SQLite

  if( pRoot==0 ){
    assert( db->mallocFailed );
    sqlite3ExprDelete(db, pLeft);
    sqlite3ExprDelete(db, pRight);
  }else{
    if( pRight ){
      pRoot->pRight = pRight;
      pRoot->flags |= EP_Propagate & pRight->flags;
    }
    if( pLeft ){
      pRoot->pLeft = pLeft;
      pRoot->flags |= EP_Propagate & pLeft->flags;
    }
    exprSetHeight(pRoot);
  }
}

/*
** Allocate an Expr node which joins as many as two subtrees.

    sqlite3ExprDelete(db, pItem->pExpr);
    sqlite3DbFree(db, pItem->zName);
    sqlite3DbFree(db, pItem->zSpan);
  }
  sqlite3DbFree(db, pList->a);
  sqlite3DbFree(db, pList);
}

/*
** Return TRUE if any expression in ExprList has any of the EP_*
** properties given by "m"
*/
int sqlite3AnyExprListHasProperty(const ExprList *pList, u32 m){
  int i;
  if( pList==0 ) return 0;
  for(i=0; i<pList->nExpr; i++){
    if( ExprHasProperty(pList->a[i].pExpr, m) ) return 1;
  }
  return 0;
}

/*
** These routines are Walker callbacks used to check expressions to
** see if they are "constant" for some definition of constant.  The
** Walker.eCode value determines the type of "constant" we are looking
** for.
**

    A.zStart = X.zStart;
    A.zEnd = &E.z[E.n];
  }
  expr(A) ::= LP(B) select(X) RP(E). {
    A.pExpr = sqlite3PExpr(pParse, TK_SELECT, 0, 0, 0);
    if( A.pExpr ){
      A.pExpr->x.pSelect = X;
      ExprSetProperty(A.pExpr, EP_xIsSelect|EP_Subquery);
      sqlite3ExprSetHeight(pParse, A.pExpr);
    }else{
      sqlite3SelectDelete(pParse->db, X);
    }
    A.zStart = B.z;
    A.zEnd = &E.z[E.n];
  }
  expr(A) ::= expr(X) in_op(N) LP select(Y) RP(E).  [IN] {
    A.pExpr = sqlite3PExpr(pParse, TK_IN, X.pExpr, 0, 0);
    if( A.pExpr ){
      A.pExpr->x.pSelect = Y;
      ExprSetProperty(A.pExpr, EP_xIsSelect|EP_Subquery);
      sqlite3ExprSetHeight(pParse, A.pExpr);
    }else{
      sqlite3SelectDelete(pParse->db, Y);
    }
    if( N ) A.pExpr = sqlite3PExpr(pParse, TK_NOT, A.pExpr, 0, 0);
    A.zStart = X.zStart;
    A.zEnd = &E.z[E.n];
  }
  expr(A) ::= expr(X) in_op(N) nm(Y) dbnm(Z). [IN] {
    SrcList *pSrc = sqlite3SrcListAppend(pParse->db, 0,&Y,&Z);
    A.pExpr = sqlite3PExpr(pParse, TK_IN, X.pExpr, 0, 0);
    if( A.pExpr ){
      A.pExpr->x.pSelect = sqlite3SelectNew(pParse, 0,pSrc,0,0,0,0,0,0,0);
      ExprSetProperty(A.pExpr, EP_xIsSelect|EP_Subquery);
      sqlite3ExprSetHeight(pParse, A.pExpr);
    }else{
      sqlite3SrcListDelete(pParse->db, pSrc);
    }
    if( N ) A.pExpr = sqlite3PExpr(pParse, TK_NOT, A.pExpr, 0, 0);
    A.zStart = X.zStart;
    A.zEnd = Z.z ? &Z.z[Z.n] : &Y.z[Y.n];
  }
  expr(A) ::= EXISTS(B) LP select(Y) RP(E). {
    Expr *p = A.pExpr = sqlite3PExpr(pParse, TK_EXISTS, 0, 0, 0);
    if( p ){
      p->x.pSelect = Y;
      ExprSetProperty(p, EP_xIsSelect|EP_Subquery);
      sqlite3ExprSetHeight(pParse, p);
    }else{
      sqlite3SelectDelete(pParse->db, Y);
    }
    A.zStart = B.z;
    A.zEnd = &E.z[E.n];
  }

** exist on the table t1, a complete scan of the data might be
** avoided.
**
** Flattening is only attempted if all of the following are true:
**
**   (1)  The subquery and the outer query do not both use aggregates.
**
**   (2)  The subquery is not an aggregate or (2a) the outer query is not a join
**        and (2b) the outer query does not use subqueries other than the one
**        FROM-clause subquery that is a candidate for flattening.  (2b is
**        due to ticket [2f7170d73bf9abf80] from 2015-02-09.)
**
**   (3)  The subquery is not the right operand of a left outer join
**        (Originally ticket #306.  Strengthened by ticket #3300)
**
**   (4)  The subquery is not DISTINCT.
**
**  (**)  At one point restrictions (4) and (5) defined a subset of DISTINCT

  if( OptimizationDisabled(db, SQLITE_QueryFlattener) ) return 0;
  pSrc = p->pSrc;
  assert( pSrc && iFrom>=0 && iFrom<pSrc->nSrc );
  pSubitem = &pSrc->a[iFrom];
  iParent = pSubitem->iCursor;
  pSub = pSubitem->pSelect;
  assert( pSub!=0 );
  if( subqueryIsAgg ){
    if( isAgg ) return 0;                                /* Restriction (1)   */
    if( pSrc->nSrc>1 ) return 0;                         /* Restriction (2a)  */
    if( (p->pWhere && ExprHasProperty(p->pWhere,EP_Subquery))
     || sqlite3AnyExprListHasProperty(p->pEList,EP_Subquery)
     || sqlite3AnyExprListHasProperty(p->pOrderBy,EP_Subquery)
    ){
      return 0;                                          /* Restriction (2b)  */
    }
  }
    
  pSubSrc = pSub->pSrc;
  assert( pSubSrc );
  /* Prior to version 3.1.2, when LIMIT and OFFSET had to be simple constants,
  ** not arbitrary expressions, we allowed some combining of LIMIT and OFFSET
  ** because they could be computed at compile-time.  But when LIMIT and OFFSET
  ** became arbitrary expressions, we were forced to add restrictions (13)
  ** and (14). */

#define EP_TokenOnly 0x004000 /* Expr struct EXPR_TOKENONLYSIZE bytes only */
#define EP_Static    0x008000 /* Held in memory not obtained from malloc() */
#define EP_MemToken  0x010000 /* Need to sqlite3DbFree() Expr.zToken */
#define EP_NoReduce  0x020000 /* Cannot EXPRDUP_REDUCE this Expr */
#define EP_Unlikely  0x040000 /* unlikely() or likelihood() function */
#define EP_ConstFunc 0x080000 /* Node is a SQLITE_FUNC_CONSTANT function */
#define EP_CanBeNull 0x100000 /* Can be null despite NOT NULL constraint */
#define EP_Subquery  0x200000 /* Tree contains a TK_SELECT operator */

/*
** Combinations of two or more EP_* flags
*/
#define EP_Propagate (EP_Collate|EP_Subquery) /* Propagate these bits up tree */

/*
** These macros can be used to test, set, or clear bits in the 
** Expr.flags field.
*/
#define ExprHasProperty(E,P)     (((E)->flags&(P))!=0)
#define ExprHasAllProperty(E,P)  (((E)->flags&(P))==(P))

Expr *sqlite3ExprFunction(Parse*,ExprList*, Token*);
void sqlite3ExprAssignVarNumber(Parse*, Expr*);
void sqlite3ExprDelete(sqlite3*, Expr*);
ExprList *sqlite3ExprListAppend(Parse*,ExprList*,Expr*);
void sqlite3ExprListSetName(Parse*,ExprList*,Token*,int);
void sqlite3ExprListSetSpan(Parse*,ExprList*,ExprSpan*);
void sqlite3ExprListDelete(sqlite3*, ExprList*);
int sqlite3AnyExprListHasProperty(const ExprList*,u32);
int sqlite3Init(sqlite3*, char**);
int sqlite3InitCallback(void*, int, char**, char**);
void sqlite3Pragma(Parse*,Token*,Token*,Token*,int);
void sqlite3ResetAllSchemasOfConnection(sqlite3*);
void sqlite3ResetOneSchema(sqlite3*,int);
void sqlite3CollapseDatabaseArray(sqlite3*);
void sqlite3BeginParse(Parse*,int);