diff options
Diffstat (limited to 'src/rowset.c')
| -rw-r--r-- | src/rowset.c | 21 |
1 files changed, 14 insertions, 7 deletions
diff --git a/src/rowset.c b/src/rowset.c index bf4382ddd..5420ab991 100644 --- a/src/rowset.c +++ b/src/rowset.c @@ -179,7 +179,9 @@ void sqlite3RowSetClear(RowSet *p){ */ static struct RowSetEntry *rowSetEntryAlloc(RowSet *p){ assert( p!=0 ); - if( p->nFresh==0 ){ + if( p->nFresh==0 ){ /*OPTIMIZATION-IF-FALSE*/ + /* We could allocate a fresh RowSetEntry each time one is needed, but it + ** is more efficient to pull a preallocated entry from the pool */ struct RowSetChunk *pNew; pNew = sqlite3DbMallocRawNN(p->db, sizeof(*pNew)); if( pNew==0 ){ @@ -213,7 +215,9 @@ void sqlite3RowSetInsert(RowSet *p, i64 rowid){ pEntry->pRight = 0; pLast = p->pLast; if( pLast ){ - if( (p->rsFlags & ROWSET_SORTED)!=0 && rowid<=pLast->v ){ + if( rowid<=pLast->v ){ /*OPTIMIZATION-IF-FALSE*/ + /* Avoid unnecessary sorts by preserving the ROWSET_SORTED flags + ** where possible */ p->rsFlags &= ~ROWSET_SORTED; } pLast->pRight = pEntry; @@ -335,16 +339,19 @@ static struct RowSetEntry *rowSetNDeepTree( ){ struct RowSetEntry *p; /* Root of the new tree */ struct RowSetEntry *pLeft; /* Left subtree */ - if( *ppList==0 ){ - return 0; + if( *ppList==0 ){ /*OPTIMIZATION-IF-TRUE*/ + /* Prevent unnecessary deep recursion when we run out of entries */ + return 0; } if( iDepth>1 ){ /*OPTIMIZATION-IF-TRUE*/ /* This branch causes a *balanced* tree to be generated. A valid tree - ** is still generated without this branch, but it is wildly unbalanced - ** and inefficient. */ + ** is still generated without this branch, but the tree is wildly + ** unbalanced and inefficient. */ pLeft = rowSetNDeepTree(ppList, iDepth-1); p = *ppList; - if( p==0 ){ + if( p==0 ){ /*OPTIMIZATION-IF-FALSE*/ + /* It is safe to always return here, but the resulting tree + ** would be unbalanced */ return pLeft; } p->pLeft = pLeft; |