Overview
| Comment: | A small performance improvement in freeSpace() by special-casing the relatively common case of an empty freelist. |
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| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: | 49f44d355ff70744e4951baca2481c7c2b6c02b3 |
| User & Date: | drh 2014-08-20 18:43:44 |
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: bc985caa 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: 49f44d35 user: drh tags: trunk | |
| 17:56 | Reimplement the freeSpace() routine in btree.c so that it runs faster. check-in: fe4fd014 user: drh tags: trunk | |
Changes
Changes to src/btree.c.
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}
/* 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;
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( iPtr==hdr+1 && 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 */
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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} /* 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); |