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Add comments to the new balance_quick() routine. (CVS 2212)

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FossilOrigin-Name: 183c42eac82b41da7905e44a43913f04acc46ade
This commit is contained in:
drh 2005-01-14 22:55:49 +00:00
parent ac245ec5af
commit f222e712a4
3 changed files with 34 additions and 9 deletions
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14
manifest
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@ -1,5 +1,5 @@
C Experimental\spatch\sto\sbalance()\s(use\s-DSQLITE_BALANCE_QUICK).\s(CVS\s2211)
D 2005-01-14T13:50:12
C Add\scomments\sto\sthe\snew\sbalance_quick()\sroutine.\s(CVS\s2212)
D 2005-01-14T22:55:49
F Makefile.in 6ce51dde6a8fe82fc12f20dec750572f6a19f56a
F Makefile.linux-gcc a9e5a0d309fa7c38e7c14d3ecf7690879d3a5457
F README a01693e454a00cc117967e3f9fdab2d4d52e9bc1
@ -29,7 +29,7 @@ F sqlite3.def dbaeb20c153e1d366e8f421b55a573f5dfc00863
F sqlite3.pc.in 985b9bf34192a549d7d370e0f0b6b34a4f61369a
F src/attach.c e49d09dad9f5f9fb10b4b0c1be5a70ae4c45e689
F src/auth.c 3b81f2a42f48a62c2c9c9b0eda31a157c681edea
F src/btree.c 1a351402dbbf5cc5f8ecf1b338f8da20c073c46e
F src/btree.c 01027e3c1b9f53f17eec964da2a3e45d253b2b87
F src/btree.h 74d19cf40ab49fd69abe9e4e12a6c321ad86c497
F src/build.c af1296e8a21a406b4f4c4f1e1365e075071219f3
F src/cursor.c f883813759742068890b1f699335872bfa8fdf41
@ -269,7 +269,7 @@ F www/tclsqlite.tcl e73f8f8e5f20e8277619433f7970060ab01088fc
F www/vdbe.tcl 095f106d93875c94b47367384ebc870517431618
F www/version3.tcl 092a01f5ef430d2c4acc0ae558d74c4bb89638a0
F www/whentouse.tcl c3b50d3ac31c54be2a1af9b488a89d22f1e6e746
P c772f75166d55192132e732e8a0ddda5926f00f2
R a2176157e002acaa6ba57b3b04bf35d8
U danielk1977
Z be978985848951cc4077641a9406e5b8
P c550d80c25ec88fceb20acabd00c21faa2d552f5
R 11aa1732839148efceafec181a4aacf2
U drh
Z 125f4f4e919590f6f1ede4bc594f0cdf

2
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@ -1 +1 @@
c550d80c25ec88fceb20acabd00c21faa2d552f5
183c42eac82b41da7905e44a43913f04acc46ade

27
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 1.232 2005/01/14 13:50:12 danielk1977 Exp $
** $Id: btree.c,v 1.233 2005/01/14 22:55:49 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
@ -3558,6 +3558,23 @@ static void assemblePage(
/* Forward reference */
static int balance(MemPage*, int);
/*
** This version of balance() handles the common special case where
** a new entry is being inserted on the extreme right-end of the
** tree, in other words, when the new entry will become the largest
** entry in the tree.
**
** Instead of trying balance the 3 right-most leaf pages, just add
** a new page to the right-hand side and put the one new entry in
** that page. This leaves the right side of the tree somewhat
** unbalanced. But odds are that we will be inserting new entries
** at the end soon afterwards so the nearly empty page will quickly
** fill up. On average.
**
** pPage is the leaf page which is the right-most page in the tree.
** pParent is its parent. pPage must have a single overflow entry
** which is also the right-most entry on the page.
*/
static int balance_quick(MemPage *pPage, MemPage *pParent){
int rc;
MemPage *pNew;
@ -3681,6 +3698,14 @@ static int balance_nonroot(MemPage *pPage){
TRACE(("BALANCE: begin page %d child of %d\n", pPage->pgno, pParent->pgno));
#ifdef SQLITE_BALANCE_QUICK
/*
** A special case: If a new entry has just been inserted into a
** table (that is, a btree with integer keys and all data at the leaves)
** an the new entry is the right-most entry in the tree (it has the
** largest key) then use the special balance_quick() routine for
** balancing. balance_quick() is much faster and results in a tighter
** packing of data in the common case.
*/
if( pPage->leaf &&
pPage->intKey &&
pPage->leafData &&