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Overview
| Comment: | A small performance improvement in freeSpace() by special-casing the relatively common case of an empty freelist. |
|---|---|
| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
49f44d355ff70744e4951baca2481c7c |
| User & Date: | drh 2014-08-20 18:43:44.510 |
Context
|
2014-08-20
| ||
| 23:38 | Enhancements to skip-scan such that it is operable when a middle column of an index is skipped while the left-most column is constrained in the WHERE clause. (check-in: bc985caa78 user: drh tags: trunk) | |
| 18:43 | A small performance improvement in freeSpace() by special-casing the relatively common case of an empty freelist. (check-in: 49f44d355f user: drh tags: trunk) | |
| 17:56 | Reimplement the freeSpace() routine in btree.c so that it runs faster. (check-in: fe4fd014b4 user: drh tags: trunk) | |
Changes
Changes to src/btree.c.
| ︙ | ︙ | |||
1326 1327 1328 1329 1330 1331 1332 | } /* The list of freeblocks must be in ascending order. Find the ** spot on the list where iStart should be inserted. */ hdr = pPage->hdrOffset; iPtr = hdr + 1; | > > > | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | < | > | > | 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 |
}
/* The list of freeblocks must be in ascending order. Find the
** spot on the list where iStart should be inserted.
*/
hdr = pPage->hdrOffset;
iPtr = hdr + 1;
if( data[iPtr+1]==0 && data[iPtr]==0 ){
iFreeBlk = 0; /* Shortcut for the case when the freelist is empty */
}else{
while( (iFreeBlk = get2byte(&data[iPtr]))>0 && iFreeBlk<iStart ){
if( iFreeBlk<iPtr+4 ) return SQLITE_CORRUPT_BKPT;
iPtr = iFreeBlk;
}
if( iFreeBlk>iLast ) return SQLITE_CORRUPT_BKPT;
assert( iFreeBlk>iPtr || iFreeBlk==0 );
/* At this point:
** iFreeBlk: First freeblock after iStart, or zero if none
** iPtr: The address of a pointer iFreeBlk
**
** Check to see if iFreeBlk should be coalesced onto the end of iStart.
*/
if( iFreeBlk && iEnd+3>=iFreeBlk ){
nFrag = iFreeBlk - iEnd;
if( iEnd>iFreeBlk ) return SQLITE_CORRUPT_BKPT;
iEnd = iFreeBlk + get2byte(&data[iFreeBlk+2]);
iSize = iEnd - iStart;
iFreeBlk = get2byte(&data[iFreeBlk]);
}
/* If iPtr is another freeblock (that is, if iPtr is not the freelist pointer
** in the page header) then check to see if iStart should be coalesced
** onto the end of iPtr.
*/
if( iPtr>hdr+1 ){
int iPtrEnd = iPtr + get2byte(&data[iPtr+2]);
if( iPtrEnd+3>=iStart ){
if( iPtrEnd>iStart ) return SQLITE_CORRUPT_BKPT;
nFrag += iStart - iPtrEnd;
iSize = iEnd - iPtr;
iStart = iPtr;
}
}
if( nFrag>data[hdr+7] ) return SQLITE_CORRUPT_BKPT;
data[hdr+7] -= nFrag;
}
if( iStart==get2byte(&data[hdr+5]) ){
/* The new freeblock is at the beginning of the cell content area,
** so just extend the cell content area rather than create another
** freelist entry */
if( iPtr!=hdr+1 ) return SQLITE_CORRUPT_BKPT;
put2byte(&data[hdr+1], iFreeBlk);
put2byte(&data[hdr+5], iEnd);
}else{
/* Insert the new freeblock into the freelist */
put2byte(&data[iPtr], iStart);
put2byte(&data[iStart], iFreeBlk);
put2byte(&data[iStart+2], iSize);
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