select.c

sqlite 嵌入式数据库的源码

      Table *pTab;
      char *zCol;
      int iCol = p->iColumn;
      for(j=0; j<pTabList->nSrc && pTabList->a[j].iCursor!=p->iTable; j++){}
      assert( j<pTabList->nSrc );
      pTab = pTabList->a[j].pTab;
      if( iCol<0 ) iCol = pTab->iPKey;
      assert( iCol==-1 || (iCol>=0 && iCol<pTab->nCol) );
      if( iCol<0 ){
        zCol = "rowid";
      }else{
        zCol = pTab->aCol[iCol].zName;
      }
      if( !shortNames && !fullNames && p->span.z && p->span.z[0] ){
        sqlite3VdbeSetColName(v, i, p->span.z, p->span.n);
      }else if( fullNames || (!shortNames && pTabList->nSrc>1) ){
        char *zName = 0;
        char *zTab;
 
        zTab = pTabList->a[j].zAlias;
        if( fullNames || zTab==0 ) zTab = pTab->zName;
        sqlite3SetString(&zName, zTab, ".", zCol, 0);
        sqlite3VdbeSetColName(v, i, zName, P3_DYNAMIC);
      }else{
        sqlite3VdbeSetColName(v, i, zCol, strlen(zCol));
      }
    }else if( p->span.z && p->span.z[0] ){
      sqlite3VdbeSetColName(v, i, p->span.z, p->span.n);
      /* sqlite3VdbeCompressSpace(v, addr); */
    }else{
      char zName[30];
      assert( p->op!=TK_COLUMN || pTabList==0 );
      sprintf(zName, "column%d", i+1);
      sqlite3VdbeSetColName(v, i, zName, 0);
    }
  }
  generateColumnTypes(pParse, pTabList, pEList);
}

#ifndef SQLITE_OMIT_COMPOUND_SELECT
/*
** Name of the connection operator, used for error messages.
*/
static const char *selectOpName(int id){
  char *z;
  switch( id ){
    case TK_ALL:       z = "UNION ALL";   break;
    case TK_INTERSECT: z = "INTERSECT";   break;
    case TK_EXCEPT:    z = "EXCEPT";      break;
    default:           z = "UNION";       break;
  }
  return z;
}
#endif /* SQLITE_OMIT_COMPOUND_SELECT */

/*
** Forward declaration
*/
static int prepSelectStmt(Parse*, Select*);

/*
** Given a SELECT statement, generate a Table structure that describes
** the result set of that SELECT.
*/
Table *sqlite3ResultSetOfSelect(Parse *pParse, char *zTabName, Select *pSelect){
  Table *pTab;
  int i, j;
  ExprList *pEList;
  Column *aCol, *pCol;

  if( prepSelectStmt(pParse, pSelect) ){
    return 0;
  }
  if( sqlite3SelectResolve(pParse, pSelect, 0) ){
    return 0;
  }
  pTab = sqliteMalloc( sizeof(Table) );
  if( pTab==0 ){
    return 0;
  }
  pTab->nRef = 1;
  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, pCol=aCol; i<pTab->nCol; i++, pCol++){
    Expr *p, *pR;
    char *zType;
    char *zName;
    char *zBasename;
    int cnt;
    NameContext sNC;
    
    /* Get an appropriate name for the column
    */
    p = pEList->a[i].pExpr;
    assert( p->pRight==0 || p->pRight->token.z==0 || p->pRight->token.z[0]!=0 );
    if( (zName = pEList->a[i].zName)!=0 ){
      /* If the column contains an "AS <name>" phrase, use <name> as the name */
      zName = sqliteStrDup(zName);
    }else if( p->op==TK_DOT 
              && (pR=p->pRight)!=0 && pR->token.z && pR->token.z[0] ){
      /* For columns of the from A.B use B as the name */
      zName = sqlite3MPrintf("%T", &pR->token);
    }else if( p->span.z && p->span.z[0] ){
      /* Use the original text of the column expression as its name */
      zName = sqlite3MPrintf("%T", &p->span);
    }else{
      /* If all else fails, make up a name */
      zName = sqlite3MPrintf("column%d", i+1);
    }
    sqlite3Dequote(zName);
    if( sqlite3_malloc_failed ){
      sqliteFree(zName);
      sqlite3DeleteTable(0, pTab);
      return 0;
    }

    /* Make sure the column name is unique.  If the name is not unique,
    ** append a integer to the name so that it becomes unique.
    */
    zBasename = zName;
    for(j=cnt=0; j<i; j++){
      if( sqlite3StrICmp(aCol[j].zName, zName)==0 ){
        zName = sqlite3MPrintf("%s:%d", zBasename, ++cnt);
        j = -1;
        if( zName==0 ) break;
      }
    }
    if( zBasename!=zName ){
      sqliteFree(zBasename);
    }
    pCol->zName = zName;

    /* Get the typename, type affinity, and collating sequence for the
    ** column.
    */
    memset(&sNC, 0, sizeof(sNC));
    sNC.pSrcList = pSelect->pSrc;
    zType = sqliteStrDup(columnType(&sNC, p));
    pCol->zType = zType;
    pCol->affinity = sqlite3ExprAffinity(p);
    pCol->pColl = sqlite3ExprCollSeq(pParse, p);
    if( !pCol->pColl ){
      pCol->pColl = pParse->db->pDfltColl;
    }
  }
  pTab->iPKey = -1;
  return pTab;
}

/*
** Prepare a SELECT statement for processing by doing the following
** things:
**
**    (1)  Make sure VDBE cursor numbers have been assigned to every
**         element of the FROM clause.
**
**    (2)  Fill in the pTabList->a[].pTab fields in the SrcList that 
**         defines FROM clause.  When views appear in the FROM clause,
**         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.
**
**    (3)  Add terms to the WHERE clause to accomodate the NATURAL keyword
**         on joins and the ON and USING clause of joins.
**
**    (4)  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 prepSelectStmt(Parse *pParse, Select *p){
  int i, j, k, rc;
  SrcList *pTabList;
  ExprList *pEList;
  Table *pTab;
  struct SrcList_item *pFrom;

  if( p==0 || p->pSrc==0 || sqlite3_malloc_failed ) return 1;
  pTabList = p->pSrc;
  pEList = p->pEList;

  /* Make sure cursor numbers have been assigned to all entries in
  ** the FROM clause of the SELECT statement.
  */
  sqlite3SrcListAssignCursors(pParse, p->pSrc);

  /* Look up every table named in the FROM clause of the select.  If
  ** an entry of the FROM clause is a subquery instead of a table or view,
  ** then create a transient table structure to describe the subquery.
  */
  for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
    if( pFrom->pTab!=0 ){
      /* This statement has already been prepared.  There is no need
      ** to go further. */
      assert( i==0 );
      return 0;
    }
    if( pFrom->zName==0 ){
#ifndef SQLITE_OMIT_SUBQUERY
      /* A sub-query in the FROM clause of a SELECT */
      assert( pFrom->pSelect!=0 );
      if( pFrom->zAlias==0 ){
        pFrom->zAlias =
          sqlite3MPrintf("sqlite_subquery_%p_", (void*)pFrom->pSelect);
      }
      assert( pFrom->pTab==0 );
      pFrom->pTab = pTab = 
        sqlite3ResultSetOfSelect(pParse, pFrom->zAlias, pFrom->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;
#endif
    }else{
      /* An ordinary table or view name in the FROM clause */
      assert( pFrom->pTab==0 );
      pFrom->pTab = pTab = 
        sqlite3LocateTable(pParse,pFrom->zName,pFrom->zDatabase);
      if( pTab==0 ){
        return 1;
      }
      pTab->nRef++;
#ifndef SQLITE_OMIT_VIEW
      if( pTab->pSelect ){
        /* We reach here if the named table is a really a view */
        if( sqlite3ViewGetColumnNames(pParse, pTab) ){
          return 1;
        }
        /* If pFrom->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( pFrom->pSelect==0 ){
          pFrom->pSelect = sqlite3SelectDup(pTab->pSelect);
        }
      }
#endif
    }
  }

  /* 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;
    int flags = pParse->db->flags;
    int longNames = (flags & SQLITE_FullColNames)!=0 &&
                      (flags & SQLITE_ShortColNames)==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 = sqlite3ExprListAppend(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 = sqlite3NameFromToken(&pE->pLeft->token);
        }else{
          zTName = 0;
        }
        for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
          Table *pTab = pFrom->pTab;
          char *zTabName = pFrom->zAlias;
          if( zTabName==0 || zTabName[0]==0 ){ 
            zTabName = pTab->zName;
          }
          if( zTName && (zTabName==0 || zTabName[0]==0 || 
                 sqlite3StrICmp(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 ){
              struct SrcList_item *pLeft = &pTabList->a[i-1];
              if( (pLeft->jointype & JT_NATURAL)!=0 &&
                        columnIndex(pLeft->pTab, zName)>=0 ){
                /* In a NATURAL join, omit the join columns from the 
                ** table on the right */
                continue;
              }
              if( sqlite3IdListIndex(pLeft->pUsing, zName)>=0 ){
                /* In a join with a USING clause, omit columns in the
                ** using clause from the table on the right. */
                continue;
              }
            }
            pRight = sqlite3Expr(TK_ID, 0, 0, 0);
            if( pRight==0 ) break;
            setToken(&pRight->token, zName);
            if( zTabName && (longNames || pTabList->nSrc>1) ){
              pLeft = sqlite3Expr(TK_ID, 0, 0, 0);
              pExpr = sqlite3Expr(TK_DOT, pLeft, pRight, 0);
              if( pExpr==0 ) break;
              setToken(&pLeft->token, zTabName);
              setToken(&pExpr->span, sqlite3MPrintf("%s.%s", zTabName, zName));
              pExpr->span.dyn = 1;
              pExpr->token.z = 0;
              pExpr->token.n = 0;
              pExpr->token.dyn = 0;
            }else{
              pExpr = pRight;
              pExpr->span = pExpr->token;
            }
            if( longNames ){
              pNew = sqlite3ExprListAppend(pNew, pExpr, &pExpr->span);
            }else{
              pNew = sqlite3ExprListAppend(pNew, pExpr, &pRight->token);
            }
          }
        }
        if( !tableSeen ){
          if( zTName ){
            sqlite3ErrorMsg(pParse, "no such table: %s", zTName);
          }else{
            sqlite3ErrorMsg(pParse, "no tables specified");
          }
          rc = 1;
        }
        sqliteFree(zTName);
      }
    }
    sqlite3ExprListDelete(pEList);
    p->pEList = pNew;
  }
  return rc;
}

#ifndef SQLITE_OMIT_COMPOUND_SELECT
/*
** 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.
*/
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 */