SQLite

  }else{
    sqlite3Fts5BufferAppendPrintf(pRc, pBuf, "(idx=%d segid=%d h=%d pgno=%d)",
        iIdx, iSegid, iHeight, iPgno
    );
  }
}

static void fts5DebugStructure(
  int *pRc,                       /* IN/OUT: error code */
  Fts5Buffer *pBuf,
  Fts5Structure *p
){
  int iLvl, iSeg;                 /* Iterate through levels, segments */

  for(iLvl=0; iLvl<p->nLevel; iLvl++){
    Fts5StructureLevel *pLvl = &p->aLevel[iLvl];
    sqlite3Fts5BufferAppendPrintf(pRc, pBuf, 
        " {lvl=%d nMerge=%d", iLvl, pLvl->nMerge
    );
    for(iSeg=0; iSeg<pLvl->nSeg; iSeg++){
      Fts5StructureSegment *pSeg = &pLvl->aSeg[iSeg];
      sqlite3Fts5BufferAppendPrintf(pRc, pBuf, 
          " {id=%d h=%d leaves=%d..%d}", pSeg->iSegid, pSeg->nHeight, 
          pSeg->pgnoFirst, pSeg->pgnoLast
      );
    }
    sqlite3Fts5BufferAppendPrintf(pRc, pBuf, "}");
  }
}



static void fts5PutU16(u8 *aOut, u16 iVal){
  aOut[0] = (iVal>>8);
  aOut[1] = (iVal&0xFF);
}

static u16 fts5GetU16(const u8 *aIn){

      fts5BufferAppendVarint(&p->rc, &buf, pLvl->aSeg[iSeg].pgnoLast);
    }
  }

  fts5DataWrite(p, FTS5_STRUCTURE_ROWID(iIdx), buf.p, buf.n);
  fts5BufferFree(&buf);
}

#if 0
static void fts5PrintStructure(const char *zCaption, Fts5Structure *pStruct){
  int rc = SQLITE_OK;
  Fts5Buffer buf;
  memset(&buf, 0, sizeof(buf));
  fts5DebugStructure(&rc, &buf, pStruct);
  fprintf(stdout, "%s: %s\n", zCaption, buf.p);
  fflush(stdout);
  fts5BufferFree(&buf);
}
#else
# define fts5PrintStructure(x,y)
#endif

/*
** Return a copy of index structure pStruct. Except, promote as many segments
** as possible to level iPromote. If an OOM occurs, NULL is returned.
*/
static void fts5StructurePromoteTo(
  Fts5Index *p,
  int iPromote,
  int szPromote,
  Fts5Structure *pStruct
){
  Fts5Structure *pNew;
  u8 *pSpace;
  int nSeg = fts5StructureCountSegments(pStruct);
  int nLvl = pStruct->nLevel;
  int nByte = (
      sizeof(Fts5Structure) + 
      sizeof(Fts5StructureLevel) * (nLvl+1) +
      sizeof(Fts5StructureSegment) * (nSeg+nLvl+1)
  );
  int iTst;

  pNew = fts5IdxMalloc(p, nByte);
  if( !pNew ) return;
  pNew->nWriteCounter = pStruct->nWriteCounter;
  pNew->nLevel = pStruct->nLevel;
  pSpace = (u8*)&pNew->aLevel[nLvl+1];

  for(iTst=0; iTst<nLvl; iTst++){
    int nCopy;
    Fts5StructureLevel *pLvlOut = &pNew->aLevel[iTst];
    pLvlOut->aSeg = (Fts5StructureSegment*)pSpace;

    if( iTst==iPromote ){
      int il, is;
      int nSegCopy = 0;

      /* Figure out the number of segments that will be promoted. */
      for(il=iTst+1; il<pStruct->nLevel; il++){
        Fts5StructureLevel *pLvl = &pStruct->aLevel[il];
        if( pLvl->nMerge ) break;
        for(is=pLvl->nSeg-1; is>=0; is--){
          Fts5StructureSegment *pSeg = &pLvl->aSeg[is];
          int sz = pSeg->pgnoLast - pSeg->pgnoFirst + 1;
          if( sz>szPromote ){
            il = pStruct->nLevel;
            break;
          }
          nSegCopy++;
        }
      }
      assert( nSegCopy>0 );
      pSpace += (nSegCopy * sizeof(Fts5StructureSegment));
      pLvlOut->nSeg = nSegCopy;

      for(il=iTst+1; il<pStruct->nLevel && nSegCopy>0; il++){
        Fts5StructureLevel *pLvl = &pStruct->aLevel[il];
        for(is=pLvl->nSeg-1; is>=0 && nSegCopy>0; is--){
          Fts5StructureSegment *pSeg = &pLvl->aSeg[is];
          nSegCopy--;
          memcpy(&pLvlOut->aSeg[nSegCopy], pSeg, sizeof(Fts5StructureSegment));
          pLvl->nSeg--;
        }
      }
      assert( nSegCopy==0 );
    }

    nCopy = pStruct->aLevel[iTst].nSeg * sizeof(Fts5StructureSegment);
    if( nCopy ) memcpy(pSpace, pStruct->aLevel[iTst].aSeg, nCopy);
    pSpace += (nCopy + sizeof(Fts5StructureSegment));
    pLvlOut->nSeg += pStruct->aLevel[iTst].nSeg;
  }

  fts5PrintStructure("NEW", pNew);
  memcpy(pStruct, pNew, nByte);
  for(iTst=0; iTst<pNew->nLevel; iTst++){
    int iOff = pNew->aLevel[iTst].aSeg - (Fts5StructureSegment*)pNew;
    pStruct->aLevel[iTst].aSeg = &((Fts5StructureSegment*)pStruct)[iOff];
  }
  sqlite3_free(pNew);
}

/*
** A new segment has just been written to level iLvl of index structure
** pStruct. This function determines if any segments should be promoted
** as a result. Segments are promoted in two scenarios:
**
**   a) If the segment just written is smaller than one or more segments
**      within the previous populated level, it is promoted to the previous
**      populated level.
**
**   b) If the segment just written is larger than the newest segment on
**      the next populated level, then that segment, and any other adjacent
**      segments that are also smaller than the one just written, are 
**      promoted. 
**
** If one or more segments are promoted, the structure object is updated
** to reflect this.
*/
static void fts5StructurePromote(
  Fts5Index *p,                   /* FTS5 backend object */
  int iLvl,                       /* Index level just updated */
  Fts5Structure *pStruct          /* Index structure */
){
  if( p->rc==SQLITE_OK ){
    int iTst;
    int iPromote = -1;
    int szPromote;                /* Promote anything this size or smaller */
    Fts5StructureSegment *pSeg;   /* Segment just written */
    Fts5StructureLevel *pTst;
    int szSeg;                    /* Size of segment just written */


    pSeg = &pStruct->aLevel[iLvl].aSeg[pStruct->aLevel[iLvl].nSeg-1];
    szSeg = (1 + pSeg->pgnoLast - pSeg->pgnoFirst);

    /* Check for condition (a) */
    for(iTst=iLvl-1; iTst>=0 && pStruct->aLevel[iTst].nSeg==0; iTst--);
    pTst = &pStruct->aLevel[iTst];
    if( iTst>=0 && pTst->nMerge==0 ){
      int i;
      int szMax = 0;
      for(i=0; i<pTst->nSeg; i++){
        int sz = pTst->aSeg[i].pgnoLast - pTst->aSeg[i].pgnoFirst + 1;
        if( sz>szMax ) szMax = sz;
      }
      if( szMax>=szSeg ){
        /* Condition (a) is true. Promote the newest segment on level 
        ** iLvl to level iTst.  */
        iPromote = iTst;
        szPromote = szMax;
      }
    }

    /* Check for condition (b) */
    if( iPromote<0 ){
      Fts5StructureLevel *pTst;
      for(iTst=iLvl+1; iTst<pStruct->nLevel; iTst++){
        pTst = &pStruct->aLevel[iTst];
        if( pTst->nSeg ) break;
      }
      if( iTst<pStruct->nLevel && pTst->nMerge==0 ){
        Fts5StructureSegment *pSeg2 = &pTst->aSeg[pTst->nSeg-1];
        int sz = pSeg2->pgnoLast - pSeg2->pgnoFirst + 1;
        if( sz<=szSeg ){
          iPromote = iLvl;
          szPromote = szSeg;
        }
      }
    }

    /* If iPromote is greater than or equal to zero at this point, then it
    ** is the level number of a level to which segments that consist of
    ** szPromote or fewer pages should be promoted. */ 
    if( iPromote>=0 ){
      fts5PrintStructure("BEFORE", pStruct);
      fts5StructurePromoteTo(p, iPromote, szPromote, pStruct);
      fts5PrintStructure("AFTER", pStruct);
    }
  }
}


/*
** If the pIter->iOff offset currently points to an entry indicating one
** or more term-less nodes, advance past it and set pIter->nEmpty to
** the number of empty child nodes.
*/

    for(iLvl=0; nBest==0 && iLvl<pStruct->nLevel; iLvl++){
      assert( pStruct->aLevel[iLvl].nSeg==0 );
    }
#endif

    if( nBest<p->nMinMerge && pStruct->aLevel[iBestLvl].nMerge==0 ) break;
    fts5IndexMergeLevel(p, iIdx, pStruct, iBestLvl, &nRem);
    fts5StructurePromote(p, iBestLvl+1, pStruct);
    assert( nRem==0 || p->rc==SQLITE_OK );
  }
}

/*
** Flush the contents of in-memory hash table iHash to a new level-0 
** segment on disk. Also update the corresponding structure record.

*/
static void fts5DecodeStructure(
  int *pRc,                       /* IN/OUT: error code */
  Fts5Buffer *pBuf,
  const u8 *pBlob, int nBlob
){
  int rc;                         /* Return code */

  Fts5Structure *p = 0;           /* Decoded structure object */

  rc = fts5StructureDecode(pBlob, nBlob, &p);
  if( rc!=SQLITE_OK ){
    *pRc = rc;
    return;
  }















  fts5DebugStructure(pRc, pBuf, p);
  fts5StructureRelease(p);
}

/*
** Buffer (a/n) is assumed to contain a list of serialized varints. Read
** each varint and append its string representation to buffer pBuf. Return
** after either the input buffer is exhausted or a 0 value is read.

  if {$iTest > 1000} { execsql { DELETE FROM t1 WHERE rowid=($iTest-1000) } }
  set new [doc]
  execsql { INSERT INTO t1 VALUES($new) }
  if {$iTest==10000} { set sz1 [db one {SELECT count(*) FROM t1_data}] }
  if {0==($iTest % 1000)} {
    set sz [db one {SELECT count(*) FROM t1_data}]
    set s [structure]
    do_execsql_test 1.$iTest.$sz.{$s} {
      INSERT INTO t1(t1) VALUES('integrity-check') 
    }
  }
}



do_execsql_test 2.0 { INSERT INTO t1(t1) VALUES('integrity-check') }



finish_test