(0, (char *) newitem, MAXALIGN(newitemsz));
/* Log the left page's new high key */
itemid = PageGetItemId(origpage, P_HIKEY);
item = (IndexTuple) PageGetItem(origpage, itemid);
XLogRegisterBufData(0, (char *) item, MAXALIGN(IndexTupleSize(item)));
/*
* Log the contents of the right page in the format understood by
* _bt_restore_page(). The whole right page will be recreated.
*
* Direct access to page is not good but faster - we should implement
* some new func in page API. Note we only store the tuples
* themselves, knowing that they were inserted in item-number order
* and so the line pointers can be reconstructed. See comments for
* _bt_restore_page().
*/
XLogRegisterBufData(1,
(char *) rightpage + ((PageHeader) rightpage)->pd_upper,
((PageHeader) rightpage)->pd_special - ((PageHeader) rightpage)->pd_upper);
xlinfo = newitemonleft ? XLOG_BTREE_SPLIT_L : XLOG_BTREE_SPLIT_R;
recptr = XLogInsert(RM_BTREE_ID, xlinfo);
PageSetLSN(origpage, recptr);
PageSetLSN(rightpage, recptr);
if (!P_RIGHTMOST(ropaque))
{
PageSetLSN(spage, recptr);
}
if (!isleaf)
{
PageSetLSN(BufferGetPage(cbuf), recptr);
}
}
END_CRIT_SECTION();
/* release the old right sibling */
if (!P_RIGHTMOST(ropaque))
_bt_relbuf(rel, sbuf);
/* release the child */
if (!isleaf)
_bt_relbuf(rel, cbuf);
/* split's done */
return rbuf;
}
/*
* _bt_insert_parent() -- Insert downlink into parent, completing split.
*
* On entry, buf and rbuf are the left and right split pages, which we
* still hold write locks on. Both locks will be released here. We
* release the rbuf lock once we have a write lock on the page that we
* intend to insert a downlink to rbuf on (i.e. buf's current parent page).
* The lock on buf is released at the same point as the lock on the parent
* page, since buf's INCOMPLETE_SPLIT flag must be cleared by the same
* atomic operation that completes the split by inserting a new downlink.
*
* stack - stack showing how we got here. Will be NULL when splitting true
* root, or during concurrent root split, where we can be inefficient
* is_root - we split the true root
* is_only - we split a page alone on its level (might have been fast root)
*/
static void
_bt_insert_parent(Relation rel,
Buffer buf,
Buffer rbuf,
BTStack stack,
bool is_root,
bool is_only)
{
/*
* Here we have to do something Lehman and Yao don't talk about: deal with
* a root split and construction of a new root. If our stack is empty
* then we have just split a node on what had been the root level when we
* descended the tree. If it was still the root then we perform a
* new-root construction. If it *wasn't* the root anymore, search to find
* the next higher level that someone constructed meanwhile, and find the
* right place to insert as for the normal case.
*
* If we have to search for the parent level, we do so by re-descending
* from the root. This is not super-efficient, but it's rare enough not
* to matter.
*/
if (is_root)
{
Buffer rootbuf;
Assert(stack == NULL);
Assert(is_only);
/* create a new root node and update the metapage */
rootbuf = _bt_newroot(rel, buf, rbuf);
/* release the split buffers */
_bt_relbuf(rel, rootbuf);
_bt_relbuf(rel, rbuf);
_bt_relbuf(rel, buf);
}
else
{
BlockNumber bknum = BufferGetBlockNumber(buf);
BlockNumber rbknum = BufferGetBlockNumber(rbuf);
Page page = BufferGetPage(buf);
IndexTuple new_item;
BTStackData fakestack;
IndexTuple ritem;
Buffer pbuf;
if (stack == NULL)
{
BTPageOpaque lpageop;
elog(DEBUG2, "concurrent ROOT page split");
lpageop = (BTPageOpaque) PageGetSpecialPointer(page);
/* Find the leftmost page at the next level up */
pbuf = _bt_get_endpoint(rel, lpageop->btpo.level + 1, false,
NULL);
/* Set up a phony stack entry pointing there */
stack = &fakestack;
stack->bts_blkno = BufferGetBlockNumber(pbuf);
stack->bts_offset = InvalidOffsetNumber;
stack->bts_btentry = InvalidBlockNumber;
stack->bts_parent = NULL;
_bt_relbuf(rel, pbuf);
}
/* get high key from left, a strict lower bound for new right page */
ritem = (IndexTuple) PageGetItem(page,
PageGetItemId(page, P_HIKEY));
/* form an index tuple that points at the new right page */
new_item = CopyIndexTuple(ritem);
BTreeInnerTupleSetDownLink(new_item, rbknum);
/*
* Re-find and write lock the parent of buf.
*
* It's possible that the location of buf's downlink has changed since
* our initial _bt_search() descent. _bt_getstackbuf() will detect
* and recover from this, updating the stack, which ensures that the
* new downlink will be inserted at the correct offset. Even buf's
* parent may have changed.
*/
stack->bts_btentry = bknum;
pbuf = _bt_getstackbuf(rel, stack);
/*
* Now we can unlock the right child. The left child will be unlocked
* by _bt_insertonpg().
*/
_bt_relbuf(rel, rbuf);
if (pbuf == InvalidBuffer)
elog(ERROR, "failed to re-find parent key in index \"%s\" for split pages %u/%u",
RelationGetRelationName(rel), bknum, rbknum);
/* Recursively update the parent */
_bt_insertonpg(rel, NULL, pbuf, buf, stack->bts_parent,
new_item, stack->bts_offset + 1,
is_only);
/* be tidy */
pfree(new_item);
}
}
/*
* _bt_finish_split() -- Finish an incomplete split
*
* A crash or other failure can leave a split incomplete. The insertion
* routines won't allow to insert on a page that is incompletely split.
* Before inserting on such a page, call _bt_finish_split().
*
* On entry, 'lbuf' must be locked in write-mode. On exit, it is unlocked
* and unpinned.
*/
void
_bt_finish_split(Relation rel, Buffer lbuf, BTStack stack)
{
Page lpage = BufferGetPage(lbuf);
BTPageOpaque lpageop = (BTPageOpaque) PageGetSpecialPointer(lpage);
Buffer rbuf;
Page rpage;
BTPageOpaque rpageop;
bool was_root;
bool was_only;
Assert(P_INCOMPLETE_SPLIT(lpageop));
/* Lock right sibling, the one missing the downlink */
rbuf = _bt_getbuf(rel, lpageop->btpo_next, BT_WRITE);
rpage = BufferGetPage(rbuf);
rpageop = (BTPageOpaque) PageGetSpecialPointer(rpage);
/* Could this be a root split? */
if (!stack)
{
Buffer metabuf;
Page metapg;
BTMetaPageData *metad;
/* acquire lock on the metapage */
metabuf = _bt_getbuf(rel, BTREE_METAPAGE, BT_WRITE);
metapg = BufferGetPage(metabuf);
metad = BTPageGetMeta(metapg);
was_root = (metad->btm_root == BufferGetBlockNumber(lbuf));
_bt_relbuf(rel, metabuf);
}
else
was_root = false;
/* Was this the only page on the level before split? */
was_only = (P_LEFTMOST(lpageop) && P_RIGHTMOST(rpageop));
elog(DEBUG1, "finishing incomplete split of %u/%u",
BufferGetBlockNumber(lbuf), BufferGetBlockNumber(rbuf));
_bt_insert_parent(rel, lbuf, rbuf, stack, was_root, was_only);
}
/*
* _bt_getstackbuf() -- Walk back up the tree one step, and find the item
* we last looked at in the parent.
*
* This is possible because we save the downlink from the parent item,
* which is enough to uniquely identify it. Insertions into the parent
* level could cause the item to move right; deletions could cause it
* to move left, but not left of the page we previously found it in.
*
* Adjusts bts_blkno & bts_offset if changed.
*
* Returns write-locked buffer, or InvalidBuffer if item not found
* (should not happen).
*/
Buffer
_bt_getstackbuf(Relation rel, BTStack stack)
{
BlockNumber blkno;
OffsetNumber start;
blkno = stack->bts_blkno;
start = stack->bts_offset;
for (;;)
{
Buffer buf;
Page page;
BTPageOpaque opaque;
buf = _bt_getbuf(rel, blkno, BT_WRITE);
page = BufferGetPage(buf);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
if (P_INCOMPLETE_SPLIT(opaque))
{
_bt_finish_split(rel, buf, stack->bts_parent);
continue;
}
if (!P_IGNORE(opaque))
{
OffsetNumber offnum,
minoff,
maxoff;
ItemId itemid;
IndexTuple item;
minoff = P_FIRSTDATAKEY(opaque);
maxoff = PageGetMaxOffsetNumber(page);
/*
* start = InvalidOffsetNumber means "search the whole page". We
* need this test anyway due to possibility that page has a high
* key now when it didn't before.
*/
if (start < minoff)
start = minoff;
/*
* Need this check too, to guard against possibility that page
* split since we visited it originally.
*/
if (start > maxoff)
start = OffsetNumberNext(maxoff);
/*
* These loops will check every item on the page --- but in an
* order that's attuned to the probability of where it actually
* is. Scan to the right first, then to the left.
*/
for (offnum = start;
offnum <= maxoff;
offnum = OffsetNumberNext(offnum))
{
itemid = PageGetItemId(page, offnum);
item = (IndexTuple) PageGetItem(page, itemid);
if (BTreeInnerTupleGetDownLink(item) == stack->bts_btentry)
{
/* Return accurate pointer to where link is now */
stack->bts_blkno = blkno;
stack->bts_offset = offnum;
return buf;
}
}
for (offnum = OffsetNumberPrev(start);
offnum >= minoff;
offnum = OffsetNumberPrev(offnum))
{
itemid = PageGetItemId(page, offnum);
item = (IndexTuple) PageGetItem(page, itemid);
if (BTreeInnerTupleGetDownLink(item) == stack->bts_btentry)
{
/* Return accurate pointer to where link is now */
stack->bts_blkno = blkno;
stack->bts_offset = offnum;
return buf;
}
}
}
/*
* The item we're looking for moved right at least one page.
*/
if (P_RIGHTMOST(opaque))
{
_bt_relbuf(rel, buf);
return InvalidBuffer;
}
blkno = opaque->btpo_next;
start = InvalidOffsetNumber;
_bt_relbuf(rel, buf);
}
}
/*
* _bt_newroot() -- Create a new root page for the index.
*
* We've just split the old root page and need to create a new one.
* In order to do this, we add a new root page to the file, then lock
* the metadata page and update it. This is guaranteed to be deadlock-
* free, because all readers release their locks on the metadata page
* before trying to lock the root, and all writers lock the root before
* trying to lock the metadata page. We have a write lock on the old
* root page, so we have not introduced any cycles into the waits-for
* graph.
*
* On entry, lbuf (the old root) and rbuf (its new peer) are write-
* locked. On exit, a new root page exists with entries for the
* two new children, metapage is updated and unlocked/unpinned.
* The new root buffer is returned to caller which has to unlock/unpin
* lbuf, rbuf & rootbuf.
*/
static Buffer
_bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
{
Buffer rootbuf;
Page lpage,
rootpage;
BlockNumber lbkno,
rbkno;
BlockNumber rootblknum;
BTPageOpaque rootopaque;
BTPageOpaque lopaque;
ItemId itemid;
IndexTuple item;
IndexTuple left_item;
Size left_item_sz;
IndexTuple right_item;
Size right_item_sz;
Buffer metabuf;
Page metapg;
BTMetaPageData *metad;
lbkno = BufferGetBlockNumber(lbuf);
rbkno = BufferGetBlockNumber(rbuf);
lpage = BufferGetPage(lbuf);
lopaque = (BTPageOpaque) PageGetSpecialPointer(lpage);
/* get a new root page */
rootbuf = _bt_getbuf(rel, P_NEW, BT_WRITE);
rootpage = BufferGetPage(rootbuf);
rootblknum = BufferGetBlockNumber(rootbuf);
/* acquire lock on the metapage */
metabuf = _bt_getbuf(rel, BTREE_METAPAGE, BT_WRITE);
metapg = BufferGetPage(metabuf);
metad = BTPageGetMeta(metapg);
/*
* Create downlink item for left page (old root). Since this will be the
* first item in a non-leaf page, it implicitly has minus-infinity key
* value, so we need not store any actual key in it.
*/
left_item_sz = sizeof(IndexTupleData);
left_item = (IndexTuple) palloc(left_item_sz);
left_item->t_info = left_item_sz;
BTreeInnerTupleSetDownLink(left_item, lbkno);
BTreeTupleSetNAtts(left_item, 0);
/*
* Create downlink item for right page. The key for it is obtained from
* the "high key" position in the left page.
*/
itemid = PageGetItemId(lpage, P_HIKEY);
right_item_sz = ItemIdGetLength(itemid);
item = (IndexTuple) PageGetItem(lpage, itemid);
right_item = CopyIndexTuple(item);
BTreeInnerTupleSetDownLink(right_item, rbkno);
/* NO EREPORT(ERROR) from here till newroot op is logged */
START_CRIT_SECTION();
/* upgrade metapage if needed */
if (metad->btm_version < BTREE_NOVAC_VERSION)
_bt_upgrademetapage(metapg);
/* set btree special data */
rootopaque = (BTPageOpaque) PageGetSpecialPointer(rootpage);
rootopaque->btpo_prev = rootopaque->btpo_next = P_NONE;
rootopaque->btpo_flags = BTP_ROOT;
rootopaque->btpo.level =
((BTPageOpaque) PageGetSpecialPointer(lpage))->btpo.level + 1;
rootopaque->btpo_cycleid = 0;
/* update metapage data */
metad->btm_root = rootblknum;
metad->btm_level = rootopaque->btpo.level;
metad->btm_fastroot = rootblknum;
metad->btm_fastlevel = rootopaque->btpo.level;
/*
* Insert the left page pointer into the new root page. The root page is
* the rightmost page on its level so there is no "high key" in it; the
* two items will go into positions P_HIKEY and P_FIRSTKEY.
*
* Note: we *must* insert the two items in item-number order, for the
* benefit of _bt_restore_page().
*/
Assert(BTreeTupleGetNAtts(left_item, rel) == 0);
if (PageAddItem(rootpage, (Item) left_item, left_item_sz, P_HIKEY,
false, false) == InvalidOffsetNumber)
elog(PANIC, "failed to add leftkey to new root page"
" while splitting block %u of index \"%s\"",
BufferGetBlockNumber(lbuf), RelationGetRelationName(rel));
/*
* insert the right page pointer into the new root page.
*/
Assert(BTreeTupleGetNAtts(right_item, rel) > 0);
Assert(BTreeTupleGetNAtts(right_item, rel) <=
IndexRelationGetNumberOfKeyAttributes(rel));
if (PageAddItem(rootpage, (Item) right_item, right_item_sz, P_FIRSTKEY,
false, false) == InvalidOffsetNumber)
elog(PANIC, "failed to add rightkey to new root page"
" while splitting block %u of index \"%s\"",
BufferGetBlockNumber(lbuf), RelationGetRelationName(rel));
/* Clear the incomplete-split flag in the left child */
Assert(P_INCOMPLETE_SPLIT(lopaque));
lopaque->btpo_flags &= ~BTP_INCOMPLETE_SPLIT;
MarkBufferDirty(lbuf);
MarkBufferDirty(rootbuf);
MarkBufferDirty(metabuf);
/* XLOG stuff */
if (RelationNeedsWAL(rel))
{
xl_btree_newroot xlrec;
XLogRecPtr recptr;
xl_btree_metadata md;
xlrec.rootblk = rootblknum;
xlrec.level = metad->btm_level;
XLogBeginInsert();
XLogRegisterData((char *) &xlrec, SizeOfBtreeNewroot);
XLogRegisterBuffer(0, rootbuf, REGBUF_WILL_INIT);
XLogRegisterBuffer(1, lbuf, REGBUF_STANDARD);
XLogRegisterBuffer(2, metabuf, REGBUF_WILL_INIT | REGBUF_STANDARD);
Assert(metad->btm_version >= BTREE_NOVAC_VERSION);
md.version = metad->btm_version;
md.root = rootblknum;
md.level = metad->btm_level;
md.fastroot = rootblknum;
md.fastlevel = metad->btm_level;
md.oldest_btpo_xact = metad->btm_oldest_btpo_xact;
md.last_cleanup_num_heap_tuples = metad->btm_last_cleanup_num_heap_tuples;
XLogRegisterBufData(2, (char *) &md, sizeof(xl_btree_metadata));
/*
* Direct access to page is not good but faster - we should implement
* some new func in page API.
*/
XLogRegisterBufData(0,
(char *) rootpage + ((PageHeader) rootpage)->pd_upper,
((PageHeader) rootpage)->pd_special -
((PageHeader) rootpage)->pd_upper);
recptr = XLogInsert(RM_BTREE_ID, XLOG_BTREE_NEWROOT);
PageSetLSN(lpage, recptr);
PageSetLSN(rootpage, recptr);
PageSetLSN(metapg, recptr);
}
END_CRIT_SECTION();
/* done with metapage */
_bt_relbuf(rel, metabuf);
pfree(left_item);
pfree(right_item);
return rootbuf;
}
/*
* _bt_pgaddtup() -- add a tuple to a particular page in the index.
*
* This routine adds the tuple to the page as requested. It does
* not affect pin/lock status, but you'd better have a write lock
* and pin on the target buffer! Don't forget to write and release
* the buffer afterwards, either.
*
* The main difference between this routine and a bare PageAddItem call
* is that this code knows that the leftmost index tuple on a non-leaf
* btree page doesn't need to have a key. Therefore, it strips such
* tuples down to just the tuple header. CAUTION: this works ONLY if
* we insert the tuples in order, so that the given itup_off does
* represent the final position of the tuple!
*/
static bool
_bt_pgaddtup(Page page,
Size itemsize,
IndexTuple itup,
OffsetNumber itup_off)
{
BTPageOpaque opaque = (BTPageOpaque) PageGetSpecialPointer(page);
IndexTupleData trunctuple;
if (!P_ISLEAF(opaque) && itup_off == P_FIRSTDATAKEY(opaque))
{
trunctuple = *itup;
trunctuple.t_info = sizeof(IndexTupleData);
/* Deliberately zero INDEX_ALT_TID_MASK bits */
BTreeTupleSetNAtts(&trunctuple, 0);
itup = &trunctuple;
itemsize = sizeof(IndexTupleData);
}
if (PageAddItem(page, (Item) itup, itemsize, itup_off,
false, false) == InvalidOffsetNumber)
return false;
return true;
}
/*
* _bt_vacuum_one_page - vacuum just one index page.
*
* Try to remove LP_DEAD items from the given page. The passed buffer
* must be exclusive-locked, but unlike a real VACUUM, we don't need a
* super-exclusive "cleanup" lock (see nbtree/README).
*/
static void
_bt_vacuum_one_page(Relation rel, Buffer buffer, Relation heapRel)
{
OffsetNumber deletable[MaxOffsetNumber];
int ndeletable = 0;
OffsetNumber offnum,
minoff,
maxoff;
Page page = BufferGetPage(buffer);
BTPageOpaque opaque = (BTPageOpaque) PageGetSpecialPointer(page);
Assert(P_ISLEAF(opaque));
/*
* Scan over all items to see which ones need to be deleted according to
* LP_DEAD flags.
*/
minoff = P_FIRSTDATAKEY(opaque);
maxoff = PageGetMaxOffsetNumber(page);
for (offnum = minoff;
offnum <= maxoff;
offnum = OffsetNumberNext(offnum))
{
ItemId itemId = PageGetItemId(page, offnum);
if (ItemIdIsDead(itemId))
deletable[ndeletable++] = offnum;
}
if (ndeletable > 0)
_bt_delitems_delete(rel, buffer, deletable, ndeletable, heapRel);
/*
* Note: if we didn't find any LP_DEAD items, then the page's
* BTP_HAS_GARBAGE hint bit is falsely set. We do not bother expending a
* separate write to clear it, however. We will clear it when we split
* the page.
*/
}
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