/* This statement is used to determine which level to read the input from
** when performing an incremental merge. It returns the absolute level number
** of the oldest level in the db that contains at least ? segments. Or,
** if no level in the FTS index contains more than ? segments, the statement
** returns zero rows.  */
/* 28 */ "SELECT level FROM %Q.'%q_segdir' GROUP BY level HAVING count(*)>=?"
         "  ORDER BY (level %% 1024) DESC LIMIT 1",

/* Estimate the upper limit on the number of leaf nodes in a new segment
** created by merging the oldest :2 segments from absolute level :1. See 
** function sqlite3Fts3Incrmerge() for details.  */
/* 29 */ "SELECT 2 * total(1 + leaves_end_block - start_block) "
         "  FROM %Q.'%q_segdir' WHERE level = ? AND idx < ?",

................................................................................
  *pnRem = nRem;
  return rc;
}

/*
** Store an incr-merge hint in the database.
*/
static int fts3IncrmergeHintStore(
  Fts3Table *p,                   /* FTS3 table handle */
  sqlite3_int64 iAbsLevel,        /* Absolute level to read input data from */
  int nMerge                      /* Number of segments to merge */
){
  char aBlob[FTS3_VARINT_MAX * 2];
  int nBlob = 0;
  int rc;
  sqlite3_stmt *pReplace = 0;

  assert( p->bHasStat );
  nBlob += sqlite3Fts3PutVarint(&aBlob[nBlob], iAbsLevel);
  nBlob += sqlite3Fts3PutVarint(&aBlob[nBlob], nMerge);


  rc = fts3SqlStmt(p, SQL_REPLACE_STAT, &pReplace, 0);
  if( rc==SQLITE_OK ){
    sqlite3_bind_int(pReplace, 1, FTS_STAT_INCRMERGEHINT);
    sqlite3_bind_blob(pReplace, 2, aBlob, nBlob, SQLITE_TRANSIENT);
    sqlite3_step(pReplace);
    rc = sqlite3_reset(pReplace);
  }

  return rc;
}

/*
** Load an incr-merge hint from the database.

**
** The incr-merge hint, if one exists, is stored in the rowid==1 row of
** the %_stat table.


*/
static int fts3IncrmergeHintLoad(
  Fts3Table *p,                   /* FTS3 table handle */
  sqlite3_int64 *piAbsLevel,      /* Absolute level to read input data from */
  int *pnMerge                    /* Number of segments to merge */
){
  sqlite3_stmt *pSelect = 0;
  int rc;

  *pnMerge = 0;
  *piAbsLevel = 0;

  rc = fts3SqlStmt(p, SQL_SELECT_STAT, &pSelect, 0);
  if( rc==SQLITE_OK ){

    sqlite3_bind_int(pSelect, 1, FTS_STAT_INCRMERGEHINT);
    if( SQLITE_ROW==sqlite3_step(pSelect) ){
      const char *aHint = sqlite3_column_blob(pSelect, 0);
      int nHint = sqlite3_column_bytes(pSelect, 0);
      if( aHint ){
        int i;
        char aBlob[FTS3_VARINT_MAX * 2];
        memcpy(aBlob, aHint, MAX(sizeof(aBlob), nHint));
        i = sqlite3Fts3GetVarint(aBlob, piAbsLevel);
        sqlite3Fts3GetVarint32(&aBlob[i], pnMerge);
      }
    }

    rc = sqlite3_reset(pSelect);

  }

  return rc;
}
















































/*
** Attempt an incremental merge that writes nMerge leaf blocks.
**
** Incremental merges happen nMin segments at a time. The two
** segments to be merged are the nMin oldest segments (the ones with
** the smallest indexes) in the highest level that contains at least
** nMin segments. Multiple merges might occur in an attempt to write the 
** quota of nMerge leaf blocks.
*/
int sqlite3Fts3Incrmerge(Fts3Table *p, int nMerge, int nMin){
  int rc;                         /* Return code */
  int nRem = nMerge;              /* Number of leaf pages yet to  be written */
  int bUseHint = 1;               /* True if hint has not yet been attempted */
  sqlite3_int64 iHintAbsLevel = 0;/* Hint level */
  int nHintSeg = 0;               /* Hint number of segments */
  int nSeg = 0;                   /* Number of input segments */
  sqlite3_int64 iAbsLevel = 0;    /* Absolute level number to work on */



  assert( nMin>=2 );







  rc = fts3IncrmergeHintLoad(p, &iHintAbsLevel, &nHintSeg);
  if( nHintSeg==0 ) bUseHint = 0;

  while( rc==SQLITE_OK && nRem>0 ){
    Fts3MultiSegReader *pCsr;       /* Cursor used to read input data */
    Fts3SegFilter *pFilter;         /* Filter used with cursor pCsr */
    IncrmergeWriter *pWriter;       /* Writer object */
    const int nAlloc = sizeof(*pCsr) + sizeof(*pFilter) + sizeof(*pWriter);

    if( bUseHint ){
      iAbsLevel = iHintAbsLevel;
      nSeg = nHintSeg;
    }else{
      sqlite3_stmt *pFindLevel = 0; /* SQL used to determine iAbsLevel */


      /* Determine which level to merge segments from. Any level, from any
      ** prefix or language index may be selected. Stack variable iAbsLevel 


      ** is set to the absolute level number of the level to merge from.  */



      rc = fts3SqlStmt(p, SQL_FIND_MERGE_LEVEL, &pFindLevel, 0);
      sqlite3_bind_int(pFindLevel, 1, nMin);
      if( sqlite3_step(pFindLevel)!=SQLITE_ROW ){
        /* There are no levels with nMin or more segments. Or an error has
         ** occurred. Either way, exit early.  */




        rc = sqlite3_reset(pFindLevel);













        iAbsLevel = 0;
        nSeg = 0;
        break;






      }
      iAbsLevel = sqlite3_column_int64(pFindLevel, 0);
      nSeg = nMin;
      sqlite3_reset(pFindLevel);
    }

    /* Allocate space for the cursor, filter and writer objects */
    pWriter = (IncrmergeWriter *)sqlite3_malloc(nAlloc);
    if( !pWriter ) return SQLITE_NOMEM;
    memset(pWriter, 0, nAlloc);
    pFilter = (Fts3SegFilter *)&pWriter[1];
    pCsr = (Fts3MultiSegReader *)&pFilter[1];





    /* Open a cursor to iterate through the contents of the oldest nSeg 
    ** indexes of absolute level iAbsLevel. If this cursor is opened using 
    ** the 'hint' parameters, it is possible that there are less than nSeg
    ** segments available in level iAbsLevel. In this case, no work is
    ** done on iAbsLevel - fall through to the next iteration of the loop 
    ** to start work on some other level.  */

    pFilter->flags = FTS3_SEGMENT_REQUIRE_POS;

    rc = fts3IncrmergeCsr(p, iAbsLevel, nSeg, pCsr);

    if( pCsr->nSegment==nSeg && SQLITE_OK==rc
     && SQLITE_OK ==(rc = sqlite3Fts3SegReaderStart(p, pCsr, pFilter))
     && SQLITE_ROW==(rc = sqlite3Fts3SegReaderStep(p, pCsr))
    ){
      int iIdx = 0;               /* Largest idx in level (iAbsLevel+1) */
      rc = fts3IncrmergeOutputIdx(p, iAbsLevel, &iIdx);
      if( rc==SQLITE_OK ){
        if( bUseHint && iIdx>0 ){
          const char *zKey = pCsr->zTerm;
................................................................................
          if( pWriter->nWork>=nRem && rc==SQLITE_ROW ) rc = SQLITE_OK;
        }while( rc==SQLITE_ROW );

        /* Update or delete the input segments */
        if( rc==SQLITE_OK ){
          nRem -= (1 + pWriter->nWork);
          rc = fts3IncrmergeChomp(p, iAbsLevel, pCsr, &nSeg);




        }
      }

      fts3IncrmergeRelease(p, pWriter, &rc);
    }

    sqlite3Fts3SegReaderFinish(pCsr);
    sqlite3_free(pWriter);
    bUseHint = 0;
  }

  /* Write the hint values into the %_stat table for the next incr-merger */
  if( rc==SQLITE_OK && (iAbsLevel!=iHintAbsLevel || nHintSeg!=nSeg) ){
    rc = fts3IncrmergeHintStore(p, iAbsLevel, nSeg);
  }



  return rc;
}

/*
** Convert the text beginning at *pz into an integer and return
** its value.  Advance *pz to point to the first character past
** the integer.

/* This statement is used to determine which level to read the input from
** when performing an incremental merge. It returns the absolute level number
** of the oldest level in the db that contains at least ? segments. Or,
** if no level in the FTS index contains more than ? segments, the statement
** returns zero rows.  */
/* 28 */ "SELECT level FROM %Q.'%q_segdir' GROUP BY level HAVING count(*)>=?"
         "  ORDER BY (level %% 1024) ASC LIMIT 1",

/* Estimate the upper limit on the number of leaf nodes in a new segment
** created by merging the oldest :2 segments from absolute level :1. See 
** function sqlite3Fts3Incrmerge() for details.  */
/* 29 */ "SELECT 2 * total(1 + leaves_end_block - start_block) "
         "  FROM %Q.'%q_segdir' WHERE level = ? AND idx < ?",

................................................................................
  *pnRem = nRem;
  return rc;
}

/*
** Store an incr-merge hint in the database.
*/
static int fts3IncrmergeHintStore(Fts3Table *p, Blob *pHint){







  sqlite3_stmt *pReplace = 0;




  int rc;                         /* Return code */

  rc = fts3SqlStmt(p, SQL_REPLACE_STAT, &pReplace, 0);
  if( rc==SQLITE_OK ){
    sqlite3_bind_int(pReplace, 1, FTS_STAT_INCRMERGEHINT);
    sqlite3_bind_blob(pReplace, 2, pHint->a, pHint->n, SQLITE_STATIC);
    sqlite3_step(pReplace);
    rc = sqlite3_reset(pReplace);
  }

  return rc;
}

/*
** Load an incr-merge hint from the database. The incr-merge hint, if one 
** exists, is stored in the rowid==1 row of the %_stat table.
**

** If successful, populate blob *pHint with the value read from the %_stat
** table and return SQLITE_OK. Otherwise, if an error occurs, return an
** SQLite error code.
*/
static int fts3IncrmergeHintLoad(Fts3Table *p, Blob *pHint){




  sqlite3_stmt *pSelect = 0;
  int rc;

  pHint->n = 0;


  rc = fts3SqlStmt(p, SQL_SELECT_STAT, &pSelect, 0);
  if( rc==SQLITE_OK ){
    int rc2;
    sqlite3_bind_int(pSelect, 1, FTS_STAT_INCRMERGEHINT);
    if( SQLITE_ROW==sqlite3_step(pSelect) ){
      const char *aHint = sqlite3_column_blob(pSelect, 0);
      int nHint = sqlite3_column_bytes(pSelect, 0);
      if( aHint ){
        blobGrowBuffer(pHint, nHint, &rc);
        if( rc==SQLITE_OK ){
          memcpy(pHint->a, aHint, nHint);
          pHint->n = nHint;

        }
      }
    }
    rc2 = sqlite3_reset(pSelect);
    if( rc==SQLITE_OK ) rc = rc2;
  }

  return rc;
}

/*
** If *pRc is not SQLITE_OK when this function is called, it is a no-op.
** Otherwise, append an entry to the hint stored in blob *pHint. Each entry
** consists of two varints, the absolute level number of the input segments 
** and the number of input segments.
**
** If successful, leave *pRc set to SQLITE_OK and return. If an error occurs,
** set *pRc to an SQLite error code before returning.
*/
static void fts3IncrmergeHintPush(
  Blob *pHint,                    /* Hint blob to append to */
  i64 iAbsLevel,                  /* First varint to store in hint */
  int nInput,                     /* Second varint to store in hint */
  int *pRc                        /* IN/OUT: Error code */
){
  blobGrowBuffer(pHint, pHint->n + 2*FTS3_VARINT_MAX, pRc);
  if( *pRc==SQLITE_OK ){
    pHint->n += sqlite3Fts3PutVarint(&pHint->a[pHint->n], iAbsLevel);
    pHint->n += sqlite3Fts3PutVarint(&pHint->a[pHint->n], (i64)nInput);
  }
}

/*
** Read the last entry (most recently pushed) from the hint blob *pHint
** and then remove the entry. Write the two values read to *piAbsLevel and 
** *pnInput before returning.
**
** If no error occurs, return SQLITE_OK. If the hint blob in *pHint does
** not contain at least two valid varints, return SQLITE_CORRUPT_VTAB.
*/
static int fts3IncrmergeHintPop(Blob *pHint, i64 *piAbsLevel, int *pnInput){
  const int nHint = pHint->n;
  int i;

  i = pHint->n-2;
  while( i>0 && (pHint->a[i-1] & 0x80) ) i--;
  while( i>0 && (pHint->a[i-1] & 0x80) ) i--;

  pHint->n = i;
  i += sqlite3Fts3GetVarint(&pHint->a[i], piAbsLevel);
  i += sqlite3Fts3GetVarint32(&pHint->a[i], pnInput);
  if( i!=nHint ) return SQLITE_CORRUPT_VTAB;

  return SQLITE_OK;
}


/*
** Attempt an incremental merge that writes nMerge leaf blocks.
**
** Incremental merges happen nMin segments at a time. The two
** segments to be merged are the nMin oldest segments (the ones with
** the smallest indexes) in the highest level that contains at least
** nMin segments. Multiple merges might occur in an attempt to write the 
** quota of nMerge leaf blocks.
*/
int sqlite3Fts3Incrmerge(Fts3Table *p, int nMerge, int nMin){
  int rc;                         /* Return code */
  int nRem = nMerge;              /* Number of leaf pages yet to  be written */
  Fts3MultiSegReader *pCsr;       /* Cursor used to read input data */
  Fts3SegFilter *pFilter;         /* Filter used with cursor pCsr */
  IncrmergeWriter *pWriter;       /* Writer object */
  int nSeg = 0;                   /* Number of input segments */
  sqlite3_int64 iAbsLevel = 0;    /* Absolute level number to work on */
  Blob hint = {0, 0, 0};          /* Hint read from %_stat table */
  int bDirtyHint = 0;             /* True if blob 'hint' has been modified */


  /* Allocate space for the cursor, filter and writer objects */
  const int nAlloc = sizeof(*pCsr) + sizeof(*pFilter) + sizeof(*pWriter);
  pWriter = (IncrmergeWriter *)sqlite3_malloc(nAlloc);
  if( !pWriter ) return SQLITE_NOMEM;
  pFilter = (Fts3SegFilter *)&pWriter[1];
  pCsr = (Fts3MultiSegReader *)&pFilter[1];

  rc = fts3IncrmergeHintLoad(p, &hint);


  while( rc==SQLITE_OK && nRem>0 ){





    const i64 nMod = FTS3_SEGDIR_MAXLEVEL * p->nIndex;



    sqlite3_stmt *pFindLevel = 0; /* SQL used to determine iAbsLevel */
    int bUseHint = 0;             /* True if attempting to append */



    /* Search the %_segdir table for the absolute level with the smallest
    ** relative level number that contains at least nMin segments, if any.
    ** If one is found, set iAbsLevel to the absolute level number and
    ** nSeg to nMin. If no level with at least nMin segments can be found, 
    ** set nSeg to -1.
    */
    rc = fts3SqlStmt(p, SQL_FIND_MERGE_LEVEL, &pFindLevel, 0);
    sqlite3_bind_int(pFindLevel, 1, nMin);
    if( sqlite3_step(pFindLevel)==SQLITE_ROW ){

      iAbsLevel = sqlite3_column_int64(pFindLevel, 0);
      nSeg = nMin;
    }else{
      nSeg = -1;
    }
    rc = sqlite3_reset(pFindLevel);

    /* If the hint read from the %_stat table is not empty, check if the
    ** last entry in it specifies a relative level smaller than or equal
    ** to the level identified by the block above (if any). If so, this 
    ** iteration of the loop will work on merging at the hinted level.
    */
    if( rc==SQLITE_OK && hint.n ){
      int nHint = hint.n;
      sqlite3_int64 iHintAbsLevel = 0;      /* Hint level */
      int nHintSeg = 0;                     /* Hint number of segments */

      rc = fts3IncrmergeHintPop(&hint, &iHintAbsLevel, &nHintSeg);
      if( nSeg<0 || (iAbsLevel % nMod) >= (iHintAbsLevel % nMod) ){
        iAbsLevel = iHintAbsLevel;
        nSeg = nHintSeg;

        bUseHint = 1;
        bDirtyHint = 1;
      }else{
        /* This undoes the effect of the HintPop() above - so that no entry
        ** is removed from the hint blob.  */
        hint.n = nHint;
      }



    }







    /* If nSeg is less that zero, then there is no level with at least
    ** nMin segments and no hint in the %_stat table. No work to do.
    ** Exit early in this case.  */
    if( nSeg<0 ) break;

    /* Open a cursor to iterate through the contents of the oldest nSeg 
    ** indexes of absolute level iAbsLevel. If this cursor is opened using 
    ** the 'hint' parameters, it is possible that there are less than nSeg
    ** segments available in level iAbsLevel. In this case, no work is
    ** done on iAbsLevel - fall through to the next iteration of the loop 
    ** to start work on some other level.  */
    memset(pWriter, 0, nAlloc);
    pFilter->flags = FTS3_SEGMENT_REQUIRE_POS;
    if( rc==SQLITE_OK ){
      rc = fts3IncrmergeCsr(p, iAbsLevel, nSeg, pCsr);
    }
    if( SQLITE_OK==rc && pCsr->nSegment==nSeg
     && SQLITE_OK==(rc = sqlite3Fts3SegReaderStart(p, pCsr, pFilter))
     && SQLITE_ROW==(rc = sqlite3Fts3SegReaderStep(p, pCsr))
    ){
      int iIdx = 0;               /* Largest idx in level (iAbsLevel+1) */
      rc = fts3IncrmergeOutputIdx(p, iAbsLevel, &iIdx);
      if( rc==SQLITE_OK ){
        if( bUseHint && iIdx>0 ){
          const char *zKey = pCsr->zTerm;
................................................................................
          if( pWriter->nWork>=nRem && rc==SQLITE_ROW ) rc = SQLITE_OK;
        }while( rc==SQLITE_ROW );

        /* Update or delete the input segments */
        if( rc==SQLITE_OK ){
          nRem -= (1 + pWriter->nWork);
          rc = fts3IncrmergeChomp(p, iAbsLevel, pCsr, &nSeg);
          if( nSeg!=0 ){
            bDirtyHint = 1;
            fts3IncrmergeHintPush(&hint, iAbsLevel, nSeg, &rc);
          }
        }
      }

      fts3IncrmergeRelease(p, pWriter, &rc);
    }

    sqlite3Fts3SegReaderFinish(pCsr);


  }

  /* Write the hint values into the %_stat table for the next incr-merger */
  if( bDirtyHint && rc==SQLITE_OK ){
    rc = fts3IncrmergeHintStore(p, &hint);
  }

  sqlite3_free(pWriter);
  sqlite3_free(hint.a);
  return rc;
}

/*
** Convert the text beginning at *pz into an integer and return
** its value.  Advance *pz to point to the first character past
** the integer.

} {
  0 {0 1 2 3 4 5 6 7} 
  1 {0 1 2 3 4 5 6 7 8 9 10 11 12 13} 
  2 {0 1 2}
}

do_execsql_test 5.3 {
  INSERT INTO t1(t1) VALUES('merge=1,4');

  SELECT level, group_concat(idx, ' ') FROM t1_segdir GROUP BY level;
} {
  0 {0 1 2 3 4 5 6 7} 
  1 {0 1 2 3 4 5 6 7 8 9 10 11 12 13} 
  2 {0 1 2 3}
}

do_execsql_test 5.4 {SELECT quote(value) from t1_stat WHERE rowid=1} {X'0104'}
do_test 5.5 {
  foreach docid [execsql {SELECT docid FROM t1}] {
    execsql {INSERT INTO t1 SELECT * FROM t1 WHERE docid=$docid}
  }
} {}

do_execsql_test 5.6 {SELECT quote(value) from t1_stat WHERE rowid=1} {X'0104'}

do_execsql_test 5.7 {
  SELECT level, group_concat(idx, ' ') FROM t1_segdir GROUP BY level;
  SELECT quote(value) from t1_stat WHERE rowid=1;
} {
  0 {0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15} 
  1 {0 1 2 3 4 5 6 7 8 9 10 11} 
  2 {0 1 2 3 4 5 6 7}
  X'0104'
}

do_execsql_test 5.8 {
  INSERT INTO t1(t1) VALUES('merge=1,4');

  SELECT level, group_concat(idx, ' ') FROM t1_segdir GROUP BY level;
  SELECT quote(value) from t1_stat WHERE rowid=1;
} {
  0 {0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15} 
  1 {0 1 2 3 4 5 6 7 8 9 10 11} 
  2 {0 1 2 3 4 5 6 7}
  3 {0}
  X'0204'
}



do_test 5.9 {
  set L [expr 16*16*8 + 16*4 + 1]
  foreach docid [execsql {
      SELECT docid FROM t1 UNION ALL SELECT docid FROM t1 LIMIT $L
  }] {
    execsql {INSERT INTO t1 SELECT * FROM t1 WHERE docid=$docid}
  }
} {}

do_execsql_test 5.10 {
  SELECT level, group_concat(idx, ' ') FROM t1_segdir GROUP BY level;
  SELECT quote(value) from t1_stat WHERE rowid=1;
} {
  0 0   1 0   2 0   3 {0 1}
  X'0204'
}

do_execsql_test 5.11 {
  INSERT INTO t1(t1) VALUES('merge=10,4');
  SELECT level, group_concat(idx, ' ') FROM t1_segdir GROUP BY level;
  SELECT quote(value) from t1_stat WHERE rowid=1;
} {
  0 0   1 0   2 0   3 {0 1}
  X'0000'
}

#-------------------------------------------------------------------------
# Test cases 6.*
#
# At one point the following test caused an assert() to fail (because the
# second 'merge=1,2' operation below actually "merges" a single input

} {
  0 {0 1 2 3 4 5 6 7} 
  1 {0 1 2 3 4 5 6 7 8 9 10 11 12 13} 
  2 {0 1 2}
}

do_execsql_test 5.3 {
  INSERT INTO t1(t1) VALUES('merge=1,5');
  INSERT INTO t1(t1) VALUES('merge=1,5');
  SELECT level, group_concat(idx, ' ') FROM t1_segdir GROUP BY level;
} {
  0 {0 1 2}
  1 {0 1 2 3 4 5 6 7 8 9 10 11 12 13 14} 
  2 {0 1 2 3}
}

do_execsql_test 5.4 {SELECT quote(value) from t1_stat WHERE rowid=1} {X'0105'}
do_test 5.5 {
  foreach docid [execsql {SELECT docid FROM t1}] {
    execsql {INSERT INTO t1 SELECT * FROM t1 WHERE docid=$docid}
  }
} {}

do_execsql_test 5.6 {SELECT quote(value) from t1_stat WHERE rowid=1} {X'0105'}

do_execsql_test 5.7 {
  SELECT level, group_concat(idx, ' ') FROM t1_segdir GROUP BY level;
  SELECT quote(value) from t1_stat WHERE rowid=1;
} {
  0 {0 1 2 3 4 5 6 7 8 9 10} 
  1 {0 1 2 3 4 5 6 7 8 9 10 11 12} 
  2 {0 1 2 3 4 5 6 7}
  X'0105'
}

do_execsql_test 5.8 {
  INSERT INTO t1(t1) VALUES('merge=1,6');
  INSERT INTO t1(t1) VALUES('merge=1,6');
  SELECT level, group_concat(idx, ' ') FROM t1_segdir GROUP BY level;
  SELECT quote(value) from t1_stat WHERE rowid=1;
} {
  0 {0 1 2 3 4} 
  1 {0 1 2 3 4 5 6 7 8 9 10 11 12 13} 
  2 {0 1 2 3 4 5 6 7 8} X'0106'


}

do_test 5.8.1 { fts3_integrity_check t1 } ok

do_test 5.9 {
  set L [expr 16*16*7 + 16*3 + 12]
  foreach docid [execsql {
      SELECT docid FROM t1 UNION ALL SELECT docid FROM t1 LIMIT $L
  }] {
    execsql {INSERT INTO t1 SELECT * FROM t1 WHERE docid=$docid}
  }
} {}

do_execsql_test 5.10 {
  SELECT level, group_concat(idx, ' ') FROM t1_segdir GROUP BY level;
  SELECT quote(value) from t1_stat WHERE rowid=1;
} {
  0 0 1 {0 1} 2 0 3 0 X'0106'

}

do_execsql_test 5.11 {
  INSERT INTO t1(t1) VALUES('merge=1,6');
  SELECT level, group_concat(idx, ' ') FROM t1_segdir GROUP BY level;
  SELECT quote(value) from t1_stat WHERE rowid=1;
} {
  0 0 1 {0 1} 2 0 3 0 X''

}

#-------------------------------------------------------------------------
# Test cases 6.*
#
# At one point the following test caused an assert() to fail (because the
# second 'merge=1,2' operation below actually "merges" a single input