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Further size reduction and performance improvement in btree.c:allocateSpace().

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FossilOrigin-Name: 1cb1cd64930a6bc371143f7d2e77eb1c51498cb0
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drh
2014-08-20 11:56:14 +00:00
parent 53d89cdfe9
commit 4c04f3c8bd
3 changed files with 19 additions and 21 deletions
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24
src/btree.c
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@@ -1222,20 +1222,15 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
return SQLITE_CORRUPT_BKPT;
}
}
/* If there is enough space between gap and top for one more cell pointer
** array entry offset, and if the freelist is not empty, then search the
** freelist looking for a free slot big enough to satisfy the request.
*/
testcase( gap+2==top );
testcase( gap+1==top );
testcase( gap==top );
if( data[hdr+7]>=60 ){
/* Always defragment highly fragmented pages */
rc = defragmentPage(pPage);
if( rc ) return rc;
top = get2byteNotZero(&data[hdr+5]);
}else if( gap+2<=top ){
/* Search the freelist looking for a free slot big enough to satisfy
** the request. The allocation is made from the first free slot in
** the list that is large enough to accommodate it.
*/
if( gap+2<=top && (data[hdr+1] || data[hdr+2]) ){
int pc, addr;
for(addr=hdr+1; (pc = get2byte(&data[addr]))>0; addr=pc){
int size; /* Size of the free slot */
@@ -1248,6 +1243,7 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
testcase( x==4 );
testcase( x==3 );
if( x<4 ){
if( data[hdr+7]>=60 ) goto defragment_page;
/* Remove the slot from the free-list. Update the number of
** fragmented bytes within the page. */
memcpy(&data[addr], &data[pc], 2);
@@ -1265,11 +1261,13 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
}
}
/* Check to make sure there is enough space in the gap to satisfy
** the allocation. If not, defragment.
/* The request could not be fulfilled using a freelist slot. Check
** to see if defragmentation is necessary.
*/
testcase( gap+2+nByte==top );
if( gap+2+nByte>top ){
defragment_page:
assert( pPage->nCell>0 );
rc = defragmentPage(pPage);
if( rc ) return rc;
top = get2byteNotZero(&data[hdr+5]);