SQLite

**    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 1.107 2004/01/25 22:44:59 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

*/
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;
}

/*
** Given the name of a column of the form X.Y.Z or Y.Z or just Z, look up
** that name in the set of source tables in pSrcList and make the pExpr 
** expression node refer back to that source column.  The following changes
** are made to pExpr:
**
**    pExpr->iDb           Set the index in db->aDb[] of the database holding
**                         the table.
**    pExpr->iTable        Set to the cursor number for the table obtained
**                         from pSrcList.
**    pExpr->iColumn       Set to the column number within the table.
**    pExpr->dataType      Set to the appropriate data type for the column.
**    pExpr->op            Set to TK_COLUMN.
**    pExpr->pLeft         Any expression this points to is deleted
**    pExpr->pRight        Any expression this points to is deleted.
**
** The pDbToken is the name of the database (the "X").  This value may be
** NULL meaning that name is of the form Y.Z or Z.  Any available database
** can be used.  The pTableToken is the name of the table (the "Y").  This
** value can be NULL if pDbToken is also NULL.  If pTableToken is NULL it
** means that the form of the name is Z and that columns from any table
** can be used.
**
** If the name cannot be resolved unambiguously, leave an error message
** in pParse and return non-zero.  Return zero on success.
*/
static int lookupName(
  Parse *pParse,      /* The parsing context */
  Token *pDbToken,     /* Name of the database containing table, or NULL */
  Token *pTableToken,  /* Name of table containing column, or NULL */
  Token *pColumnToken, /* Name of the column. */
  SrcList *pSrcList,   /* List of tables used to resolve column names */
  ExprList *pEList,    /* List of expressions used to resolve "AS" */
  Expr *pExpr          /* Make this EXPR node point to the selected column */
){
  char *zDb = 0;       /* Name of the database.  The "X" in X.Y.Z */
  char *zTab = 0;      /* Name of the table.  The "Y" in X.Y.Z or Y.Z */
  char *zCol = 0;      /* Name of the column.  The "Z" */
  int i, j;            /* Loop counters */
  int cnt = 0;         /* Number of matching column names */
  int cntTab = 0;      /* Number of matching table names */
  sqlite *db;          /* The database */

  assert( pColumnToken && pColumnToken->z ); /* The Z in X.Y.Z cannot be NULL */
  if( pDbToken && pDbToken->z ){
    zDb = sqliteStrNDup(pDbToken->z, pDbToken->n);
    sqliteDequote(zDb);
  }else{
    zDb = 0;
  }
  if( pTableToken && pTableToken->z ){
    zTab = sqliteStrNDup(pTableToken->z, pTableToken->n);
    sqliteDequote(zTab);
  }else{
    assert( zDb==0 );
    zTab = 0;
  }
  zCol = sqliteStrNDup(pColumnToken->z, pColumnToken->n);
  sqliteDequote(zCol);
  if( sqlite_malloc_failed ){
    return 1;  /* Leak memory (zDb and zTab) if malloc fails */
  }
  assert( zTab==0 || pEList==0 );

  pExpr->iTable = -1;
  for(i=0; i<pSrcList->nSrc; i++){
    struct SrcList_item *pItem = &pSrcList->a[i];
    Table *pTab = pItem->pTab;
    Column *pCol;

    if( pTab==0 ) continue;
    assert( pTab->nCol>0 );
    if( zTab ){
      if( pItem->zAlias ){
        char *zTabName = pItem->zAlias;
        if( sqliteStrICmp(zTabName, zTab)!=0 ) continue;
      }else{
        char *zTabName = pTab->zName;
        if( zTabName==0 || sqliteStrICmp(zTabName, zTab)!=0 ) continue;
        if( zDb!=0 && sqliteStrICmp(db->aDb[pTab->iDb].zName, zDb)!=0 ){
          continue;
        }
      }
    }
    if( 0==(cntTab++) ){
      pExpr->iTable = pItem->iCursor;
      pExpr->iDb = pTab->iDb;
    }
    for(j=0, pCol=pTab->aCol; j<pTab->nCol; j++, pCol++){
      if( sqliteStrICmp(pCol->zName, zCol)==0 ){
        cnt++;
        pExpr->iTable = pItem->iCursor;
        pExpr->iDb = pTab->iDb;
        /* Substitute the rowid (column -1) for the INTEGER PRIMARY KEY */
        pExpr->iColumn = j==pTab->iPKey ? -1 : j;
        pExpr->dataType = pCol->sortOrder & SQLITE_SO_TYPEMASK;
        break;
      }
    }
  }

  /* If we have not already resolved the name, then maybe 
  ** it is a new.* or old.* trigger argument reference
  */
  if( zDb==0 && zTab!=0 && cnt==0 && pParse->trigStack!=0 ){
    TriggerStack *pTriggerStack = pParse->trigStack;
    Table *pTab = 0;
    if( pTriggerStack->newIdx != -1 && sqliteStrICmp("new", zTab) == 0 ){
      pExpr->iTable = pTriggerStack->newIdx;
      assert( pTriggerStack->pTab );
      pTab = pTriggerStack->pTab;
    }else if( pTriggerStack->oldIdx != -1 && sqliteStrICmp("old", zTab) == 0 ){
      pExpr->iTable = pTriggerStack->oldIdx;
      assert( pTriggerStack->pTab );
      pTab = pTriggerStack->pTab;
    }

    if( pTab ){ 
      int j;
      Column *pCol = pTab->aCol;
      
      pExpr->iDb = pTab->iDb;
      cntTab++;
      for(j=0; j < pTab->nCol; j++, pCol++) {
        if( sqliteStrICmp(pCol->zName, zCol)==0 ){
          cnt++;
          pExpr->iColumn = j==pTab->iPKey ? -1 : j;
          pExpr->dataType = pCol->sortOrder & SQLITE_SO_TYPEMASK;
          break;
        }
      }
    }
  }

  /*
  ** Perhaps the name is a reference to the ROWID
  */
  if( cnt==0 && cntTab==1 && sqliteIsRowid(zCol) ){
    cnt = 1;
    pExpr->iColumn = -1;
    pExpr->dataType = SQLITE_SO_NUM;
  }

  /*
  ** If the input is of the form Z (not Y.Z or X.Y.Z) then the name Z
  ** might refer to an result-set alias.  This happens, for example, when
  ** we are resolving names in the WHERE clause of the following command:
  **
  **     SELECT a+b AS x FROM table WHERE x<10;
  **
  ** 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!=0 ){
    for(j=0; j<pEList->nExpr; j++){
      char *zAs = pEList->a[j].zName;
      if( zAs!=0 && sqliteStrICmp(zAs, zCol)==0 ){
        assert( pExpr->pLeft==0 && pExpr->pRight==0 );
        pExpr->op = TK_AS;
        pExpr->iColumn = j;
        pExpr->pLeft = sqliteExprDup(pEList->a[j].pExpr);
        sqliteFree(zCol);
        assert( zTab==0 && zDb==0 );
        return 0;
      }
    } 
  }

  /*
  ** 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.
  */
  if( cnt==0 && zTab==0 && pColumnToken->z[0]=='"' ){
    sqliteFree(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 ){
    char *z = 0;
    char *zErr;
    zErr = cnt==0 ? "no such column: %s" : "ambiguous column name: %s";
    if( zDb ){
      sqliteSetString(&z, zDb, ".", zTab, ".", zCol, 0);
    }else if( zTab ){
      sqliteSetString(&z, zTab, ".", zCol, 0);
    }else{
      z = sqliteStrDup(zCol);
    }
    sqliteErrorMsg(pParse, zErr, z);
    sqliteFree(z);
  }

  /* Clean up and return
  */
  sqliteFree(zDb);
  sqliteFree(zTab);
  sqliteFree(zCol);
  sqliteExprDelete(pExpr->pLeft);
  pExpr->pLeft = 0;
  sqliteExprDelete(pExpr->pRight);
  pExpr->pRight = 0;
  pExpr->op = TK_COLUMN;
  sqliteAuthRead(pParse, pExpr, pSrcList);
  return cnt!=1;
}

/*
** 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

** 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.
*/
int sqliteExprResolveIds(
  Parse *pParse,     /* The parser context */
  SrcList *pSrcList, /* List of tables used to resolve column names */
  ExprList *pEList,  /* List of expressions used to resolve "AS" */
  Expr *pExpr        /* The expression to be analyzed. */
){
  int i;

  if( pExpr==0 || pSrcList==0 ) return 0;
  for(i=0; i<pSrcList->nSrc; i++){
    assert( pSrcList->a[i].iCursor>=0 && pSrcList->a[i].iCursor<pParse->nTab );
  }
  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 columnd.








    */
    case TK_ID: {



      if( lookupName(pParse, 0, 0, &pExpr->token, pSrcList, pEList, pExpr) ){



















































        return 1;






      }
      break; 
    }
  
    /* 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;




      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;

      }




      if( lookupName(pParse, pDb, pTable, pColumn, pSrcList, 0, pExpr) ){

        return 1;




      }






      break;
    }

    case TK_IN: {
      Vdbe *v = sqliteGetVdbe(pParse);
      if( v==0 ) return 1;
      if( sqliteExprResolveIds(pParse, pSrcList, pEList, pExpr->pLeft) ){
        return 1;
      }
      if( pExpr->pSelect ){
        /* Case 1:     expr IN (SELECT ...)
        **
        ** Generate code to write the results of the select into a temporary
        ** table.  The cursor number of the temporary table has already

      }
      break;
    }

    /* For all else, just recursively walk the tree */
    default: {
      if( pExpr->pLeft
      && sqliteExprResolveIds(pParse, pSrcList, pEList, pExpr->pLeft) ){
        return 1;
      }
      if( pExpr->pRight 
      && sqliteExprResolveIds(pParse, pSrcList, pEList, pExpr->pRight) ){
        return 1;
      }
      if( pExpr->pList ){
        int i;
        ExprList *pList = pExpr->pList;
        for(i=0; i<pList->nExpr; i++){
          Expr *pArg = pList->a[i].pExpr;
          if( sqliteExprResolveIds(pParse, pSrcList, pEList, pArg) ){
            return 1;
          }
        }
      }
    }
  }
  return 0;