select.c

sqlite数据库管理系统开放源码

Table *sqliteResultSetOfSelect(Parse *pParse, char *zTabName, Select *pSelect){
  Table *pTab;
  int i, j;
  ExprList *pEList;
  Column *aCol;

  if( fillInColumnList(pParse, pSelect) ){
    return 0;
  }
  pTab = sqliteMalloc( sizeof(Table) );
  if( pTab==0 ){
    return 0;
  }
  pTab->zName = zTabName ? sqliteStrDup(zTabName) : 0;
  pEList = pSelect->pEList;
  pTab->nCol = pEList->nExpr;
  assert( pTab->nCol>0 );
  pTab->aCol = aCol = sqliteMalloc( sizeof(pTab->aCol[0])*pTab->nCol );
  for(i=0; i<pTab->nCol; i++){
    Expr *p, *pR;
    if( pEList->a[i].zName ){
      aCol[i].zName = sqliteStrDup(pEList->a[i].zName);
    }else if( (p=pEList->a[i].pExpr)->op==TK_DOT 
               && (pR=p->pRight)!=0 && pR->token.z && pR->token.z[0] ){
      int cnt;
      sqliteSetNString(&aCol[i].zName, pR->token.z, pR->token.n, 0);
      for(j=cnt=0; j<i; j++){
        if( sqliteStrICmp(aCol[j].zName, aCol[i].zName)==0 ){
          int n;
          char zBuf[30];
          sprintf(zBuf,"_%d",++cnt);
          n = strlen(zBuf);
          sqliteSetNString(&aCol[i].zName, pR->token.z, pR->token.n, zBuf, n,0);
          j = -1;
        }
      }
    }else if( p->span.z && p->span.z[0] ){
      sqliteSetNString(&pTab->aCol[i].zName, p->span.z, p->span.n, 0);
    }else{
      char zBuf[30];
      sprintf(zBuf, "column%d", i+1);
      aCol[i].zName = sqliteStrDup(zBuf);
    }
    sqliteDequote(aCol[i].zName);
  }
  pTab->iPKey = -1;
  return pTab;
}

/*
** For the given SELECT statement, do three things.
**
**    (1)  Fill in the pTabList->a[].pTab fields in the SrcList that 
**         defines the set of tables that should be scanned.  For views,
**         fill pTabList->a[].pSelect with a copy of the SELECT statement
**         that implements the view.  A copy is made of the view's SELECT
**         statement so that we can freely modify or delete that statement
**         without worrying about messing up the presistent representation
**         of the view.
**
**    (2)  Add terms to the WHERE clause to accomodate the NATURAL keyword
**         on joins and the ON and USING clause of joins.
**
**    (3)  Scan the list of columns in the result set (pEList) looking
**         for instances of the "*" operator or the TABLE.* operator.
**         If found, expand each "*" to be every column in every table
**         and TABLE.* to be every column in TABLE.
**
** Return 0 on success.  If there are problems, leave an error message
** in pParse and return non-zero.
*/
static int fillInColumnList(Parse *pParse, Select *p){
  int i, j, k, rc;
  SrcList *pTabList;
  ExprList *pEList;
  Table *pTab;

  if( p==0 || p->pSrc==0 ) return 1;
  pTabList = p->pSrc;
  pEList = p->pEList;

  /* Look up every table in the table list.
  */
  for(i=0; i<pTabList->nSrc; i++){
    if( pTabList->a[i].pTab ){
      /* This routine has run before!  No need to continue */
      return 0;
    }
    if( pTabList->a[i].zName==0 ){
      /* A sub-query in the FROM clause of a SELECT */
      assert( pTabList->a[i].pSelect!=0 );
      if( pTabList->a[i].zAlias==0 ){
        char zFakeName[60];
        sprintf(zFakeName, "sqlite_subquery_%p_",
           (void*)pTabList->a[i].pSelect);
        sqliteSetString(&pTabList->a[i].zAlias, zFakeName, 0);
      }
      pTabList->a[i].pTab = pTab = 
        sqliteResultSetOfSelect(pParse, pTabList->a[i].zAlias,
                                        pTabList->a[i].pSelect);
      if( pTab==0 ){
        return 1;
      }
      /* The isTransient flag indicates that the Table structure has been
      ** dynamically allocated and may be freed at any time.  In other words,
      ** pTab is not pointing to a persistent table structure that defines
      ** part of the schema. */
      pTab->isTransient = 1;
    }else{
      /* An ordinary table or view name in the FROM clause */
      pTabList->a[i].pTab = pTab = 
        sqliteLocateTable(pParse,pTabList->a[i].zName,pTabList->a[i].zDatabase);
      if( pTab==0 ){
        return 1;
      }
      if( pTab->pSelect ){
        /* We reach here if the named table is a really a view */
        if( sqliteViewGetColumnNames(pParse, pTab) ){
          return 1;
        }
        /* If pTabList->a[i].pSelect!=0 it means we are dealing with a
        ** view within a view.  The SELECT structure has already been
        ** copied by the outer view so we can skip the copy step here
        ** in the inner view.
        */
        if( pTabList->a[i].pSelect==0 ){
          pTabList->a[i].pSelect = sqliteSelectDup(pTab->pSelect);
        }
      }
    }
  }

  /* Process NATURAL keywords, and ON and USING clauses of joins.
  */
  if( sqliteProcessJoin(pParse, p) ) return 1;

  /* For every "*" that occurs in the column list, insert the names of
  ** all columns in all tables.  And for every TABLE.* insert the names
  ** of all columns in TABLE.  The parser inserted a special expression
  ** with the TK_ALL operator for each "*" that it found in the column list.
  ** The following code just has to locate the TK_ALL expressions and expand
  ** each one to the list of all columns in all tables.
  **
  ** The first loop just checks to see if there are any "*" operators
  ** that need expanding.
  */
  for(k=0; k<pEList->nExpr; k++){
    Expr *pE = pEList->a[k].pExpr;
    if( pE->op==TK_ALL ) break;
    if( pE->op==TK_DOT && pE->pRight && pE->pRight->op==TK_ALL
         && pE->pLeft && pE->pLeft->op==TK_ID ) break;
  }
  rc = 0;
  if( k<pEList->nExpr ){
    /*
    ** If we get here it means the result set contains one or more "*"
    ** operators that need to be expanded.  Loop through each expression
    ** in the result set and expand them one by one.
    */
    struct ExprList_item *a = pEList->a;
    ExprList *pNew = 0;
    for(k=0; k<pEList->nExpr; k++){
      Expr *pE = a[k].pExpr;
      if( pE->op!=TK_ALL &&
           (pE->op!=TK_DOT || pE->pRight==0 || pE->pRight->op!=TK_ALL) ){
        /* This particular expression does not need to be expanded.
        */
        pNew = sqliteExprListAppend(pNew, a[k].pExpr, 0);
        pNew->a[pNew->nExpr-1].zName = a[k].zName;
        a[k].pExpr = 0;
        a[k].zName = 0;
      }else{
        /* This expression is a "*" or a "TABLE.*" and needs to be
        ** expanded. */
        int tableSeen = 0;      /* Set to 1 when TABLE matches */
        char *zTName;           /* text of name of TABLE */
        if( pE->op==TK_DOT && pE->pLeft ){
          zTName = sqliteTableNameFromToken(&pE->pLeft->token);
        }else{
          zTName = 0;
        }
        for(i=0; i<pTabList->nSrc; i++){
          Table *pTab = pTabList->a[i].pTab;
          char *zTabName = pTabList->a[i].zAlias;
          if( zTabName==0 || zTabName[0]==0 ){ 
            zTabName = pTab->zName;
          }
          if( zTName && (zTabName==0 || zTabName[0]==0 || 
                 sqliteStrICmp(zTName, zTabName)!=0) ){
            continue;
          }
          tableSeen = 1;
          for(j=0; j<pTab->nCol; j++){
            Expr *pExpr, *pLeft, *pRight;
            char *zName = pTab->aCol[j].zName;

            if( i>0 && (pTabList->a[i-1].jointype & JT_NATURAL)!=0 &&
                columnIndex(pTabList->a[i-1].pTab, zName)>=0 ){
              /* In a NATURAL join, omit the join columns from the 
              ** table on the right */
              continue;
            }
            if( i>0 && sqliteIdListIndex(pTabList->a[i-1].pUsing, zName)>=0 ){
              /* In a join with a USING clause, omit columns in the
              ** using clause from the table on the right. */
              continue;
            }
            pRight = sqliteExpr(TK_ID, 0, 0, 0);
            if( pRight==0 ) break;
            pRight->token.z = zName;
            pRight->token.n = strlen(zName);
            pRight->token.dyn = 0;
            if( zTabName && pTabList->nSrc>1 ){
              pLeft = sqliteExpr(TK_ID, 0, 0, 0);
              pExpr = sqliteExpr(TK_DOT, pLeft, pRight, 0);
              if( pExpr==0 ) break;
              pLeft->token.z = zTabName;
              pLeft->token.n = strlen(zTabName);
              pLeft->token.dyn = 0;
              sqliteSetString((char**)&pExpr->span.z, zTabName, ".", zName, 0);
              pExpr->span.n = strlen(pExpr->span.z);
              pExpr->span.dyn = 1;
              pExpr->token.z = 0;
              pExpr->token.n = 0;
              pExpr->token.dyn = 0;
            }else{
              pExpr = pRight;
              pExpr->span = pExpr->token;
            }
            pNew = sqliteExprListAppend(pNew, pExpr, 0);
          }
        }
        if( !tableSeen ){
          if( zTName ){
            sqliteErrorMsg(pParse, "no such table: %s", zTName);
          }else{
            sqliteErrorMsg(pParse, "no tables specified");
          }
          rc = 1;
        }
        sqliteFree(zTName);
      }
    }
    sqliteExprListDelete(pEList);
    p->pEList = pNew;
  }
  return rc;
}

/*
** This routine recursively unlinks the Select.pSrc.a[].pTab pointers
** in a select structure.  It just sets the pointers to NULL.  This
** routine is recursive in the sense that if the Select.pSrc.a[].pSelect
** pointer is not NULL, this routine is called recursively on that pointer.
**
** This routine is called on the Select structure that defines a
** VIEW in order to undo any bindings to tables.  This is necessary
** because those tables might be DROPed by a subsequent SQL command.
** If the bindings are not removed, then the Select.pSrc->a[].pTab field
** will be left pointing to a deallocated Table structure after the
** DROP and a coredump will occur the next time the VIEW is used.
*/
void sqliteSelectUnbind(Select *p){
  int i;
  SrcList *pSrc = p->pSrc;
  Table *pTab;
  if( p==0 ) return;
  for(i=0; i<pSrc->nSrc; i++){
    if( (pTab = pSrc->a[i].pTab)!=0 ){
      if( pTab->isTransient ){
        sqliteDeleteTable(0, pTab);
      }
      pSrc->a[i].pTab = 0;
      if( pSrc->a[i].pSelect ){
        sqliteSelectUnbind(pSrc->a[i].pSelect);
      }
    }
  }
}

/*
** This routine associates entries in an ORDER BY expression list with
** columns in a result.  For each ORDER BY expression, the opcode of
** the top-level node is changed to TK_COLUMN and the iColumn value of
** the top-level node is filled in with column number and the iTable
** value of the top-level node is filled with iTable parameter.
**
** If there are prior SELECT clauses, they are processed first.  A match
** in an earlier SELECT takes precedence over a later SELECT.
**
** Any entry that does not match is flagged as an error.  The number
** of errors is returned.
**
** This routine does NOT correctly initialize the Expr.dataType  field
** of the ORDER BY expressions.  The multiSelectSortOrder() routine
** must be called to do that after the individual select statements
** have all been analyzed.  This routine is unable to compute Expr.dataType
** because it must be called before the individual select statements
** have been analyzed.
*/
static int matchOrderbyToColumn(
  Parse *pParse,          /* A place to leave error messages */
  Select *pSelect,        /* Match to result columns of this SELECT */
  ExprList *pOrderBy,     /* The ORDER BY values to match against columns */
  int iTable,             /* Insert this value in iTable */
  int mustComplete        /* If TRUE all ORDER BYs must match */
){
  int nErr = 0;
  int i, j;
  ExprList *pEList;

  if( pSelect==0 || pOrderBy==0 ) return 1;
  if( mustComplete ){
    for(i=0; i<pOrderBy->nExpr; i++){ pOrderBy->a[i].done = 0; }
  }
  if( fillInColumnList(pParse, pSelect) ){
    return 1;
  }
  if( pSelect->pPrior ){
    if( matchOrderbyToColumn(pParse, pSelect->pPrior, pOrderBy, iTable, 0) ){
      return 1;
    }
  }
  pEList = pSelect->pEList;
  for(i=0; i<pOrderBy->nExpr; i++){
    Expr *pE = pOrderBy->a[i].pExpr;
    int iCol = -1;
    if( pOrderBy->a[i].done ) continue;
    if( sqliteExprIsInteger(pE, &iCol) ){
      if( iCol<=0 || iCol>pEList->nExpr ){
        sqliteErrorMsg(pParse,
          "ORDER BY position %d should be between 1 and %d",
          iCol, pEList->nExpr);
        nErr++;
        break;
      }
      if( !mustComplete ) continue;
      iCol--;
    }
    for(j=0; iCol<0 && j<pEList->nExpr; j++){
      if( pEList->a[j].zName && (pE->op==TK_ID || pE->op==TK_STRING) ){
        char *zName, *zLabel;
        zName = pEList->a[j].zName;
        assert( pE->token.z );
        zLabel = sqliteStrNDup(pE->token.z, pE->token.n);
        sqliteDequote(zLabel);
        if( sqliteStrICmp(zName, zLabel)==0 ){ 
          iCol = j;
        }
        sqliteFree(zLabel);
      }
      if( iCol<0 && sqliteExprCompare(pE, pEList->a[j].pExpr) ){
        iCol = j;
      }
    }
    if( iCol>=0 ){
      pE->op = TK_COLUMN;
      pE->iColumn = iCol;
      pE->iTable = iTable;
      pOrderBy->a[i].done = 1;
    }
    if( iCol<0 && mustComplete ){
      sqliteErrorMsg(pParse,
        "ORDER BY term number %d does not match any result column", i+1);
      nErr++;
      break;
    }
  }
  return nErr;  
}

/*
** Get a VDBE for the given parser context.  Create a new one if necessary.
** If an error occurs, return NULL and leave a message in pParse.
*/
Vdbe *sqliteGetVdbe(Parse *pParse){
  Vdbe *v = pParse->pVdbe;
  if( v==0 ){
    v = pParse->pVdbe = sqliteVdbeCreate(pParse->db);
  }
  return v;
}

/*
** This routine sets the Expr.dataType field on all elements of
** the pOrderBy expression list.  The pOrderBy list will have been
** set up by matchOrderbyToColumn().  Hence each expression has
** a TK_COLUMN as its root node.  The Expr.iColumn refers to a 
** column in the result set.   The datatype is set to SQLITE_SO_TEXT
** if the corresponding column in p and every SELECT to the left of
** p has a datatype of SQLITE_SO_TEXT.  If the cooressponding column
** in p or any of the left SELECTs is SQLITE_SO_NUM, then the datatype
** of the order-by expression is set to SQLITE_SO_NUM.