vdbe.c

一个小型的嵌入式数据库

  ** The complete record text is always available for pseudo-tables and
  ** when we are decoded a record from the stack.  If the record is stored
  ** in a cursor, the complete record text might be available in the 
  ** pC->aRow cache.  Or it might not be.  If the data is unavailable,
  ** zRec is set to NULL.
  **
  ** We also compute the number of columns in the record.  For cursors,
  ** the number of columns is stored in the Cursor.nField element.  For
  ** records on the stack, the next entry down on the stack is an integer
  ** which is the number of records.
  */
  assert( p1<0 || p->apCsr[p1]!=0 );
  if( p1<0 ){
    /* Take the record off of the stack */
    Mem *pRec = &pTos[p1];
    Mem *pCnt = &pRec[-1];
    assert( pRec>=p->aStack );
    assert( pRec->flags & MEM_Blob );
    payloadSize = pRec->n;
    zRec = pRec->z;
    assert( pCnt>=p->aStack );
    assert( pCnt->flags & MEM_Int );
    nField = pCnt->i;
    pCrsr = 0;
  }else if( (pC = p->apCsr[p1])->pCursor!=0 ){
    /* The record is stored in a B-Tree */
    rc = sqlite3VdbeCursorMoveto(pC);
    if( rc ) goto abort_due_to_error;
    zRec = 0;
    pCrsr = pC->pCursor;
    if( pC->nullRow ){
      payloadSize = 0;
    }else if( pC->cacheValid ){
      payloadSize = pC->payloadSize;
      zRec = pC->aRow;
    }else if( pC->keyAsData ){
      i64 payloadSize64;
      sqlite3BtreeKeySize(pCrsr, &payloadSize64);
      payloadSize = payloadSize64;
    }else{
      sqlite3BtreeDataSize(pCrsr, &payloadSize);
    }
    nField = pC->nField;
#ifndef SQLITE_OMIT_TRIGGER
  }else if( pC->pseudoTable ){
    /* The record is the sole entry of a pseudo-table */
    payloadSize = pC->nData;
    zRec = pC->pData;
    pC->cacheValid = 0;
    assert( payloadSize==0 || zRec!=0 );
    nField = pC->nField;
    pCrsr = 0;
#endif
  }else{
    zRec = 0;
    payloadSize = 0;
    pCrsr = 0;
    nField = 0;
  }

  /* If payloadSize is 0, then just push a NULL onto the stack. */
  if( payloadSize==0 ){
    pTos->flags = MEM_Null;
    break;
  }

  assert( p2<nField );

  /* Read and parse the table header.  Store the results of the parse
  ** into the record header cache fields of the cursor.
  */
  if( pC && pC->cacheValid ){
    aType = pC->aType;
    aOffset = pC->aOffset;
  }else{
    int avail;    /* Number of bytes of available data */
    if( pC && pC->aType ){
      aType = pC->aType;
    }else{
      aType = sqliteMallocRaw( 2*nField*sizeof(aType) );
    }
    aOffset = &aType[nField];
    if( aType==0 ){
      goto no_mem;
    }

    /* Figure out how many bytes are in the header */
    if( zRec ){
      zData = zRec;
    }else{
      if( pC->keyAsData ){
        zData = (char*)sqlite3BtreeKeyFetch(pCrsr, &avail);
      }else{
        zData = (char*)sqlite3BtreeDataFetch(pCrsr, &avail);
      }
      /* If KeyFetch()/DataFetch() managed to get the entire payload,
      ** save the payload in the pC->aRow cache.  That will save us from
      ** having to make additional calls to fetch the content portion of
      ** the record.
      */
      if( avail>=payloadSize ){
        zRec = pC->aRow = zData;
      }else{
        pC->aRow = 0;
      }
    }
    idx = sqlite3GetVarint32(zData, &szHdr);


    /* The KeyFetch() or DataFetch() above are fast and will get the entire
    ** record header in most cases.  But they will fail to get the complete
    ** record header if the record header does not fit on a single page
    ** in the B-Tree.  When that happens, use sqlite3VdbeMemFromBtree() to
    ** acquire the complete header text.
    */
    if( !zRec && avail<szHdr ){
      rc = sqlite3VdbeMemFromBtree(pCrsr, 0, szHdr, pC->keyAsData, &sMem);
      if( rc!=SQLITE_OK ){
        goto op_column_out;
      }
      zData = sMem.z;
    }

    /* Scan the header and use it to fill in the aType[] and aOffset[]
    ** arrays.  aType[i] will contain the type integer for the i-th
    ** column and aOffset[i] will contain the offset from the beginning
    ** of the record to the start of the data for the i-th column
    */
    offset = szHdr;
    assert( offset>0 );
    i = 0;
    while( idx<szHdr && i<nField && offset<=payloadSize ){
      aOffset[i] = offset;
      idx += sqlite3GetVarint32(&zData[idx], &aType[i]);
      offset += sqlite3VdbeSerialTypeLen(aType[i]);
      i++;
    }
    Release(&sMem);
    sMem.flags = MEM_Null;

    /* If i is less that nField, then there are less fields in this
    ** record than SetNumColumns indicated there are columns in the
    ** table. Set the offset for any extra columns not present in
    ** the record to 0. This tells code below to push a NULL onto the
    ** stack instead of deserializing a value from the record.
    */
    while( i<nField ){
      aOffset[i++] = 0;
    }

    /* The header should end at the start of data and the data should
    ** end at last byte of the record. If this is not the case then
    ** we are dealing with a malformed record.
    */
    if( idx!=szHdr || offset!=payloadSize ){
      rc = SQLITE_CORRUPT;
      goto op_column_out;
    }

    /* Remember all aType and aColumn information if we have a cursor
    ** to remember it in. */
    if( pC ){
      pC->payloadSize = payloadSize;
      pC->aType = aType;
      pC->aOffset = aOffset;
      pC->cacheValid = 1;
    }
  }

  /* Get the column information. If aOffset[p2] is non-zero, then 
  ** deserialize the value from the record. If aOffset[p2] is zero,
  ** then there are not enough fields in the record to satisfy the
  ** request. The value is NULL in this case.
  */
  if( aOffset[p2] ){
    assert( rc==SQLITE_OK );
    if( zRec ){
      zData = &zRec[aOffset[p2]];
    }else{
      len = sqlite3VdbeSerialTypeLen(aType[p2]);
      rc = sqlite3VdbeMemFromBtree(pCrsr, aOffset[p2], len,pC->keyAsData,&sMem);
      if( rc!=SQLITE_OK ){
        goto op_column_out;
      }
      zData = sMem.z;
    }
    sqlite3VdbeSerialGet(zData, aType[p2], pTos);
    pTos->enc = db->enc;
  }else{
    pTos->flags = MEM_Null;
  }

  /* If we dynamically allocated space to hold the data (in the
  ** sqlite3VdbeMemFromBtree() call above) then transfer control of that
  ** dynamically allocated space over to the pTos structure rather.
  ** This prevents a memory copy.
  */
  if( (sMem.flags & MEM_Dyn)!=0 ){
    assert( pTos->flags & MEM_Ephem );
    assert( pTos->flags & (MEM_Str|MEM_Blob) );
    assert( pTos->z==sMem.z );
    assert( sMem.flags & MEM_Term );
    pTos->flags &= ~MEM_Ephem;
    pTos->flags |= MEM_Dyn|MEM_Term;
  }

  /* pTos->z might be pointing to sMem.zShort[].  Fix that so that we
  ** can abandon sMem */
  rc = sqlite3VdbeMemMakeWriteable(pTos);

op_column_out:
  /* Release the aType[] memory if we are not dealing with cursor */
  if( !pC || !pC->aType ){
    sqliteFree(aType);
  }
  break;
}

/* Opcode: MakeRecord P1 P2 P3
**
** Convert the top abs(P1) entries of the stack into a single entry
** suitable for use as a data record in a database table or as a key
** in an index.  The details of the format are irrelavant as long as
** the OP_Column opcode can decode the record later and as long as the
** sqlite3VdbeRecordCompare function will correctly compare two encoded
** records.  Refer to source code comments for the details of the record
** format.
**
** The original stack entries are popped from the stack if P1>0 but
** remain on the stack if P1<0.
**
** The P2 argument is divided into two 16-bit words before it is processed.
** If the hi-word is non-zero, then an extra integer is read from the stack
** and appended to the record as a varint.  If the low-word of P2 is not
** zero and one or more of the entries are NULL, then jump to the value of
** the low-word of P2.  This feature can be used to skip a uniqueness test
** on indices.
**
** P3 may be a string that is P1 characters long.  The nth character of the
** string indicates the column affinity that should be used for the nth
** field of the index key (i.e. the first character of P3 corresponds to the
** lowest element on the stack).
**
** The mapping from character to affinity is as follows:
**    'n' = NUMERIC.
**    'i' = INTEGER.
**    't' = TEXT.
**    'o' = NONE.
**
** If P3 is NULL then all index fields have the affinity NONE.
*/
case OP_MakeRecord: {
  /* Assuming the record contains N fields, the record format looks
  ** like this:
  **
  ** ------------------------------------------------------------------------
  ** | hdr-size | type 0 | type 1 | ... | type N-1 | data0 | ... | data N-1 | 
  ** ------------------------------------------------------------------------
  **
  ** Data(0) is taken from the lowest element of the stack and data(N-1) is
  ** the top of the stack.
  **
  ** Each type field is a varint representing the serial type of the 
  ** corresponding data element (see sqlite3VdbeSerialType()). The
  ** hdr-size field is also a varint which is the offset from the beginning
  ** of the record to data0.
  */
  unsigned char *zNewRecord;
  unsigned char *zCsr;
  Mem *pRec;
  Mem *pRowid = 0;
  int nData = 0;         /* Number of bytes of data space */
  int nHdr = 0;          /* Number of bytes of header space */
  int nByte = 0;         /* Space required for this record */
  u32 serial_type;       /* Type field */
  int containsNull = 0;  /* True if any of the data fields are NULL */
  char zTemp[NBFS];      /* Space to hold small records */
  Mem *pData0;

  int leaveOnStack;      /* If true, leave the entries on the stack */
  int nField;            /* Number of fields in the record */
  int jumpIfNull;        /* Jump here if non-zero and any entries are NULL. */
  int addRowid;          /* True to append a rowid column at the end */
  char *zAffinity;       /* The affinity string for the record */

  leaveOnStack = ((pOp->p1<0)?1:0);
  nField = pOp->p1 * (leaveOnStack?-1:1);
  jumpIfNull = (pOp->p2 & 0x00FFFFFF);
  addRowid = ((pOp->p2>>24) & 0x0000FFFF)?1:0;
  zAffinity = pOp->p3;

  pData0 = &pTos[1-nField];
  assert( pData0>=p->aStack );
  containsNull = 0;

  /* Loop through the elements that will make up the record to figure
  ** out how much space is required for the new record.
  */
  for(pRec=pData0; pRec<=pTos; pRec++){
    if( zAffinity ){
      applyAffinity(pRec, zAffinity[pRec-pData0], db->enc);
    }
    if( pRec->flags&MEM_Null ){
      containsNull = 1;
    }
    serial_type = sqlite3VdbeSerialType(pRec);
    nData += sqlite3VdbeSerialTypeLen(serial_type);
    nHdr += sqlite3VarintLen(serial_type);
  }

  /* If we have to append a varint rowid to this record, set 'rowid'
  ** to the value of the rowid and increase nByte by the amount of space
  ** required to store it and the 0x00 seperator byte.
  */
  if( addRowid ){
    pRowid = &pTos[0-nField];
    assert( pRowid>=p->aStack );
    Integerify(pRowid);
    serial_type = sqlite3VdbeSerialType(pRowid);
    nData += sqlite3VdbeSerialTypeLen(serial_type);
    nHdr += sqlite3VarintLen(serial_type);
  }

  /* Add the initial header varint and total the size */
  nHdr += sqlite3VarintLen(nHdr);
  nByte = nHdr+nData;

  /* Allocate space for the new record. */
  if( nByte>sizeof(zTemp) ){
    zNewRecord = sqliteMallocRaw(nByte);
    if( !zNewRecord ){
      goto no_mem;
    }
  }else{
    zNewRecord = zTemp;
  }

  /* Write the record */
  zCsr = zNewRecord;
  zCsr += sqlite3PutVarint(zCsr, nHdr);
  for(pRec=pData0; pRec<=pTos; pRec++){
    serial_type = sqlite3VdbeSerialType(pRec);
    zCsr += sqlite3PutVarint(zCsr, serial_type);      /* serial type */
  }
  if( addRowid ){
    zCsr += sqlite3PutVarint(zCsr, sqlite3VdbeSerialType(pRowid));
  }
  for(pRec=pData0; pRec<=pTos; pRec++){
    zCsr += sqlite3VdbeSerialPut(zCsr, pRec);  /* serial data */
  }
  if( addRowid ){
    zCsr += sqlite3VdbeSerialPut(zCsr, pRowid);
  }
  assert( zCsr==(zNewRecord+nByte) );

  /* Pop entries off the stack if required. Push the new record on. */
  if( !leaveOnStack ){
    popStack(&pTos, nField+addRowid);
  }
  pTos++;
  pTos->n = nByte;
  if( nByte<=sizeof(zTemp) ){
    assert( zNewRecord==(unsigned char *)zTemp );
    pTos->z = pTos->zShort;
    memcpy(pTos->zShort, zTemp, nByte);
    pTos->flags = MEM_Blob | MEM_Short;
  }else{
    assert( zNewRecord!=(unsigned char *)zTemp );
    pTos->z = zNewRecord;
    pTos->flags = MEM_Blob | MEM_Dyn;
    pTos->xDel = 0;
  }

  /* If a NULL was encountered and jumpIfNull is non-zero, take the jump. */
  if( jumpIfNull && containsNull ){
    pc = jumpIfNull - 1;
  }
  break;
}

/* Opcode: Statement P1 * *
**
** Begin an individual statement transaction which is part of a larger
** BEGIN..COMMIT transaction.  This is needed so that the statement
** can be rolled back after an error without having to roll back the
** entire transaction.  The statement transaction will automatically
** commit when the VDBE halts.
**
** The statement is begun on the database file with index P1.  The main
** database file has an index of 0 and the file used for temporary tables
** has an index of 1.
*/
case OP_Statement: {
  int i = pOp->p1;
  Btree *pBt;
  if( i>=0 && i<db->nDb && (pBt = db->aDb[i].pBt) && !(db->autoCommit) ){
    assert( sqlite3BtreeIsInTrans(pBt) );
    if( !sqlite3BtreeIsInStmt(pBt) ){
      rc = sqlite3BtreeBeginStmt(pBt);
    }
  }
  break;
}

/* Opcode: AutoCommit P1 P2 *
**
** Set the database auto-commit flag to P1 (1 or 0). If P2 is true, roll
** back any currently active btree transactions. If there are any active
** VMs (apart from this one), then the COMMIT or ROLLBACK statement fails.
**
** This instruction causes the VM to halt.
*/
case OP_AutoCommit: {
  u8 i = pOp->p1;
  u8 rollback = pOp->p2;

  assert( i==1 || i==0 );
  assert( i==1 || rollback==0 );

  assert( db->activeVdbeCnt>0 );  /* At least this one VM is active */

  if( db->activeVdbeCnt>1 && i && !db->autoCommit ){
    /* If this instruction implements a COMMIT or ROLLBACK, other VMs are
    ** still running, and a transaction is active, return an error indicating
    ** that the other VMs must complete first. 
    */
    sqlite3SetString(&p