select.c

qt-x11-opensource-src-4.1.4.tar.gz源码

**
** A jump to addrRepeat is made and the K values are popped from the
** stack if the top N elements are not distinct.
*/
static void codeDistinct(
  Vdbe *v,           /* Generate code into this VM */
  int iTab,          /* A sorting index used to test for distinctness */
  int addrRepeat,    /* Jump to here if not distinct */
  int N,             /* The top N elements of the stack must be distinct */
  int K              /* Pop K elements from the stack if indistinct */
){
#if NULL_ALWAYS_DISTINCT
  sqlite3VdbeAddOp(v, OP_IsNull, -N, sqlite3VdbeCurrentAddr(v)+6);
#endif
  sqlite3VdbeAddOp(v, OP_MakeRecord, -N, 0);
  sqlite3VdbeAddOp(v, OP_Distinct, iTab, sqlite3VdbeCurrentAddr(v)+3);
  sqlite3VdbeAddOp(v, OP_Pop, K, 0);
  sqlite3VdbeAddOp(v, OP_Goto, 0, addrRepeat);
  VdbeComment((v, "# skip indistinct records"));
  sqlite3VdbeAddOp(v, OP_IdxInsert, iTab, 0);
}


/*
** This routine generates the code for the inside of the inner loop
** of a SELECT.
**
** 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 */
  char *aff               /* affinity string if eDest is SRT_Union */
){
  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++){
      sqlite3VdbeAddOp(v, OP_Column, srcTab, i);
    }
  }else{
    nColumn = pEList->nExpr;
    sqlite3ExprCodeExprList(pParse, pEList);
  }

  /* 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 ){
    int n = pEList->nExpr;
    codeDistinct(v, distinct, iContinue, n, n+1);
    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.
    */
#ifndef SQLITE_OMIT_COMPOUND_SELECT
    case SRT_Union: {
      sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, NULL_ALWAYS_DISTINCT);
      if( aff ){
        sqlite3VdbeChangeP3(v, -1, aff, P3_STATIC);
      }
      sqlite3VdbeAddOp(v, OP_IdxInsert, 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 = sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, NULL_ALWAYS_DISTINCT);
      sqlite3VdbeChangeP3(v, -1, aff, P3_STATIC);
      sqlite3VdbeAddOp(v, OP_NotFound, iParm, addr+3);
      sqlite3VdbeAddOp(v, OP_Delete, iParm, 0);
      break;
    }
#endif

    /* Store the result as data using a unique key.
    */
    case SRT_Table:
    case SRT_VirtualTab: {
      sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0);
      if( pOrderBy ){
        pushOntoSorter(pParse, v, pOrderBy);
      }else{
        sqlite3VdbeAddOp(v, OP_NewRowid, iParm, 0);
        sqlite3VdbeAddOp(v, OP_Pull, 1, 0);
        sqlite3VdbeAddOp(v, OP_Insert, iParm, 0);
      }
      break;
    }

#ifndef SQLITE_OMIT_SUBQUERY
    /* 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 = sqlite3VdbeCurrentAddr(v);
      int addr2;

      assert( nColumn==1 );
      sqlite3VdbeAddOp(v, OP_NotNull, -1, addr1+3);
      sqlite3VdbeAddOp(v, OP_Pop, 1, 0);
      addr2 = sqlite3VdbeAddOp(v, OP_Goto, 0, 0);
      if( pOrderBy ){
        /* At first glance you would think we could optimize out the
        ** ORDER BY in this case since the order of entries in the set
        ** does not matter.  But there might be a LIMIT clause, in which
        ** case the order does matter */
        pushOntoSorter(pParse, v, pOrderBy);
      }else{
        char aff = (iParm>>16)&0xFF;
        aff = sqlite3CompareAffinity(pEList->a[0].pExpr, aff);
        sqlite3VdbeOp3(v, OP_MakeRecord, 1, 0, &aff, 1);
        sqlite3VdbeAddOp(v, OP_IdxInsert, (iParm&0x0000FFFF), 0);
      }
      sqlite3VdbeJumpHere(v, addr2);
      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_Exists:
    case SRT_Mem: {
      assert( nColumn==1 );
      if( pOrderBy ){
        pushOntoSorter(pParse, v, pOrderBy);
      }else{
        sqlite3VdbeAddOp(v, OP_MemStore, iParm, 1);
        sqlite3VdbeAddOp(v, OP_Goto, 0, iBreak);
      }
      break;
    }
#endif /* #ifndef SQLITE_OMIT_SUBQUERY */

    /* Send the data to the callback function or to a subroutine.  In the
    ** case of a subroutine, the subroutine itself is responsible for
    ** popping the data from the stack.
    */
    case SRT_Subroutine:
    case SRT_Callback: {
      if( pOrderBy ){
        sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0);
        pushOntoSorter(pParse, v, pOrderBy);
      }else if( eDest==SRT_Subroutine ){
        sqlite3VdbeAddOp(v, OP_Gosub, 0, iParm);
      }else{
        sqlite3VdbeAddOp(v, OP_Callback, nColumn, 0);
      }
      break;
    }

#if !defined(SQLITE_OMIT_TRIGGER)
    /* 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 );
      sqlite3VdbeAddOp(v, OP_Pop, nColumn, 0);
      break;
    }
#endif
  }
  return 0;
}

/*
** Given an expression list, generate a KeyInfo structure that records
** the collating sequence for each expression in that expression list.
**
** If the ExprList is an ORDER BY or GROUP BY clause then the resulting
** KeyInfo structure is appropriate for initializing a virtual index to
** implement that clause.  If the ExprList is the result set of a SELECT
** then the KeyInfo structure is appropriate for initializing a virtual
** index to implement a DISTINCT test.
**
** Space to hold the KeyInfo structure is obtain from malloc.  The calling
** function is responsible for seeing that this structure is eventually
** freed.  Add the KeyInfo structure to the P3 field of an opcode using
** P3_KEYINFO_HANDOFF is the usual way of dealing with this.
*/
static KeyInfo *keyInfoFromExprList(Parse *pParse, ExprList *pList){
  sqlite3 *db = pParse->db;
  int nExpr;
  KeyInfo *pInfo;
  struct ExprList_item *pItem;
  int i;

  nExpr = pList->nExpr;
  pInfo = sqliteMalloc( sizeof(*pInfo) + nExpr*(sizeof(CollSeq*)+1) );
  if( pInfo ){
    pInfo->aSortOrder = (char*)&pInfo->aColl[nExpr];
    pInfo->nField = nExpr;
    pInfo->enc = db->enc;
    for(i=0, pItem=pList->a; i<nExpr; i++, pItem++){
      CollSeq *pColl;
      pColl = sqlite3ExprCollSeq(pParse, pItem->pExpr);
      if( !pColl ){
        pColl = db->pDfltColl;
      }
      pInfo->aColl[i] = pColl;
      pInfo->aSortOrder[i] = pItem->sortOrder;
    }
  }
  return pInfo;
}


/*
** 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(
  Parse *pParse,   /* The parsing context */
  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 brk = sqlite3VdbeMakeLabel(v);
  int cont = sqlite3VdbeMakeLabel(v);
  int addr;
  int iTab;
  ExprList *pOrderBy = p->pOrderBy;

  iTab = pOrderBy->iECursor;
  addr = 1 + sqlite3VdbeAddOp(v, OP_Sort, iTab, brk);
  codeLimiter(v, p, cont, brk, 0);
  sqlite3VdbeAddOp(v, OP_Column, iTab, pOrderBy->nExpr + 1);
  switch( eDest ){
    case SRT_Table:
    case SRT_VirtualTab: {
      sqlite3VdbeAddOp(v, OP_NewRowid, iParm, 0);
      sqlite3VdbeAddOp(v, OP_Pull, 1, 0);
      sqlite3VdbeAddOp(v, OP_Insert, iParm, 0);
      break;
    }
#ifndef SQLITE_OMIT_SUBQUERY
    case SRT_Set: {
      assert( nColumn==1 );
      sqlite3VdbeAddOp(v, OP_NotNull, -1, sqlite3VdbeCurrentAddr(v)+3);
      sqlite3VdbeAddOp(v, OP_Pop, 1, 0);
      sqlite3VdbeAddOp(v, OP_Goto, 0, sqlite3VdbeCurrentAddr(v)+3);
      sqlite3VdbeOp3(v, OP_MakeRecord, 1, 0, "n", P3_STATIC);
      sqlite3VdbeAddOp(v, OP_IdxInsert, (iParm&0x0000FFFF), 0);
      break;
    }
    case SRT_Exists:
    case SRT_Mem: {
      assert( nColumn==1 );
      sqlite3VdbeAddOp(v, OP_MemStore, iParm, 1);
      sqlite3VdbeAddOp(v, OP_Goto, 0, brk);
      break;
    }
#endif
    case SRT_Callback:
    case SRT_Subroutine: {
      int i;
      sqlite3VdbeAddOp(v, OP_Integer, p->pEList->nExpr, 0);
      sqlite3VdbeAddOp(v, OP_Pull, 1, 0);
      for(i=0; i<nColumn; i++){
        sqlite3VdbeAddOp(v, OP_Column, -1-i, i);
      }
      if( eDest==SRT_Callback ){
        sqlite3VdbeAddOp(v, OP_Callback, nColumn, 0);
      }else{
        sqlite3VdbeAddOp(v, OP_Gosub, 0, iParm);
      }
      sqlite3VdbeAddOp(v, OP_Pop, 2, 0);
      break;
    }
    default: {
      /* Do nothing */
      break;
    }
  }
  sqlite3VdbeResolveLabel(v, cont);
  sqlite3VdbeAddOp(v, OP_Next, iTab, addr);
  sqlite3VdbeResolveLabel(v, brk);
}

/*
** Return a pointer to a string containing the 'declaration type' of the
** expression pExpr. The string may be treated as static by the caller.
**
** If the declaration type is the exact datatype definition extracted from
** the original CREATE TABLE statement if the expression is a column.
** 
** The declaration type for an expression is either TEXT, NUMERIC or ANY.
** The declaration type for a ROWID field is INTEGER.
*/
static const char *columnType(NameContext *pNC, Expr *pExpr){
  char const *zType;
  int j;
  if( pExpr==0 || pNC->pSrcList==0 ) return 0;

  /* The TK_AS operator can only occur in ORDER BY, GROUP BY, HAVING,
  ** and LIMIT clauses.  But pExpr originates in the result set of a
  ** SELECT.  So pExpr can never contain an AS operator.
  */
  assert( pExpr->op!=TK_AS );

  switch( pExpr->op ){
    case TK_COLUMN: {
      Table *pTab = 0;
      int iCol = pExpr->iColumn;
      while( pNC && !pTab ){
        SrcList *pTabList = pNC->pSrcList;
        for(j=0;j<pTabList->nSrc && pTabList->a[j].iCursor!=pExpr->iTable;j++);
        if( j<pTabList->nSrc ){
          pTab = pTabList->a[j].pTab;
        }else{
          pNC = pNC->pNext;
        }
      }
      if( pTab==0 ){
        /* FIX ME:
        ** This can occurs if you have something like "SELECT new.x;" inside
        ** a trigger.  In other words, if you reference the special "new"
        ** table in the result set of a select.  We do not have a good way
        ** to find the actual table type, so call it "TEXT".  This is really
        ** something of a bug, but I do not know how to fix it.
        **
        ** This code does not produce the correct answer - it just prevents
        ** a segfault.  See ticket #1229.
        */
        zType = "TEXT";
        break;
      }
      assert( 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;
      }
      break;
    }
#ifndef SQLITE_OMIT_SUBQUERY
    case TK_SELECT: {
      NameContext sNC;
      Select *pS = pExpr->pSelect;
      sNC.pSrcList = pExpr->pSelect->pSrc;
      sNC.pNext = pNC;
      zType = columnType(&sNC, pS->pEList->a[0].pExpr); 
      break;
    }
#endif
    default: