SQLite

  char *zSnippet; /* Snippet text */
  int nSnippet;   /* strlen(zSnippet) */
} Snippet;


typedef enum QueryType {
  QUERY_GENERIC,   /* table scan */
  QUERY_DOCID,     /* lookup by docid */
  QUERY_FULLTEXT   /* QUERY_FULLTEXT + [i] is a full-text search for column i*/
} QueryType;

typedef enum fulltext_statement {
  CONTENT_INSERT_STMT,
  CONTENT_SELECT_STMT,
  CONTENT_UPDATE_STMT,

    if( rc!=SQLITE_OK ) return rc;
  }

  *ppStmt = v->pLeafSelectStmts[idx];
  return SQLITE_OK;
}

/* insert into %_content (docid, ...) values ([docid], [pValues])
** If the docid contains SQL NULL, then a unique docid will be
** generated.
*/
static int content_insert(fulltext_vtab *v, sqlite3_value *docid,
                          sqlite3_value **pValues){
  sqlite3_stmt *s;
  int i;
  int rc = sql_get_statement(v, CONTENT_INSERT_STMT, &s);
  if( rc!=SQLITE_OK ) return rc;

  rc = sqlite3_bind_value(s, 1, docid);
  if( rc!=SQLITE_OK ) return rc;

  for(i=0; i<v->nColumn; ++i){
    rc = sqlite3_bind_value(s, 2+i, pValues[i]);
    if( rc!=SQLITE_OK ) return rc;
  }

  return sql_single_step(s);
}

/* update %_content set col0 = pValues[0], col1 = pValues[1], ...
 *                  where docid = [iDocid] */
static int content_update(fulltext_vtab *v, sqlite3_value **pValues,
                          sqlite_int64 iDocid){
  sqlite3_stmt *s;
  int i;
  int rc = sql_get_statement(v, CONTENT_UPDATE_STMT, &s);
  if( rc!=SQLITE_OK ) return rc;

  for(i=0; i<v->nColumn; ++i){
    rc = sqlite3_bind_value(s, 1+i, pValues[i]);
    if( rc!=SQLITE_OK ) return rc;
  }

  rc = sqlite3_bind_int64(s, 1+v->nColumn, iDocid);
  if( rc!=SQLITE_OK ) return rc;

  return sql_single_step(s);
}

static void freeStringArray(int nString, const char **pString){
  int i;

  for (i=0 ; i < nString ; ++i) {
    if( pString[i]!=NULL ) free((void *) pString[i]);
  }
  free((void *) pString);
}

/* select * from %_content where docid = [iDocid]
 * The caller must delete the returned array and all strings in it.
 * null fields will be NULL in the returned array.
 *
 * TODO: Perhaps we should return pointer/length strings here for consistency
 * with other code which uses pointer/length. */
static int content_select(fulltext_vtab *v, sqlite_int64 iDocid,
                          const char ***pValues){
  sqlite3_stmt *s;
  const char **values;
  int i;
  int rc;

  *pValues = NULL;

  rc = sql_get_statement(v, CONTENT_SELECT_STMT, &s);
  if( rc!=SQLITE_OK ) return rc;

  rc = sqlite3_bind_int64(s, 1, iDocid);
  if( rc!=SQLITE_OK ) return rc;

  rc = sqlite3_step(s);
  if( rc!=SQLITE_ROW ) return rc;

  values = (const char **) malloc(v->nColumn * sizeof(const char *));
  for(i=0; i<v->nColumn; ++i){

    return SQLITE_OK;
  }

  freeStringArray(v->nColumn, values);
  return rc;
}

/* delete from %_content where docid = [iDocid ] */
static int content_delete(fulltext_vtab *v, sqlite_int64 iDocid){
  sqlite3_stmt *s;
  int rc = sql_get_statement(v, CONTENT_DELETE_STMT, &s);
  if( rc!=SQLITE_OK ) return rc;

  rc = sqlite3_bind_int64(s, 1, iDocid);
  if( rc!=SQLITE_OK ) return rc;

  return sql_single_step(s);
}

/* insert into %_segments values ([pData])
**   returns assigned blockid in *piBlockid
*/
static int block_insert(fulltext_vtab *v, const char *pData, int nData,
                        sqlite_int64 *piBlockid){
  sqlite3_stmt *s;
  int rc = sql_get_statement(v, BLOCK_INSERT_STMT, &s);
  if( rc!=SQLITE_OK ) return rc;

  rc = sqlite3_bind_blob(s, 1, pData, nData, SQLITE_STATIC);
  if( rc!=SQLITE_OK ) return rc;

  rc = sqlite3_step(s);
  if( rc==SQLITE_ROW ) return SQLITE_ERROR;
  if( rc!=SQLITE_DONE ) return rc;

  /* blockid column is an alias for rowid. */
  *piBlockid = sqlite3_last_insert_rowid(v->db);
  return SQLITE_OK;
}

/* delete from %_segments
**   where blockid between [iStartBlockid] and [iEndBlockid]
**
** Deletes the range of blocks, inclusive, used to delete the blocks
** which form a segment.
*/
static int block_delete(fulltext_vtab *v,
                        sqlite_int64 iStartBlockid, sqlite_int64 iEndBlockid){
  sqlite3_stmt *s;

  rc = constructVtab(db, (fts3Hash *)pAux, &spec, ppVTab, pzErr);
  clearTableSpec(&spec);
  return rc;
}

/* The %_content table holds the text of each document, with
** the docid column exposed as the SQLite rowid for the table.
*/
/* TODO(shess) This comment needs elaboration to match the updated
** code.  Work it into the top-of-file comment at that time.
*/
static int fulltextCreate(sqlite3 *db, void *pAux,
                          int argc, const char * const *argv,
                          sqlite3_vtab **ppVTab, char **pzErr){

  for(i=0; i<pInfo->nConstraint; ++i){
    const struct sqlite3_index_constraint *pConstraint;
    pConstraint = &pInfo->aConstraint[i];
    if( pConstraint->usable ) {
      if( pConstraint->iColumn==-1 &&
          pConstraint->op==SQLITE_INDEX_CONSTRAINT_EQ ){
        pInfo->idxNum = QUERY_DOCID;      /* lookup by docid */
        TRACE(("FTS3 QUERY_DOCID\n"));
      } else if( pConstraint->iColumn>=0 &&
                 pConstraint->op==SQLITE_INDEX_CONSTRAINT_MATCH ){
        /* full-text search */
        pInfo->idxNum = QUERY_FULLTEXT + pConstraint->iColumn;
        TRACE(("FTS3 QUERY_FULLTEXT %d\n", pConstraint->iColumn));
      } else continue;

      pInfo->aConstraintUsage[i].argvIndex = 1;
      pInfo->aConstraintUsage[i].omit = 1;

      /* An arbitrary value for now.
       * TODO: Perhaps docid matches should be considered cheaper than
       * full-text searches. */
      pInfo->estimatedCost = 1.0;   

      return SQLITE_OK;
    }
  }
  pInfo->idxNum = QUERY_GENERIC;

** This is the xFilter interface for the virtual table.  See
** the virtual table xFilter method documentation for additional
** information.
**
** If idxNum==QUERY_GENERIC then do a full table scan against
** the %_content table.
**
** If idxNum==QUERY_DOCID then do a docid lookup for a single entry
** in the %_content table.
**
** If idxNum>=QUERY_FULLTEXT then use the full text index.  The
** column on the left-hand side of the MATCH operator is column
** number idxNum-QUERY_FULLTEXT, 0 indexed.  argv[0] is the right-hand
** side of the MATCH operator.
*/

  if( rc!=SQLITE_OK ) return rc;

  c->iCursorType = idxNum;
  switch( idxNum ){
    case QUERY_GENERIC:
      break;

    case QUERY_DOCID:
      rc = sqlite3_bind_int64(c->pStmt, 1, sqlite3_value_int64(argv[0]));
      if( rc!=SQLITE_OK ) return rc;
      break;

    default:   /* full-text search */
    {
      const char *zQuery = (const char *)sqlite3_value_text(argv[0]);

    */
    sqlite3_result_blob(pContext, &c, sizeof(c), SQLITE_TRANSIENT);
  }
  return SQLITE_OK;
}

/* This is the xRowid method.  The SQLite core calls this routine to
** retrieve the rowid for the current row of the result set.  fts3
** exposes %_content.docid as the rowid for the virtual table.  The
** rowid should be written to *pRowid.
*/
static int fulltextRowid(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){
  fulltext_cursor *c = (fulltext_cursor *) pCursor;

  *pRowid = sqlite3_column_int64(c->pStmt, 0);
  return SQLITE_OK;

  ** not durable.  *ponder*
  */
  pTokenizer->pModule->xClose(pCursor);
  return rc;
}

/* Add doclists for all terms in [pValues] to pendingTerms table. */
static int insertTerms(fulltext_vtab *v, sqlite_int64 iDocid,
                       sqlite3_value **pValues){
  int i;
  for(i = 0; i < v->nColumn ; ++i){
    char *zText = (char*)sqlite3_value_text(pValues[i]);
    int rc = buildTerms(v, iDocid, zText, i);
    if( rc!=SQLITE_OK ) return rc;
  }
  return SQLITE_OK;
}

/* Add empty doclists for all terms in the given row's content to
** pendingTerms.
*/
static int deleteTerms(fulltext_vtab *v, sqlite_int64 iDocid){
  const char **pValues;
  int i, rc;

  /* TODO(shess) Should we allow such tables at all? */
  if( DL_DEFAULT==DL_DOCIDS ) return SQLITE_ERROR;

  rc = content_select(v, iDocid, &pValues);
  if( rc!=SQLITE_OK ) return rc;

  for(i = 0 ; i < v->nColumn; ++i) {
    rc = buildTerms(v, iDocid, pValues[i], -1);
    if( rc!=SQLITE_OK ) break;
  }

  freeStringArray(v->nColumn, pValues);
  return SQLITE_OK;
}

/* TODO(shess) Refactor the code to remove this forward decl. */
static int initPendingTerms(fulltext_vtab *v, sqlite_int64 iDocid);

/* Insert a row into the %_content table; set *piDocid to be the ID of the
** new row.  Add doclists for terms to pendingTerms.
*/
static int index_insert(fulltext_vtab *v, sqlite3_value *pRequestDocid,
                        sqlite3_value **pValues, sqlite_int64 *piDocid){
  int rc;

  rc = content_insert(v, pRequestDocid, pValues);  /* execute an SQL INSERT */
  if( rc!=SQLITE_OK ) return rc;

  /* docid column is an alias for rowid. */
  *piDocid = sqlite3_last_insert_rowid(v->db);
  rc = initPendingTerms(v, *piDocid);
  if( rc!=SQLITE_OK ) return rc;

  return insertTerms(v, *piDocid, pValues);
}

/* Delete a row from the %_content table; add empty doclists for terms
** to pendingTerms.
*/
static int index_delete(fulltext_vtab *v, sqlite_int64 iRow){
  int rc = initPendingTerms(v, iRow);

  v->iPrevDocid = iDocid;
  return SQLITE_OK;
}

/* This function implements the xUpdate callback; it's the top-level entry
 * point for inserting, deleting or updating a row in a full-text table. */
static int fulltextUpdate(sqlite3_vtab *pVtab, int nArg, sqlite3_value **ppArg,
                          sqlite_int64 *pRowid){
  fulltext_vtab *v = (fulltext_vtab *) pVtab;
  int rc;

  TRACE(("FTS3 Update %p\n", pVtab));

  if( nArg<2 ){
    rc = index_delete(v, sqlite3_value_int64(ppArg[0]));