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Overview
Comment:Avoid allocating large objects on the stack in the incremental BLOB I/O interface. (CVS 6703)
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SHA1: ea7dfde700fb57ed0ecb5000a55abbf45aa1e09d
User & Date: drh 2009-06-01 19:53:31
Context
2009-06-02
15:21
Add the vdbe-compress.tcl script which automatically refactors the sqlite3VdbeExec() routine to use less stack space. Use this script when constructing the amalgamation. (CVS 6704) check-in: 7f433918 user: drh tags: trunk
2009-06-01
19:53
Avoid allocating large objects on the stack in the incremental BLOB I/O interface. (CVS 6703) check-in: ea7dfde7 user: drh tags: trunk
18:18
Malloc for space to hold the Parse object in sqlite3_prepare() and friends. Or, if compiled with SQLITE_USE_ALLOCA, obtain space for the object from alloca(). (CVS 6702) check-in: c7c0c58e user: drh tags: trunk
Changes
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Changes to src/vdbeblob.c.

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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains code used to implement incremental BLOB I/O.
**
** $Id: vdbeblob.c,v 1.32 2009/05/09 15:17:47 drh Exp $
*/

#include "sqliteInt.h"
#include "vdbeInt.h"

#ifndef SQLITE_OMIT_INCRBLOB

................................................................................
    {OP_ResultRow, 1, 0, 0},       /* 7  */
    {OP_Close, 0, 0, 0},           /* 8  */
    {OP_Halt, 0, 0, 0},            /* 9 */
  };

  Vdbe *v = 0;
  int rc = SQLITE_OK;
  char zErr[128];



  *ppBlob = 0;
  zErr[0] = 0;
  sqlite3_mutex_enter(db->mutex);
  do {
    Parse sParse;
    Table *pTab;




    memset(&sParse, 0, sizeof(Parse));
    sParse.db = db;

    if( sqlite3SafetyOn(db) ){


      sqlite3_mutex_leave(db->mutex);
      return SQLITE_MISUSE;
    }

    sqlite3BtreeEnterAll(db);
    pTab = sqlite3LocateTable(&sParse, 0, zTable, zDb);
    if( pTab && IsVirtual(pTab) ){
      pTab = 0;
      sqlite3ErrorMsg(&sParse, "cannot open virtual table: %s", zTable);
    }
#ifndef SQLITE_OMIT_VIEW
    if( pTab && pTab->pSelect ){
      pTab = 0;
      sqlite3ErrorMsg(&sParse, "cannot open view: %s", zTable);
    }
#endif
    if( !pTab ){
      if( sParse.zErrMsg ){
        sqlite3_snprintf(sizeof(zErr), zErr, "%s", sParse.zErrMsg);


      }
      sqlite3DbFree(db, sParse.zErrMsg);
      rc = SQLITE_ERROR;
      (void)sqlite3SafetyOff(db);
      sqlite3BtreeLeaveAll(db);
      goto blob_open_out;
    }

    /* Now search pTab for the exact column. */
    for(iCol=0; iCol < pTab->nCol; iCol++) {
      if( sqlite3StrICmp(pTab->aCol[iCol].zName, zColumn)==0 ){
        break;
      }
    }
    if( iCol==pTab->nCol ){

      sqlite3_snprintf(sizeof(zErr), zErr, "no such column: \"%s\"", zColumn);
      rc = SQLITE_ERROR;
      (void)sqlite3SafetyOff(db);
      sqlite3BtreeLeaveAll(db);
      goto blob_open_out;
    }

    /* If the value is being opened for writing, check that the
................................................................................
    */
    if( flags ){
      Index *pIdx;
      for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
        int j;
        for(j=0; j<pIdx->nColumn; j++){
          if( pIdx->aiColumn[j]==iCol ){
            sqlite3_snprintf(sizeof(zErr), zErr,

                             "cannot open indexed column for writing");
            rc = SQLITE_ERROR;
            (void)sqlite3SafetyOff(db);
            sqlite3BtreeLeaveAll(db);
            goto blob_open_out;
          }
        }
................................................................................
    }

    sqlite3_bind_int64((sqlite3_stmt *)v, 1, iRow);
    rc = sqlite3_step((sqlite3_stmt *)v);
    if( rc!=SQLITE_ROW ){
      nAttempt++;
      rc = sqlite3_finalize((sqlite3_stmt *)v);

      sqlite3_snprintf(sizeof(zErr), zErr, sqlite3_errmsg(db));
      v = 0;
    }
  } while( nAttempt<5 && rc==SQLITE_SCHEMA );

  if( rc==SQLITE_ROW ){
    /* The row-record has been opened successfully. Check that the
    ** column in question contains text or a blob. If it contains
    ** text, it is up to the caller to get the encoding right.
    */
    Incrblob *pBlob;
    u32 type = v->apCsr[0]->aType[iCol];

    if( type<12 ){

      sqlite3_snprintf(sizeof(zErr), zErr, "cannot open value of type %s",
          type==0?"null": type==7?"real": "integer"
      );
      rc = SQLITE_ERROR;
      goto blob_open_out;
    }
    pBlob = (Incrblob *)sqlite3DbMallocZero(db, sizeof(Incrblob));
    if( db->mallocFailed ){
................................................................................
    pBlob->pStmt = (sqlite3_stmt *)v;
    pBlob->iOffset = v->apCsr[0]->aOffset[iCol];
    pBlob->nByte = sqlite3VdbeSerialTypeLen(type);
    pBlob->db = db;
    *ppBlob = (sqlite3_blob *)pBlob;
    rc = SQLITE_OK;
  }else if( rc==SQLITE_OK ){

    sqlite3_snprintf(sizeof(zErr), zErr, "no such rowid: %lld", iRow);
    rc = SQLITE_ERROR;
  }

blob_open_out:
  zErr[sizeof(zErr)-1] = '\0';
  if( v && (rc!=SQLITE_OK || db->mallocFailed) ){
    sqlite3VdbeFinalize(v);
  }
  sqlite3Error(db, rc, (rc==SQLITE_OK?0:zErr));


  rc = sqlite3ApiExit(db, rc);
  sqlite3_mutex_leave(db->mutex);
  return rc;
}

/*
** Close a blob handle that was previously created using







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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains code used to implement incremental BLOB I/O.
**
** $Id: vdbeblob.c,v 1.33 2009/06/01 19:53:31 drh Exp $
*/

#include "sqliteInt.h"
#include "vdbeInt.h"

#ifndef SQLITE_OMIT_INCRBLOB

................................................................................
    {OP_ResultRow, 1, 0, 0},       /* 7  */
    {OP_Close, 0, 0, 0},           /* 8  */
    {OP_Halt, 0, 0, 0},            /* 9 */
  };

  Vdbe *v = 0;
  int rc = SQLITE_OK;
  char *zErr = 0;
  Table *pTab;
  Parse *pParse;

  *ppBlob = 0;

  sqlite3_mutex_enter(db->mutex);

  pParse = sqlite3StackAllocRaw(db, sizeof(*pParse));
  if( pParse==0 ){
    rc = SQLITE_NOMEM;
    goto blob_open_out;
  }
  do {
    memset(pParse, 0, sizeof(Parse));
    pParse->db = db;

    if( sqlite3SafetyOn(db) ){
      sqlite3DbFree(db, zErr);
      sqlite3StackFree(db, pParse);
      sqlite3_mutex_leave(db->mutex);
      return SQLITE_MISUSE;
    }

    sqlite3BtreeEnterAll(db);
    pTab = sqlite3LocateTable(pParse, 0, zTable, zDb);
    if( pTab && IsVirtual(pTab) ){
      pTab = 0;
      sqlite3ErrorMsg(pParse, "cannot open virtual table: %s", zTable);
    }
#ifndef SQLITE_OMIT_VIEW
    if( pTab && pTab->pSelect ){
      pTab = 0;
      sqlite3ErrorMsg(pParse, "cannot open view: %s", zTable);
    }
#endif
    if( !pTab ){
      if( pParse->zErrMsg ){
        sqlite3DbFree(db, zErr);
        zErr = pParse->zErrMsg;
        pParse->zErrMsg = 0;
      }

      rc = SQLITE_ERROR;
      (void)sqlite3SafetyOff(db);
      sqlite3BtreeLeaveAll(db);
      goto blob_open_out;
    }

    /* Now search pTab for the exact column. */
    for(iCol=0; iCol < pTab->nCol; iCol++) {
      if( sqlite3StrICmp(pTab->aCol[iCol].zName, zColumn)==0 ){
        break;
      }
    }
    if( iCol==pTab->nCol ){
      sqlite3DbFree(db, zErr);
      zErr = sqlite3MPrintf(db, "no such column: \"%s\"", zColumn);
      rc = SQLITE_ERROR;
      (void)sqlite3SafetyOff(db);
      sqlite3BtreeLeaveAll(db);
      goto blob_open_out;
    }

    /* If the value is being opened for writing, check that the
................................................................................
    */
    if( flags ){
      Index *pIdx;
      for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
        int j;
        for(j=0; j<pIdx->nColumn; j++){
          if( pIdx->aiColumn[j]==iCol ){
            sqlite3DbFree(db, zErr);
            zErr = sqlite3MPrintf(db,
                             "cannot open indexed column for writing");
            rc = SQLITE_ERROR;
            (void)sqlite3SafetyOff(db);
            sqlite3BtreeLeaveAll(db);
            goto blob_open_out;
          }
        }
................................................................................
    }

    sqlite3_bind_int64((sqlite3_stmt *)v, 1, iRow);
    rc = sqlite3_step((sqlite3_stmt *)v);
    if( rc!=SQLITE_ROW ){
      nAttempt++;
      rc = sqlite3_finalize((sqlite3_stmt *)v);
      sqlite3DbFree(db, zErr);
      zErr = sqlite3MPrintf(db, sqlite3_errmsg(db));
      v = 0;
    }
  } while( nAttempt<5 && rc==SQLITE_SCHEMA );

  if( rc==SQLITE_ROW ){
    /* The row-record has been opened successfully. Check that the
    ** column in question contains text or a blob. If it contains
    ** text, it is up to the caller to get the encoding right.
    */
    Incrblob *pBlob;
    u32 type = v->apCsr[0]->aType[iCol];

    if( type<12 ){
      sqlite3DbFree(db, zErr);
      zErr = sqlite3MPrintf(db, "cannot open value of type %s",
          type==0?"null": type==7?"real": "integer"
      );
      rc = SQLITE_ERROR;
      goto blob_open_out;
    }
    pBlob = (Incrblob *)sqlite3DbMallocZero(db, sizeof(Incrblob));
    if( db->mallocFailed ){
................................................................................
    pBlob->pStmt = (sqlite3_stmt *)v;
    pBlob->iOffset = v->apCsr[0]->aOffset[iCol];
    pBlob->nByte = sqlite3VdbeSerialTypeLen(type);
    pBlob->db = db;
    *ppBlob = (sqlite3_blob *)pBlob;
    rc = SQLITE_OK;
  }else if( rc==SQLITE_OK ){
    sqlite3DbFree(db, zErr);
    zErr = sqlite3MPrintf(db, "no such rowid: %lld", iRow);
    rc = SQLITE_ERROR;
  }

blob_open_out:

  if( v && (rc!=SQLITE_OK || db->mallocFailed) ){
    sqlite3VdbeFinalize(v);
  }
  sqlite3Error(db, rc, zErr);
  sqlite3DbFree(db, zErr);
  sqlite3StackFree(db, pParse);
  rc = sqlite3ApiExit(db, rc);
  sqlite3_mutex_leave(db->mutex);
  return rc;
}

/*
** Close a blob handle that was previously created using