Combine the ExprList_item objects and the ExprList wrapper into a single

memory allocation, for improved performance and reduced footprint.

FossilOrigin-Name: 2b6560ad88b92820c383bcdc1e30c06f8b081ef7c6d9b1af71d2bb76c83e35cd

3 files changed, 19 insertions, 26 deletions

diff --git a/src/expr.c b/src/expr.c
index ce948be69..8d935764a 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -1305,15 +1305,11 @@ ExprList *sqlite3ExprListDup(sqlite3 *db, ExprList *p, int flags){
   Expr *pPriorSelectCol = 0;
   assert( db!=0 );
   if( p==0 ) return 0;
-  pNew = sqlite3DbMallocRawNN(db, sizeof(*pNew) );
+  pNew = sqlite3DbMallocRawNN(db, 
+             sizeof(*pNew)+sizeof(pNew->a[0])*(p->nExpr-1) );
   if( pNew==0 ) return 0;
-  pNew->nExpr = i = p->nExpr;
-  if( (flags & EXPRDUP_REDUCE)==0 ) for(i=1; i<p->nExpr; i+=i){}
-  pNew->a = pItem = sqlite3DbMallocRawNN(db,  i*sizeof(p->a[0]) );
-  if( pItem==0 ){
-    sqlite3DbFree(db, pNew);
-    return 0;
-  } 
+  pNew->nAlloc = pNew->nExpr = p->nExpr;
+  pItem = pNew->a;
   pOldItem = p->a;
   for(i=0; i<p->nExpr; i++, pItem++, pOldItem++){
     Expr *pOldExpr = pOldItem->pExpr;
@@ -1475,6 +1471,7 @@ ExprList *sqlite3ExprListAppend(
   ExprList *pList,        /* List to which to append. Might be NULL */
   Expr *pExpr             /* Expression to be appended. Might be NULL */
 ){
+  struct ExprList_item *pItem;
   sqlite3 *db = pParse->db;
   assert( db!=0 );
   if( pList==0 ){
@@ -1483,23 +1480,20 @@ ExprList *sqlite3ExprListAppend(
       goto no_mem;
     }
     pList->nExpr = 0;
-    pList->a = sqlite3DbMallocRawNN(db, sizeof(pList->a[0]));
-    if( pList->a==0 ) goto no_mem;
-  }else if( (pList->nExpr & (pList->nExpr-1))==0 ){
-    struct ExprList_item *a;
-    assert( pList->nExpr>0 );
-    a = sqlite3DbRealloc(db, pList->a, pList->nExpr*2*sizeof(pList->a[0]));
-    if( a==0 ){
+    pList->nAlloc = 1;
+  }else if( pList->nExpr==pList->nAlloc ){
+    ExprList *pNew;
+    pNew = sqlite3DbRealloc(db, pList, 
+             sizeof(*pList)+(2*pList->nAlloc - 1)*sizeof(pList->a[0]));
+    if( pNew==0 ){
       goto no_mem;
     }
-    pList->a = a;
-  }
-  assert( pList->a!=0 );
-  if( 1 ){
-    struct ExprList_item *pItem = &pList->a[pList->nExpr++];
-    memset(pItem, 0, sizeof(*pItem));
-    pItem->pExpr = pExpr;
+    pList = pNew;
+    pList->nAlloc *= 2;
   }
+  pItem = &pList->a[pList->nExpr++];
+  memset(pItem, 0, sizeof(*pItem));
+  pItem->pExpr = pExpr;
   return pList;
 
 no_mem:     
@@ -1665,13 +1659,11 @@ void sqlite3ExprListCheckLength(
 static SQLITE_NOINLINE void exprListDeleteNN(sqlite3 *db, ExprList *pList){
   int i;
   struct ExprList_item *pItem;
-  assert( pList->a!=0 || pList->nExpr==0 );
   for(pItem=pList->a, i=0; i<pList->nExpr; i++, pItem++){
     sqlite3ExprDelete(db, pItem->pExpr);
     sqlite3DbFree(db, pItem->zName);
     sqlite3DbFree(db, pItem->zSpan);
   }
-  sqlite3DbFree(db, pList->a);
   sqlite3DbFree(db, pList);
 }
 void sqlite3ExprListDelete(sqlite3 *db, ExprList *pList){
diff --git a/src/select.c b/src/select.c
index bb055c789..297b4d719 100644
--- a/src/select.c
+++ b/src/select.c
@@ -2900,7 +2900,7 @@ static int multiSelectOrderBy(
         if( pNew==0 ) return SQLITE_NOMEM_BKPT;
         pNew->flags |= EP_IntValue;
         pNew->u.iValue = i;
-        pOrderBy = sqlite3ExprListAppend(pParse, pOrderBy, pNew);
+        p->pOrderBy = pOrderBy = sqlite3ExprListAppend(pParse, pOrderBy, pNew);
         if( pOrderBy ) pOrderBy->a[nOrderBy++].u.x.iOrderByCol = (u16)i;
       }
     }
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 271ea9a3e..a0acec471 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -2443,6 +2443,7 @@ struct Expr {
 */
 struct ExprList {
   int nExpr;             /* Number of expressions on the list */
+  int nAlloc;            /* Number of a[] slots allocated */
   struct ExprList_item { /* For each expression in the list */
     Expr *pExpr;            /* The parse tree for this expression */
     char *zName;            /* Token associated with this expression */
@@ -2458,7 +2459,7 @@ struct ExprList {
       } x;
       int iConstExprReg;      /* Register in which Expr value is cached */
     } u;
-  } *a;                  /* Alloc a power of two greater or equal to nExpr */
+  } a[1];                  /* One slot for each expression in the list */
 };
 
 /*