SQLite

        && apSegment[nMerge]->aNode
        && apSegment[nMerge]->nTerm==nTerm 
        && 0==memcmp(zTerm, apSegment[nMerge]->zTerm, nTerm)
    ){
      nMerge++;
    }

    assert( isIgnoreEmpty==0 || (isRequirePos && isColFilter==0) );
    if( nMerge==1 && !isIgnoreEmpty ){
      Fts3SegReader *p0 = apSegment[0];
      rc = xFunc(p, pContext, zTerm, nTerm, p0->aDoclist, p0->nDoclist);
      if( rc!=SQLITE_OK ) goto finished;
    }else{
      int nDoclist = 0;           /* Size of doclist */
      sqlite3_int64 iPrev = 0;    /* Previous docid stored in doclist */

** an SQLite error code is returned.
*/
static int fts3SegmentMerge(Fts3Table *p, int iLevel){
  int i;                          /* Iterator variable */
  int rc;                         /* Return code */
  int iIdx;                       /* Index of new segment */
  int iNewLevel;                  /* Level to create new segment at */
  sqlite3_stmt *pStmt = 0;
  SegmentWriter *pWriter = 0;
  int nSegment = 0;               /* Number of segments being merged */
  Fts3SegReader **apSegment = 0;  /* Array of Segment iterators */
  Fts3SegReader *pPending = 0;    /* Iterator for pending-terms */
  Fts3SegFilter filter;           /* Segment term filter condition */

  if( iLevel<0 ){
    /* This call is to merge all segments in the database to a single
    ** segment. The level of the new segment is equal to the the numerically 
    ** greatest segment level currently present in the database. The index
    ** of the new segment is always 0.
    */
    iIdx = 0;
    rc = sqlite3Fts3SegReaderPending(p, 0, 0, 1, &pPending);
    if( rc!=SQLITE_OK ) goto finished;



    rc = fts3SegmentCountMax(p, &nSegment, &iNewLevel);
    if( rc!=SQLITE_OK ) goto finished;
    nSegment += (pPending!=0);
    if( nSegment<=1 ){
      return SQLITE_DONE;
    }
  }else{
    /* This call is to merge all segments at level iLevel. Find the next
    ** available segment index at level iLevel+1. The call to
    ** fts3AllocateSegdirIdx() will merge the segments at level iLevel+1 to 
    ** a single iLevel+2 segment if necessary.
    */
    iNewLevel = iLevel+1;
    rc = fts3AllocateSegdirIdx(p, iNewLevel, &iIdx);
    if( rc!=SQLITE_OK ) goto finished;
    rc = fts3SegmentCount(p, iLevel, &nSegment);
    if( rc!=SQLITE_OK ) goto finished;
  }

  assert( nSegment>0 );
  assert( iNewLevel>=0 );

  /* Allocate space for an array of pointers to segment iterators. */
  apSegment = (Fts3SegReader**)sqlite3_malloc(sizeof(Fts3SegReader *)*nSegment);
  if( !apSegment ){
    rc = SQLITE_NOMEM;
    goto finished;
  }
  memset(apSegment, 0, sizeof(Fts3SegReader *)*nSegment);

  /* Allocate a Fts3SegReader structure for each segment being merged. A 
  ** Fts3SegReader stores the state data required to iterate through all 
  ** entries on all leaves of a single segment. 
  */
  assert( SQL_SELECT_LEVEL+1==SQL_SELECT_ALL_LEVEL);
  rc = fts3SqlStmt(p, SQL_SELECT_LEVEL+(iLevel<0), &pStmt, 0);
  if( rc!=SQLITE_OK ) goto finished;
  sqlite3_bind_int(pStmt, 1, iLevel);
  for(i=0; SQLITE_ROW==(sqlite3_step(pStmt)); i++){
    rc = fts3SegReaderNew(p, pStmt, i, &apSegment[i]);
    if( rc!=SQLITE_OK ){
      goto finished;
    }
  }
  rc = sqlite3_reset(pStmt);
  if( pPending ){
    apSegment[i] = pPending;
    pPending = 0;
  }
  pStmt = 0;
  if( rc!=SQLITE_OK ) goto finished;

  memset(&filter, 0, sizeof(Fts3SegFilter));
  filter.flags = FTS3_SEGMENT_REQUIRE_POS;
  filter.flags |= (iLevel<0 ? FTS3_SEGMENT_IGNORE_EMPTY : 0);

  fts3SegWriterFree(pWriter);
  if( apSegment ){
    for(i=0; i<nSegment; i++){
      sqlite3Fts3SegReaderFree(p, apSegment[i]);
    }
    sqlite3_free(apSegment);
  }
  sqlite3Fts3SegReaderFree(p, pPending);
  sqlite3_reset(pStmt);
  return rc;
}


/* 
** Flush the contents of pendingTerms to a level 0 segment.

set testdir [file dirname $argv0]
source $testdir/tester.tcl

# If this build does not include FTS3, skip the tests in this file.
#
ifcapable !fts3 { finish_test ; return }
source $testdir/fts3_common.tcl
source $testdir/malloc_common.tcl

set DO_MALLOC_TEST 0

#--------------------------------------------------------------------------
# When it first needs to read a block from the %_segments table, the FTS3 
# module compiles an SQL statement for that purpose. The statement is 
# stored and reused each subsequent time a block is read. This test case 

# assumes that the content of each internal node will be less than
# $nodesize bytes, where $nodesize is the advisory node size. If this turns
# out to be untrue, then an extra buffer must be malloc'd for each term.
# This test case tests these paths and the effects of said mallocs failing
# by inserting insert a document with some fairly large terms into a
# full-text table with a very small node-size. 
#
# Test this handling of large terms in three contexts:
#
#   1. When flushing the pending-terms table.
#   2. When optimizing the data structures using the INSERT syntax. 
#   2. When optimizing the data structures using the deprecated SELECT syntax. 
#
do_test fts3cov-5.1 {
  execsql {
    CREATE VIRTUAL TABLE t4 USING fts3(x);
    INSERT INTO t4(t4) VALUES('nodesize=24');
  }
} {}
set DO_MALLOC_TEST 1

# Test when flushing pending-terms table.
do_write_test fts3cov-5.2 t4_content {
  INSERT INTO t4
    SELECT 'ItisanancientMarinerAndhestoppethoneofthreeAA' UNION ALL
    SELECT 'ItisanancientMarinerAndhestoppethoneofthreeBB' UNION ALL
    SELECT 'ItisanancientMarinerAndhestoppethoneofthreeCC' UNION ALL
    SELECT 'BythylonggreybeardandglitteringeyeNowwhereforestoppstAA' UNION ALL
    SELECT 'BythylonggreybeardandglitteringeyeNowwhereforestoppstBB' UNION ALL
    SELECT 'BythylonggreybeardandglitteringeyeNowwhereforestoppstCC'
}

# Test when optimizing via INSERT.
do_test fts3cov-5.3 { execsql { INSERT INTO t4 VALUES('extra!') } } {}
do_write_test fts3cov-5.2 t4_segments { INSERT INTO t4(t4) VALUES('optimize') }

# Test when optimizing via SELECT.
do_test fts3cov-5.5 { execsql { INSERT INTO t4 VALUES('more extra!') } } {}
do_write_test fts3cov-5.6 t4_segments {
  SELECT * FROM (SELECT optimize(t4) FROM t4 LIMIT 1)
  EXCEPT SELECT 'Index optimized'
}

#-------------------------------------------------------------------------
# When merging all segments at a given level to create a single segment
# at level+1, FTS3 runs a query of the form:
#
#   SELECT count(*) FROM %_segdir WHERE level = ?
#
# The query is compiled the first time this operation is required and
# reused thereafter. This test aims to test the effects of an OOM while
# preparing and executing this query for the first time.
#
# Then, keep inserting rows into the table so that the effects of an OOM
# while re-executing the same query can also be tested.
#
do_test fts3cov-6.1 {
  execsql { CREATE VIRTUAL TABLE t5 USING fts3(x) }
  for {set i 0} {$i<16} {incr i} { execsql "INSERT INTO t5 VALUES('term$i')" }
  execsql { SELECT count(*) FROM t5_segdir }
} {16}

# First time.
db close
sqlite3 db test.db
do_write_test fts3cov-6.2 t5_content {
  INSERT INTO t5 VALUES('segment number 16!');
}

# Second time.
do_test fts3cov-6.3 {
  for {set i 1} {$i<16} {incr i} { execsql "INSERT INTO t5 VALUES('term$i')" }
  execsql { SELECT count(*) FROM t5_segdir }
} {17}
do_write_test fts3cov-6.4 t5_content {
  INSERT INTO t5 VALUES('segment number 16!');
}

#-------------------------------------------------------------------------
# Update the docid of a row. Test this in two scenarios:
#
#   1. When the row being updated is the only row in the table.
#   2. When it is not.
#
# The two cases above take different paths because in case 1 all data 
# structures can simply be emptied before inserting the new row record.
# In case 2, the data structures actually have to be updated.
#
do_test fts3cov-7.1 {
  execsql {
    CREATE VIRTUAL TABLE t7 USING fts3(a, b, c);
    INSERT INTO t7 VALUES('A', 'B', 'C');
    UPDATE t7 SET docid = 5;
    SELECT docid, * FROM t7;
  }
} {5 A B C}
do_test fts3cov-7.2 {
  execsql {
    INSERT INTO t7 VALUES('D', 'E', 'F');
    UPDATE t7 SET docid = 1 WHERE docid = 6;
    SELECT docid, * FROM t7;
  }
} {1 D E F 5 A B C}

#-------------------------------------------------------------------------
# If a set of documents are modified within a transaction, the 
# pending-terms table must be flushed each time a document with a docid
# less than or equal to the previous docid is modified. 
#
# This test checks the effects of an OOM error occuring when the 
# pending-terms table is flushed for this reason as part of a DELETE 
# statement.
#
do_malloc_test fts3cov-8 -sqlprep {
  BEGIN;
    CREATE VIRTUAL TABLE t8 USING fts3;
    INSERT INTO t8 VALUES('the output of each batch run');
    INSERT INTO t8 VALUES('(possibly a day''s work)');
    INSERT INTO t8 VALUES('was written to two separate disks');
  COMMIT;
} -sqlbody {
  BEGIN;
    DELETE FROM t8 WHERE rowid = 3;
    DELETE FROM t8 WHERE rowid = 2;
    DELETE FROM t8 WHERE rowid = 1;
  COMMIT;
}

#-------------------------------------------------------------------------
# Test some branches in the code that handles "special" inserts like:
#
#   INSERT INTO t1(t1) VALUES('optimize');
#
# Also test that an optimize (INSERT method) works on an empty table.
#
set DO_MALLOC_TEST 0
do_test fts3cov-9.1 {
  execsql { CREATE VIRTUAL TABLE xx USING fts3 }
} {}
do_error_test fts3cov-9.2 {
  INSERT INTO xx(xx) VALUES('optimise');   -- British spelling
} {SQL logic error or missing database}
do_error_test fts3cov-9.3 {
  INSERT INTO xx(xx) VALUES('short');
} {SQL logic error or missing database}
do_error_test fts3cov-9.4 {
  INSERT INTO xx(xx) VALUES('waytoolongtobecorrect');
} {SQL logic error or missing database}
do_test fts3cov-9.5 {
  execsql { INSERT INTO xx(xx) VALUES('optimize') }
} {}

#-------------------------------------------------------------------------
# Test that a table can be optimized in the middle of a transaction when
# the pending-terms table is non-empty. This case involves some extra
# branches because data must be read not only from the database, but
# also from the pending-terms table.
#
do_malloc_test fts3cov-10 -sqlprep {
  CREATE VIRTUAL TABLE t10 USING fts3;
  INSERT INTO t10 VALUES('Optimising images for the web is a tricky business');
  BEGIN;
    INSERT INTO t10 VALUES('You have to get the right balance between');
} -sqlbody {
  INSERT INTO t10(t10) VALUES('optimize');
}

#-------------------------------------------------------------------------
# Test a full-text query for a term that was once in the index, but is
# no longer.
#
do_test fts3cov-11.1 {
  execsql { 
    CREATE VIRTUAL TABLE xx USING fts3;
    INSERT INTO xx VALUES('one two three');
    INSERT INTO xx VALUES('four five six');
    DELETE FROM xx WHERE docid = 1;
  }
  execsql { SELECT * FROM xx WHERE xx MATCH 'two' }
} {}

finish_test