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Change the btree node balancers to sort nodes into accending order. This

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improves insert and delete speed by 25%. (CVS 409)

FossilOrigin-Name: abbb999d4fc3fe142567b6ede5e625e7bf0da714
This commit is contained in:
drh
2002-03-02 19:00:31 +00:00
parent 832508b7ea
commit f9ffac96a7
4 changed files with 52 additions and 11 deletions
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36
src/btree.c
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@@ -9,7 +9,7 @@
** May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.55 2002/02/19 22:43:59 drh Exp $
** $Id: btree.c,v 1.56 2002/03/02 19:00:31 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
@@ -2104,6 +2104,40 @@ static int balance(Btree *pBt, MemPage *pPage, BtCursor *pCur){
apNew[i]->isInit = 1;
}
/*
** Put the new pages in accending order. This helps to
** keep entries in the disk file in order so that a scan
** of the table is a linear scan through the file. That
** in turn helps the operating system to deliver pages
** from the disk more rapidly.
**
** An O(n^2) insertion sort algorithm is used, but since
** n is never more than 3, that should not be a problem.
**
** This one optimization makes the database about 25%
** faster for large insertions and deletions.
*/
for(i=0; i<k-1; i++){
int minV = pgnoNew[i];
int minI = i;
for(j=i+1; j<k; j++){
if( pgnoNew[j]<minV ){
minI = j;
minV = pgnoNew[j];
}
}
if( minI>i ){
int t;
MemPage *pT;
t = pgnoNew[i];
pT = apNew[i];
pgnoNew[i] = pgnoNew[minI];
apNew[i] = apNew[minI];
pgnoNew[minI] = t;
apNew[minI] = pT;
}
}
/*
** Evenly distribute the data in apCell[] across the new pages.
** Insert divider cells into pParent as necessary.