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Remove block number field from nbtree stack.

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The initial value of the nbtree stack downlink block number field
recorded during an initial descent of the tree wasn't actually used.
Both _bt_getstackbuf() callers overwrote the value with their own value.

Remove the block number field from the stack struct, and add a child
block number argument to _bt_getstackbuf() in its place.  This makes the
overall design of _bt_getstackbuf() clearer.

Author: Peter Geoghegan
Reviewed-By: Anastasia Lubennikova
Discussion: https://postgr.es/m/CAH2-Wzmx+UbXt2YNOUCZ-a04VdXU=S=OHuAuD7Z8uQq-PXTYUg@mail.gmail.com
This commit is contained in:
Peter Geoghegan
2019-08-14 11:32:35 -07:00
parent fded4773eb
commit 9c02cf5661
5 changed files with 50 additions and 42 deletions
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16
src/include/access/nbtree.h
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@@ -403,20 +403,16 @@ typedef struct BTMetaPageData
#define BT_WRITE BUFFER_LOCK_EXCLUSIVE
/*
* BTStackData -- As we descend a tree, we push the (location, downlink)
* pairs from internal pages onto a private stack. If we split a
* leaf, we use this stack to walk back up the tree and insert data
* into parent pages (and possibly to split them, too). Lehman and
* Yao's update algorithm guarantees that under no circumstances can
* our private stack give us an irredeemably bad picture up the tree.
* Again, see the paper for details.
* BTStackData -- As we descend a tree, we push the location of pivot
* tuples whose downlink we are about to follow onto a private stack. If
* we split a leaf, we use this stack to walk back up the tree and insert
* data into its parent page at the correct location. We may also have to
* recursively split a grandparent of the leaf page (and so on).
*/
typedef struct BTStackData
{
BlockNumber bts_blkno;
OffsetNumber bts_offset;
BlockNumber bts_btentry;
struct BTStackData *bts_parent;
} BTStackData;
@@ -731,7 +727,7 @@ extern void _bt_parallel_advance_array_keys(IndexScanDesc scan);
*/
extern bool _bt_doinsert(Relation rel, IndexTuple itup,
IndexUniqueCheck checkUnique, Relation heapRel);
extern Buffer _bt_getstackbuf(Relation rel, BTStack stack);
extern Buffer _bt_getstackbuf(Relation rel, BTStack stack, BlockNumber child);
extern void _bt_finish_split(Relation rel, Buffer bbuf, BTStack stack);
/*