select.c

sqlite数据库管理系统开放源码

**
** If srcTab and nColumn are both zero, then the pEList expressions
** are evaluated in order to get the data for this row.  If nColumn>0
** then data is pulled from srcTab and pEList is used only to get the
** datatypes for each column.
*/
static int selectInnerLoop(
  Parse *pParse,          /* The parser context */
  Select *p,              /* The complete select statement being coded */
  ExprList *pEList,       /* List of values being extracted */
  int srcTab,             /* Pull data from this table */
  int nColumn,            /* Number of columns in the source table */
  ExprList *pOrderBy,     /* If not NULL, sort results using this key */
  int distinct,           /* If >=0, make sure results are distinct */
  int eDest,              /* How to dispose of the results */
  int iParm,              /* An argument to the disposal method */
  int iContinue,          /* Jump here to continue with next row */
  int iBreak              /* Jump here to break out of the inner loop */
){
  Vdbe *v = pParse->pVdbe;
  int i;
  int hasDistinct;        /* True if the DISTINCT keyword is present */

  if( v==0 ) return 0;
  assert( pEList!=0 );

  /* If there was a LIMIT clause on the SELECT statement, then do the check
  ** to see if this row should be output.
  */
  hasDistinct = distinct>=0 && pEList && pEList->nExpr>0;
  if( pOrderBy==0 && !hasDistinct ){
    codeLimiter(v, p, iContinue, iBreak, 0);
  }

  /* Pull the requested columns.
  */
  if( nColumn>0 ){
    for(i=0; i<nColumn; i++){
      sqliteVdbeAddOp(v, OP_Column, srcTab, i);
    }
  }else{
    nColumn = pEList->nExpr;
    for(i=0; i<pEList->nExpr; i++){
      sqliteExprCode(pParse, pEList->a[i].pExpr);
    }
  }

  /* If the DISTINCT keyword was present on the SELECT statement
  ** and this row has been seen before, then do not make this row
  ** part of the result.
  */
  if( hasDistinct ){
#if NULL_ALWAYS_DISTINCT
    sqliteVdbeAddOp(v, OP_IsNull, -pEList->nExpr, sqliteVdbeCurrentAddr(v)+7);
#endif
    sqliteVdbeAddOp(v, OP_MakeKey, pEList->nExpr, 1);
    if( pParse->db->file_format>=4 ) sqliteAddKeyType(v, pEList);
    sqliteVdbeAddOp(v, OP_Distinct, distinct, sqliteVdbeCurrentAddr(v)+3);
    sqliteVdbeAddOp(v, OP_Pop, pEList->nExpr+1, 0);
    sqliteVdbeAddOp(v, OP_Goto, 0, iContinue);
    sqliteVdbeAddOp(v, OP_String, 0, 0);
    sqliteVdbeAddOp(v, OP_PutStrKey, distinct, 0);
    if( pOrderBy==0 ){
      codeLimiter(v, p, iContinue, iBreak, nColumn);
    }
  }

  switch( eDest ){
    /* In this mode, write each query result to the key of the temporary
    ** table iParm.
    */
    case SRT_Union: {
      sqliteVdbeAddOp(v, OP_MakeRecord, nColumn, NULL_ALWAYS_DISTINCT);
      sqliteVdbeAddOp(v, OP_String, 0, 0);
      sqliteVdbeAddOp(v, OP_PutStrKey, iParm, 0);
      break;
    }

    /* Store the result as data using a unique key.
    */
    case SRT_Table:
    case SRT_TempTable: {
      sqliteVdbeAddOp(v, OP_MakeRecord, nColumn, 0);
      if( pOrderBy ){
        pushOntoSorter(pParse, v, pOrderBy);
      }else{
        sqliteVdbeAddOp(v, OP_NewRecno, iParm, 0);
        sqliteVdbeAddOp(v, OP_Pull, 1, 0);
        sqliteVdbeAddOp(v, OP_PutIntKey, iParm, 0);
      }
      break;
    }

    /* Construct a record from the query result, but instead of
    ** saving that record, use it as a key to delete elements from
    ** the temporary table iParm.
    */
    case SRT_Except: {
      int addr;
      addr = sqliteVdbeAddOp(v, OP_MakeRecord, nColumn, NULL_ALWAYS_DISTINCT);
      sqliteVdbeAddOp(v, OP_NotFound, iParm, addr+3);
      sqliteVdbeAddOp(v, OP_Delete, iParm, 0);
      break;
    }

    /* If we are creating a set for an "expr IN (SELECT ...)" construct,
    ** then there should be a single item on the stack.  Write this
    ** item into the set table with bogus data.
    */
    case SRT_Set: {
      int addr1 = sqliteVdbeCurrentAddr(v);
      int addr2;
      assert( nColumn==1 );
      sqliteVdbeAddOp(v, OP_NotNull, -1, addr1+3);
      sqliteVdbeAddOp(v, OP_Pop, 1, 0);
      addr2 = sqliteVdbeAddOp(v, OP_Goto, 0, 0);
      if( pOrderBy ){
        pushOntoSorter(pParse, v, pOrderBy);
      }else{
        sqliteVdbeAddOp(v, OP_String, 0, 0);
        sqliteVdbeAddOp(v, OP_PutStrKey, iParm, 0);
      }
      sqliteVdbeChangeP2(v, addr2, sqliteVdbeCurrentAddr(v));
      break;
    }

    /* If this is a scalar select that is part of an expression, then
    ** store the results in the appropriate memory cell and break out
    ** of the scan loop.
    */
    case SRT_Mem: {
      assert( nColumn==1 );
      if( pOrderBy ){
        pushOntoSorter(pParse, v, pOrderBy);
      }else{
        sqliteVdbeAddOp(v, OP_MemStore, iParm, 1);
        sqliteVdbeAddOp(v, OP_Goto, 0, iBreak);
      }
      break;
    }

    /* Send the data to the callback function.
    */
    case SRT_Callback:
    case SRT_Sorter: {
      if( pOrderBy ){
        sqliteVdbeAddOp(v, OP_SortMakeRec, nColumn, 0);
        pushOntoSorter(pParse, v, pOrderBy);
      }else{
        assert( eDest==SRT_Callback );
        sqliteVdbeAddOp(v, OP_Callback, nColumn, 0);
      }
      break;
    }

    /* Invoke a subroutine to handle the results.  The subroutine itself
    ** is responsible for popping the results off of the stack.
    */
    case SRT_Subroutine: {
      if( pOrderBy ){
        sqliteVdbeAddOp(v, OP_MakeRecord, nColumn, 0);
        pushOntoSorter(pParse, v, pOrderBy);
      }else{
        sqliteVdbeAddOp(v, OP_Gosub, 0, iParm);
      }
      break;
    }

    /* Discard the results.  This is used for SELECT statements inside
    ** the body of a TRIGGER.  The purpose of such selects is to call
    ** user-defined functions that have side effects.  We do not care
    ** about the actual results of the select.
    */
    default: {
      assert( eDest==SRT_Discard );
      sqliteVdbeAddOp(v, OP_Pop, nColumn, 0);
      break;
    }
  }
  return 0;
}

/*
** If the inner loop was generated using a non-null pOrderBy argument,
** then the results were placed in a sorter.  After the loop is terminated
** we need to run the sorter and output the results.  The following
** routine generates the code needed to do that.
*/
static void generateSortTail(
  Select *p,       /* The SELECT statement */
  Vdbe *v,         /* Generate code into this VDBE */
  int nColumn,     /* Number of columns of data */
  int eDest,       /* Write the sorted results here */
  int iParm        /* Optional parameter associated with eDest */
){
  int end1 = sqliteVdbeMakeLabel(v);
  int end2 = sqliteVdbeMakeLabel(v);
  int addr;
  if( eDest==SRT_Sorter ) return;
  sqliteVdbeAddOp(v, OP_Sort, 0, 0);
  addr = sqliteVdbeAddOp(v, OP_SortNext, 0, end1);
  codeLimiter(v, p, addr, end2, 1);
  switch( eDest ){
    case SRT_Callback: {
      sqliteVdbeAddOp(v, OP_SortCallback, nColumn, 0);
      break;
    }
    case SRT_Table:
    case SRT_TempTable: {
      sqliteVdbeAddOp(v, OP_NewRecno, iParm, 0);
      sqliteVdbeAddOp(v, OP_Pull, 1, 0);
      sqliteVdbeAddOp(v, OP_PutIntKey, iParm, 0);
      break;
    }
    case SRT_Set: {
      assert( nColumn==1 );
      sqliteVdbeAddOp(v, OP_NotNull, -1, sqliteVdbeCurrentAddr(v)+3);
      sqliteVdbeAddOp(v, OP_Pop, 1, 0);
      sqliteVdbeAddOp(v, OP_Goto, 0, sqliteVdbeCurrentAddr(v)+3);
      sqliteVdbeAddOp(v, OP_String, 0, 0);
      sqliteVdbeAddOp(v, OP_PutStrKey, iParm, 0);
      break;
    }
    case SRT_Mem: {
      assert( nColumn==1 );
      sqliteVdbeAddOp(v, OP_MemStore, iParm, 1);
      sqliteVdbeAddOp(v, OP_Goto, 0, end1);
      break;
    }
    case SRT_Subroutine: {
      int i;
      for(i=0; i<nColumn; i++){
        sqliteVdbeAddOp(v, OP_Column, -1-i, i);
      }
      sqliteVdbeAddOp(v, OP_Gosub, 0, iParm);
      sqliteVdbeAddOp(v, OP_Pop, 1, 0);
      break;
    }
    default: {
      /* Do nothing */
      break;
    }
  }
  sqliteVdbeAddOp(v, OP_Goto, 0, addr);
  sqliteVdbeResolveLabel(v, end2);
  sqliteVdbeAddOp(v, OP_Pop, 1, 0);
  sqliteVdbeResolveLabel(v, end1);
  sqliteVdbeAddOp(v, OP_SortReset, 0, 0);
}

/*
** Generate code that will tell the VDBE the datatypes of
** columns in the result set.
**
** This routine only generates code if the "PRAGMA show_datatypes=on"
** has been executed.  The datatypes are reported out in the azCol
** parameter to the callback function.  The first N azCol[] entries
** are the names of the columns, and the second N entries are the
** datatypes for the columns.
**
** The "datatype" for a result that is a column of a type is the
** datatype definition extracted from the CREATE TABLE statement.
** The datatype for an expression is either TEXT or NUMERIC.  The
** datatype for a ROWID field is INTEGER.
*/
static void generateColumnTypes(
  Parse *pParse,      /* Parser context */
  SrcList *pTabList,  /* List of tables */
  ExprList *pEList    /* Expressions defining the result set */
){
  Vdbe *v = pParse->pVdbe;
  int i, j;
  for(i=0; i<pEList->nExpr; i++){
    Expr *p = pEList->a[i].pExpr;
    char *zType = 0;
    if( p==0 ) continue;
    if( p->op==TK_COLUMN && pTabList ){
      Table *pTab;
      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 ){
        zType = "INTEGER";
      }else{
        zType = pTab->aCol[iCol].zType;
      }
    }else{
      if( sqliteExprType(p)==SQLITE_SO_TEXT ){
        zType = "TEXT";
      }else{
        zType = "NUMERIC";
      }
    }
    sqliteVdbeOp3(v, OP_ColumnName, i + pEList->nExpr, 0, zType, 0);
  }
}

/*
** Generate code that will tell the VDBE the names of columns
** in the result set.  This information is used to provide the
** azCol[] values in the callback.
*/
static void generateColumnNames(
  Parse *pParse,      /* Parser context */
  SrcList *pTabList,  /* List of tables */
  ExprList *pEList    /* Expressions defining the result set */
){
  Vdbe *v = pParse->pVdbe;
  int i, j;
  sqlite *db = pParse->db;
  int fullNames, shortNames;

  assert( v!=0 );
  if( pParse->colNamesSet || v==0 || sqlite_malloc_failed ) return;
  pParse->colNamesSet = 1;
  fullNames = (db->flags & SQLITE_FullColNames)!=0;
  shortNames = (db->flags & SQLITE_ShortColNames)!=0;
  for(i=0; i<pEList->nExpr; i++){
    Expr *p;
    int p2 = i==pEList->nExpr-1;
    p = pEList->a[i].pExpr;
    if( p==0 ) continue;
    if( pEList->a[i].zName ){
      char *zName = pEList->a[i].zName;
      sqliteVdbeOp3(v, OP_ColumnName, i, p2, zName, 0);
      continue;
    }
    if( p->op==TK_COLUMN && pTabList ){
      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] ){
        int addr = sqliteVdbeOp3(v,OP_ColumnName, i, p2, p->span.z, p->span.n);
        sqliteVdbeCompressSpace(v, addr);
      }else if( fullNames || (!shortNames && pTabList->nSrc>1) ){
        char *zName = 0;
        char *zTab;
 
        zTab = pTabList->a[j].zAlias;
        if( fullNames || zTab==0 ) zTab = pTab->zName;
        sqliteSetString(&zName, zTab, ".", zCol, 0);
        sqliteVdbeOp3(v, OP_ColumnName, i, p2, zName, P3_DYNAMIC);
      }else{
        sqliteVdbeOp3(v, OP_ColumnName, i, p2, zCol, 0);
      }
    }else if( p->span.z && p->span.z[0] ){
      int addr = sqliteVdbeOp3(v,OP_ColumnName, i, p2, p->span.z, p->span.n);
      sqliteVdbeCompressSpace(v, addr);
    }else{
      char zName[30];
      assert( p->op!=TK_COLUMN || pTabList==0 );
      sprintf(zName, "column%d", i+1);
      sqliteVdbeOp3(v, OP_ColumnName, i, p2, zName, 0);
    }
  }
}

/*
** 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;
}

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

/*
** Given a SELECT statement, generate a Table structure that describes
** the result set of that SELECT.
*/