*
*
* 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 $
*
*-------------------------------------------------------------------------
*/
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,
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);
/* 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);
{
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))
{
}
/* 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);
/*
* _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;
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.
*/
return InvalidTransactionId;
}
-/*----------
- * _bt_insertonpg() -- Insert a tuple on a particular page in the index.
- *
- * 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.)
+
+/*
+ * _bt_findinsertloc() -- Finds an insert location for a tuple
*
- * 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
* 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 */
"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.
- *----------
- */
- bool movedright = false;
+ Buffer rbuf;
- while (PageGetFreeSpace(page) < itemsz)
+ /*
+ * before considering moving right, see if we can obtain enough
+ * space by erasing LP_DELETE items
+ */
+ if (P_ISLEAF(lpageop) && P_HAS_GARBAGE(lpageop))
{
- Buffer rbuf;
-
- /*
- * 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 */
- }
+ _bt_vacuum_one_page(rel, buf);
- /*
- * 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;
+ /* remember that we vacuumed this page, because that makes
+ * the hint supplied by the caller invalid */
+ vacuumed = true;
- 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?
*
/* 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 */
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