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Optimization to the ExprList object to make it slightly smaller and faster.

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FossilOrigin-Name: 4da49a95c0f07ed7790169e8833c3e2dacda504a3d997f567572020148abe30b
This commit is contained in:
drh
2017-09-15 15:17:48 +00:00
parent 154896e8d2
commit a19543fe70
4 changed files with 27 additions and 14 deletions
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21
src/expr.c
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@@ -1305,7 +1305,11 @@ ExprList *sqlite3ExprListDup(sqlite3 *db, ExprList *p, int flags){
pNew = sqlite3DbMallocRawNN(db,
sizeof(*pNew)+sizeof(pNew->a[0])*(p->nExpr-1) );
if( pNew==0 ) return 0;
pNew->nAlloc = pNew->nExpr = p->nExpr;
pNew->nExpr = p->nExpr;
/* After being duplicated, the ExprList may not be expanded again using
** Append() because Append() assumes that the number of slots in
** ExprList.a[] is a power of 2 */
VVA_ONLY( pNew->bFixedSize = 1 );
pItem = pNew->a;
pOldItem = p->a;
for(i=0; i<p->nExpr; i++, pItem++, pOldItem++){
@@ -1459,6 +1463,13 @@ Select *sqlite3SelectDup(sqlite3 *db, Select *p, int flags){
** Add a new element to the end of an expression list. If pList is
** initially NULL, then create a new expression list.
**
** The pList argument must be either NULL or a pointer to an ExprList
** obtained from a prior call to sqlite3ExprListAppend(). This routine
** may not be used with an ExprList obtained from sqlite3ExprListDup().
** Reason: This routine assumes that the number of slots in pList->a[]
** is a power of two. That is true for sqlite3ExprListAppend() returns
** but is not necessarily true from the return value of sqlite3ExprListDup().
**
** If a memory allocation error occurs, the entire list is freed and
** NULL is returned. If non-NULL is returned, then it is guaranteed
** that the new entry was successfully appended.
@@ -1471,22 +1482,22 @@ ExprList *sqlite3ExprListAppend(
struct ExprList_item *pItem;
sqlite3 *db = pParse->db;
assert( db!=0 );
assert( pList==0 || pList->bFixedSize==0 );
if( pList==0 ){
pList = sqlite3DbMallocRawNN(db, sizeof(ExprList) );
if( pList==0 ){
goto no_mem;
}
pList->nExpr = 0;
pList->nAlloc = 1;
}else if( pList->nExpr==pList->nAlloc ){
VVA_ONLY( pList->bFixedSize = 0 );
}else if( (pList->nExpr & (pList->nExpr-1))==0 ){
ExprList *pNew;
pNew = sqlite3DbRealloc(db, pList,
sizeof(*pList)+(2*pList->nAlloc - 1)*sizeof(pList->a[0]));
sizeof(*pList)+(2*pList->nExpr - 1)*sizeof(pList->a[0]));
if( pNew==0 ){
goto no_mem;
}
pList = pNew;
pList->nAlloc *= 2;
}
pItem = &pList->a[pList->nExpr++];
assert( offsetof(struct ExprList_item,zName)==sizeof(pItem->pExpr) );