SQLite

  a = sqlite3_column_blob(pStmt, 0);
  a += sqlite3Fts3GetVarint(a, &nDoc);
  *pnDoc = (u32)nDoc;

  if( paLen ) *paLen = a;
  return SQLITE_OK;
}

typedef struct LcsIterator LcsIterator;
struct LcsIterator {
  Fts3Expr *pExpr;                /* Pointer to phrase expression */
  char *pRead;                    /* Cursor used to iterate through aDoclist */
  int iPosOffset;                 /* Tokens count up to end of this phrase */
  int iCol;                       /* Current column number */
  int iPos;                       /* Current position */
};

#define LCS_ITERATOR_FINISHED 0x7FFFFFFF;

static int fts3MatchinfoLcsCb(
  Fts3Expr *pExpr,                /* Phrase expression node */
  int iPhrase,                    /* Phrase number (numbered from zero) */
  void *pCtx                      /* Pointer to MatchInfo structure */
){
  LcsIterator *aIter = (LcsIterator *)pCtx;
  aIter[iPhrase].pExpr = pExpr;
  return SQLITE_OK;
}

static int fts3LcsIteratorAdvance(LcsIterator *pIter){
  char *pRead = pIter->pRead;
  sqlite3_int64 iRead;
  int rc = 0;

  pRead += sqlite3Fts3GetVarint(pRead, &iRead);
  if( iRead==0 ){
    pIter->iCol = LCS_ITERATOR_FINISHED;
    rc = 1;
  }else{
    if( iRead==1 ){
      pRead += sqlite3Fts3GetVarint(pRead, &iRead);
      pIter->iCol = iRead;
      pIter->iPos = pIter->iPosOffset;
      pRead += sqlite3Fts3GetVarint(pRead, &iRead);
      rc = 1;
    }
    pIter->iPos += (iRead-2);
  }

  pIter->pRead = pRead;
  return rc;
}
  
static int fts3MatchinfoLcs(Fts3Cursor *pCsr, MatchInfo *pInfo){
  LcsIterator *aIter;
  int i;
  int iCol;
  int nToken = 0;

  /* Allocate and populate the array of LcsIterator objects. The array
  ** contains one element for each matchable phrase in the query.
  **/
  aIter = sqlite3_malloc(sizeof(LcsIterator) * pCsr->nPhrase);
  if( !aIter ) return SQLITE_NOMEM;
  memset(aIter, 0, sizeof(LcsIterator) * pCsr->nPhrase);
  (void)fts3ExprIterate(pCsr->pExpr, fts3MatchinfoLcsCb, (void*)aIter);

  for(i=0; i<pInfo->nPhrase; i++){
    LcsIterator *pIter = &aIter[i];
    nToken -= pIter->pExpr->pPhrase->nToken;
    pIter->iPosOffset = nToken;
    pIter->pRead = sqlite3Fts3FindPositions(pIter->pExpr, pCsr->iPrevId, -1);
    if( pIter->pRead ){
      pIter->iPos = pIter->iPosOffset;
      fts3LcsIteratorAdvance(&aIter[i]);
    }else{
      pIter->iCol = LCS_ITERATOR_FINISHED;
    }
  }

  for(iCol=0; iCol<pInfo->nCol; iCol++){
    int nLcs = 0;
    int nLive = 0;

    for(i=0; i<pInfo->nPhrase; i++){
      assert( aIter[i].iCol>=iCol );
      if( aIter[i].iCol==iCol ) nLive++;
    }

    while( nLive>0 ){
      LcsIterator *pAdv = 0;
      int nThisLcs = 0;
      char *aRead;
      sqlite3_int64 iRead;

      for(i=0; i<pInfo->nPhrase; i++){
        LcsIterator *pIter = &aIter[i];
        int nToken = pIter->pExpr->pPhrase->nToken;

        if( iCol!=pIter->iCol ){  
          nThisLcs = 0;
          continue;
        }

        if( pAdv==0 || pIter->iPos<pAdv->iPos ){
          pAdv = pIter;
        }

        if( nThisLcs==0 || pIter->iPos==pIter[-1].iPos ){
          nThisLcs++;
        }else{
          nThisLcs = 1;
        }

        if( nThisLcs>nLcs ) nLcs = nThisLcs;
      }
      if( fts3LcsIteratorAdvance(pAdv) ) nLive--;
    }

    pInfo->aMatchinfo[iCol] = nLcs;
  }

  sqlite3_free(aIter);
}

static int fts3MatchinfoValues(
  Fts3Cursor *pCsr,               /* FTS3 cursor object */
  int bGlobal,                    /* True to grab the global stats */
  MatchInfo *pInfo,               /* Matchinfo context object */
  const char *zArg                /* Matchinfo format string */
){

          }
          (void)fts3ExprIterate(pExpr, fts3ExprGlobalHitsCb,(void*)pInfo);
        }
        (void)fts3ExprIterate(pExpr, fts3ExprLocalHitsCb,(void*)pInfo);
        break;
      }

      case FTS3_MATCHINFO_LCS:
        fts3MatchinfoLcs(pCsr, pInfo);
        break;

      default:
        assert( !"this cannot happen" );
    }

    pInfo->aMatchinfo += fts3MatchinfoSize(pInfo, zArg[i]);
  }

  sqlite3_reset(pSelect);
  return rc;

int sqlite3Fts3SelectDocsize(
  Fts3Table *pTab,                /* Fts3 table handle */
  sqlite3_int64 iDocid,           /* Docid to read size data for */
  sqlite3_stmt **ppStmt           /* OUT: Statement handle */
){
  return fts3SelectDocsize(pTab, SQL_SELECT_DOCSIZE, iDocid, ppStmt);
}

void sqlite3Fts3MatchinfoLcs(Fts3Expr *pExpr, u32 *aOut){
}

/*
** Similar to fts3SqlStmt(). Except, after binding the parameters in
** array apVal[] to the SQL statement identified by eStmt, the statement
** is executed.
**
** Returns SQLITE_OK if the statement is successfully executed, or an

  1 {}
  2 { INSERT INTO t2(t2) VALUES('optimize') }
  3 { UPDATE t2_segments SET block = zeroblob(length(block)) 
      WHERE length(block)>10000;
  }
} {
  execsql $sql

  do_execsql_test 2.2.$tn {
    SELECT mit(matchinfo(t2, 'pcxnal')) FROM t2 WHERE t2 MATCH 'a b';
  } [list                                          \
    [list 2 1  1 54 54  1 3 3  54 372 7]        \
    [list 2 1  1 54 54  1 3 3  54 372 7]        \
  ]
}

do_execsql_test 4.1.0 {
  CREATE VIRTUAL TABLE t4 USING fts4(x, y);
  INSERT INTO t4 VALUES('a b c d e', 'f g h i j');
  INSERT INTO t4 VALUES('f g h i j', 'a b c d e');
}

do_matchinfo_test 4.1.1 t4 {t4 MATCH 'a b c'} {
  p {3 3}
  c {2 2}
  x {
    {1 1 1   0 1 1   1 1 1   0 1 1   1 1 1   0 1 1}
    {0 1 1   1 1 1   0 1 1   1 1 1   0 1 1   1 1 1}
  }
  n {2 2}
  l {{5 5} {5 5}}
  a {{5 5} {5 5}}

  s {{3 0} {0 3}}

  xxxxxxxxxxxxxxxxxx - pcx - xpc - ccc - pppxpcpcx - laxnpc -
  xpxsscplax -
}

do_matchinfo_test 4.1.2 t4 {t4 MATCH '"g h i"'} {
  p {1 1}
  c {2 2}
  x {
    {0 1 1   1 1 1}
    {1 1 1   0 1 1}
  }
  n {2 2}
  l {{5 5} {5 5}}
  a {{5 5} {5 5}}

  s {{0 1} {1 0}}

  xxxxxxxxxxxxxxxxxx - pcx - xpc - ccc - pppxpcpcx - laxnpc -
  sxsxs -
}

do_matchinfo_test 4.1.3 t4 {t4 MATCH 'a b'}     { s {{2 0} {0 2}} }
do_matchinfo_test 4.1.4 t4 {t4 MATCH '"a b" c'} { s {{2 0} {0 2}} }
do_matchinfo_test 4.1.5 t4 {t4 MATCH 'a "b c"'} { s {{2 0} {0 2}} }
do_matchinfo_test 4.1.6 t4 {t4 MATCH 'd d'}     { s {{1 0} {0 1}} }

do_execsql_test 4.2.0 {
  CREATE VIRTUAL TABLE t5 USING fts4;
  INSERT INTO t5 VALUES('a a a a a');
  INSERT INTO t5 VALUES('a b a b a');
  INSERT INTO t5 VALUES('c b c b c');
}
do_matchinfo_test 4.2.1 t5 {t5 MATCH 'a a'}         { s {2 1} }
do_matchinfo_test 4.2.2 t5 {t5 MATCH 'a b'}         { s {2} }
do_matchinfo_test 4.2.3 t5 {t5 MATCH 'a b a'}       { s {3} }
do_matchinfo_test 4.2.4 t5 {t5 MATCH 'a a a'}       { s {3 1} }
do_matchinfo_test 4.2.5 t5 {t5 MATCH '"a b" "a b"'} { s {2} }
do_matchinfo_test 4.2.6 t5 {t5 MATCH 'a OR b'}      { s {1 2 1} }

do_execsql_test 4.3.0 "INSERT INTO t5 VALUES('x y [string repeat {b } 50000]')";
do_execsql_test 4.3.0 "INSERT INTO t5 VALUES('x y [string repeat {x } 50000]')";

#do_matchinfo_test 4.3.1 t5 {t5 MATCH 'a a'}         { s {2 1} }
#do_matchinfo_test 4.3.2 t5 {t5 MATCH 'a b'}         { s {2} }
#do_matchinfo_test 4.3.3 t5 {t5 MATCH 'a b a'}       { s {3} }
#do_matchinfo_test 4.3.4 t5 {t5 MATCH 'a a a'}       { s {3 1} }
#do_matchinfo_test 4.3.5 t5 {t5 MATCH '"a b" "a b"'} { s {2} }
#do_matchinfo_test 4.3.6 t5 {t5 MATCH 'a OR b'}      { s {1 2 1 1} }
#
#do_execsql_test 4.4.0 {
#  UPDATE t5_segments 
#  SET block = zeroblob(length(block)) 
#  WHERE length(block)>10000;
#}
#
#do_matchinfo_test 4.4.1 t5 {t5 MATCH 'a a'}         { s {2 1} }
#do_matchinfo_test 4.4.2 t5 {t5 MATCH 'a b'}         { s {2} }
#do_matchinfo_test 4.4.3 t5 {t5 MATCH 'a b a'}       { s {3} }
#do_matchinfo_test 4.4.4 t5 {t5 MATCH 'a a a'}       { s {3 1} }
#do_matchinfo_test 4.4.5 t5 {t5 MATCH '"a b" "a b"'} { s {2} }
#do_matchinfo_test 4.4.6 t5 {t5 MATCH 'a OR b'}      { s {1 2 1 1} }


finish_test