select.c

最新的sqlite3.6.2源代码

      pDelete = p->pPrior;
      p->pPrior = pPrior;
      p->pOrderBy = 0;
      sqlite3ExprDelete(db, p->pLimit);
      p->pLimit = pLimit;
      p->pOffset = pOffset;
      p->iLimit = 0;
      p->iOffset = 0;
      if( rc ){
        goto multi_select_end;
      }


      /* Convert the data in the temporary table into whatever form
      ** it is that we currently need.
      */      
      if( dest.eDest!=priorOp || unionTab!=dest.iParm ){
        int iCont, iBreak, iStart;
        assert( p->pEList );
        if( dest.eDest==SRT_Output ){
          Select *pFirst = p;
          while( pFirst->pPrior ) pFirst = pFirst->pPrior;
          generateColumnNames(pParse, 0, pFirst->pEList);
        }
        iBreak = sqlite3VdbeMakeLabel(v);
        iCont = sqlite3VdbeMakeLabel(v);
        computeLimitRegisters(pParse, p, iBreak);
        sqlite3VdbeAddOp2(v, OP_Rewind, unionTab, iBreak);
        iStart = sqlite3VdbeCurrentAddr(v);
        selectInnerLoop(pParse, p, p->pEList, unionTab, p->pEList->nExpr,
                        0, -1, &dest, iCont, iBreak);
        sqlite3VdbeResolveLabel(v, iCont);
        sqlite3VdbeAddOp2(v, OP_Next, unionTab, iStart);
        sqlite3VdbeResolveLabel(v, iBreak);
        sqlite3VdbeAddOp2(v, OP_Close, unionTab, 0);
      }
      break;
    }
    case TK_INTERSECT: {
      int tab1, tab2;
      int iCont, iBreak, iStart;
      Expr *pLimit, *pOffset;
      int addr;
      SelectDest intersectdest;
      int r1;

      /* INTERSECT is different from the others since it requires
      ** two temporary tables.  Hence it has its own case.  Begin
      ** by allocating the tables we will need.
      */
      tab1 = pParse->nTab++;
      tab2 = pParse->nTab++;
      assert( p->pOrderBy==0 );

      addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tab1, 0);
      assert( p->addrOpenEphm[0] == -1 );
      p->addrOpenEphm[0] = addr;
      p->pRightmost->selFlags |= SF_UsesEphemeral;
      assert( p->pEList );

      /* Code the SELECTs to our left into temporary table "tab1".
      */
      sqlite3SelectDestInit(&intersectdest, SRT_Union, tab1);
      rc = sqlite3Select(pParse, pPrior, &intersectdest);
      if( rc ){
        goto multi_select_end;
      }

      /* Code the current SELECT into temporary table "tab2"
      */
      addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tab2, 0);
      assert( p->addrOpenEphm[1] == -1 );
      p->addrOpenEphm[1] = addr;
      p->pPrior = 0;
      pLimit = p->pLimit;
      p->pLimit = 0;
      pOffset = p->pOffset;
      p->pOffset = 0;
      intersectdest.iParm = tab2;
      rc = sqlite3Select(pParse, p, &intersectdest);
      pDelete = p->pPrior;
      p->pPrior = pPrior;
      sqlite3ExprDelete(db, p->pLimit);
      p->pLimit = pLimit;
      p->pOffset = pOffset;
      if( rc ){
        goto multi_select_end;
      }

      /* Generate code to take the intersection of the two temporary
      ** tables.
      */
      assert( p->pEList );
      if( dest.eDest==SRT_Output ){
        Select *pFirst = p;
        while( pFirst->pPrior ) pFirst = pFirst->pPrior;
        generateColumnNames(pParse, 0, pFirst->pEList);
      }
      iBreak = sqlite3VdbeMakeLabel(v);
      iCont = sqlite3VdbeMakeLabel(v);
      computeLimitRegisters(pParse, p, iBreak);
      sqlite3VdbeAddOp2(v, OP_Rewind, tab1, iBreak);
      r1 = sqlite3GetTempReg(pParse);
      iStart = sqlite3VdbeAddOp2(v, OP_RowKey, tab1, r1);
      sqlite3VdbeAddOp3(v, OP_NotFound, tab2, iCont, r1);
      sqlite3ReleaseTempReg(pParse, r1);
      selectInnerLoop(pParse, p, p->pEList, tab1, p->pEList->nExpr,
                      0, -1, &dest, iCont, iBreak);
      sqlite3VdbeResolveLabel(v, iCont);
      sqlite3VdbeAddOp2(v, OP_Next, tab1, iStart);
      sqlite3VdbeResolveLabel(v, iBreak);
      sqlite3VdbeAddOp2(v, OP_Close, tab2, 0);
      sqlite3VdbeAddOp2(v, OP_Close, tab1, 0);
      break;
    }
  }

  /* Compute collating sequences used by 
  ** temporary tables needed to implement the compound select.
  ** Attach the KeyInfo structure to all temporary tables.
  **
  ** This section is run by the right-most SELECT statement only.
  ** SELECT statements to the left always skip this part.  The right-most
  ** SELECT might also skip this part if it has no ORDER BY clause and
  ** no temp tables are required.
  */
  if( p->selFlags & SF_UsesEphemeral ){
    int i;                        /* Loop counter */
    KeyInfo *pKeyInfo;            /* Collating sequence for the result set */
    Select *pLoop;                /* For looping through SELECT statements */
    CollSeq **apColl;             /* For looping through pKeyInfo->aColl[] */
    int nCol;                     /* Number of columns in result set */

    assert( p->pRightmost==p );
    nCol = p->pEList->nExpr;
    pKeyInfo = sqlite3DbMallocZero(db,
                       sizeof(*pKeyInfo)+nCol*(sizeof(CollSeq*) + 1));
    if( !pKeyInfo ){
      rc = SQLITE_NOMEM;
      goto multi_select_end;
    }

    pKeyInfo->enc = ENC(db);
    pKeyInfo->nField = nCol;

    for(i=0, apColl=pKeyInfo->aColl; i<nCol; i++, apColl++){
      *apColl = multiSelectCollSeq(pParse, p, i);
      if( 0==*apColl ){
        *apColl = db->pDfltColl;
      }
    }

    for(pLoop=p; pLoop; pLoop=pLoop->pPrior){
      for(i=0; i<2; i++){
        int addr = pLoop->addrOpenEphm[i];
        if( addr<0 ){
          /* If [0] is unused then [1] is also unused.  So we can
          ** always safely abort as soon as the first unused slot is found */
          assert( pLoop->addrOpenEphm[1]<0 );
          break;
        }
        sqlite3VdbeChangeP2(v, addr, nCol);
        sqlite3VdbeChangeP4(v, addr, (char*)pKeyInfo, P4_KEYINFO);
        pLoop->addrOpenEphm[i] = -1;
      }
    }
    sqlite3DbFree(db, pKeyInfo);
  }

multi_select_end:
  pDest->iMem = dest.iMem;
  pDest->nMem = dest.nMem;
  sqlite3SelectDelete(db, pDelete);
  return rc;
}
#endif /* SQLITE_OMIT_COMPOUND_SELECT */

/*
** Code an output subroutine for a coroutine implementation of a
** SELECT statment.
**
** The data to be output is contained in pIn->iMem.  There are
** pIn->nMem columns to be output.  pDest is where the output should
** be sent.
**
** regReturn is the number of the register holding the subroutine
** return address.
**
** If regPrev>0 then it is a the first register in a vector that
** records the previous output.  mem[regPrev] is a flag that is false
** if there has been no previous output.  If regPrev>0 then code is
** generated to suppress duplicates.  pKeyInfo is used for comparing
** keys.
**
** If the LIMIT found in p->iLimit is reached, jump immediately to
** iBreak.
*/
static int generateOutputSubroutine(
  Parse *pParse,          /* Parsing context */
  Select *p,              /* The SELECT statement */
  SelectDest *pIn,        /* Coroutine supplying data */
  SelectDest *pDest,      /* Where to send the data */
  int regReturn,          /* The return address register */
  int regPrev,            /* Previous result register.  No uniqueness if 0 */
  KeyInfo *pKeyInfo,      /* For comparing with previous entry */
  int p4type,             /* The p4 type for pKeyInfo */
  int iBreak              /* Jump here if we hit the LIMIT */
){
  Vdbe *v = pParse->pVdbe;
  int iContinue;
  int addr;

  addr = sqlite3VdbeCurrentAddr(v);
  iContinue = sqlite3VdbeMakeLabel(v);

  /* Suppress duplicates for UNION, EXCEPT, and INTERSECT 
  */
  if( regPrev ){
    int j1, j2;
    j1 = sqlite3VdbeAddOp1(v, OP_IfNot, regPrev);
    j2 = sqlite3VdbeAddOp4(v, OP_Compare, pIn->iMem, regPrev+1, pIn->nMem,
                              (char*)pKeyInfo, p4type);
    sqlite3VdbeAddOp3(v, OP_Jump, j2+2, iContinue, j2+2);
    sqlite3VdbeJumpHere(v, j1);
    sqlite3ExprCodeCopy(pParse, pIn->iMem, regPrev+1, pIn->nMem);
    sqlite3VdbeAddOp2(v, OP_Integer, 1, regPrev);
  }
  if( pParse->db->mallocFailed ) return 0;

  /* Suppress the the first OFFSET entries if there is an OFFSET clause
  */
  codeOffset(v, p, iContinue);

  switch( pDest->eDest ){
    /* Store the result as data using a unique key.
    */
    case SRT_Table:
    case SRT_EphemTab: {
      int r1 = sqlite3GetTempReg(pParse);
      int r2 = sqlite3GetTempReg(pParse);
      sqlite3VdbeAddOp3(v, OP_MakeRecord, pIn->iMem, pIn->nMem, r1);
      sqlite3VdbeAddOp2(v, OP_NewRowid, pDest->iParm, r2);
      sqlite3VdbeAddOp3(v, OP_Insert, pDest->iParm, r1, r2);
      sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
      sqlite3ReleaseTempReg(pParse, r2);
      sqlite3ReleaseTempReg(pParse, r1);
      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 r1;
      assert( pIn->nMem==1 );
      p->affinity = 
         sqlite3CompareAffinity(p->pEList->a[0].pExpr, pDest->affinity);
      r1 = sqlite3GetTempReg(pParse);
      sqlite3VdbeAddOp4(v, OP_MakeRecord, pIn->iMem, 1, r1, &p->affinity, 1);
      sqlite3ExprCacheAffinityChange(pParse, pIn->iMem, 1);
      sqlite3VdbeAddOp2(v, OP_IdxInsert, pDest->iParm, r1);
      sqlite3ReleaseTempReg(pParse, r1);
      break;
    }

#if 0  /* Never occurs on an ORDER BY query */
    /* If any row exist in the result set, record that fact and abort.
    */
    case SRT_Exists: {
      sqlite3VdbeAddOp2(v, OP_Integer, 1, pDest->iParm);
      /* The LIMIT clause will terminate the loop for us */
      break;
    }
#endif

    /* 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( pIn->nMem==1 );
      sqlite3ExprCodeMove(pParse, pIn->iMem, pDest->iParm, 1);
      /* The LIMIT clause will jump out of the loop for us */
      break;
    }
#endif /* #ifndef SQLITE_OMIT_SUBQUERY */

    /* The results are stored in a sequence of registers
    ** starting at pDest->iMem.  Then the co-routine yields.
    */
    case SRT_Coroutine: {
      if( pDest->iMem==0 ){
        pDest->iMem = sqlite3GetTempRange(pParse, pIn->nMem);
        pDest->nMem = pIn->nMem;
      }
      sqlite3ExprCodeMove(pParse, pIn->iMem, pDest->iMem, pDest->nMem);
      sqlite3VdbeAddOp1(v, OP_Yield, pDest->iParm);
      break;
    }

    /* Results are stored in a sequence of registers.  Then the
    ** OP_ResultRow opcode is used to cause sqlite3_step() to return
    ** the next row of result.
    */
    case SRT_Output: {
      sqlite3VdbeAddOp2(v, OP_ResultRow, pIn->iMem, pIn->nMem);
      sqlite3ExprCacheAffinityChange(pParse, pIn->iMem, pIn->nMem);
      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: {
      break;
    }
#endif
  }

  /* Jump to the end of the loop if the LIMIT is reached.
  */
  if( p->iLimit ){
    sqlite3VdbeAddOp2(v, OP_AddImm, p->iLimit, -1);
    sqlite3VdbeAddOp2(v, OP_IfZero, p->iLimit, iBreak);
  }

  /* Generate the subroutine return
  */
  sqlite3VdbeResolveLabel(v, iContinue);
  sqlite3VdbeAddOp1(v, OP_Return, regReturn);

  return addr;
}

/*
** Alternative compound select code generator for cases when there
** is an ORDER BY clause.
**
** We assume a query of the following form:
**
**      <selectA>  <operator>  <selectB>  ORDER BY <orderbylist>
**
** <operator> is one of UNION ALL, UNION, EXCEPT, or INTERSECT.  The idea
** is to code both <selectA> and <selectB> with the ORDER BY clause as
** co-routines.  Then run the co-routines in parallel and merge the results
** into the output.  In addition to the two coroutines (called selectA and
** selectB) there are 7 subroutines:
**
**    outA:    Move the output of the selectA coroutine into the output
**             of the compound query.
**
**    outB:    Move the output of the selectB coroutine into the output
**             of the compound query.  (Only generated for UNION and
**             UNION ALL.  EXCEPT and INSERTSECT never output a row that
**             appears only in B.)
**
**    AltB:    Called when there is data from both coroutines and A<B.
**
**    AeqB:    Called when there is data from both coroutines and A==B.
**
**    AgtB:    Called when there is data from both coroutines and A>B.
**
**    EofA:    Called when data is exhausted from selectA.
**
**    EofB:    Called when data is exhausted from selectB.
**
** The implementation of the latter five subroutines depend on which 
** <operator> is used:
**
**
**             UNION ALL         UNION            EXCEPT          INTERSECT
**          -------------  -----------------  --------------  -----------------
**   AltB:   outA, nextA      outA, nextA       outA, nextA         nextA
**
**   AeqB:   outA, nextA         nextA             nextA         outA, nextA
**
**   AgtB:   outB, nextB      outB, nextB          nextB            nextB
**
**   EofA:   outB, nextB      outB, nextB          halt             halt
**
**   EofB:   outA, nextA      outA, nextA       outA, nextA         halt
**
** In the AltB, AeqB, and AgtB subroutines, an EOF on A following nextA
** causes an immediate jump to EofA and an EOF on B following nextB causes
** an immediate jump to EofB.  Within EofA and EofB, and EOF on entry or
** following nextX causes a jump to the end of the select processing.
**
** Duplicate removal in the UNION, EXCEPT, and INTERSECT cases is handled
** w