SQLite

  char *p2 = a2;
  char *p;
  char *aOut;
  int bFirstOut = 0;

  *paOut = 0;
  *pnOut = 0;

  /* Allocate space for the output. Both the input and output doclists
  ** are delta encoded. If they are in ascending order (bDescDoclist==0),
  ** then the first docid in each list is simply encoded as a varint. For
  ** each subsequent docid, the varint stored is the difference between the
  ** current and previous docid (a positive number - since the list is in
  ** ascending order).
  **
  ** The first docid written to the output is therefore encoded using the 
  ** same number of bytes as it is in whichever of the input lists it is
  ** read from. And each subsequent docid read from the same input list 
  ** consumes either the same or less bytes as it did in the input (since
  ** the difference between it and the previous value in the output must
  ** be a positive value less than or equal to the delta value read from 
  ** the input list). The same argument applies to all but the first docid
  ** read from the 'other' list. And to the contents of all position lists
  ** that will be copied and merged from the input to the output.
  **
  ** However, if the first docid copied to the output is a negative number,
  ** then the encoding of the first docid from the 'other' input list may
  ** be larger in the output than it was in the input (since the delta value
  ** may be a larger positive integer than the actual docid).
  **
  ** The space required to store the output is therefore the sum of the
  ** sizes of the two inputs, plus enough space for exactly one of the input
  ** docids to grow. 
  **
  ** A symetric argument may be made if the doclists are in descending 
  ** order.
  */
  aOut = sqlite3_malloc(n1+n2+FTS3_VARINT_MAX-1);
  if( !aOut ) return SQLITE_NOMEM;

  p = aOut;
  fts3GetDeltaVarint3(&p1, pEnd1, 0, &i1);
  fts3GetDeltaVarint3(&p2, pEnd2, 0, &i2);
  while( p1 || p2 ){
    sqlite3_int64 iDiff = DOCID_CMP(i1, i2);

      fts3PoslistCopy(&p, &p2);
      fts3GetDeltaVarint3(&p2, pEnd2, bDescDoclist, &i2);
    }
  }

  *paOut = aOut;
  *pnOut = (p-aOut);
  assert( *pnOut<=n1+n2+FTS3_VARINT_MAX-1 );
  return SQLITE_OK;
}

/*
** This function does a "phrase" merge of two doclists. In a phrase merge,
** the output contains a copy of each position from the right-hand input
** doclist for which there is a position in the left-hand input doclist

    INSERT INTO t2 VALUES('cc aa');
    SELECT docid FROM t2 WHERE t2 MATCH 'aa';
  END;
} {3 1}
do_execsql_test 2.3 {
  SELECT docid FROM t2 WHERE t2 MATCH 'aa';
} {3 1}

#-------------------------------------------------------------------------
# Test that ticket [56be976859] has been fixed.
#
do_execsql_test 3.1 {
  CREATE VIRTUAL TABLE t3 USING fts4(x, order=DESC);
  INSERT INTO t3(docid, x) VALUES(113382409004785664, 'aa');
  INSERT INTO t3(docid, x) VALUES(1, 'ab');
  SELECT rowid FROM t3 WHERE x MATCH 'a*' ORDER BY docid DESC;
} {113382409004785664 1}
do_execsql_test 3.2 {
  CREATE VIRTUAL TABLE t4 USING fts4(x);
  INSERT INTO t4(docid, x) VALUES(-113382409004785664, 'aa');
  INSERT INTO t4(docid, x) VALUES(1, 'ab');
  SELECT rowid FROM t4 WHERE x MATCH 'a*';
} {-113382409004785664 1}



finish_test