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If a rollback mode transaction reduces the size of the database file, avoid actually truncating the file until after the transaction has been committed (but before the db has been unlocked). This means pages that are removed from the database by truncating the file need not be journalled.

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FossilOrigin-Name: b73847f17b7ae1298dfc52de6c4c4bc809bc77a3
This commit is contained in:
dan
2013-02-23 16:40:46 +00:00
parent f38b65a85d
commit bc1a3c6ce2
7 changed files with 89 additions and 81 deletions
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17
src/backup.c
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@@ -462,7 +462,6 @@ int sqlite3_backup_step(sqlite3_backup *p, int nPage){
nDestTruncate = nSrcPage * (pgszSrc/pgszDest);
}
assert( nDestTruncate>0 );
sqlite3PagerTruncateImage(pDestPager, nDestTruncate);
if( pgszSrc<pgszDest ){
/* If the source page-size is smaller than the destination page-size,
@@ -476,6 +475,8 @@ int sqlite3_backup_step(sqlite3_backup *p, int nPage){
*/
const i64 iSize = (i64)pgszSrc * (i64)nSrcPage;
sqlite3_file * const pFile = sqlite3PagerFile(pDestPager);
Pgno iPg;
int nDstPage;
i64 iOff;
i64 iEnd;
@@ -486,12 +487,23 @@ int sqlite3_backup_step(sqlite3_backup *p, int nPage){
&& iSize>=PENDING_BYTE && iSize<=PENDING_BYTE+pgszDest
));
/* This call ensures that all data required to recreate the original
/* This block ensures that all data required to recreate the original
** database has been stored in the journal for pDestPager and the
** journal synced to disk. So at this point we may safely modify
** the database file in any way, knowing that if a power failure
** occurs, the original database will be reconstructed from the
** journal file. */
sqlite3PagerPagecount(pDestPager, &nDstPage);
for(iPg=nDestTruncate; rc==SQLITE_OK && iPg<=(Pgno)nDstPage; iPg++){
if( iPg!=PENDING_BYTE_PAGE(p->pDest->pBt) ){
DbPage *pPg;
rc = sqlite3PagerGet(pDestPager, iPg, &pPg);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite(pPg);
sqlite3PagerUnref(pPg);
}
}
}
rc = sqlite3PagerCommitPhaseOne(pDestPager, 0, 1);
/* Write the extra pages and truncate the database file as required */
@@ -519,6 +531,7 @@ int sqlite3_backup_step(sqlite3_backup *p, int nPage){
rc = sqlite3PagerSync(pDestPager);
}
}else{
sqlite3PagerTruncateImage(pDestPager, nDestTruncate);
rc = sqlite3PagerCommitPhaseOne(pDestPager, 0, 0);
}