database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-28 23:42:10 +03:00
Code Activity

nbtree: Tweak _bt_pgaddtup() comments.

Browse Source 
Make it clear that _bt_pgaddtup() truncates the first data item on an
internal page because its key is supposed to be treated as minus
infinity within _bt_compare().
This commit is contained in:
Peter Geoghegan
2019-11-18 13:04:53 -08:00
parent bf2efc55da
commit 2110f71696
2 changed files with 7 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
src/backend/access/nbtree/nbtinsert.c
View File

@ -2230,10 +2230,10 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
* *
* The main difference between this routine and a bare PageAddItem call * The main difference between this routine and a bare PageAddItem call
* is that this code knows that the leftmost index tuple on a non-leaf * is that this code knows that the leftmost index tuple on a non-leaf
* btree page doesn't need to have a key. Therefore, it strips such * btree page has a key that must be treated as minus infinity.
* tuples down to just the tuple header. CAUTION: this works ONLY if * Therefore, it truncates away all attributes. CAUTION: this works
* we insert the tuples in order, so that the given itup_off does * ONLY if we insert the tuples in order, so that the given itup_off
* represent the final position of the tuple! * does represent the final position of the tuple!
*/ */
static bool static bool
_bt_pgaddtup(Page page, _bt_pgaddtup(Page page,
@ -2248,7 +2248,6 @@ _bt_pgaddtup(Page page,
{ {
trunctuple = *itup; trunctuple = *itup;
trunctuple.t_info = sizeof(IndexTupleData); trunctuple.t_info = sizeof(IndexTupleData);
/* Deliberately zero INDEX_ALT_TID_MASK bits */
BTreeTupleSetNAtts(&trunctuple, 0); BTreeTupleSetNAtts(&trunctuple, 0);
itup = &trunctuple; itup = &trunctuple;
itemsize = sizeof(IndexTupleData); itemsize = sizeof(IndexTupleData);

7
src/backend/access/nbtree/nbtsort.c
View File

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