SQLite

/*
** Iterator pIter currently points to the first rowid in a doclist. This
** function sets the iterator up so that iterates in reverse order through
** the doclist.
*/
static void fts5SegIterReverse(Fts5Index *p, int iIdx, Fts5SegIter *pIter){
  Fts5DlidxIter *pDlidx = pIter->pDlidx;
  Fts5Data *pLast = 0;
  int pgnoLast = 0;

  if( pDlidx ){
    /* If the doclist-iterator is already at EOF, then the current doclist
    ** contains no entries except those on the current page. */
    if( fts5DlidxIterEof(p, pDlidx)==0 ){
      int iSegid = pIter->pSeg->iSegid;
      pgnoLast = pDlidx->iLeafPgno;
      pLast = fts5DataRead(p, FTS5_SEGMENT_ROWID(iIdx, iSegid, 0, pgnoLast));
    }else{
      pIter->iLeafOffset -= sqlite3Fts5GetVarintLen(pIter->nPos*2+pIter->bDel);
    }
  }else{
    int iOff;                               /* Byte offset within pLeaf */
    Fts5Data *pLeaf = pIter->pLeaf;         /* Current leaf data */

    /* Currently, Fts5SegIter.iLeafOffset (and iOff) points to the first 
    ** byte of position-list content for the current rowid. Back it up
    ** so that it points to the start of the position-list size field. */
    pIter->iLeafOffset -= sqlite3Fts5GetVarintLen(pIter->nPos*2+pIter->bDel);
    iOff = pIter->iLeafOffset;
    assert( iOff>=4 );

    /* Search for a new term within the current leaf. If one can be found,
    ** then this page contains the largest rowid for the current term. */
    while( iOff<pLeaf->n ){
      int nPos;

  Fts5Buffer buf;
  memset(&buf, 0, sizeof(Fts5Buffer));
  for(i=0; i<pIter->nSeg; i++){
    Fts5SegIter *pSeg = &pIter->aSeg[i];
    if( pSeg->pSeg==0 ){
      /* no-op */
    }else if( pSeg->pLeaf==0 ){
      /* All keys from this input segment have been transfered to the output.
      ** Set both the first and last page-numbers to 0 to indicate that the
      ** segment is now empty. */
      pSeg->pSeg->pgnoLast = 0;
      pSeg->pSeg->pgnoFirst = 0;
    }else{
      int iOff = pSeg->iTermLeafOffset;     /* Offset on new first leaf page */
      i64 iLeafRowid;
      Fts5Data *pData;
      int iId = pSeg->pSeg->iSegid;

      }

      fts5DlidxIterFree(pDlidx);
      fts5DlidxIterTestReverse(p, iIdx, iSegid, iter.iLeaf);
    }
  }

  /* Either iter.iLeaf must be the rightmost leaf-page in the segment, or 
  ** else the segment has been completely emptied by an ongoing merge
  ** operation. */
  if( p->rc==SQLITE_OK 
   && iter.iLeaf!=pSeg->pgnoLast 
   && (pSeg->pgnoFirst || pSeg->pgnoLast) 
  ){
    p->rc = FTS5_CORRUPT;
  }

  fts5BtreeIterFree(&iter);
}

/*

# 2015 April 21
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
#
# This test is focused on really large position lists. Those that require
# 4 or 5 byte position-list size varints. Because of the amount of memory
# required, these tests only run on 64-bit platforms.
#

source [file join [file dirname [info script]] fts5_common.tcl]
set testprefix fts5bigpl

if { $tcl_platform(wordSize)<8 } {
  finish_test
  return
}

do_execsql_test 1.0 { CREATE VIRTUAL TABLE t1 USING fts5(x) }

do_test 1.1 {
  foreach t {a b c d e f g h i j} {
    set doc [string repeat "$t " 1200000]
    execsql { INSERT INTO t1 VALUES($doc) }
  }
  execsql { INSERT INTO t1(t1) VALUES('integrity-check') }
} {}

do_test 1.2 {
  execsql { DELETE FROM t1 }
  foreach t {"a b" "b a" "c d" "d c"} {
    set doc [string repeat "$t " 600000]
    execsql { INSERT INTO t1 VALUES($doc) }
  }
  execsql { INSERT INTO t1(t1) VALUES('integrity-check') }
} {}


# 5-byte varint. This test takes 30 seconds or so on a 2014 workstation.
# The generated database is roughly 635MiB.
#
do_test 2.1...slow {
  execsql { DELETE FROM t1 }
  foreach t {a} {
    set doc [string repeat "$t " 150000000]
    execsql { INSERT INTO t1 VALUES($doc) }
  }
  execsql { INSERT INTO t1(t1) VALUES('integrity-check') }
} {}

finish_test