expr.c

sqlite-3.4.1,嵌入式数据库.是一个功能强大的开源数据库,给学习和研发以及小型公司的发展带来了全所未有的好处.

/*
** 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 1.300 2007/06/25 16:29:34 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Return the 'affinity' of the expression pExpr if any.
**
** If pExpr is a column, a reference to a column via an 'AS' alias,
** or a sub-select with a column as the return value, then the 
** affinity of that column is returned. Otherwise, 0x00 is returned,
** indicating no affinity for the expression.
**
** i.e. the WHERE clause expresssions in the following statements all
** have an affinity:
**
** CREATE TABLE t1(a);
** SELECT * FROM t1 WHERE a;
** SELECT a AS b FROM t1 WHERE b;
** SELECT * FROM t1 WHERE (select a from t1);
*/
char sqlite3ExprAffinity(Expr *pExpr){
  int op = pExpr->op;
  if( op==TK_SELECT ){
    return sqlite3ExprAffinity(pExpr->pSelect->pEList->a[0].pExpr);
  }
#ifndef SQLITE_OMIT_CAST
  if( op==TK_CAST ){
    return sqlite3AffinityType(&pExpr->token);
  }
#endif
  return pExpr->affinity;
}

/*
** Set the collating sequence for expression pExpr to be the collating
** sequence named by pToken.   Return a pointer to the revised expression.
** The collating sequence is marked as "explicit" using the EP_ExpCollate
** flag.  An explicit collating sequence will override implicit
** collating sequences.
*/
Expr *sqlite3ExprSetColl(Parse *pParse, Expr *pExpr, Token *pName){
  CollSeq *pColl;
  if( pExpr==0 ) return 0;
  pColl = sqlite3LocateCollSeq(pParse, (char*)pName->z, pName->n);
  if( pColl ){
    pExpr->pColl = pColl;
    pExpr->flags |= EP_ExpCollate;
  }
  return pExpr;
}

/*
** Return the default collation sequence for the expression pExpr. If
** there is no default collation type, return 0.
*/
CollSeq *sqlite3ExprCollSeq(Parse *pParse, Expr *pExpr){
  CollSeq *pColl = 0;
  if( pExpr ){
    int op;
    pColl = pExpr->pColl;
    op = pExpr->op;
    if( (op==TK_CAST || op==TK_UPLUS) && !pColl ){
      return sqlite3ExprCollSeq(pParse, pExpr->pLeft);
    }
  }
  if( sqlite3CheckCollSeq(pParse, pColl) ){ 
    pColl = 0;
  }
  return pColl;
}

/*
** pExpr is an operand of a comparison operator.  aff2 is the
** type affinity of the other operand.  This routine returns the
** type affinity that should be used for the comparison operator.
*/
char sqlite3CompareAffinity(Expr *pExpr, char aff2){
  char aff1 = sqlite3ExprAffinity(pExpr);
  if( aff1 && aff2 ){
    /* Both sides of the comparison are columns. If one has numeric
    ** affinity, use that. Otherwise use no affinity.
    */
    if( sqlite3IsNumericAffinity(aff1) || sqlite3IsNumericAffinity(aff2) ){
      return SQLITE_AFF_NUMERIC;
    }else{
      return SQLITE_AFF_NONE;
    }
  }else if( !aff1 && !aff2 ){
    /* Neither side of the comparison is a column.  Compare the
    ** results directly.
    */
    return SQLITE_AFF_NONE;
  }else{
    /* One side is a column, the other is not. Use the columns affinity. */
    assert( aff1==0 || aff2==0 );
    return (aff1 + aff2);
  }
}

/*
** pExpr is a comparison operator.  Return the type affinity that should
** be applied to both operands prior to doing the comparison.
*/
static char comparisonAffinity(Expr *pExpr){
  char aff;
  assert( pExpr->op==TK_EQ || pExpr->op==TK_IN || pExpr->op==TK_LT ||
          pExpr->op==TK_GT || pExpr->op==TK_GE || pExpr->op==TK_LE ||
          pExpr->op==TK_NE );
  assert( pExpr->pLeft );
  aff = sqlite3ExprAffinity(pExpr->pLeft);
  if( pExpr->pRight ){
    aff = sqlite3CompareAffinity(pExpr->pRight, aff);
  }
  else if( pExpr->pSelect ){
    aff = sqlite3CompareAffinity(pExpr->pSelect->pEList->a[0].pExpr, aff);
  }
  else if( !aff ){
    aff = SQLITE_AFF_NONE;
  }
  return aff;
}

/*
** pExpr is a comparison expression, eg. '=', '<', IN(...) etc.
** idx_affinity is the affinity of an indexed column. Return true
** if the index with affinity idx_affinity may be used to implement
** the comparison in pExpr.
*/
int sqlite3IndexAffinityOk(Expr *pExpr, char idx_affinity){
  char aff = comparisonAffinity(pExpr);
  switch( aff ){
    case SQLITE_AFF_NONE:
      return 1;
    case SQLITE_AFF_TEXT:
      return idx_affinity==SQLITE_AFF_TEXT;
    default:
      return sqlite3IsNumericAffinity(idx_affinity);
  }
}

/*
** Return the P1 value that should be used for a binary comparison
** opcode (OP_Eq, OP_Ge etc.) used to compare pExpr1 and pExpr2.
** If jumpIfNull is true, then set the low byte of the returned
** P1 value to tell the opcode to jump if either expression
** evaluates to NULL.
*/
static int binaryCompareP1(Expr *pExpr1, Expr *pExpr2, int jumpIfNull){
  char aff = sqlite3ExprAffinity(pExpr2);
  return ((int)sqlite3CompareAffinity(pExpr1, aff))+(jumpIfNull?0x100:0);
}

/*
** Return a pointer to the collation sequence that should be used by
** a binary comparison operator comparing pLeft and pRight.
**
** If the left hand expression has a collating sequence type, then it is
** used. Otherwise the collation sequence for the right hand expression
** is used, or the default (BINARY) if neither expression has a collating
** type.
**
** Argument pRight (but not pLeft) may be a null pointer. In this case,
** it is not considered.
*/
CollSeq* sqlite3BinaryCompareCollSeq(
  Parse *pParse, 
  Expr *pLeft, 
  Expr *pRight
){
  CollSeq *pColl;
  assert( pLeft );
  if( pLeft->flags & EP_ExpCollate ){
    assert( pLeft->pColl );
    pColl = pLeft->pColl;
  }else if( pRight && pRight->flags & EP_ExpCollate ){
    assert( pRight->pColl );
    pColl = pRight->pColl;
  }else{
    pColl = sqlite3ExprCollSeq(pParse, pLeft);
    if( !pColl ){
      pColl = sqlite3ExprCollSeq(pParse, pRight);
    }
  }
  return pColl;
}

/*
** Generate code for a comparison operator.
*/
static int codeCompare(
  Parse *pParse,    /* The parsing (and code generating) context */
  Expr *pLeft,      /* The left operand */
  Expr *pRight,     /* The right operand */
  int opcode,       /* The comparison opcode */
  int dest,         /* Jump here if true.  */
  int jumpIfNull    /* If true, jump if either operand is NULL */
){
  int p1 = binaryCompareP1(pLeft, pRight, jumpIfNull);
  CollSeq *p3 = sqlite3BinaryCompareCollSeq(pParse, pLeft, pRight);
  return sqlite3VdbeOp3(pParse->pVdbe, opcode, p1, dest, (void*)p3, P3_COLLSEQ);
}

/*
** 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 *sqlite3Expr(int op, Expr *pLeft, Expr *pRight, const Token *pToken){
  Expr *pNew;
  pNew = sqliteMalloc( sizeof(Expr) );
  if( pNew==0 ){
    /* When malloc fails, delete pLeft and pRight. Expressions passed to 
    ** this function must always be allocated with sqlite3Expr() for this 
    ** reason. 
    */
    sqlite3ExprDelete(pLeft);
    sqlite3ExprDelete(pRight);
    return 0;
  }
  pNew->op = op;
  pNew->pLeft = pLeft;
  pNew->pRight = pRight;
  pNew->iAgg = -1;
  if( pToken ){
    assert( pToken->dyn==0 );
    pNew->span = pNew->token = *pToken;
  }else if( pLeft ){
    if( pRight ){
      sqlite3ExprSpan(pNew, &pLeft->span, &pRight->span);
      if( pRight->flags & EP_ExpCollate ){
        pNew->flags |= EP_ExpCollate;
        pNew->pColl = pRight->pColl;
      }
    }
    if( pLeft->flags & EP_ExpCollate ){
      pNew->flags |= EP_ExpCollate;
      pNew->pColl = pLeft->pColl;
    }
  }

  sqlite3ExprSetHeight(pNew);
  return pNew;
}

/*
** Works like sqlite3Expr() but frees its pLeft and pRight arguments
** if it fails due to a malloc problem.
*/
Expr *sqlite3ExprOrFree(int op, Expr *pLeft, Expr *pRight, const Token *pToken){
  Expr *pNew = sqlite3Expr(op, pLeft, pRight, pToken);
  if( pNew==0 ){
    sqlite3ExprDelete(pLeft);
    sqlite3ExprDelete(pRight);
  }
  return pNew;
}

/*
** When doing a nested parse, you can include terms in an expression
** that look like this:   #0 #1 #2 ...  These terms refer to elements
** on the stack.  "#0" means the top of the stack.
** "#1" means the next down on the stack.  And so forth.
**
** This routine is called by the parser to deal with on of those terms.
** It immediately generates code to store the value in a memory location.
** The returns an expression that will code to extract the value from
** that memory location as needed.
*/
Expr *sqlite3RegisterExpr(Parse *pParse, Token *pToken){
  Vdbe *v = pParse->pVdbe;
  Expr *p;
  int depth;
  if( pParse->nested==0 ){
    sqlite3ErrorMsg(pParse, "near \"%T\": syntax error", pToken);
    return sqlite3Expr(TK_NULL, 0, 0, 0);
  }
  if( v==0 ) return 0;
  p = sqlite3Expr(TK_REGISTER, 0, 0, pToken);
  if( p==0 ){
    return 0;  /* Malloc failed */
  }
  depth = atoi((char*)&pToken->z[1]);
  p->iTable = pParse->nMem++;
  sqlite3VdbeAddOp(v, OP_Dup, depth, 0);
  sqlite3VdbeAddOp(v, OP_MemStore, p->iTable, 1);
  return p;
}

/*
** Join two expressions using an AND operator.  If either expression is
** NULL, then just return the other expression.
*/
Expr *sqlite3ExprAnd(Expr *pLeft, Expr *pRight){
  if( pLeft==0 ){
    return pRight;
  }else if( pRight==0 ){
    return pLeft;
  }else{
    return sqlite3Expr(TK_AND, pLeft, pRight, 0);
  }
}

/*
** Set the Expr.span field of the given expression to span all
** text between the two given tokens.
*/
void sqlite3ExprSpan(Expr *pExpr, Token *pLeft, Token *pRight){
  assert( pRight!=0 );
  assert( pLeft!=0 );
  if( !sqlite3MallocFailed() && pRight->z && pLeft->z ){
    assert( pLeft->dyn==0 || pLeft->z[pLeft->n]==0 );
    if( pLeft->dyn==0 && pRight->dyn==0 ){
      pExpr->span.z = pLeft->z;
      pExpr->span.n = pRight->n + (pRight->z - pLeft->z);
    }else{
      pExpr->span.z = 0;
    }
  }
}

/*
** Construct a new expression node for a function with multiple
** arguments.
*/
Expr *sqlite3ExprFunction(ExprList *pList, Token *pToken){
  Expr *pNew;
  assert( pToken );
  pNew = sqliteMalloc( sizeof(Expr) );
  if( pNew==0 ){
    sqlite3ExprListDelete(pList); /* Avoid leaking memory when malloc fails */
    return 0;
  }
  pNew->op = TK_FUNCTION;
  pNew->pList = pList;
  assert( pToken->dyn==0 );
  pNew->token = *pToken;
  pNew->span = pNew->token;

  sqlite3ExprSetHeight(pNew);
  return pNew;
}

/*
** Assign a variable number to an expression that encodes a wildcard
** in the original SQL statement.  
**
** Wildcards consisting of a single "?" are assigned the next sequential
** variable number.
**
** Wildcards of the form "?nnn" are assigned the number "nnn".  We make
** sure "nnn" is not too be to avoid a denial of service attack when
** the SQL statement comes from an external source.
**
** Wildcards of the form ":aaa" or "$aaa" are assigned the same number
** as the previous instance of the same wildcard.  Or if this is the first
** instance of the wildcard, the next sequenial variable number is
** assigned.
*/
void sqlite3ExprAssignVarNumber(Parse *pParse, Expr *pExpr){
  Token *pToken;
  if( pExpr==0 ) return;
  pToken = &pExpr->token;
  assert( pToken->n>=1 );
  assert( pToken->z!=0 );
  assert( pToken->z[0]!=0 );
  if( pToken->n==1 ){
    /* Wildcard of the form "?".  Assign the next variable number */
    pExpr->iTable = ++pParse->nVar;
  }else if( pToken->z[0]=='?' ){
    /* Wildcard of the form "?nnn".  Convert "nnn" to an integer and
    ** use it as the variable number */
    int i;
    pExpr->iTable = i = atoi((char*)&pToken->z[1]);
    if( i<1 || i>SQLITE_MAX_VARIABLE_NUMBER ){
      sqlite3ErrorMsg(pParse, "variable number must be between ?1 and ?%d",
          SQLITE_MAX_VARIABLE_NUMBER);
    }
    if( i>pParse->nVar ){
      pParse->nVar = i;
    }
  }else{
    /* Wildcards of the form ":aaa" or "$aaa".  Reuse the same variable
    ** number as the prior appearance of the same name, or if the name
    ** has never appeared before, reuse the same variable number
    */
    int i, n;
    n = pToken->n;
    for(i=0; i<pParse->nVarExpr; i++){
      Expr *pE;
      if( (pE = pParse->apVarExpr[i])!=0
          && pE->token.n==n
          && memcmp(pE->token.z, pToken->z, n)==0 ){
        pExpr->iTable = pE->iTable;
        break;
      }
    }
    if( i>=pParse->nVarExpr ){