SQLite: Check-in [2e838db8]

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Overview

Comment:	Simplify the math slightly, and reduce by one the number of loop iterations, for the loop in balance_nonroot() that moves cells between pages.
Downloads:	Tarball \| ZIP archive \| SQL archive
Timelines:	family \| ancestors \| descendants \| both \| trunk
Files:	files \| file ages \| folders
SHA1:	2e838db82e533598b3cb00011c04fc0d5a896895
User & Date:	drh 2014-10-31 12:22:00

Context

2014-10-31
14:26		Simplify the logic in the cell redistribution loop of balance_nonroot(). Enhance and clarify comments and add assert() statements for additional verification of correctness. check-in: a07078b6 user: drh tags: trunk
12:22		Simplify the math slightly, and reduce by one the number of loop iterations, for the loop in balance_nonroot() that moves cells between pages. check-in: 2e838db8 user: drh tags: trunk
10:31		Add the "varint.c" utility program in the tool directory. check-in: ea5d56be user: drh tags: trunk

Changes

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Changes to src/btree.c.

  **
  **   2) If cells are to be removed from the end of the page and shifted
  **      to the right-hand sibling, it is not safe to update the page until 
  **      the right-hand sibling (apNew[i+1]) has already been updated.
  **
  ** If neither of the above apply, the page is safe to update.
  */
  for(i=0; i<nNew*2; i++){
    int iPg = (i>=nNew ? i-nNew : nNew-1-i);


    if( abDone[iPg]==0 
     && (iPg==0 || cntOld[iPg-1]>=cntNew[iPg-1] || abDone[iPg-1])
     && (cntNew[iPg]>=cntOld[iPg] || abDone[iPg+1])
    ){
      int iNew;
      int iOld;
      int nNewCell;








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  **
  **   2) If cells are to be removed from the end of the page and shifted
  **      to the right-hand sibling, it is not safe to update the page until 
  **      the right-hand sibling (apNew[i+1]) has already been updated.
  **
  ** If neither of the above apply, the page is safe to update.
  */
  for(i=1-nNew; i<nNew; i++){
    int iPg = i<0 ? -i : i;
    /* iPg takes values from nNew-1 down to 0 then back up to nNew-1 again */
    assert( iPg>=0 && iPg<nNew );
    if( abDone[iPg]==0 
     && (iPg==0 || cntOld[iPg-1]>=cntNew[iPg-1] || abDone[iPg-1])
     && (cntNew[iPg]>=cntOld[iPg] || abDone[iPg+1])
    ){
      int iNew;
      int iOld;
      int nNewCell;