expr.c

SQLite is a software library that implements a self-contained, serverless, zero-configuration, trans

  int eType = 0;
  int iTab = pParse->nTab++;

  /* The follwing if(...) expression is true if the SELECT is of the 
  ** simple form:
  **
  **     SELECT <column> FROM <table>
  **
  ** If this is the case, it may be possible to use an existing table
  ** or index instead of generating an epheremal table.
  */
  if( sqlite3_enable_in_opt
   && (p=pX->pSelect)!=0 && !p->pPrior
   && !p->isDistinct && !p->isAgg && !p->pGroupBy
   && p->pSrc && p->pSrc->nSrc==1 && !p->pSrc->a[0].pSelect
   && p->pSrc->a[0].pTab && !p->pSrc->a[0].pTab->pSelect
   && p->pEList->nExpr==1 && p->pEList->a[0].pExpr->op==TK_COLUMN
   && !p->pLimit && !p->pOffset && !p->pWhere
  ){
    sqlite3 *db = pParse->db;
    Index *pIdx;
    Expr *pExpr = p->pEList->a[0].pExpr;
    int iCol = pExpr->iColumn;
    Vdbe *v = sqlite3GetVdbe(pParse);

    /* This function is only called from two places. In both cases the vdbe
    ** has already been allocated. So assume sqlite3GetVdbe() is always
    ** successful here.
    */
    assert(v);
    if( iCol<0 ){
      int iMem = ++pParse->nMem;
      int iAddr;
      Table *pTab = p->pSrc->a[0].pTab;
      int iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
      sqlite3VdbeUsesBtree(v, iDb);

      iAddr = sqlite3VdbeAddOp1(v, OP_If, iMem);
      sqlite3VdbeAddOp2(v, OP_Integer, 1, iMem);

      sqlite3OpenTable(pParse, iTab, iDb, pTab, OP_OpenRead);
      eType = IN_INDEX_ROWID;

      sqlite3VdbeJumpHere(v, iAddr);
    }else{
      /* The collation sequence used by the comparison. If an index is to 
      ** be used in place of a temp-table, it must be ordered according
      ** to this collation sequence.
      */
      CollSeq *pReq = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pExpr);

      /* Check that the affinity that will be used to perform the 
      ** comparison is the same as the affinity of the column. If
      ** it is not, it is not possible to use any index.
      */
      Table *pTab = p->pSrc->a[0].pTab;
      char aff = comparisonAffinity(pX);
      int affinity_ok = (pTab->aCol[iCol].affinity==aff||aff==SQLITE_AFF_NONE);

      for(pIdx=pTab->pIndex; pIdx && eType==0 && affinity_ok; pIdx=pIdx->pNext){
        if( (pIdx->aiColumn[0]==iCol)
         && (pReq==sqlite3FindCollSeq(db, ENC(db), pIdx->azColl[0], -1, 0))
         && (!mustBeUnique || (pIdx->nColumn==1 && pIdx->onError!=OE_None))
        ){
          int iDb;
          int iMem = ++pParse->nMem;
          int iAddr;
          char *pKey;
  
          pKey = (char *)sqlite3IndexKeyinfo(pParse, pIdx);
          iDb = sqlite3SchemaToIndex(db, pIdx->pSchema);
          sqlite3VdbeUsesBtree(v, iDb);

          iAddr = sqlite3VdbeAddOp1(v, OP_If, iMem);
          sqlite3VdbeAddOp2(v, OP_Integer, 1, iMem);
  
          sqlite3VdbeAddOp2(v, OP_SetNumColumns, 0, pIdx->nColumn);
          sqlite3VdbeAddOp4(v, OP_OpenRead, iTab, pIdx->tnum, iDb,
                               pKey,P4_KEYINFO_HANDOFF);
          VdbeComment((v, "%s", pIdx->zName));
          eType = IN_INDEX_INDEX;

          sqlite3VdbeJumpHere(v, iAddr);
        }
      }
    }
  }

  if( eType==0 ){
    sqlite3CodeSubselect(pParse, pX);
    eType = IN_INDEX_EPH;
  }else{
    pX->iTable = iTab;
  }
  return eType;
}
#endif

/*
** Generate code for scalar subqueries used as an expression
** and IN operators.  Examples:
**
**     (SELECT a FROM b)          -- subquery
**     EXISTS (SELECT a FROM b)   -- EXISTS subquery
**     x IN (4,5,11)              -- IN operator with list on right-hand side
**     x IN (SELECT a FROM b)     -- IN operator with subquery on the right
**
** The pExpr parameter describes the expression that contains the IN
** operator or subquery.
*/
#ifndef SQLITE_OMIT_SUBQUERY
void sqlite3CodeSubselect(Parse *pParse, Expr *pExpr){
  int testAddr = 0;                       /* One-time test address */
  Vdbe *v = sqlite3GetVdbe(pParse);
  if( v==0 ) return;


  /* This code must be run in its entirety every time it is encountered
  ** if any of the following is true:
  **
  **    *  The right-hand side is a correlated subquery
  **    *  The right-hand side is an expression list containing variables
  **    *  We are inside a trigger
  **
  ** If all of the above are false, then we can run this code just once
  ** save the results, and reuse the same result on subsequent invocations.
  */
  if( !ExprHasAnyProperty(pExpr, EP_VarSelect) && !pParse->trigStack ){
    int mem = ++pParse->nMem;
    sqlite3VdbeAddOp1(v, OP_If, mem);
    testAddr = sqlite3VdbeAddOp2(v, OP_Integer, 1, mem);
    assert( testAddr>0 || pParse->db->mallocFailed );
  }

  switch( pExpr->op ){
    case TK_IN: {
      char affinity;
      KeyInfo keyInfo;
      int addr;        /* Address of OP_OpenEphemeral instruction */

      affinity = sqlite3ExprAffinity(pExpr->pLeft);

      /* Whether this is an 'x IN(SELECT...)' or an 'x IN(<exprlist>)'
      ** expression it is handled the same way. A virtual table is 
      ** filled with single-field index keys representing the results
      ** from the SELECT or the <exprlist>.
      **
      ** If the 'x' expression is a column value, or the SELECT...
      ** statement returns a column value, then the affinity of that
      ** column is used to build the index keys. If both 'x' and the
      ** SELECT... statement are columns, then numeric affinity is used
      ** if either column has NUMERIC or INTEGER affinity. If neither
      ** 'x' nor the SELECT... statement are columns, then numeric affinity
      ** is used.
      */
      pExpr->iTable = pParse->nTab++;
      addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pExpr->iTable, 1);
      memset(&keyInfo, 0, sizeof(keyInfo));
      keyInfo.nField = 1;

      if( pExpr->pSelect ){
        /* Case 1:     expr IN (SELECT ...)
        **
        ** Generate code to write the results of the select into the temporary
        ** table allocated and opened above.
        */
        SelectDest dest;
        ExprList *pEList;

        sqlite3SelectDestInit(&dest, SRT_Set, pExpr->iTable);
        dest.affinity = (int)affinity;
        assert( (pExpr->iTable&0x0000FFFF)==pExpr->iTable );
        if( sqlite3Select(pParse, pExpr->pSelect, &dest, 0, 0, 0, 0) ){
          return;
        }
        pEList = pExpr->pSelect->pEList;
        if( pEList && pEList->nExpr>0 ){ 
          keyInfo.aColl[0] = sqlite3BinaryCompareCollSeq(pParse, pExpr->pLeft,
              pEList->a[0].pExpr);
        }
      }else if( pExpr->pList ){
        /* Case 2:     expr IN (exprlist)
        **
        ** For each expression, build an index key from the evaluation and
        ** store it in the temporary table. If <expr> is a column, then use
        ** that columns affinity when building index keys. If <expr> is not
        ** a column, use numeric affinity.
        */
        int i;
        ExprList *pList = pExpr->pList;
        struct ExprList_item *pItem;
        int r1, r2;

        if( !affinity ){
          affinity = SQLITE_AFF_NONE;
        }
        keyInfo.aColl[0] = pExpr->pLeft->pColl;

        /* Loop through each expression in <exprlist>. */
        r1 = sqlite3GetTempReg(pParse);
        r2 = sqlite3GetTempReg(pParse);
        for(i=pList->nExpr, pItem=pList->a; i>0; i--, pItem++){
          Expr *pE2 = pItem->pExpr;

          /* If the expression is not constant then we will need to
          ** disable the test that was generated above that makes sure
          ** this code only executes once.  Because for a non-constant
          ** expression we need to rerun this code each time.
          */
          if( testAddr && !sqlite3ExprIsConstant(pE2) ){
            sqlite3VdbeChangeToNoop(v, testAddr-1, 2);
            testAddr = 0;
          }

          /* Evaluate the expression and insert it into the temp table */
          pParse->disableColCache++;
          sqlite3ExprCode(pParse, pE2, r1);
          assert( pParse->disableColCache>0 );
          pParse->disableColCache--;
          sqlite3VdbeAddOp4(v, OP_MakeRecord, r1, 1, r2, &affinity, 1);
          sqlite3ExprCacheAffinityChange(pParse, r1, 1);
          sqlite3VdbeAddOp2(v, OP_IdxInsert, pExpr->iTable, r2);
        }
        sqlite3ReleaseTempReg(pParse, r1);
        sqlite3ReleaseTempReg(pParse, r2);
      }
      sqlite3VdbeChangeP4(v, addr, (void *)&keyInfo, P4_KEYINFO);
      break;
    }

    case TK_EXISTS:
    case TK_SELECT: {
      /* This has to be a scalar SELECT.  Generate code to put the
      ** value of this select in a memory cell and record the number
      ** of the memory cell in iColumn.
      */
      static const Token one = { (u8*)"1", 0, 1 };
      Select *pSel;
      SelectDest dest;

      pSel = pExpr->pSelect;
      sqlite3SelectDestInit(&dest, 0, ++pParse->nMem);
      if( pExpr->op==TK_SELECT ){
        dest.eDest = SRT_Mem;
        sqlite3VdbeAddOp2(v, OP_Null, 0, dest.iParm);
        VdbeComment((v, "Init subquery result"));
      }else{
        dest.eDest = SRT_Exists;
        sqlite3VdbeAddOp2(v, OP_Integer, 0, dest.iParm);
        VdbeComment((v, "Init EXISTS result"));
      }
      sqlite3ExprDelete(pSel->pLimit);
      pSel->pLimit = sqlite3PExpr(pParse, TK_INTEGER, 0, 0, &one);
      if( sqlite3Select(pParse, pSel, &dest, 0, 0, 0, 0) ){
        return;
      }
      pExpr->iColumn = dest.iParm;
      break;
    }
  }

  if( testAddr ){
    sqlite3VdbeJumpHere(v, testAddr-1);
  }

  return;
}
#endif /* SQLITE_OMIT_SUBQUERY */

/*
** Duplicate an 8-byte value
*/
static char *dup8bytes(Vdbe *v, const char *in){
  char *out = sqlite3DbMallocRaw(sqlite3VdbeDb(v), 8);
  if( out ){
    memcpy(out, in, 8);
  }
  return out;
}

/*
** Generate an instruction that will put the floating point
** value described by z[0..n-1] into register iMem.
**
** The z[] string will probably not be zero-terminated.  But the 
** z[n] character is guaranteed to be something that does not look
** like the continuation of the number.
*/
static void codeReal(Vdbe *v, const char *z, int n, int negateFlag, int iMem){
  assert( z || v==0 || sqlite3VdbeDb(v)->mallocFailed );
  if( z ){
    double value;
    char *zV;
    assert( !isdigit(z[n]) );
    sqlite3AtoF(z, &value);
    if( negateFlag ) value = -value;
    zV = dup8bytes(v, (char*)&value);
    sqlite3VdbeAddOp4(v, OP_Real, 0, iMem, 0, zV, P4_REAL);
  }
}


/*
** Generate an instruction that will put the integer describe by
** text z[0..n-1] into register iMem.
**
** The z[] string will probably not be zero-terminated.  But the 
** z[n] character is guaranteed to be something that does not look
** like the continuation of the number.
*/
static void codeInteger(Vdbe *v, const char *z, int n, int negFlag, int iMem){
  assert( z || v==0 || sqlite3VdbeDb(v)->mallocFailed );
  if( z ){
    int i;
    assert( !isdigit(z[n]) );
    if( sqlite3GetInt32(z, &i) ){
      if( negFlag ) i = -i;
      sqlite3VdbeAddOp2(v, OP_Integer, i, iMem);
    }else if( sqlite3FitsIn64Bits(z, negFlag) ){
      i64 value;
      char *zV;
      sqlite3Atoi64(z, &value);
      if( negFlag ) value = -value;
      zV = dup8bytes(v, (char*)&value);
      sqlite3VdbeAddOp4(v, OP_Int64, 0, iMem, 0, zV, P4_INT64);
    }else{
      codeReal(v, z, n, negFlag, iMem);
    }
  }
}


/*
** Generate code that will extract the iColumn-th column from
** table pTab and store the column value in a register.  An effort
** is made to store the column value in register iReg, but this is
** not guaranteed.  The location of the column value is returned.
**
** There must be an open cursor to pTab in iTable when this routine
** is called.  If iColumn<0 then code is generated that extracts the rowid.
**
** This routine might attempt to reuse the value of the column that
** has already been loaded into a register.  The value will always
** be used if it has not undergone any affinity changes.  But if
** an affinity change has occurred, then the cached value will only be
** used if allowAffChng is true.
*/
int sqlite3ExprCodeGetColumn(
  Parse *pParse,   /* Parsing and code generating context */
  Table *pTab,     /* Description of the table we are reading from */
  int iColumn,     /* Index of the table column */
  int iTable,      /* The cursor pointing to the table */
  int iReg,        /* Store results here */
  int allowAffChng /* True if prior affinity changes are OK */
){
  Vdbe *v = pParse->pVdbe;
  int i;
  struct yColCache *p;

  for(i=0, p=pParse->aColCache; i<pParse->nColCache; i++, p++){
    if( p->iTable==iTable && p->iColumn==iColumn
           && (!p->affChange || allowAffChng) ){
#if 0
      sqlite3VdbeAddOp0(v, OP_Noop);
      VdbeComment((v, "OPT: tab%d.col%d -> r%d", iTable, iColumn, p->iReg));
#endif
      return p->iReg;
    }
  }  
  assert( v!=0 );
  if( iColumn<0 ){
    int op = (pTab && IsVirtual(pTab)) ? OP_VRowid : OP_Rowid;
    sqlite3VdbeAddOp2(v, op, iTable, iReg);
  }else if( pTab==0 ){
    sqlite3VdbeAddOp3(v, OP_Column, iTable, iColumn, iReg);
  }else{
    int op = IsVirtual(pTab) ? OP_VColumn : OP_Column;
    sqlite3VdbeAddOp3(v, op, iTable, iColumn, iReg);
    sqlite3ColumnDefault(v, pTab, iColumn);
#ifndef SQLITE_OMIT_FLOATING_POINT
    if( pTab->aCol[iColumn].affinity==SQLITE_AFF_REAL ){
      sqlite3VdbeAddOp1(v, OP_RealAffinity, iReg);
    }
#endif
  }
  if( pParse->disableColCache==0 ){
    i = pParse->iColCache;
    p = &pParse->aColCache[i];
    p->iTable = iTable;
    p->iColumn = iColumn;
    p->iReg = iReg;
    p->affChange = 0;
    i++;
    if( i>=ArraySize(pParse->aColCache) ) i = 0;
    if( i>pParse->nColCache ) pParse->nColCache = i;
    pParse->iColCache = i;
  }
  return iReg;
}

/*
** Clear all column cache entries associated with the vdbe
** cursor with curs