expr.c

SQLite 2.8.6 源代码,用来在Linux/Unix/Windows上编译安装.它是一个小型的数据库,但是非常好用,速度也快,一般的数据库查询之类的操作据统计比MySQL,PostgreSQL

/*
** 2001 September 15
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.98 2003/07/30 12:34:12 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Construct a new expression node and return a pointer to it.  Memory
** for this node is obtained from sqliteMalloc().  The calling function
** is responsible for making sure the node eventually gets freed.
*/
Expr *sqliteExpr(int op, Expr *pLeft, Expr *pRight, Token *pToken){
  Expr *pNew;
  pNew = sqliteMalloc( sizeof(Expr) );
  if( pNew==0 ){
    sqliteExprDelete(pLeft);
    sqliteExprDelete(pRight);
    return 0;
  }
  pNew->op = op;
  pNew->pLeft = pLeft;
  pNew->pRight = pRight;
  if( pToken ){
    assert( pToken->dyn==0 );
    pNew->token = *pToken;
    pNew->span = *pToken;
  }else{
    pNew->token.dyn = 0;
    pNew->token.z = 0;
    pNew->token.n = 0;
    if( pLeft && pRight ){
      sqliteExprSpan(pNew, &pLeft->span, &pRight->span);
    }else{
      pNew->span = pNew->token;
    }
  }
  return pNew;
}

/*
** Set the Expr.span field of the given expression to span all
** text between the two given tokens.
*/
void sqliteExprSpan(Expr *pExpr, Token *pLeft, Token *pRight){
  if( pExpr && pRight && pRight->z && pLeft && pLeft->z ){
    if( pLeft->dyn==0 && pRight->dyn==0 ){
      pExpr->span.z = pLeft->z;
      pExpr->span.n = pRight->n + Addr(pRight->z) - Addr(pLeft->z);
    }else{
      pExpr->span.z = 0;
      pExpr->span.n = 0;
      pExpr->span.dyn = 0;
    }
  }
}

/*
** Construct a new expression node for a function with multiple
** arguments.
*/
Expr *sqliteExprFunction(ExprList *pList, Token *pToken){
  Expr *pNew;
  pNew = sqliteMalloc( sizeof(Expr) );
  if( pNew==0 ){
    sqliteExprListDelete(pList);
    return 0;
  }
  pNew->op = TK_FUNCTION;
  pNew->pList = pList;
  pNew->token.dyn = 0;
  if( pToken ){
    assert( pToken->dyn==0 );
    pNew->token = *pToken;
  }else{
    pNew->token.z = 0;
    pNew->token.n = 0;
  }
  pNew->span = pNew->token;
  return pNew;
}

/*
** Recursively delete an expression tree.
*/
void sqliteExprDelete(Expr *p){
  if( p==0 ) return;
  if( p->span.dyn && p->span.z ) sqliteFree((char*)p->span.z);
  if( p->token.dyn && p->token.z ) sqliteFree((char*)p->token.z);
  if( p->pLeft ) sqliteExprDelete(p->pLeft);
  if( p->pRight ) sqliteExprDelete(p->pRight);
  if( p->pList ) sqliteExprListDelete(p->pList);
  if( p->pSelect ) sqliteSelectDelete(p->pSelect);
  sqliteFree(p);
}


/*
** The following group of routines make deep copies of expressions,
** expression lists, ID lists, and select statements.  The copies can
** be deleted (by being passed to their respective ...Delete() routines)
** without effecting the originals.
**
** The expression list, ID, and source lists return by sqliteExprListDup(),
** sqliteIdListDup(), and sqliteSrcListDup() can not be further expanded 
** by subsequent calls to sqlite*ListAppend() routines.
**
** Any tables that the SrcList might point to are not duplicated.
*/
Expr *sqliteExprDup(Expr *p){
  Expr *pNew;
  if( p==0 ) return 0;
  pNew = sqliteMallocRaw( sizeof(*p) );
  if( pNew==0 ) return 0;
  memcpy(pNew, p, sizeof(*pNew));
  if( p->token.z!=0 ){
    pNew->token.z = sqliteStrDup(p->token.z);
    pNew->token.dyn = 1;
  }else{
    pNew->token.z = 0;
    pNew->token.n = 0;
    pNew->token.dyn = 0;
  }
  pNew->span.z = 0;
  pNew->span.n = 0;
  pNew->span.dyn = 0;
  pNew->pLeft = sqliteExprDup(p->pLeft);
  pNew->pRight = sqliteExprDup(p->pRight);
  pNew->pList = sqliteExprListDup(p->pList);
  pNew->pSelect = sqliteSelectDup(p->pSelect);
  return pNew;
}
void sqliteTokenCopy(Token *pTo, Token *pFrom){
  if( pTo->dyn ) sqliteFree((char*)pTo->z);
  if( pFrom->z ){
    pTo->n = pFrom->n;
    pTo->z = sqliteStrNDup(pFrom->z, pFrom->n);
    pTo->dyn = 1;
  }else{
    pTo->n = 0;
    pTo->z = 0;
    pTo->dyn = 0;
  }
}
ExprList *sqliteExprListDup(ExprList *p){
  ExprList *pNew;
  int i;
  if( p==0 ) return 0;
  pNew = sqliteMalloc( sizeof(*pNew) );
  if( pNew==0 ) return 0;
  pNew->nExpr = pNew->nAlloc = p->nExpr;
  pNew->a = sqliteMalloc( p->nExpr*sizeof(p->a[0]) );
  if( pNew->a==0 ) return 0;
  for(i=0; i<p->nExpr; i++){
    Expr *pNewExpr, *pOldExpr;
    pNew->a[i].pExpr = pNewExpr = sqliteExprDup(pOldExpr = p->a[i].pExpr);
    if( pOldExpr->span.z!=0 && pNewExpr ){
      /* Always make a copy of the span for top-level expressions in the
      ** expression list.  The logic in SELECT processing that determines
      ** the names of columns in the result set needs this information */
      sqliteTokenCopy(&pNewExpr->span, &pOldExpr->span);
    }
    assert( pNewExpr==0 || pNewExpr->span.z!=0 
            || pOldExpr->span.z==0 || sqlite_malloc_failed );
    pNew->a[i].zName = sqliteStrDup(p->a[i].zName);
    pNew->a[i].sortOrder = p->a[i].sortOrder;
    pNew->a[i].isAgg = p->a[i].isAgg;
    pNew->a[i].done = 0;
  }
  return pNew;
}
SrcList *sqliteSrcListDup(SrcList *p){
  SrcList *pNew;
  int i;
  int nByte;
  if( p==0 ) return 0;
  nByte = sizeof(*p) + (p->nSrc>0 ? sizeof(p->a[0]) * (p->nSrc-1) : 0);
  pNew = sqliteMalloc( nByte );
  if( pNew==0 ) return 0;
  pNew->nSrc = pNew->nAlloc = p->nSrc;
  for(i=0; i<p->nSrc; i++){
    pNew->a[i].zDatabase = sqliteStrDup(p->a[i].zDatabase);
    pNew->a[i].zName = sqliteStrDup(p->a[i].zName);
    pNew->a[i].zAlias = sqliteStrDup(p->a[i].zAlias);
    pNew->a[i].jointype = p->a[i].jointype;
    pNew->a[i].iCursor = p->a[i].iCursor;
    pNew->a[i].pTab = 0;
    pNew->a[i].pSelect = sqliteSelectDup(p->a[i].pSelect);
    pNew->a[i].pOn = sqliteExprDup(p->a[i].pOn);
    pNew->a[i].pUsing = sqliteIdListDup(p->a[i].pUsing);
  }
  return pNew;
}
IdList *sqliteIdListDup(IdList *p){
  IdList *pNew;
  int i;
  if( p==0 ) return 0;
  pNew = sqliteMalloc( sizeof(*pNew) );
  if( pNew==0 ) return 0;
  pNew->nId = pNew->nAlloc = p->nId;
  pNew->a = sqliteMalloc( p->nId*sizeof(p->a[0]) );
  if( pNew->a==0 ) return 0;
  for(i=0; i<p->nId; i++){
    pNew->a[i].zName = sqliteStrDup(p->a[i].zName);
    pNew->a[i].idx = p->a[i].idx;
  }
  return pNew;
}
Select *sqliteSelectDup(Select *p){
  Select *pNew;
  if( p==0 ) return 0;
  pNew = sqliteMalloc( sizeof(*p) );
  if( pNew==0 ) return 0;
  pNew->isDistinct = p->isDistinct;
  pNew->pEList = sqliteExprListDup(p->pEList);
  pNew->pSrc = sqliteSrcListDup(p->pSrc);
  pNew->pWhere = sqliteExprDup(p->pWhere);
  pNew->pGroupBy = sqliteExprListDup(p->pGroupBy);
  pNew->pHaving = sqliteExprDup(p->pHaving);
  pNew->pOrderBy = sqliteExprListDup(p->pOrderBy);
  pNew->op = p->op;
  pNew->pPrior = sqliteSelectDup(p->pPrior);
  pNew->nLimit = p->nLimit;
  pNew->nOffset = p->nOffset;
  pNew->zSelect = 0;
  pNew->iLimit = -1;
  pNew->iOffset = -1;
  return pNew;
}


/*
** Add a new element to the end of an expression list.  If pList is
** initially NULL, then create a new expression list.
*/
ExprList *sqliteExprListAppend(ExprList *pList, Expr *pExpr, Token *pName){
  int i;
  if( pList==0 ){
    pList = sqliteMalloc( sizeof(ExprList) );
    if( pList==0 ){
      sqliteExprDelete(pExpr);
      return 0;
    }
    pList->nAlloc = 0;
  }
  if( pList->nAlloc<=pList->nExpr ){
    struct ExprList_item *a;
    pList->nAlloc = pList->nAlloc*2 + 4;
    a = sqliteRealloc(pList->a, pList->nAlloc*sizeof(pList->a[0]));
    if( a==0 ){
      sqliteExprDelete(pExpr);
      return pList;
    }
    pList->a = a;
  }
  if( pExpr || pName ){
    i = pList->nExpr++;
    pList->a[i].pExpr = pExpr;
    pList->a[i].zName = 0;
    if( pName ){
      sqliteSetNString(&pList->a[i].zName, pName->z, pName->n, 0);
      sqliteDequote(pList->a[i].zName);
    }
  }
  return pList;
}

/*
** Delete an entire expression list.
*/
void sqliteExprListDelete(ExprList *pList){
  int i;
  if( pList==0 ) return;
  for(i=0; i<pList->nExpr; i++){
    sqliteExprDelete(pList->a[i].pExpr);
    sqliteFree(pList->a[i].zName);
  }
  sqliteFree(pList->a);
  sqliteFree(pList);
}

/*
** Walk an expression tree.  Return 1 if the expression is constant
** and 0 if it involves variables.
**
** For the purposes of this function, a double-quoted string (ex: "abc")
** is considered a variable but a single-quoted string (ex: 'abc') is
** a constant.
*/
int sqliteExprIsConstant(Expr *p){
  switch( p->op ){
    case TK_ID:
    case TK_COLUMN:
    case TK_DOT:
    case TK_FUNCTION:
      return 0;
    case TK_NULL:
    case TK_STRING:
    case TK_INTEGER:
    case TK_FLOAT:
      return 1;
    default: {
      if( p->pLeft && !sqliteExprIsConstant(p->pLeft) ) return 0;
      if( p->pRight && !sqliteExprIsConstant(p->pRight) ) return 0;
      if( p->pList ){
        int i;
        for(i=0; i<p->pList->nExpr; i++){
          if( !sqliteExprIsConstant(p->pList->a[i].pExpr) ) return 0;
        }
      }
      return p->pLeft!=0 || p->pRight!=0 || (p->pList && p->pList->nExpr>0);
    }
  }
  return 0;
}

/*
** If the given expression codes a constant integer, return 1 and put
** the value of the integer in *pValue.  If the expression is not an
** integer, return 0 and leave *pValue unchanged.
*/
int sqliteExprIsInteger(Expr *p, int *pValue){
  switch( p->op ){
    case TK_INTEGER: {
      *pValue = atoi(p->token.z);
      return 1;
    }
    case TK_STRING: {
      const char *z = p->token.z;
      int n = p->token.n;
      if( n>0 && z[0]=='-' ){ z++; n--; }
      while( n>0 && *z && isdigit(*z) ){ z++; n--; }
      if( n==0 ){
        *pValue = atoi(p->token.z);
        return 1;
      }
      break;
    }
    case TK_UPLUS: {
      return sqliteExprIsInteger(p->pLeft, pValue);
    }
    case TK_UMINUS: {
      int v;
      if( sqliteExprIsInteger(p->pLeft, &v) ){
        *pValue = -v;
        return 1;
      }
      break;
    }
    default: break;
  }
  return 0;
}

/*
** Return TRUE if the given string is a row-id column name.
*/
int sqliteIsRowid(const char *z){
  if( sqliteStrICmp(z, "_ROWID_")==0 ) return 1;
  if( sqliteStrICmp(z, "ROWID")==0 ) return 1;
  if( sqliteStrICmp(z, "OID")==0 ) return 1;
  return 0;
}

/*
** This routine walks an expression tree and resolves references to
** table columns.  Nodes of the form ID.ID or ID resolve into an
** index to the table in the table list and a column offset.  The 
** Expr.opcode for such nodes is changed to TK_COLUMN.  The Expr.iTable
** value is changed to the index of the referenced table in pTabList
** plus the "base" value.  The base value will ultimately become the
** VDBE cursor number for a cursor that is pointing into the referenced
** table.  The Expr.iColumn value is changed to the index of the column 
** of the referenced table.  The Expr.iColumn value for the special
** ROWID column is -1.  Any INTEGER PRIMARY KEY column is tried as an
** alias for ROWID.
**
** We also check for instances of the IN operator.  IN comes in two
** forms:
**
**           expr IN (exprlist)
** and
**           expr IN (SELECT ...)
**
** The first form is handled by creating a set holding the list
** of allowed values.  The second form causes the SELECT to generate 
** a temporary table.
**
** This routine also looks for scalar SELECTs that are part of an expression.
** If it finds any, it generates code to write the value of that select
** into a memory cell.
**
** Unknown columns or tables provoke an error.  The function returns
** the number of errors seen and leaves an error message on pParse->zErrMsg.
*/