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Fix a race condition in the sorter.

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FossilOrigin-Name: 32ccf3ae18531682dfd039fa8df6ad9a907ac455
This commit is contained in:
dan
2014-05-03 19:33:00 +00:00
parent 0d51def29e
commit e18e90ebaf
5 changed files with 55 additions and 25 deletions
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21
src/vdbesort.c
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@@ -651,6 +651,7 @@ static int vdbePmaReaderNext(PmaReader *pIter){
int rc = SQLITE_OK; /* Return Code */
u64 nRec = 0; /* Size of record in bytes */
if( pIter->iReadOff>=pIter->iEof ){
IncrMerger *pIncr = pIter->pIncr;
int bEof = 1;
@@ -1844,10 +1845,18 @@ static int vdbeIncrInitMerger(
){
int rc = SQLITE_OK; /* Return code */
int i; /* For iterating through PmaReader objects */
int nTree = pMerger->nTree;
for(i=0; rc==SQLITE_OK && i<pMerger->nTree; i++){
for(i=0; rc==SQLITE_OK && i<nTree; i++){
if( eMode==INCRINIT_ROOT ){
rc = vdbePmaReaderNext(&pMerger->aIter[i]);
/* Iterators should be normally initialized in order, as if they are
** reading from the same temp file this makes for more linear file IO.
** However, in the INCRINIT_ROOT case, if iterator aIter[nTask-1] is
** in use it will block the vdbePmaReaderNext() call while it uses
** the main thread to fill its buffer. So calling PmaReaderNext()
** on this iterator before any of the multi-threaded iterators takes
** better advantage of multi-processor hardware. */
rc = vdbePmaReaderNext(&pMerger->aIter[nTree-i-1]);
}else{
rc = vdbePmaReaderIncrInit(&pMerger->aIter[i], INCRINIT_NORMAL);
}
@@ -2196,7 +2205,13 @@ static int vdbeSorterSetupMerge(VdbeSorter *pSorter){
for(iTask=0; rc==SQLITE_OK && iTask<pSorter->nTask; iTask++){
PmaReader *p = &pMain->aIter[iTask];
assert( p->pIncr==0 || p->pIncr->pTask==&pSorter->aTask[iTask] );
if( p->pIncr ){ rc = vdbePmaReaderBgIncrInit(p); }
if( p->pIncr ){
if( iTask==pSorter->nTask-1 ){
rc = vdbePmaReaderIncrInit(p, INCRINIT_TASK);
}else{
rc = vdbePmaReaderBgIncrInit(p);
}
}
}
}
}