expr.c

SQLite is a software library that implements a self-contained, serverless, zero-configuration, trans

    ** In cases like this, replace pExpr with a copy of the expression that
    ** forms the result set entry ("a+b" in the example) and return immediately.
    ** Note that the expression in the result set should have already been
    ** resolved by the time the WHERE clause is resolved.
    */
    if( cnt==0 && (pEList = pNC->pEList)!=0 && zTab==0 ){
      for(j=0; j<pEList->nExpr; j++){
        char *zAs = pEList->a[j].zName;
        if( zAs!=0 && sqlite3StrICmp(zAs, zCol)==0 ){
          Expr *pDup, *pOrig;
          assert( pExpr->pLeft==0 && pExpr->pRight==0 );
          assert( pExpr->pList==0 );
          assert( pExpr->pSelect==0 );
          pOrig = pEList->a[j].pExpr;
          if( !pNC->allowAgg && ExprHasProperty(pOrig, EP_Agg) ){
            sqlite3ErrorMsg(pParse, "misuse of aliased aggregate %s", zAs);
            sqlite3_free(zCol);
            return 2;
          }
          pDup = sqlite3ExprDup(db, pOrig);
          if( pExpr->flags & EP_ExpCollate ){
            pDup->pColl = pExpr->pColl;
            pDup->flags |= EP_ExpCollate;
          }
          if( pExpr->span.dyn ) sqlite3_free((char*)pExpr->span.z);
          if( pExpr->token.dyn ) sqlite3_free((char*)pExpr->token.z);
          memcpy(pExpr, pDup, sizeof(*pExpr));
          sqlite3_free(pDup);
          cnt = 1;
          pMatch = 0;
          assert( zTab==0 && zDb==0 );
          goto lookupname_end_2;
        }
      } 
    }

    /* Advance to the next name context.  The loop will exit when either
    ** we have a match (cnt>0) or when we run out of name contexts.
    */
    if( cnt==0 ){
      pNC = pNC->pNext;
    }
  }

  /*
  ** If X and Y are NULL (in other words if only the column name Z is
  ** supplied) and the value of Z is enclosed in double-quotes, then
  ** Z is a string literal if it doesn't match any column names.  In that
  ** case, we need to return right away and not make any changes to
  ** pExpr.
  **
  ** Because no reference was made to outer contexts, the pNC->nRef
  ** fields are not changed in any context.
  */
  if( cnt==0 && zTab==0 && pColumnToken->z[0]=='"' ){
    sqlite3_free(zCol);
    return 0;
  }

  /*
  ** cnt==0 means there was not match.  cnt>1 means there were two or
  ** more matches.  Either way, we have an error.
  */
  if( cnt!=1 ){
    const char *zErr;
    zErr = cnt==0 ? "no such column" : "ambiguous column name";
    if( zDb ){
      sqlite3ErrorMsg(pParse, "%s: %s.%s.%s", zErr, zDb, zTab, zCol);
    }else if( zTab ){
      sqlite3ErrorMsg(pParse, "%s: %s.%s", zErr, zTab, zCol);
    }else{
      sqlite3ErrorMsg(pParse, "%s: %s", zErr, zCol);
    }
    pTopNC->nErr++;
  }

  /* If a column from a table in pSrcList is referenced, then record
  ** this fact in the pSrcList.a[].colUsed bitmask.  Column 0 causes
  ** bit 0 to be set.  Column 1 sets bit 1.  And so forth.  If the
  ** column number is greater than the number of bits in the bitmask
  ** then set the high-order bit of the bitmask.
  */
  if( pExpr->iColumn>=0 && pMatch!=0 ){
    int n = pExpr->iColumn;
    testcase( n==sizeof(Bitmask)*8-1 );
    if( n>=sizeof(Bitmask)*8 ){
      n = sizeof(Bitmask)*8-1;
    }
    assert( pMatch->iCursor==pExpr->iTable );
    pMatch->colUsed |= ((Bitmask)1)<<n;
  }

lookupname_end:
  /* Clean up and return
  */
  sqlite3_free(zDb);
  sqlite3_free(zTab);
  sqlite3ExprDelete(pExpr->pLeft);
  pExpr->pLeft = 0;
  sqlite3ExprDelete(pExpr->pRight);
  pExpr->pRight = 0;
  pExpr->op = TK_COLUMN;
lookupname_end_2:
  sqlite3_free(zCol);
  if( cnt==1 ){
    assert( pNC!=0 );
    sqlite3AuthRead(pParse, pExpr, pSchema, pNC->pSrcList);
    if( pMatch && !pMatch->pSelect ){
      pExpr->pTab = pMatch->pTab;
    }
    /* Increment the nRef value on all name contexts from TopNC up to
    ** the point where the name matched. */
    for(;;){
      assert( pTopNC!=0 );
      pTopNC->nRef++;
      if( pTopNC==pNC ) break;
      pTopNC = pTopNC->pNext;
    }
    return 0;
  } else {
    return 1;
  }
}

/*
** This routine is designed as an xFunc for walkExprTree().
**
** Resolve symbolic names into TK_COLUMN operators for the current
** node in the expression tree.  Return 0 to continue the search down
** the tree or 2 to abort the tree walk.
**
** This routine also does error checking and name resolution for
** function names.  The operator for aggregate functions is changed
** to TK_AGG_FUNCTION.
*/
static int nameResolverStep(void *pArg, Expr *pExpr){
  NameContext *pNC = (NameContext*)pArg;
  Parse *pParse;

  if( pExpr==0 ) return 1;
  assert( pNC!=0 );
  pParse = pNC->pParse;

  if( ExprHasAnyProperty(pExpr, EP_Resolved) ) return 1;
  ExprSetProperty(pExpr, EP_Resolved);
#ifndef NDEBUG
  if( pNC->pSrcList && pNC->pSrcList->nAlloc>0 ){
    SrcList *pSrcList = pNC->pSrcList;
    int i;
    for(i=0; i<pNC->pSrcList->nSrc; i++){
      assert( pSrcList->a[i].iCursor>=0 && pSrcList->a[i].iCursor<pParse->nTab);
    }
  }
#endif
  switch( pExpr->op ){
    /* Double-quoted strings (ex: "abc") are used as identifiers if
    ** possible.  Otherwise they remain as strings.  Single-quoted
    ** strings (ex: 'abc') are always string literals.
    */
    case TK_STRING: {
      if( pExpr->token.z[0]=='\'' ) break;
      /* Fall thru into the TK_ID case if this is a double-quoted string */
    }
    /* A lone identifier is the name of a column.
    */
    case TK_ID: {
      lookupName(pParse, 0, 0, &pExpr->token, pNC, pExpr);
      return 1;
    }
  
    /* A table name and column name:     ID.ID
    ** Or a database, table and column:  ID.ID.ID
    */
    case TK_DOT: {
      Token *pColumn;
      Token *pTable;
      Token *pDb;
      Expr *pRight;

      /* if( pSrcList==0 ) break; */
      pRight = pExpr->pRight;
      if( pRight->op==TK_ID ){
        pDb = 0;
        pTable = &pExpr->pLeft->token;
        pColumn = &pRight->token;
      }else{
        assert( pRight->op==TK_DOT );
        pDb = &pExpr->pLeft->token;
        pTable = &pRight->pLeft->token;
        pColumn = &pRight->pRight->token;
      }
      lookupName(pParse, pDb, pTable, pColumn, pNC, pExpr);
      return 1;
    }

    /* Resolve function names
    */
    case TK_CONST_FUNC:
    case TK_FUNCTION: {
      ExprList *pList = pExpr->pList;    /* The argument list */
      int n = pList ? pList->nExpr : 0;  /* Number of arguments */
      int no_such_func = 0;       /* True if no such function exists */
      int wrong_num_args = 0;     /* True if wrong number of arguments */
      int is_agg = 0;             /* True if is an aggregate function */
      int i;
      int auth;                   /* Authorization to use the function */
      int nId;                    /* Number of characters in function name */
      const char *zId;            /* The function name. */
      FuncDef *pDef;              /* Information about the function */
      int enc = ENC(pParse->db);  /* The database encoding */

      zId = (char*)pExpr->token.z;
      nId = pExpr->token.n;
      pDef = sqlite3FindFunction(pParse->db, zId, nId, n, enc, 0);
      if( pDef==0 ){
        pDef = sqlite3FindFunction(pParse->db, zId, nId, -1, enc, 0);
        if( pDef==0 ){
          no_such_func = 1;
        }else{
          wrong_num_args = 1;
        }
      }else{
        is_agg = pDef->xFunc==0;
      }
#ifndef SQLITE_OMIT_AUTHORIZATION
      if( pDef ){
        auth = sqlite3AuthCheck(pParse, SQLITE_FUNCTION, 0, pDef->zName, 0);
        if( auth!=SQLITE_OK ){
          if( auth==SQLITE_DENY ){
            sqlite3ErrorMsg(pParse, "not authorized to use function: %s",
                                    pDef->zName);
            pNC->nErr++;
          }
          pExpr->op = TK_NULL;
          return 1;
        }
      }
#endif
      if( is_agg && !pNC->allowAgg ){
        sqlite3ErrorMsg(pParse, "misuse of aggregate function %.*s()", nId,zId);
        pNC->nErr++;
        is_agg = 0;
      }else if( no_such_func ){
        sqlite3ErrorMsg(pParse, "no such function: %.*s", nId, zId);
        pNC->nErr++;
      }else if( wrong_num_args ){
        sqlite3ErrorMsg(pParse,"wrong number of arguments to function %.*s()",
             nId, zId);
        pNC->nErr++;
      }
      if( is_agg ){
        pExpr->op = TK_AGG_FUNCTION;
        pNC->hasAgg = 1;
      }
      if( is_agg ) pNC->allowAgg = 0;
      for(i=0; pNC->nErr==0 && i<n; i++){
        walkExprTree(pList->a[i].pExpr, nameResolverStep, pNC);
      }
      if( is_agg ) pNC->allowAgg = 1;
      /* FIX ME:  Compute pExpr->affinity based on the expected return
      ** type of the function 
      */
      return is_agg;
    }
#ifndef SQLITE_OMIT_SUBQUERY
    case TK_SELECT:
    case TK_EXISTS:
#endif
    case TK_IN: {
      if( pExpr->pSelect ){
        int nRef = pNC->nRef;
#ifndef SQLITE_OMIT_CHECK
        if( pNC->isCheck ){
          sqlite3ErrorMsg(pParse,"subqueries prohibited in CHECK constraints");
        }
#endif
        sqlite3SelectResolve(pParse, pExpr->pSelect, pNC);
        assert( pNC->nRef>=nRef );
        if( nRef!=pNC->nRef ){
          ExprSetProperty(pExpr, EP_VarSelect);
        }
      }
      break;
    }
#ifndef SQLITE_OMIT_CHECK
    case TK_VARIABLE: {
      if( pNC->isCheck ){
        sqlite3ErrorMsg(pParse,"parameters prohibited in CHECK constraints");
      }
      break;
    }
#endif
  }
  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.
**
** Also resolve function names and check the functions for proper
** usage.  Make sure all function names are recognized and all functions
** have the correct number of arguments.  Leave an error message
** in pParse->zErrMsg if anything is amiss.  Return the number of errors.
**
** If the expression contains aggregate functions then set the EP_Agg
** property on the expression.
*/
int sqlite3ExprResolveNames( 
  NameContext *pNC,       /* Namespace to resolve expressions in. */
  Expr *pExpr             /* The expression to be analyzed. */
){
  int savedHasAgg;

  if( pExpr==0 ) return 0;
#if SQLITE_MAX_EXPR_DEPTH>0
  {
    int mxDepth = pNC->pParse->db->aLimit[SQLITE_LIMIT_EXPR_DEPTH];
    if( (pExpr->nHeight+pNC->pParse->nHeight)>mxDepth ){
      sqlite3ErrorMsg(pNC->pParse, 
         "Expression tree is too large (maximum depth %d)", mxDepth
      );
      return 1;
    }
    pNC->pParse->nHeight += pExpr->nHeight;
  }
#endif
  savedHasAgg = pNC->hasAgg;
  pNC->hasAgg = 0;
  walkExprTree(pExpr, nameResolverStep, pNC);
#if SQLITE_MAX_EXPR_DEPTH>0
  pNC->pParse->nHeight -= pExpr->nHeight;
#endif
  if( pNC->nErr>0 ){
    ExprSetProperty(pExpr, EP_Error);
  }
  if( pNC->hasAgg ){
    ExprSetProperty(pExpr, EP_Agg);
  }else if( savedHasAgg ){
    pNC->hasAgg = 1;
  }
  return ExprHasProperty(pExpr, EP_Error);
}

/*
** A pointer instance of this structure is used to pass information
** through walkExprTree into codeSubqueryStep().
*/
typedef struct QueryCoder QueryCoder;
struct QueryCoder {
  Parse *pParse;       /* The parsing context */
  NameContext *pNC;    /* Namespace of first enclosing query */
};

#ifdef SQLITE_TEST
  int sqlite3_enable_in_opt = 1;
#else
  #define sqlite3_enable_in_opt 1
#endif

/*
** This function is used by the implementation of the IN (...) operator.
** It's job is to find or create a b-tree structure that may be used
** either to test for membership of the (...) set or to iterate through
** its members, skipping duplicates.
**
** The cursor opened on the structure (database table, database index 
** or ephermal table) is stored in pX->iTable before this function returns.
** The returned value indicates the structure type, as follows:
**
**   IN_INDEX_ROWID - The cursor was opened on a database table.
**   IN_INDEX_INDEX - The cursor was opened on a database index.
**   IN_INDEX_EPH -   The cursor was opened on a specially created and
**                    populated epheremal table.
**
** An existing structure may only be used if the SELECT is of the simple
** form:
**
**     SELECT <column> FROM <table>
**
** If the mustBeUnique parameter is false, the structure will be used 
** for fast set membership tests. In this case an epheremal table must 
** be used unless <column> is an INTEGER PRIMARY KEY or an index can 
** be found with <column> as its left-most column.
**
** If mustBeUnique is true, then the structure will be used to iterate
** through the set members, skipping any duplicates. In this case an
** epheremal table must be used unless the selected <column> is guaranteed
** to be unique - either because it is an INTEGER PRIMARY KEY or it
** is unique by virtue of a constraint or implicit index.
*/
#ifndef SQLITE_OMIT_SUBQUERY
int sqlite3FindInIndex(Parse *pParse, Expr *pX, int mustBeUnique){
  Select *p;