mirror of
https://github.com/postgres/postgres.git
synced 2025-05-28 05:21:27 +03:00
9aefd56669
or contradictory keys even in cross-data-type scenarios. This is another benefit of the opfamily rewrite: we can find the needed comparison operators now.
1463 lines
44 KiB
C
1463 lines
44 KiB
C
/*-------------------------------------------------------------------------
|
|
*
|
|
* nbtsearch.c
|
|
* Search code for postgres btrees.
|
|
*
|
|
*
|
|
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
|
|
* Portions Copyright (c) 1994, Regents of the University of California
|
|
*
|
|
* IDENTIFICATION
|
|
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtsearch.c,v 1.109 2006/12/28 23:16:39 tgl Exp $
|
|
*
|
|
*-------------------------------------------------------------------------
|
|
*/
|
|
|
|
#include "postgres.h"
|
|
|
|
#include "access/genam.h"
|
|
#include "access/nbtree.h"
|
|
#include "pgstat.h"
|
|
#include "utils/lsyscache.h"
|
|
|
|
|
|
static bool _bt_readpage(IndexScanDesc scan, ScanDirection dir,
|
|
OffsetNumber offnum);
|
|
static bool _bt_steppage(IndexScanDesc scan, ScanDirection dir);
|
|
static Buffer _bt_walk_left(Relation rel, Buffer buf);
|
|
static bool _bt_endpoint(IndexScanDesc scan, ScanDirection dir);
|
|
|
|
|
|
/*
|
|
* _bt_search() -- Search the tree for a particular scankey,
|
|
* or more precisely for the first leaf page it could be on.
|
|
*
|
|
* The passed scankey must be an insertion-type scankey (see nbtree/README),
|
|
* but it can omit the rightmost column(s) of the index.
|
|
*
|
|
* When nextkey is false (the usual case), we are looking for the first
|
|
* item >= scankey. When nextkey is true, we are looking for the first
|
|
* item strictly greater than scankey.
|
|
*
|
|
* Return value is a stack of parent-page pointers. *bufP is set to the
|
|
* address of the leaf-page buffer, which is read-locked and pinned.
|
|
* No locks are held on the parent pages, however!
|
|
*
|
|
* NOTE that the returned buffer is read-locked regardless of the access
|
|
* parameter. However, access = BT_WRITE will allow an empty root page
|
|
* to be created and returned. When access = BT_READ, an empty index
|
|
* will result in *bufP being set to InvalidBuffer.
|
|
*/
|
|
BTStack
|
|
_bt_search(Relation rel, int keysz, ScanKey scankey, bool nextkey,
|
|
Buffer *bufP, int access)
|
|
{
|
|
BTStack stack_in = NULL;
|
|
|
|
/* Get the root page to start with */
|
|
*bufP = _bt_getroot(rel, access);
|
|
|
|
/* If index is empty and access = BT_READ, no root page is created. */
|
|
if (!BufferIsValid(*bufP))
|
|
return (BTStack) NULL;
|
|
|
|
/* Loop iterates once per level descended in the tree */
|
|
for (;;)
|
|
{
|
|
Page page;
|
|
BTPageOpaque opaque;
|
|
OffsetNumber offnum;
|
|
ItemId itemid;
|
|
IndexTuple itup;
|
|
BlockNumber blkno;
|
|
BlockNumber par_blkno;
|
|
BTStack new_stack;
|
|
|
|
/*
|
|
* Race -- the page we just grabbed may have split since we read its
|
|
* pointer in the parent (or metapage). If it has, we may need to
|
|
* move right to its new sibling. Do that.
|
|
*/
|
|
*bufP = _bt_moveright(rel, *bufP, keysz, scankey, nextkey, BT_READ);
|
|
|
|
/* if this is a leaf page, we're done */
|
|
page = BufferGetPage(*bufP);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
if (P_ISLEAF(opaque))
|
|
break;
|
|
|
|
/*
|
|
* Find the appropriate item on the internal page, and get the child
|
|
* page that it points to.
|
|
*/
|
|
offnum = _bt_binsrch(rel, *bufP, keysz, scankey, nextkey);
|
|
itemid = PageGetItemId(page, offnum);
|
|
itup = (IndexTuple) PageGetItem(page, itemid);
|
|
blkno = ItemPointerGetBlockNumber(&(itup->t_tid));
|
|
par_blkno = BufferGetBlockNumber(*bufP);
|
|
|
|
/*
|
|
* We need to save the location of the index entry we chose in the
|
|
* parent page on a stack. In case we split the tree, we'll use the
|
|
* stack to work back up to the parent page. We also save the actual
|
|
* downlink (TID) to uniquely identify the index entry, in case it
|
|
* moves right while we're working lower in the tree. See the paper
|
|
* by Lehman and Yao for how this is detected and handled. (We use the
|
|
* child link to disambiguate duplicate keys in the index -- Lehman
|
|
* and Yao disallow duplicate keys.)
|
|
*/
|
|
new_stack = (BTStack) palloc(sizeof(BTStackData));
|
|
new_stack->bts_blkno = par_blkno;
|
|
new_stack->bts_offset = offnum;
|
|
memcpy(&new_stack->bts_btentry, itup, sizeof(IndexTupleData));
|
|
new_stack->bts_parent = stack_in;
|
|
|
|
/* drop the read lock on the parent page, acquire one on the child */
|
|
*bufP = _bt_relandgetbuf(rel, *bufP, blkno, BT_READ);
|
|
|
|
/* okay, all set to move down a level */
|
|
stack_in = new_stack;
|
|
}
|
|
|
|
return stack_in;
|
|
}
|
|
|
|
/*
|
|
* _bt_moveright() -- move right in the btree if necessary.
|
|
*
|
|
* When we follow a pointer to reach a page, it is possible that
|
|
* the page has changed in the meanwhile. If this happens, we're
|
|
* guaranteed that the page has "split right" -- that is, that any
|
|
* data that appeared on the page originally is either on the page
|
|
* or strictly to the right of it.
|
|
*
|
|
* This routine decides whether or not we need to move right in the
|
|
* tree by examining the high key entry on the page. If that entry
|
|
* is strictly less than the scankey, or <= the scankey in the nextkey=true
|
|
* case, then we followed the wrong link and we need to move right.
|
|
*
|
|
* The passed scankey must be an insertion-type scankey (see nbtree/README),
|
|
* but it can omit the rightmost column(s) of the index.
|
|
*
|
|
* When nextkey is false (the usual case), we are looking for the first
|
|
* item >= scankey. When nextkey is true, we are looking for the first
|
|
* item strictly greater than scankey.
|
|
*
|
|
* On entry, we have the buffer pinned and a lock of the type specified by
|
|
* 'access'. If we move right, we release the buffer and lock and acquire
|
|
* the same on the right sibling. Return value is the buffer we stop at.
|
|
*/
|
|
Buffer
|
|
_bt_moveright(Relation rel,
|
|
Buffer buf,
|
|
int keysz,
|
|
ScanKey scankey,
|
|
bool nextkey,
|
|
int access)
|
|
{
|
|
Page page;
|
|
BTPageOpaque opaque;
|
|
int32 cmpval;
|
|
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
/*
|
|
* When nextkey = false (normal case): if the scan key that brought us to
|
|
* this page is > the high key stored on the page, then the page has split
|
|
* and we need to move right. (If the scan key is equal to the high key,
|
|
* we might or might not need to move right; have to scan the page first
|
|
* anyway.)
|
|
*
|
|
* When nextkey = true: move right if the scan key is >= page's high key.
|
|
*
|
|
* The page could even have split more than once, so scan as far as
|
|
* needed.
|
|
*
|
|
* We also have to move right if we followed a link that brought us to a
|
|
* dead page.
|
|
*/
|
|
cmpval = nextkey ? 0 : 1;
|
|
|
|
while (!P_RIGHTMOST(opaque) &&
|
|
(P_IGNORE(opaque) ||
|
|
_bt_compare(rel, keysz, scankey, page, P_HIKEY) >= cmpval))
|
|
{
|
|
/* step right one page */
|
|
BlockNumber rblkno = opaque->btpo_next;
|
|
|
|
buf = _bt_relandgetbuf(rel, buf, rblkno, access);
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
}
|
|
|
|
if (P_IGNORE(opaque))
|
|
elog(ERROR, "fell off the end of \"%s\"",
|
|
RelationGetRelationName(rel));
|
|
|
|
return buf;
|
|
}
|
|
|
|
/*
|
|
* _bt_binsrch() -- Do a binary search for a key on a particular page.
|
|
*
|
|
* The passed scankey must be an insertion-type scankey (see nbtree/README),
|
|
* but it can omit the rightmost column(s) of the index.
|
|
*
|
|
* When nextkey is false (the usual case), we are looking for the first
|
|
* item >= scankey. When nextkey is true, we are looking for the first
|
|
* item strictly greater than scankey.
|
|
*
|
|
* On a leaf page, _bt_binsrch() returns the OffsetNumber of the first
|
|
* key >= given scankey, or > scankey if nextkey is true. (NOTE: in
|
|
* particular, this means it is possible to return a value 1 greater than the
|
|
* number of keys on the page, if the scankey is > all keys on the page.)
|
|
*
|
|
* On an internal (non-leaf) page, _bt_binsrch() returns the OffsetNumber
|
|
* of the last key < given scankey, or last key <= given scankey if nextkey
|
|
* is true. (Since _bt_compare treats the first data key of such a page as
|
|
* minus infinity, there will be at least one key < scankey, so the result
|
|
* always points at one of the keys on the page.) This key indicates the
|
|
* right place to descend to be sure we find all leaf keys >= given scankey
|
|
* (or leaf keys > given scankey when nextkey is true).
|
|
*
|
|
* This procedure is not responsible for walking right, it just examines
|
|
* the given page. _bt_binsrch() has no lock or refcount side effects
|
|
* on the buffer.
|
|
*/
|
|
OffsetNumber
|
|
_bt_binsrch(Relation rel,
|
|
Buffer buf,
|
|
int keysz,
|
|
ScanKey scankey,
|
|
bool nextkey)
|
|
{
|
|
Page page;
|
|
BTPageOpaque opaque;
|
|
OffsetNumber low,
|
|
high;
|
|
int32 result,
|
|
cmpval;
|
|
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
low = P_FIRSTDATAKEY(opaque);
|
|
high = PageGetMaxOffsetNumber(page);
|
|
|
|
/*
|
|
* If there are no keys on the page, return the first available slot. Note
|
|
* this covers two cases: the page is really empty (no keys), or it
|
|
* contains only a high key. The latter case is possible after vacuuming.
|
|
* This can never happen on an internal page, however, since they are
|
|
* never empty (an internal page must have children).
|
|
*/
|
|
if (high < low)
|
|
return low;
|
|
|
|
/*
|
|
* Binary search to find the first key on the page >= scan key, or first
|
|
* key > scankey when nextkey is true.
|
|
*
|
|
* For nextkey=false (cmpval=1), the loop invariant is: all slots before
|
|
* 'low' are < scan key, all slots at or after 'high' are >= scan key.
|
|
*
|
|
* For nextkey=true (cmpval=0), the loop invariant is: all slots before
|
|
* 'low' are <= scan key, all slots at or after 'high' are > scan key.
|
|
*
|
|
* We can fall out when high == low.
|
|
*/
|
|
high++; /* establish the loop invariant for high */
|
|
|
|
cmpval = nextkey ? 0 : 1; /* select comparison value */
|
|
|
|
while (high > low)
|
|
{
|
|
OffsetNumber mid = low + ((high - low) / 2);
|
|
|
|
/* We have low <= mid < high, so mid points at a real slot */
|
|
|
|
result = _bt_compare(rel, keysz, scankey, page, mid);
|
|
|
|
if (result >= cmpval)
|
|
low = mid + 1;
|
|
else
|
|
high = mid;
|
|
}
|
|
|
|
/*
|
|
* At this point we have high == low, but be careful: they could point
|
|
* past the last slot on the page.
|
|
*
|
|
* On a leaf page, we always return the first key >= scan key (resp. >
|
|
* scan key), which could be the last slot + 1.
|
|
*/
|
|
if (P_ISLEAF(opaque))
|
|
return low;
|
|
|
|
/*
|
|
* On a non-leaf page, return the last key < scan key (resp. <= scan key).
|
|
* There must be one if _bt_compare() is playing by the rules.
|
|
*/
|
|
Assert(low > P_FIRSTDATAKEY(opaque));
|
|
|
|
return OffsetNumberPrev(low);
|
|
}
|
|
|
|
/*----------
|
|
* _bt_compare() -- Compare scankey to a particular tuple on the page.
|
|
*
|
|
* The passed scankey must be an insertion-type scankey (see nbtree/README),
|
|
* but it can omit the rightmost column(s) of the index.
|
|
*
|
|
* keysz: number of key conditions to be checked (might be less than the
|
|
* number of index columns!)
|
|
* page/offnum: location of btree item to be compared to.
|
|
*
|
|
* This routine returns:
|
|
* <0 if scankey < tuple at offnum;
|
|
* 0 if scankey == tuple at offnum;
|
|
* >0 if scankey > tuple at offnum.
|
|
* NULLs in the keys are treated as sortable values. Therefore
|
|
* "equality" does not necessarily mean that the item should be
|
|
* returned to the caller as a matching key!
|
|
*
|
|
* CRUCIAL NOTE: on a non-leaf page, the first data key is assumed to be
|
|
* "minus infinity": this routine will always claim it is less than the
|
|
* scankey. The actual key value stored (if any, which there probably isn't)
|
|
* does not matter. This convention allows us to implement the Lehman and
|
|
* Yao convention that the first down-link pointer is before the first key.
|
|
* See backend/access/nbtree/README for details.
|
|
*----------
|
|
*/
|
|
int32
|
|
_bt_compare(Relation rel,
|
|
int keysz,
|
|
ScanKey scankey,
|
|
Page page,
|
|
OffsetNumber offnum)
|
|
{
|
|
TupleDesc itupdesc = RelationGetDescr(rel);
|
|
BTPageOpaque opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
IndexTuple itup;
|
|
int i;
|
|
|
|
/*
|
|
* Force result ">" if target item is first data item on an internal page
|
|
* --- see NOTE above.
|
|
*/
|
|
if (!P_ISLEAF(opaque) && offnum == P_FIRSTDATAKEY(opaque))
|
|
return 1;
|
|
|
|
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
|
|
|
|
/*
|
|
* The scan key is set up with the attribute number associated with each
|
|
* term in the key. It is important that, if the index is multi-key, the
|
|
* scan contain the first k key attributes, and that they be in order. If
|
|
* you think about how multi-key ordering works, you'll understand why
|
|
* this is.
|
|
*
|
|
* We don't test for violation of this condition here, however. The
|
|
* initial setup for the index scan had better have gotten it right (see
|
|
* _bt_first).
|
|
*/
|
|
|
|
for (i = 1; i <= keysz; i++)
|
|
{
|
|
Datum datum;
|
|
bool isNull;
|
|
int32 result;
|
|
|
|
datum = index_getattr(itup, scankey->sk_attno, itupdesc, &isNull);
|
|
|
|
/* see comments about NULLs handling in btbuild */
|
|
if (scankey->sk_flags & SK_ISNULL) /* key is NULL */
|
|
{
|
|
if (isNull)
|
|
result = 0; /* NULL "=" NULL */
|
|
else
|
|
result = 1; /* NULL ">" NOT_NULL */
|
|
}
|
|
else if (isNull) /* key is NOT_NULL and item is NULL */
|
|
{
|
|
result = -1; /* NOT_NULL "<" NULL */
|
|
}
|
|
else
|
|
{
|
|
/*
|
|
* The sk_func needs to be passed the index value as left arg and
|
|
* the sk_argument as right arg (they might be of different
|
|
* types). Since it is convenient for callers to think of
|
|
* _bt_compare as comparing the scankey to the index item, we have
|
|
* to flip the sign of the comparison result.
|
|
*
|
|
* Note: curious-looking coding is to avoid overflow if comparison
|
|
* function returns INT_MIN. There is no risk of overflow for
|
|
* positive results.
|
|
*/
|
|
result = DatumGetInt32(FunctionCall2(&scankey->sk_func,
|
|
datum,
|
|
scankey->sk_argument));
|
|
result = (result < 0) ? 1 : -result;
|
|
}
|
|
|
|
/* if the keys are unequal, return the difference */
|
|
if (result != 0)
|
|
return result;
|
|
|
|
scankey++;
|
|
}
|
|
|
|
/* if we get here, the keys are equal */
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* _bt_first() -- Find the first item in a scan.
|
|
*
|
|
* We need to be clever about the direction of scan, the search
|
|
* conditions, and the tree ordering. We find the first item (or,
|
|
* if backwards scan, the last item) in the tree that satisfies the
|
|
* qualifications in the scan key. On success exit, the page containing
|
|
* the current index tuple is pinned but not locked, and data about
|
|
* the matching tuple(s) on the page has been loaded into so->currPos,
|
|
* and scan->xs_ctup.t_self is set to the heap TID of the current tuple.
|
|
*
|
|
* If there are no matching items in the index, we return FALSE, with no
|
|
* pins or locks held.
|
|
*
|
|
* Note that scan->keyData[], and the so->keyData[] scankey built from it,
|
|
* are both search-type scankeys (see nbtree/README for more about this).
|
|
* Within this routine, we build a temporary insertion-type scankey to use
|
|
* in locating the scan start position.
|
|
*/
|
|
bool
|
|
_bt_first(IndexScanDesc scan, ScanDirection dir)
|
|
{
|
|
Relation rel = scan->indexRelation;
|
|
BTScanOpaque so = (BTScanOpaque) scan->opaque;
|
|
Buffer buf;
|
|
BTStack stack;
|
|
OffsetNumber offnum;
|
|
StrategyNumber strat;
|
|
bool nextkey;
|
|
bool goback;
|
|
ScanKey startKeys[INDEX_MAX_KEYS];
|
|
ScanKeyData scankeys[INDEX_MAX_KEYS];
|
|
int keysCount = 0;
|
|
int i;
|
|
StrategyNumber strat_total;
|
|
|
|
pgstat_count_index_scan(&scan->xs_pgstat_info);
|
|
|
|
/*
|
|
* Examine the scan keys and eliminate any redundant keys; also mark the
|
|
* keys that must be matched to continue the scan.
|
|
*/
|
|
_bt_preprocess_keys(scan);
|
|
|
|
/*
|
|
* Quit now if _bt_preprocess_keys() discovered that the scan keys can
|
|
* never be satisfied (eg, x == 1 AND x > 2).
|
|
*/
|
|
if (!so->qual_ok)
|
|
return false;
|
|
|
|
/*----------
|
|
* Examine the scan keys to discover where we need to start the scan.
|
|
*
|
|
* We want to identify the keys that can be used as starting boundaries;
|
|
* these are =, >, or >= keys for a forward scan or =, <, <= keys for
|
|
* a backwards scan. We can use keys for multiple attributes so long as
|
|
* the prior attributes had only =, >= (resp. =, <=) keys. Once we accept
|
|
* a > or < boundary or find an attribute with no boundary (which can be
|
|
* thought of as the same as "> -infinity"), we can't use keys for any
|
|
* attributes to its right, because it would break our simplistic notion
|
|
* of what initial positioning strategy to use.
|
|
*
|
|
* When the scan keys include cross-type operators, _bt_preprocess_keys
|
|
* may not be able to eliminate redundant keys; in such cases we will
|
|
* arbitrarily pick a usable one for each attribute. This is correct
|
|
* but possibly not optimal behavior. (For example, with keys like
|
|
* "x >= 4 AND x >= 5" we would elect to scan starting at x=4 when
|
|
* x=5 would be more efficient.) Since the situation only arises given
|
|
* a poorly-worded query plus an incomplete opfamily, live with it.
|
|
*
|
|
* When both equality and inequality keys appear for a single attribute
|
|
* (again, only possible when cross-type operators appear), we *must*
|
|
* select one of the equality keys for the starting point, because
|
|
* _bt_checkkeys() will stop the scan as soon as an equality qual fails.
|
|
* For example, if we have keys like "x >= 4 AND x = 10" and we elect to
|
|
* start at x=4, we will fail and stop before reaching x=10. If multiple
|
|
* equality quals survive preprocessing, however, it doesn't matter which
|
|
* one we use --- by definition, they are either redundant or
|
|
* contradictory.
|
|
*
|
|
* In this loop, row-comparison keys are treated the same as keys on their
|
|
* first (leftmost) columns. We'll add on lower-order columns of the row
|
|
* comparison below, if possible.
|
|
*
|
|
* The selected scan keys (at most one per index column) are remembered by
|
|
* storing their addresses into the local startKeys[] array.
|
|
*----------
|
|
*/
|
|
strat_total = BTEqualStrategyNumber;
|
|
if (so->numberOfKeys > 0)
|
|
{
|
|
AttrNumber curattr;
|
|
ScanKey chosen;
|
|
ScanKey cur;
|
|
|
|
/*
|
|
* chosen is the so-far-chosen key for the current attribute, if any.
|
|
* We don't cast the decision in stone until we reach keys for the
|
|
* next attribute.
|
|
*/
|
|
curattr = 1;
|
|
chosen = NULL;
|
|
|
|
/*
|
|
* Loop iterates from 0 to numberOfKeys inclusive; we use the last
|
|
* pass to handle after-last-key processing. Actual exit from the
|
|
* loop is at one of the "break" statements below.
|
|
*/
|
|
for (cur = so->keyData, i = 0;; cur++, i++)
|
|
{
|
|
if (i >= so->numberOfKeys || cur->sk_attno != curattr)
|
|
{
|
|
/*
|
|
* Done looking at keys for curattr. If we didn't find a
|
|
* usable boundary key, quit; else save the boundary key
|
|
* pointer in startKeys.
|
|
*/
|
|
if (chosen == NULL)
|
|
break;
|
|
startKeys[keysCount++] = chosen;
|
|
|
|
/*
|
|
* Adjust strat_total, and quit if we have stored a > or <
|
|
* key.
|
|
*/
|
|
strat = chosen->sk_strategy;
|
|
if (strat != BTEqualStrategyNumber)
|
|
{
|
|
strat_total = strat;
|
|
if (strat == BTGreaterStrategyNumber ||
|
|
strat == BTLessStrategyNumber)
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* Done if that was the last attribute, or if next key is not
|
|
* in sequence (implying no boundary key is available for the
|
|
* next attribute).
|
|
*/
|
|
if (i >= so->numberOfKeys ||
|
|
cur->sk_attno != curattr + 1)
|
|
break;
|
|
|
|
/*
|
|
* Reset for next attr.
|
|
*/
|
|
curattr = cur->sk_attno;
|
|
chosen = NULL;
|
|
}
|
|
|
|
/* Can we use this key as a starting boundary for this attr? */
|
|
switch (cur->sk_strategy)
|
|
{
|
|
case BTLessStrategyNumber:
|
|
case BTLessEqualStrategyNumber:
|
|
if (chosen == NULL && ScanDirectionIsBackward(dir))
|
|
chosen = cur;
|
|
break;
|
|
case BTEqualStrategyNumber:
|
|
/* override any non-equality choice */
|
|
chosen = cur;
|
|
break;
|
|
case BTGreaterEqualStrategyNumber:
|
|
case BTGreaterStrategyNumber:
|
|
if (chosen == NULL && ScanDirectionIsForward(dir))
|
|
chosen = cur;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If we found no usable boundary keys, we have to start from one end of
|
|
* the tree. Walk down that edge to the first or last key, and scan from
|
|
* there.
|
|
*/
|
|
if (keysCount == 0)
|
|
return _bt_endpoint(scan, dir);
|
|
|
|
/*
|
|
* We want to start the scan somewhere within the index. Set up an
|
|
* insertion scankey we can use to search for the boundary point we
|
|
* identified above. The insertion scankey is built in the local
|
|
* scankeys[] array, using the keys identified by startKeys[].
|
|
*/
|
|
Assert(keysCount <= INDEX_MAX_KEYS);
|
|
for (i = 0; i < keysCount; i++)
|
|
{
|
|
ScanKey cur = startKeys[i];
|
|
|
|
Assert(cur->sk_attno == i + 1);
|
|
|
|
if (cur->sk_flags & SK_ROW_HEADER)
|
|
{
|
|
/*
|
|
* Row comparison header: look to the first row member instead.
|
|
*
|
|
* The member scankeys are already in insertion format (ie, they
|
|
* have sk_func = 3-way-comparison function), but we have to watch
|
|
* out for nulls, which _bt_preprocess_keys didn't check. A null
|
|
* in the first row member makes the condition unmatchable, just
|
|
* like qual_ok = false.
|
|
*/
|
|
cur = (ScanKey) DatumGetPointer(cur->sk_argument);
|
|
Assert(cur->sk_flags & SK_ROW_MEMBER);
|
|
if (cur->sk_flags & SK_ISNULL)
|
|
return false;
|
|
memcpy(scankeys + i, cur, sizeof(ScanKeyData));
|
|
|
|
/*
|
|
* If the row comparison is the last positioning key we accepted,
|
|
* try to add additional keys from the lower-order row members.
|
|
* (If we accepted independent conditions on additional index
|
|
* columns, we use those instead --- doesn't seem worth trying to
|
|
* determine which is more restrictive.) Note that this is OK
|
|
* even if the row comparison is of ">" or "<" type, because the
|
|
* condition applied to all but the last row member is effectively
|
|
* ">=" or "<=", and so the extra keys don't break the positioning
|
|
* scheme.
|
|
*/
|
|
if (i == keysCount - 1)
|
|
{
|
|
while (!(cur->sk_flags & SK_ROW_END))
|
|
{
|
|
cur++;
|
|
Assert(cur->sk_flags & SK_ROW_MEMBER);
|
|
if (cur->sk_attno != keysCount + 1)
|
|
break; /* out-of-sequence, can't use it */
|
|
if (cur->sk_flags & SK_ISNULL)
|
|
break; /* can't use null keys */
|
|
Assert(keysCount < INDEX_MAX_KEYS);
|
|
memcpy(scankeys + keysCount, cur, sizeof(ScanKeyData));
|
|
keysCount++;
|
|
}
|
|
break; /* done with outer loop */
|
|
}
|
|
}
|
|
else
|
|
{
|
|
/*
|
|
* Ordinary comparison key. Transform the search-style scan key
|
|
* to an insertion scan key by replacing the sk_func with the
|
|
* appropriate btree comparison function.
|
|
*
|
|
* If scankey operator is not a cross-type comparison, we can use
|
|
* the cached comparison function; otherwise gotta look it up in
|
|
* the catalogs. (That can't lead to infinite recursion, since no
|
|
* indexscan initiated by syscache lookup will use cross-data-type
|
|
* operators.)
|
|
*
|
|
* We support the convention that sk_subtype == InvalidOid means
|
|
* the opclass input type; this is a hack to simplify life for
|
|
* ScanKeyInit().
|
|
*/
|
|
if (cur->sk_subtype == rel->rd_opcintype[i] ||
|
|
cur->sk_subtype == InvalidOid)
|
|
{
|
|
FmgrInfo *procinfo;
|
|
|
|
procinfo = index_getprocinfo(rel, cur->sk_attno, BTORDER_PROC);
|
|
ScanKeyEntryInitializeWithInfo(scankeys + i,
|
|
cur->sk_flags,
|
|
cur->sk_attno,
|
|
InvalidStrategy,
|
|
cur->sk_subtype,
|
|
procinfo,
|
|
cur->sk_argument);
|
|
}
|
|
else
|
|
{
|
|
RegProcedure cmp_proc;
|
|
|
|
cmp_proc = get_opfamily_proc(rel->rd_opfamily[i],
|
|
rel->rd_opcintype[i],
|
|
cur->sk_subtype,
|
|
BTORDER_PROC);
|
|
if (!RegProcedureIsValid(cmp_proc))
|
|
elog(ERROR, "missing support function %d(%u,%u) for attribute %d of index \"%s\"",
|
|
BTORDER_PROC, rel->rd_opcintype[i], cur->sk_subtype,
|
|
cur->sk_attno, RelationGetRelationName(rel));
|
|
ScanKeyEntryInitialize(scankeys + i,
|
|
cur->sk_flags,
|
|
cur->sk_attno,
|
|
InvalidStrategy,
|
|
cur->sk_subtype,
|
|
cmp_proc,
|
|
cur->sk_argument);
|
|
}
|
|
}
|
|
}
|
|
|
|
/*----------
|
|
* Examine the selected initial-positioning strategy to determine exactly
|
|
* where we need to start the scan, and set flag variables to control the
|
|
* code below.
|
|
*
|
|
* If nextkey = false, _bt_search and _bt_binsrch will locate the first
|
|
* item >= scan key. If nextkey = true, they will locate the first
|
|
* item > scan key.
|
|
*
|
|
* If goback = true, we will then step back one item, while if
|
|
* goback = false, we will start the scan on the located item.
|
|
*
|
|
* it's yet other place to add some code later for is(not)null ...
|
|
*----------
|
|
*/
|
|
switch (strat_total)
|
|
{
|
|
case BTLessStrategyNumber:
|
|
|
|
/*
|
|
* Find first item >= scankey, then back up one to arrive at last
|
|
* item < scankey. (Note: this positioning strategy is only used
|
|
* for a backward scan, so that is always the correct starting
|
|
* position.)
|
|
*/
|
|
nextkey = false;
|
|
goback = true;
|
|
break;
|
|
|
|
case BTLessEqualStrategyNumber:
|
|
|
|
/*
|
|
* Find first item > scankey, then back up one to arrive at last
|
|
* item <= scankey. (Note: this positioning strategy is only used
|
|
* for a backward scan, so that is always the correct starting
|
|
* position.)
|
|
*/
|
|
nextkey = true;
|
|
goback = true;
|
|
break;
|
|
|
|
case BTEqualStrategyNumber:
|
|
|
|
/*
|
|
* If a backward scan was specified, need to start with last equal
|
|
* item not first one.
|
|
*/
|
|
if (ScanDirectionIsBackward(dir))
|
|
{
|
|
/*
|
|
* This is the same as the <= strategy. We will check at the
|
|
* end whether the found item is actually =.
|
|
*/
|
|
nextkey = true;
|
|
goback = true;
|
|
}
|
|
else
|
|
{
|
|
/*
|
|
* This is the same as the >= strategy. We will check at the
|
|
* end whether the found item is actually =.
|
|
*/
|
|
nextkey = false;
|
|
goback = false;
|
|
}
|
|
break;
|
|
|
|
case BTGreaterEqualStrategyNumber:
|
|
|
|
/*
|
|
* Find first item >= scankey. (This is only used for forward
|
|
* scans.)
|
|
*/
|
|
nextkey = false;
|
|
goback = false;
|
|
break;
|
|
|
|
case BTGreaterStrategyNumber:
|
|
|
|
/*
|
|
* Find first item > scankey. (This is only used for forward
|
|
* scans.)
|
|
*/
|
|
nextkey = true;
|
|
goback = false;
|
|
break;
|
|
|
|
default:
|
|
/* can't get here, but keep compiler quiet */
|
|
elog(ERROR, "unrecognized strat_total: %d", (int) strat_total);
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* Use the manufactured insertion scan key to descend the tree and
|
|
* position ourselves on the target leaf page.
|
|
*/
|
|
stack = _bt_search(rel, keysCount, scankeys, nextkey, &buf, BT_READ);
|
|
|
|
/* don't need to keep the stack around... */
|
|
_bt_freestack(stack);
|
|
|
|
/* remember which buffer we have pinned, if any */
|
|
so->currPos.buf = buf;
|
|
|
|
if (!BufferIsValid(buf))
|
|
{
|
|
/* Only get here if index is completely empty */
|
|
return false;
|
|
}
|
|
|
|
/* initialize moreLeft/moreRight appropriately for scan direction */
|
|
if (ScanDirectionIsForward(dir))
|
|
{
|
|
so->currPos.moreLeft = false;
|
|
so->currPos.moreRight = true;
|
|
}
|
|
else
|
|
{
|
|
so->currPos.moreLeft = true;
|
|
so->currPos.moreRight = false;
|
|
}
|
|
so->numKilled = 0; /* just paranoia */
|
|
so->markItemIndex = -1; /* ditto */
|
|
|
|
/* position to the precise item on the page */
|
|
offnum = _bt_binsrch(rel, buf, keysCount, scankeys, nextkey);
|
|
|
|
/*
|
|
* If nextkey = false, we are positioned at the first item >= scan key, or
|
|
* possibly at the end of a page on which all the existing items are less
|
|
* than the scan key and we know that everything on later pages is greater
|
|
* than or equal to scan key.
|
|
*
|
|
* If nextkey = true, we are positioned at the first item > scan key, or
|
|
* possibly at the end of a page on which all the existing items are less
|
|
* than or equal to the scan key and we know that everything on later
|
|
* pages is greater than scan key.
|
|
*
|
|
* The actually desired starting point is either this item or the prior
|
|
* one, or in the end-of-page case it's the first item on the next page or
|
|
* the last item on this page. Adjust the starting offset if needed. (If
|
|
* this results in an offset before the first item or after the last one,
|
|
* _bt_readpage will report no items found, and then we'll step to the
|
|
* next page as needed.)
|
|
*/
|
|
if (goback)
|
|
offnum = OffsetNumberPrev(offnum);
|
|
|
|
/*
|
|
* Now load data from the first page of the scan.
|
|
*/
|
|
if (!_bt_readpage(scan, dir, offnum))
|
|
{
|
|
/*
|
|
* There's no actually-matching data on this page. Try to advance to
|
|
* the next page. Return false if there's no matching data at all.
|
|
*/
|
|
if (!_bt_steppage(scan, dir))
|
|
return false;
|
|
}
|
|
|
|
/* Drop the lock, but not pin, on the current page */
|
|
LockBuffer(so->currPos.buf, BUFFER_LOCK_UNLOCK);
|
|
|
|
/* OK, itemIndex says what to return */
|
|
scan->xs_ctup.t_self = so->currPos.items[so->currPos.itemIndex].heapTid;
|
|
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* _bt_next() -- Get the next item in a scan.
|
|
*
|
|
* On entry, so->currPos describes the current page, which is pinned
|
|
* but not locked, and so->currPos.itemIndex identifies which item was
|
|
* previously returned.
|
|
*
|
|
* On successful exit, scan->xs_ctup.t_self is set to the TID of the
|
|
* next heap tuple, and so->currPos is updated as needed.
|
|
*
|
|
* On failure exit (no more tuples), we release pin and set
|
|
* so->currPos.buf to InvalidBuffer.
|
|
*/
|
|
bool
|
|
_bt_next(IndexScanDesc scan, ScanDirection dir)
|
|
{
|
|
BTScanOpaque so = (BTScanOpaque) scan->opaque;
|
|
|
|
/*
|
|
* Advance to next tuple on current page; or if there's no more, try to
|
|
* step to the next page with data.
|
|
*/
|
|
if (ScanDirectionIsForward(dir))
|
|
{
|
|
if (++so->currPos.itemIndex > so->currPos.lastItem)
|
|
{
|
|
/* We must acquire lock before applying _bt_steppage */
|
|
Assert(BufferIsValid(so->currPos.buf));
|
|
LockBuffer(so->currPos.buf, BT_READ);
|
|
if (!_bt_steppage(scan, dir))
|
|
return false;
|
|
/* Drop the lock, but not pin, on the new page */
|
|
LockBuffer(so->currPos.buf, BUFFER_LOCK_UNLOCK);
|
|
}
|
|
}
|
|
else
|
|
{
|
|
if (--so->currPos.itemIndex < so->currPos.firstItem)
|
|
{
|
|
/* We must acquire lock before applying _bt_steppage */
|
|
Assert(BufferIsValid(so->currPos.buf));
|
|
LockBuffer(so->currPos.buf, BT_READ);
|
|
if (!_bt_steppage(scan, dir))
|
|
return false;
|
|
/* Drop the lock, but not pin, on the new page */
|
|
LockBuffer(so->currPos.buf, BUFFER_LOCK_UNLOCK);
|
|
}
|
|
}
|
|
|
|
/* OK, itemIndex says what to return */
|
|
scan->xs_ctup.t_self = so->currPos.items[so->currPos.itemIndex].heapTid;
|
|
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* _bt_readpage() -- Load data from current index page into so->currPos
|
|
*
|
|
* Caller must have pinned and read-locked so->currPos.buf; the buffer's state
|
|
* is not changed here. Also, currPos.moreLeft and moreRight must be valid;
|
|
* they are updated as appropriate. All other fields of so->currPos are
|
|
* initialized from scratch here.
|
|
*
|
|
* We scan the current page starting at offnum and moving in the indicated
|
|
* direction. All items matching the scan keys are loaded into currPos.items.
|
|
* moreLeft or moreRight (as appropriate) is cleared if _bt_checkkeys reports
|
|
* that there can be no more matching tuples in the current scan direction.
|
|
*
|
|
* Returns true if any matching items found on the page, false if none.
|
|
*/
|
|
static bool
|
|
_bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum)
|
|
{
|
|
BTScanOpaque so = (BTScanOpaque) scan->opaque;
|
|
Page page;
|
|
BTPageOpaque opaque;
|
|
OffsetNumber minoff;
|
|
OffsetNumber maxoff;
|
|
int itemIndex;
|
|
bool continuescan;
|
|
|
|
/* we must have the buffer pinned and locked */
|
|
Assert(BufferIsValid(so->currPos.buf));
|
|
|
|
page = BufferGetPage(so->currPos.buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
minoff = P_FIRSTDATAKEY(opaque);
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
|
|
/*
|
|
* we must save the page's right-link while scanning it; this tells us
|
|
* where to step right to after we're done with these items. There is no
|
|
* corresponding need for the left-link, since splits always go right.
|
|
*/
|
|
so->currPos.nextPage = opaque->btpo_next;
|
|
|
|
if (ScanDirectionIsForward(dir))
|
|
{
|
|
/* load items[] in ascending order */
|
|
itemIndex = 0;
|
|
|
|
offnum = Max(offnum, minoff);
|
|
|
|
while (offnum <= maxoff)
|
|
{
|
|
if (_bt_checkkeys(scan, page, offnum, dir, &continuescan))
|
|
{
|
|
/* tuple passes all scan key conditions, so remember it */
|
|
/* _bt_checkkeys put the heap ptr into scan->xs_ctup.t_self */
|
|
so->currPos.items[itemIndex].heapTid = scan->xs_ctup.t_self;
|
|
so->currPos.items[itemIndex].indexOffset = offnum;
|
|
itemIndex++;
|
|
}
|
|
if (!continuescan)
|
|
{
|
|
/* there can't be any more matches, so stop */
|
|
so->currPos.moreRight = false;
|
|
break;
|
|
}
|
|
|
|
offnum = OffsetNumberNext(offnum);
|
|
}
|
|
|
|
Assert(itemIndex <= MaxIndexTuplesPerPage);
|
|
so->currPos.firstItem = 0;
|
|
so->currPos.lastItem = itemIndex - 1;
|
|
so->currPos.itemIndex = 0;
|
|
}
|
|
else
|
|
{
|
|
/* load items[] in descending order */
|
|
itemIndex = MaxIndexTuplesPerPage;
|
|
|
|
offnum = Min(offnum, maxoff);
|
|
|
|
while (offnum >= minoff)
|
|
{
|
|
if (_bt_checkkeys(scan, page, offnum, dir, &continuescan))
|
|
{
|
|
/* tuple passes all scan key conditions, so remember it */
|
|
/* _bt_checkkeys put the heap ptr into scan->xs_ctup.t_self */
|
|
itemIndex--;
|
|
so->currPos.items[itemIndex].heapTid = scan->xs_ctup.t_self;
|
|
so->currPos.items[itemIndex].indexOffset = offnum;
|
|
}
|
|
if (!continuescan)
|
|
{
|
|
/* there can't be any more matches, so stop */
|
|
so->currPos.moreLeft = false;
|
|
break;
|
|
}
|
|
|
|
offnum = OffsetNumberPrev(offnum);
|
|
}
|
|
|
|
Assert(itemIndex >= 0);
|
|
so->currPos.firstItem = itemIndex;
|
|
so->currPos.lastItem = MaxIndexTuplesPerPage - 1;
|
|
so->currPos.itemIndex = MaxIndexTuplesPerPage - 1;
|
|
}
|
|
|
|
return (so->currPos.firstItem <= so->currPos.lastItem);
|
|
}
|
|
|
|
/*
|
|
* _bt_steppage() -- Step to next page containing valid data for scan
|
|
*
|
|
* On entry, so->currPos.buf must be pinned and read-locked. We'll drop
|
|
* the lock and pin before moving to next page.
|
|
*
|
|
* On success exit, we hold pin and read-lock on the next interesting page,
|
|
* and so->currPos is updated to contain data from that page.
|
|
*
|
|
* If there are no more matching records in the given direction, we drop all
|
|
* locks and pins, set so->currPos.buf to InvalidBuffer, and return FALSE.
|
|
*/
|
|
static bool
|
|
_bt_steppage(IndexScanDesc scan, ScanDirection dir)
|
|
{
|
|
BTScanOpaque so = (BTScanOpaque) scan->opaque;
|
|
Relation rel;
|
|
Page page;
|
|
BTPageOpaque opaque;
|
|
|
|
/* we must have the buffer pinned and locked */
|
|
Assert(BufferIsValid(so->currPos.buf));
|
|
|
|
/* Before leaving current page, deal with any killed items */
|
|
if (so->numKilled > 0)
|
|
_bt_killitems(scan, true);
|
|
|
|
/*
|
|
* Before we modify currPos, make a copy of the page data if there was a
|
|
* mark position that needs it.
|
|
*/
|
|
if (so->markItemIndex >= 0)
|
|
{
|
|
/* bump pin on current buffer for assignment to mark buffer */
|
|
IncrBufferRefCount(so->currPos.buf);
|
|
memcpy(&so->markPos, &so->currPos,
|
|
offsetof(BTScanPosData, items[1]) +
|
|
so->currPos.lastItem * sizeof(BTScanPosItem));
|
|
so->markPos.itemIndex = so->markItemIndex;
|
|
so->markItemIndex = -1;
|
|
}
|
|
|
|
rel = scan->indexRelation;
|
|
|
|
if (ScanDirectionIsForward(dir))
|
|
{
|
|
/* Walk right to the next page with data */
|
|
/* We must rely on the previously saved nextPage link! */
|
|
BlockNumber blkno = so->currPos.nextPage;
|
|
|
|
/* Remember we left a page with data */
|
|
so->currPos.moreLeft = true;
|
|
|
|
for (;;)
|
|
{
|
|
/* if we're at end of scan, release the buffer and return */
|
|
if (blkno == P_NONE || !so->currPos.moreRight)
|
|
{
|
|
_bt_relbuf(rel, so->currPos.buf);
|
|
so->currPos.buf = InvalidBuffer;
|
|
return false;
|
|
}
|
|
/* step right one page */
|
|
so->currPos.buf = _bt_relandgetbuf(rel, so->currPos.buf,
|
|
blkno, BT_READ);
|
|
/* check for deleted page */
|
|
page = BufferGetPage(so->currPos.buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
if (!P_IGNORE(opaque))
|
|
{
|
|
/* see if there are any matches on this page */
|
|
/* note that this will clear moreRight if we can stop */
|
|
if (_bt_readpage(scan, dir, P_FIRSTDATAKEY(opaque)))
|
|
break;
|
|
}
|
|
/* nope, keep going */
|
|
blkno = opaque->btpo_next;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
/* Remember we left a page with data */
|
|
so->currPos.moreRight = true;
|
|
|
|
/*
|
|
* Walk left to the next page with data. This is much more complex
|
|
* than the walk-right case because of the possibility that the page
|
|
* to our left splits while we are in flight to it, plus the
|
|
* possibility that the page we were on gets deleted after we leave
|
|
* it. See nbtree/README for details.
|
|
*/
|
|
for (;;)
|
|
{
|
|
/* Done if we know there are no matching keys to the left */
|
|
if (!so->currPos.moreLeft)
|
|
{
|
|
_bt_relbuf(rel, so->currPos.buf);
|
|
so->currPos.buf = InvalidBuffer;
|
|
return false;
|
|
}
|
|
|
|
/* Step to next physical page */
|
|
so->currPos.buf = _bt_walk_left(rel, so->currPos.buf);
|
|
|
|
/* if we're physically at end of index, return failure */
|
|
if (so->currPos.buf == InvalidBuffer)
|
|
return false;
|
|
|
|
/*
|
|
* Okay, we managed to move left to a non-deleted page. Done if
|
|
* it's not half-dead and contains matching tuples. Else loop back
|
|
* and do it all again.
|
|
*/
|
|
page = BufferGetPage(so->currPos.buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
if (!P_IGNORE(opaque))
|
|
{
|
|
/* see if there are any matches on this page */
|
|
/* note that this will clear moreLeft if we can stop */
|
|
if (_bt_readpage(scan, dir, PageGetMaxOffsetNumber(page)))
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* _bt_walk_left() -- step left one page, if possible
|
|
*
|
|
* The given buffer must be pinned and read-locked. This will be dropped
|
|
* before stepping left. On return, we have pin and read lock on the
|
|
* returned page, instead.
|
|
*
|
|
* Returns InvalidBuffer if there is no page to the left (no lock is held
|
|
* in that case).
|
|
*
|
|
* When working on a non-leaf level, it is possible for the returned page
|
|
* to be half-dead; the caller should check that condition and step left
|
|
* again if it's important.
|
|
*/
|
|
static Buffer
|
|
_bt_walk_left(Relation rel, Buffer buf)
|
|
{
|
|
Page page;
|
|
BTPageOpaque opaque;
|
|
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
for (;;)
|
|
{
|
|
BlockNumber obknum;
|
|
BlockNumber lblkno;
|
|
BlockNumber blkno;
|
|
int tries;
|
|
|
|
/* if we're at end of tree, release buf and return failure */
|
|
if (P_LEFTMOST(opaque))
|
|
{
|
|
_bt_relbuf(rel, buf);
|
|
break;
|
|
}
|
|
/* remember original page we are stepping left from */
|
|
obknum = BufferGetBlockNumber(buf);
|
|
/* step left */
|
|
blkno = lblkno = opaque->btpo_prev;
|
|
buf = _bt_relandgetbuf(rel, buf, blkno, BT_READ);
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
/*
|
|
* If this isn't the page we want, walk right till we find what we
|
|
* want --- but go no more than four hops (an arbitrary limit). If we
|
|
* don't find the correct page by then, the most likely bet is that
|
|
* the original page got deleted and isn't in the sibling chain at all
|
|
* anymore, not that its left sibling got split more than four times.
|
|
*
|
|
* Note that it is correct to test P_ISDELETED not P_IGNORE here,
|
|
* because half-dead pages are still in the sibling chain. Caller
|
|
* must reject half-dead pages if wanted.
|
|
*/
|
|
tries = 0;
|
|
for (;;)
|
|
{
|
|
if (!P_ISDELETED(opaque) && opaque->btpo_next == obknum)
|
|
{
|
|
/* Found desired page, return it */
|
|
return buf;
|
|
}
|
|
if (P_RIGHTMOST(opaque) || ++tries > 4)
|
|
break;
|
|
blkno = opaque->btpo_next;
|
|
buf = _bt_relandgetbuf(rel, buf, blkno, BT_READ);
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
}
|
|
|
|
/* Return to the original page to see what's up */
|
|
buf = _bt_relandgetbuf(rel, buf, obknum, BT_READ);
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
if (P_ISDELETED(opaque))
|
|
{
|
|
/*
|
|
* It was deleted. Move right to first nondeleted page (there
|
|
* must be one); that is the page that has acquired the deleted
|
|
* one's keyspace, so stepping left from it will take us where we
|
|
* want to be.
|
|
*/
|
|
for (;;)
|
|
{
|
|
if (P_RIGHTMOST(opaque))
|
|
elog(ERROR, "fell off the end of \"%s\"",
|
|
RelationGetRelationName(rel));
|
|
blkno = opaque->btpo_next;
|
|
buf = _bt_relandgetbuf(rel, buf, blkno, BT_READ);
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
if (!P_ISDELETED(opaque))
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* Now return to top of loop, resetting obknum to point to this
|
|
* nondeleted page, and try again.
|
|
*/
|
|
}
|
|
else
|
|
{
|
|
/*
|
|
* It wasn't deleted; the explanation had better be that the page
|
|
* to the left got split or deleted. Without this check, we'd go
|
|
* into an infinite loop if there's anything wrong.
|
|
*/
|
|
if (opaque->btpo_prev == lblkno)
|
|
elog(ERROR, "could not find left sibling in \"%s\"",
|
|
RelationGetRelationName(rel));
|
|
/* Okay to try again with new lblkno value */
|
|
}
|
|
}
|
|
|
|
return InvalidBuffer;
|
|
}
|
|
|
|
/*
|
|
* _bt_get_endpoint() -- Find the first or last page on a given tree level
|
|
*
|
|
* If the index is empty, we will return InvalidBuffer; any other failure
|
|
* condition causes ereport(). We will not return a dead page.
|
|
*
|
|
* The returned buffer is pinned and read-locked.
|
|
*/
|
|
Buffer
|
|
_bt_get_endpoint(Relation rel, uint32 level, bool rightmost)
|
|
{
|
|
Buffer buf;
|
|
Page page;
|
|
BTPageOpaque opaque;
|
|
OffsetNumber offnum;
|
|
BlockNumber blkno;
|
|
IndexTuple itup;
|
|
|
|
/*
|
|
* If we are looking for a leaf page, okay to descend from fast root;
|
|
* otherwise better descend from true root. (There is no point in being
|
|
* smarter about intermediate levels.)
|
|
*/
|
|
if (level == 0)
|
|
buf = _bt_getroot(rel, BT_READ);
|
|
else
|
|
buf = _bt_gettrueroot(rel);
|
|
|
|
if (!BufferIsValid(buf))
|
|
{
|
|
/* empty index... */
|
|
return InvalidBuffer;
|
|
}
|
|
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
for (;;)
|
|
{
|
|
/*
|
|
* If we landed on a deleted page, step right to find a live page
|
|
* (there must be one). Also, if we want the rightmost page, step
|
|
* right if needed to get to it (this could happen if the page split
|
|
* since we obtained a pointer to it).
|
|
*/
|
|
while (P_IGNORE(opaque) ||
|
|
(rightmost && !P_RIGHTMOST(opaque)))
|
|
{
|
|
blkno = opaque->btpo_next;
|
|
if (blkno == P_NONE)
|
|
elog(ERROR, "fell off the end of \"%s\"",
|
|
RelationGetRelationName(rel));
|
|
buf = _bt_relandgetbuf(rel, buf, blkno, BT_READ);
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
}
|
|
|
|
/* Done? */
|
|
if (opaque->btpo.level == level)
|
|
break;
|
|
if (opaque->btpo.level < level)
|
|
elog(ERROR, "btree level %u not found", level);
|
|
|
|
/* Descend to leftmost or rightmost child page */
|
|
if (rightmost)
|
|
offnum = PageGetMaxOffsetNumber(page);
|
|
else
|
|
offnum = P_FIRSTDATAKEY(opaque);
|
|
|
|
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
|
|
blkno = ItemPointerGetBlockNumber(&(itup->t_tid));
|
|
|
|
buf = _bt_relandgetbuf(rel, buf, blkno, BT_READ);
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
}
|
|
|
|
return buf;
|
|
}
|
|
|
|
/*
|
|
* _bt_endpoint() -- Find the first or last page in the index, and scan
|
|
* from there to the first key satisfying all the quals.
|
|
*
|
|
* This is used by _bt_first() to set up a scan when we've determined
|
|
* that the scan must start at the beginning or end of the index (for
|
|
* a forward or backward scan respectively). Exit conditions are the
|
|
* same as for _bt_first().
|
|
*/
|
|
static bool
|
|
_bt_endpoint(IndexScanDesc scan, ScanDirection dir)
|
|
{
|
|
Relation rel = scan->indexRelation;
|
|
BTScanOpaque so = (BTScanOpaque) scan->opaque;
|
|
Buffer buf;
|
|
Page page;
|
|
BTPageOpaque opaque;
|
|
OffsetNumber start;
|
|
|
|
/*
|
|
* Scan down to the leftmost or rightmost leaf page. This is a simplified
|
|
* version of _bt_search(). We don't maintain a stack since we know we
|
|
* won't need it.
|
|
*/
|
|
buf = _bt_get_endpoint(rel, 0, ScanDirectionIsBackward(dir));
|
|
|
|
if (!BufferIsValid(buf))
|
|
{
|
|
/* empty index... */
|
|
so->currPos.buf = InvalidBuffer;
|
|
return false;
|
|
}
|
|
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
Assert(P_ISLEAF(opaque));
|
|
|
|
if (ScanDirectionIsForward(dir))
|
|
{
|
|
/* There could be dead pages to the left, so not this: */
|
|
/* Assert(P_LEFTMOST(opaque)); */
|
|
|
|
start = P_FIRSTDATAKEY(opaque);
|
|
}
|
|
else if (ScanDirectionIsBackward(dir))
|
|
{
|
|
Assert(P_RIGHTMOST(opaque));
|
|
|
|
start = PageGetMaxOffsetNumber(page);
|
|
}
|
|
else
|
|
{
|
|
elog(ERROR, "invalid scan direction: %d", (int) dir);
|
|
start = 0; /* keep compiler quiet */
|
|
}
|
|
|
|
/* remember which buffer we have pinned */
|
|
so->currPos.buf = buf;
|
|
|
|
/* initialize moreLeft/moreRight appropriately for scan direction */
|
|
if (ScanDirectionIsForward(dir))
|
|
{
|
|
so->currPos.moreLeft = false;
|
|
so->currPos.moreRight = true;
|
|
}
|
|
else
|
|
{
|
|
so->currPos.moreLeft = true;
|
|
so->currPos.moreRight = false;
|
|
}
|
|
so->numKilled = 0; /* just paranoia */
|
|
so->markItemIndex = -1; /* ditto */
|
|
|
|
/*
|
|
* Now load data from the first page of the scan.
|
|
*/
|
|
if (!_bt_readpage(scan, dir, start))
|
|
{
|
|
/*
|
|
* There's no actually-matching data on this page. Try to advance to
|
|
* the next page. Return false if there's no matching data at all.
|
|
*/
|
|
if (!_bt_steppage(scan, dir))
|
|
return false;
|
|
}
|
|
|
|
/* Drop the lock, but not pin, on the current page */
|
|
LockBuffer(so->currPos.buf, BUFFER_LOCK_UNLOCK);
|
|
|
|
/* OK, itemIndex says what to return */
|
|
scan->xs_ctup.t_self = so->currPos.items[so->currPos.itemIndex].heapTid;
|
|
|
|
return true;
|
|
}
|