Many hyperlinks are disabled.
Use anonymous login
to enable hyperlinks.
Overview
| Comment: | Minor performance improvement and size reduction for the btree-page space allocator. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
73637d12e31f5489efe37d8cf4ab50a1 |
| User & Date: | drh 2014-08-20 00:54:46 |
Context
|
2014-08-20
| ||
| 10:42 | Fix a typo in the showdb usage message. check-in: 6c66beae user: dan tags: trunk | |
| 00:54 | Minor performance improvement and size reduction for the btree-page space allocator. check-in: 73637d12 user: drh tags: trunk | |
|
2014-08-19
| ||
| 23:04 | Modify the memsubsys1-3.1.4 test so that it does not fail arbitrarily due to variations in the behavior of system malloc(). check-in: d280157d user: drh tags: trunk | |
Changes
Changes to src/btree.c.
1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 .... 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 .... 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 |
** the first two bytes past the cell pointer area since presumably this
** allocation is being made in order to insert a new cell, so we will
** also end up needing a new cell pointer.
*/
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 */
int usableSize; /* Usable size of the page */
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( pPage->pBt );
................................................................................
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( nByte>=0 ); /* Minimum cell size is 4 */
assert( pPage->nFree>=nByte );
assert( pPage->nOverflow==0 );
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;
testcase( gap+2==top );
testcase( gap+1==top );
testcase( gap==top );
if( nFrag>=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
................................................................................
int x = size - nByte;
testcase( x==4 );
testcase( x==3 );
if( x<4 ){
/* 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);
}else if( size+pc > usableSize ){
return SQLITE_CORRUPT_BKPT;
}else{
/* The slot remains on the free-list. Reduce its size to account
** for the portion used by the new allocation. */
put2byte(&data[pc+2], x);
}
|
< < > | > > > > | > > | | |
1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 .... 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 .... 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 |
** the first two bytes past the cell pointer area since presumably this
** allocation is being made in order to insert a new cell, so we will
** also end up needing a new cell pointer.
*/
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 top; /* First byte of cell content area */
int gap; /* First byte of gap between cell pointers and cell content */
int rc; /* Integer return code */
int usableSize; /* Usable size of the page */
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( pPage->pBt );
................................................................................
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( nByte>=0 ); /* Minimum cell size is 4 */
assert( pPage->nFree>=nByte );
assert( pPage->nOverflow==0 );
usableSize = pPage->pBt->usableSize;
assert( nByte < usableSize-8 );
assert( pPage->cellOffset == hdr + 12 - 4*pPage->leaf );
gap = pPage->cellOffset + 2*pPage->nCell;
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( 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
................................................................................
int x = size - nByte;
testcase( x==4 );
testcase( x==3 );
if( x<4 ){
/* 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)x;
}else if( size+pc > usableSize ){
return SQLITE_CORRUPT_BKPT;
}else{
/* The slot remains on the free-list. Reduce its size to account
** for the portion used by the new allocation. */
put2byte(&data[pc+2], x);
}
|