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Minor performance improvement and size reduction for the btree-page space

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allocator.

FossilOrigin-Name: 73637d12e31f5489efe37d8cf4ab50a1911d4c75
This commit is contained in:
drh
2014-08-20 00:54:46 +00:00
parent dfd1547b48
commit 75b31dc9ad
3 changed files with 18 additions and 13 deletions
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17
src/btree.c
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@@ -1197,7 +1197,6 @@ static int defragmentPage(MemPage *pPage){
static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
const int hdr = pPage->hdrOffset; /* Local cache of pPage->hdrOffset */
u8 * const data = pPage->aData; /* Local cache of pPage->aData */
int nFrag; /* Number of fragmented bytes on pPage */
int top; /* First byte of cell content area */
int gap; /* First byte of gap between cell pointers and cell content */
int rc; /* Integer return code */
@@ -1212,16 +1211,22 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
usableSize = pPage->pBt->usableSize;
assert( nByte < usableSize-8 );
nFrag = data[hdr+7];
assert( pPage->cellOffset == hdr + 12 - 4*pPage->leaf );
gap = pPage->cellOffset + 2*pPage->nCell;
top = get2byteNotZero(&data[hdr+5]);
if( gap>top ) return SQLITE_CORRUPT_BKPT;
assert( gap<=65536 );
top = get2byte(&data[hdr+5]);
if( gap>top ){
if( top==0 ){
top = 65536;
}else{
return SQLITE_CORRUPT_BKPT;
}
}
testcase( gap+2==top );
testcase( gap+1==top );
testcase( gap==top );
if( nFrag>=60 ){
if( data[hdr+7]>=60 ){
/* Always defragment highly fragmented pages */
rc = defragmentPage(pPage);
if( rc ) return rc;
@@ -1246,7 +1251,7 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
/* Remove the slot from the free-list. Update the number of
** fragmented bytes within the page. */
memcpy(&data[addr], &data[pc], 2);
data[hdr+7] = (u8)(nFrag + x);
data[hdr+7] += (u8)x;
}else if( size+pc > usableSize ){
return SQLITE_CORRUPT_BKPT;
}else{