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Commit2110f71

Browse files
nbtree: Tweak _bt_pgaddtup() comments.
Make it clear that _bt_pgaddtup() truncates the first data item on aninternal page because its key is supposed to be treated as minusinfinity within _bt_compare().
1 parentbf2efc5 commit2110f71

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2 files changed

+7
-9
lines changed

2 files changed

+7
-9
lines changed

‎src/backend/access/nbtree/nbtinsert.c

Lines changed: 4 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -2230,10 +2230,10 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
22302230
*
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*The main difference between this routine and a bare PageAddItem call
22322232
*is that this code knows that the leftmost index tuple on a non-leaf
2233-
*btree pagedoesn't need to havea key. Therefore, it strips such
2234-
*tuples down to just the tuple header. CAUTION: this works ONLY if
2235-
*we insert the tuples in order, so that the given itup_off does
2236-
*represent the final position of the tuple!
2233+
*btree pagehasa key that must be treated as minus infinity.
2234+
*Therefore, it truncates away all attributes. CAUTION: this works
2235+
*ONLY ifwe insert the tuples in order, so that the given itup_off
2236+
*doesrepresent the final position of the tuple!
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*/
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staticbool
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_bt_pgaddtup(Pagepage,
@@ -2248,7 +2248,6 @@ _bt_pgaddtup(Page page,
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{
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trunctuple=*itup;
22502250
trunctuple.t_info=sizeof(IndexTupleData);
2251-
/* Deliberately zero INDEX_ALT_TID_MASK bits */
22522251
BTreeTupleSetNAtts(&trunctuple,0);
22532252
itup=&trunctuple;
22542253
itemsize=sizeof(IndexTupleData);

‎src/backend/access/nbtree/nbtsort.c

Lines changed: 3 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -756,9 +756,9 @@ _bt_slideleft(Page page)
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* Add an item to a page being built.
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*
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* The main difference between this routine and a bare PageAddItem call
759-
* is that this code knows that the leftmost data item on a non-leaf
760-
*btreepagedoesn't need to have a key. Therefore, it strips such
761-
*items down to just the item header.
759+
* is that this code knows that the leftmost data item on a non-leaf btree
760+
* pagehas a key that must be treated as minus infinity. Therefore, it
761+
*truncates away all attributes.
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*
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* This is almost like nbtinsert.c's _bt_pgaddtup(), but we can't use
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* that because it assumes that P_RIGHTMOST() will return the correct
@@ -778,7 +778,6 @@ _bt_sortaddtup(Page page,
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{
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trunctuple=*itup;
780780
trunctuple.t_info=sizeof(IndexTupleData);
781-
/* Deliberately zero INDEX_ALT_TID_MASK bits */
782781
BTreeTupleSetNAtts(&trunctuple,0);
783782
itup=&trunctuple;
784783
itemsize=sizeof(IndexTupleData);

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