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Split _bt_insertonpg to two functions. 

Heikki Linnakangas
This commit is contained in:
Bruce Momjian 2007-03-03 20:13:06 +00:00
parent 63c678d17b
commit bc292937ae
1 changed files with 190 additions and 142 deletions
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332
src/backend/access/nbtree/nbtinsert.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtinsert.c,v 1.152 2007/02/21 20:02:17 momjian Exp $
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtinsert.c,v 1.153 2007/03/03 20:13:06 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -46,13 +46,18 @@ typedef struct
static Buffer _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf);
static TransactionId _bt_check_unique(Relation rel, IndexTuple itup,
Relation heapRel, Buffer buf,
Relation heapRel, Buffer buf, OffsetNumber ioffset,
ScanKey itup_scankey);
static void _bt_findinsertloc(Relation rel,
Buffer *bufptr,
OffsetNumber *offsetptr,
int keysz,
ScanKey scankey,
IndexTuple newtup);
static void _bt_insertonpg(Relation rel, Buffer buf,
BTStack stack,
int keysz, ScanKey scankey,
IndexTuple itup,
OffsetNumber afteritem,
OffsetNumber newitemoff,
bool split_only_page);
static Buffer _bt_split(Relation rel, Buffer buf, OffsetNumber firstright,
OffsetNumber newitemoff, Size newitemsz,
@ -86,6 +91,7 @@ _bt_doinsert(Relation rel, IndexTuple itup,
ScanKey itup_scankey;
BTStack stack;
Buffer buf;
OffsetNumber offset;
/* we need an insertion scan key to do our search, so build one */
itup_scankey = _bt_mkscankey(rel, itup);
@ -94,6 +100,8 @@ top:
/* find the first page containing this key */
stack = _bt_search(rel, natts, itup_scankey, false, &buf, BT_WRITE);
offset = InvalidOffsetNumber;
/* trade in our read lock for a write lock */
LockBuffer(buf, BUFFER_LOCK_UNLOCK);
LockBuffer(buf, BT_WRITE);
@ -128,7 +136,8 @@ top:
{
TransactionId xwait;
xwait = _bt_check_unique(rel, itup, heapRel, buf, itup_scankey);
offset = _bt_binsrch(rel, buf, natts, itup_scankey, false);
xwait = _bt_check_unique(rel, itup, heapRel, buf, offset, itup_scankey);
if (TransactionIdIsValid(xwait))
{
@ -142,7 +151,8 @@ top:
}
/* do the insertion */
_bt_insertonpg(rel, buf, stack, natts, itup_scankey, itup, 0, false);
_bt_findinsertloc(rel, &buf, &offset, natts, itup_scankey, itup);
_bt_insertonpg(rel, buf, stack, itup, offset, false);
/* be tidy */
_bt_freestack(stack);
@ -152,18 +162,21 @@ top:
/*
* _bt_check_unique() -- Check for violation of unique index constraint
*
* offset points to the first possible item that could conflict. It can
* also point to end-of-page, which means that the first tuple to check
* is the first tuple on the next page.
*
* 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().
*/
static TransactionId
_bt_check_unique(Relation rel, IndexTuple itup, Relation heapRel,
Buffer buf, ScanKey itup_scankey)
Buffer buf, OffsetNumber offset, ScanKey itup_scankey)
{
TupleDesc itupdesc = RelationGetDescr(rel);
int natts = rel->rd_rel->relnatts;
OffsetNumber offset,
maxoff;
OffsetNumber maxoff;
Page page;
BTPageOpaque opaque;
Buffer nbuf = InvalidBuffer;
@ -172,12 +185,6 @@ _bt_check_unique(Relation rel, IndexTuple itup, Relation heapRel,
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
maxoff = PageGetMaxOffsetNumber(page);
/*
* Find first item >= proposed new item. Note we could also get a pointer
* to end-of-page here.
*/
offset = _bt_binsrch(rel, buf, natts, itup_scankey, false);
/*
* Scan over all equal tuples, looking for live conflicts.
*/
@ -342,33 +349,11 @@ _bt_check_unique(Relation rel, IndexTuple itup, Relation heapRel,
return InvalidTransactionId;
}
/*----------
* _bt_insertonpg() -- Insert a tuple on a particular page in the index.
/*
* _bt_findinsertloc() -- Finds an insert location for a tuple
*
* This recursive procedure does the following things:
*
* + finds the right place to insert the tuple.
* + if necessary, splits the target page (making sure that the
* split is equitable as far as post-insert free space goes).
* + 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 right 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.
*
* If 'afteritem' is >0 then the new tuple must be inserted after the
* existing item of that number, noplace else. If 'afteritem' is 0
* then the procedure finds the exact spot to insert it by searching.
* (keysz and scankey parameters are used ONLY if afteritem == 0.
* The scankey must be an insertion-type scankey.)
*
* NOTE: if the new key is equal to one or more existing keys, we can
* 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
@ -379,36 +364,40 @@ _bt_check_unique(Relation rel, IndexTuple itup, Relation heapRel,
* Once we have chosen the page to put the key on, we'll insert it before
* any existing equal keys because of the way _bt_binsrch() works.
*
* The locking interactions in this code are critical. You should
* grok Lehman and Yao's paper before making any changes. In addition,
* you need to understand how we disambiguate duplicate keys in this
* implementation, in order to be able to find our location using
* L&Y "move right" operations. Since we may insert duplicate user
* keys, and since these dups may propagate up the tree, we use the
* 'afteritem' parameter to position ourselves correctly for the
* insertion on internal pages.
*----------
* If there's not enough room in the space, we try to make room by
* removing any LP_DELETEd tuples.
*
* On entry, *buf and *offsetptr point to the first legal position
* where the new tuple could be inserted. The caller should hold an
* exclusive lock on *buf. *offsetptr can also be set to
* InvalidOffsetNumber, in which case the function will search the right
* location within the page if needed. On exit, they point to the chosen
* insert location. If findinsertloc decided to move right, the lock and
* pin on the original page will be released and the new page returned to
* the caller is exclusively locked instead.
*
* newtup is the new tuple we're inserting, and scankey is an insertion
* type scan key for it.
*/
static void
_bt_insertonpg(Relation rel,
Buffer buf,
BTStack stack,
int keysz,
ScanKey scankey,
IndexTuple itup,
OffsetNumber afteritem,
bool split_only_page)
_bt_findinsertloc(Relation rel,
Buffer *bufptr,
OffsetNumber *offsetptr,
int keysz,
ScanKey scankey,
IndexTuple newtup)
{
Page page;
Buffer buf = *bufptr;
Page page = BufferGetPage(buf);
Size itemsz;
BTPageOpaque lpageop;
bool movedright, vacuumed;
OffsetNumber newitemoff;
OffsetNumber firstright = InvalidOffsetNumber;
Size itemsz;
OffsetNumber firstlegaloff = *offsetptr;
page = BufferGetPage(buf);
lpageop = (BTPageOpaque) PageGetSpecialPointer(page);
itemsz = IndexTupleDSize(*itup);
itemsz = IndexTupleDSize(*newtup);
itemsz = MAXALIGN(itemsz); /* be safe, PageAddItem will do this but we
* need to be consistent */
@ -429,96 +418,155 @@ _bt_insertonpg(Relation rel,
"Consider a function index of an MD5 hash of the value, "
"or use full text indexing.")));
/*
* Determine exactly where new item will go.
/*----------
* If we will need to split the page to put the item on this page,
* check whether we can put the tuple somewhere to the right,
* instead. 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). Currently 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.
*----------
*/
if (afteritem > 0)
newitemoff = afteritem + 1;
else
movedright = false;
vacuumed = false;
while (PageGetFreeSpace(page) < itemsz)
{
/*----------
* If we will need to split the page to put the item here,
* check whether we can put the tuple somewhere to the right,
* instead. 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). Currently 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.
*----------
Buffer rbuf;
/*
* before considering moving right, see if we can obtain enough
* space by erasing LP_DELETE items
*/
bool movedright = false;
while (PageGetFreeSpace(page) < itemsz)
if (P_ISLEAF(lpageop) && P_HAS_GARBAGE(lpageop))
{
Buffer rbuf;
_bt_vacuum_one_page(rel, buf);
/*
* before considering moving right, see if we can obtain enough
* space by erasing LP_DELETE items
*/
if (P_ISLEAF(lpageop) && P_HAS_GARBAGE(lpageop))
{
_bt_vacuum_one_page(rel, buf);
if (PageGetFreeSpace(page) >= itemsz)
break; /* OK, now we have enough space */
}
/* remember that we vacuumed this page, because that makes
* the hint supplied by the caller invalid */
vacuumed = true;
/*
* nope, so check conditions (b) and (c) enumerated above
*/
if (P_RIGHTMOST(lpageop) ||
_bt_compare(rel, keysz, scankey, page, P_HIKEY) != 0 ||
random() <= (MAX_RANDOM_VALUE / 100))
break;
/*
* step right to next non-dead page
*
* must write-lock that 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.
*/
rbuf = InvalidBuffer;
for (;;)
{
BlockNumber rblkno = lpageop->btpo_next;
rbuf = _bt_relandgetbuf(rel, rbuf, rblkno, BT_WRITE);
page = BufferGetPage(rbuf);
lpageop = (BTPageOpaque) PageGetSpecialPointer(page);
if (!P_IGNORE(lpageop))
break;
if (P_RIGHTMOST(lpageop))
elog(ERROR, "fell off the end of \"%s\"",
RelationGetRelationName(rel));
}
_bt_relbuf(rel, buf);
buf = rbuf;
movedright = true;
if (PageGetFreeSpace(page) >= itemsz)
break; /* OK, now we have enough space */
}
/*
* Now we are on the right page, so find the insert position. If we
* moved right at all, we know we should insert at the start of the
* page, else must find the position by searching.
* nope, so check conditions (b) and (c) enumerated above
*/
if (movedright)
newitemoff = P_FIRSTDATAKEY(lpageop);
else
newitemoff = _bt_binsrch(rel, buf, keysz, scankey, false);
if (P_RIGHTMOST(lpageop) ||
_bt_compare(rel, keysz, scankey, page, P_HIKEY) != 0 ||
random() <= (MAX_RANDOM_VALUE / 100))
break;
/*
* step right to next non-dead page
*
* must write-lock that 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.
*/
rbuf = InvalidBuffer;
for (;;)
{
BlockNumber rblkno = lpageop->btpo_next;
rbuf = _bt_relandgetbuf(rel, rbuf, rblkno, BT_WRITE);
page = BufferGetPage(rbuf);
lpageop = (BTPageOpaque) PageGetSpecialPointer(page);
if (!P_IGNORE(lpageop))
break;
if (P_RIGHTMOST(lpageop))
elog(ERROR, "fell off the end of \"%s\"",
RelationGetRelationName(rel));
}
_bt_relbuf(rel, buf);
buf = rbuf;
movedright = true;
vacuumed = false;
}
/*
* Now we are on the right page, so find the insert position. If we
* moved right at all, we know we should insert at the start of the
* page. If we didn't move right, we can use the firstlegaloff hint
* if the caller supplied one, unless we vacuumed the page which
* might have moved tuples around making the hint invalid. If we
* didn't move right or can't use the hint, find the position
* by searching.
*/
if (movedright)
newitemoff = P_FIRSTDATAKEY(lpageop);
else if(firstlegaloff != InvalidOffsetNumber && !vacuumed)
newitemoff = firstlegaloff;
else
newitemoff = _bt_binsrch(rel, buf, keysz, scankey, false);
*bufptr = buf;
*offsetptr = newitemoff;
}
/*----------
* _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 (making sure that the
* split is equitable as far as post-insert free space goes).
* + 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 right 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.
*
* The locking interactions in this code are critical. You should
* grok Lehman and Yao's paper before making any changes. In addition,
* you need to understand how we disambiguate duplicate keys in this
* implementation, in order to be able to find our location using
* L&Y "move right" operations. Since we may insert duplicate user
* keys, and since these dups may propagate up the tree, we use the
* 'afteritem' parameter to position ourselves correctly for the
* insertion on internal pages.
*----------
*/
static void
_bt_insertonpg(Relation rel,
Buffer buf,
BTStack stack,
IndexTuple itup,
OffsetNumber newitemoff,
bool split_only_page)
{
Page page;
BTPageOpaque lpageop;
OffsetNumber firstright = InvalidOffsetNumber;
Size itemsz;
page = BufferGetPage(buf);
lpageop = (BTPageOpaque) PageGetSpecialPointer(page);
itemsz = IndexTupleDSize(*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?
*
@ -1427,7 +1475,7 @@ _bt_insert_parent(Relation rel,
/* Recursively update the parent */
_bt_insertonpg(rel, pbuf, stack->bts_parent,
0, NULL, new_item, stack->bts_offset,
new_item, stack->bts_offset + 1,
is_only);
/* be tidy */