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Commite25d462

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nbtree: Rename _bt_search() variables.
Make some of the variable names in _bt_search() consistent withcorresponding variables within _bt_getstackbuf(). This naming scheme isclearer because the variable names always express a relationship betweenthe currently locked buffer/page and some other page.
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1 file changed

+21
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1 file changed

+21
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‎src/backend/access/nbtree/nbtsearch.c

Lines changed: 21 additions & 24 deletions
Original file line numberDiff line numberDiff line change
@@ -82,9 +82,10 @@ _bt_drop_lock_and_maybe_pin(IndexScanDesc scan, BTScanPos sp)
8282
* The passed scankey is an insertion-type scankey (see nbtree/README),
8383
* but it can omit the rightmost column(s) of the index.
8484
*
85-
* Return value is a stack of parent-page pointers. *bufP is set to the
86-
* address of the leaf-page buffer, which is locked and pinned. No locks
87-
* are held on the parent pages, however!
85+
* Return value is a stack of parent-page pointers (i.e. there is no entry for
86+
* the leaf level/page). *bufP is set to the address of the leaf-page buffer,
87+
* which is locked and pinned. No locks are held on the parent pages,
88+
* however!
8889
*
8990
* If the snapshot parameter is not NULL, "old snapshot" checking will take
9091
* place during the descent through the tree. This is not needed when
@@ -118,21 +119,20 @@ _bt_search(Relation rel, BTScanInsert key, Buffer *bufP, int access,
118119
OffsetNumberoffnum;
119120
ItemIditemid;
120121
IndexTupleitup;
121-
BlockNumberblkno;
122-
BlockNumberpar_blkno;
122+
BlockNumberchild;
123123
BTStacknew_stack;
124124

125125
/*
126126
* Race -- the page we just grabbed may have split since we read its
127-
*pointer inthe parent (or metapage). If it has, we may need to
128-
* move right to its new sibling. Do that.
127+
*downlink inits parentpage(orthemetapage). If it has, we may
128+
*need tomove right to its new sibling. Do that.
129129
*
130130
* In write-mode, allow _bt_moveright to finish any incomplete splits
131131
* along the way. Strictly speaking, we'd only need to finish an
132132
* incomplete split on the leaf page we're about to insert to, not on
133-
* any of the upper levels (they are taken care of in _bt_getstackbuf,
134-
*if the leaf page is split and we insert to the parent page). But
135-
*this is a goodopportunity to finish splits of internal pages too.
133+
* any of the upper levels (internal pages with incomplete splits are
134+
*also taken care of in _bt_getstackbuf). But this is a good
135+
* opportunity to finish splits of internal pages too.
136136
*/
137137
*bufP=_bt_moveright(rel,key,*bufP, (access==BT_WRITE),stack_in,
138138
page_access,snapshot);
@@ -144,25 +144,23 @@ _bt_search(Relation rel, BTScanInsert key, Buffer *bufP, int access,
144144
break;
145145

146146
/*
147-
* Find the appropriateitemonthe internalpage, and get the child
148-
* page thatit points to.
147+
* Find the appropriatepivot tupleonthispage. Its downlink points
148+
*to the childpage thatwe're about to descend to.
149149
*/
150150
offnum=_bt_binsrch(rel,key,*bufP);
151151
itemid=PageGetItemId(page,offnum);
152152
itup= (IndexTuple)PageGetItem(page,itemid);
153153
Assert(BTreeTupleIsPivot(itup)|| !key->heapkeyspace);
154-
blkno=BTreeTupleGetDownLink(itup);
155-
par_blkno=BufferGetBlockNumber(*bufP);
154+
child=BTreeTupleGetDownLink(itup);
156155

157156
/*
158-
* We need to save the location of the pivot tuple we chose in the
159-
* parent page on a stack. If we need to split a page, we'll use the
160-
* stack to work back up to its parent page. If caller ends up
161-
* splitting a page one level down, it usually ends up inserting a new
162-
* pivot tuple/downlink immediately after the location recorded here.
157+
* We need to save the location of the pivot tuple we chose in a new
158+
* stack entry for this page/level. If caller ends up splitting a
159+
* page one level down, it usually ends up inserting a new pivot
160+
* tuple/downlink immediately after the location recorded here.
163161
*/
164162
new_stack= (BTStack)palloc(sizeof(BTStackData));
165-
new_stack->bts_blkno=par_blkno;
163+
new_stack->bts_blkno=BufferGetBlockNumber(*bufP);
166164
new_stack->bts_offset=offnum;
167165
new_stack->bts_parent=stack_in;
168166

@@ -174,8 +172,8 @@ _bt_search(Relation rel, BTScanInsert key, Buffer *bufP, int access,
174172
if (opaque->btpo.level==1&&access==BT_WRITE)
175173
page_access=BT_WRITE;
176174

177-
/* drop the read lock on theparentpage, acquire one onthe child */
178-
*bufP=_bt_relandgetbuf(rel,*bufP,blkno,page_access);
175+
/* drop the read lock on the page,thenacquire one onits child */
176+
*bufP=_bt_relandgetbuf(rel,*bufP,child,page_access);
179177

180178
/* okay, all set to move down a level */
181179
stack_in=new_stack;
@@ -196,8 +194,7 @@ _bt_search(Relation rel, BTScanInsert key, Buffer *bufP, int access,
196194
* If the page was split between the time that we surrendered our read
197195
* lock and acquired our write lock, then this page may no longer be
198196
* the right place for the key we want to insert. In this case, we
199-
* need to move right in the tree. See Lehman and Yao for an
200-
* excruciatingly precise description.
197+
* need to move right in the tree.
201198
*/
202199
*bufP=_bt_moveright(rel,key,*bufP, true,stack_in,BT_WRITE,
203200
snapshot);

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