sqlite3session S db main
  S attach t1
  execsql { INSERT INTO t1 VALUES(1, 'Sukhothai') }
  execsql { INSERT INTO t1 VALUES(2, 'Ayutthaya') }
  execsql { INSERT INTO t1 VALUES(3, 'Thonburi') }
} {}
do_changeset_test 2.1.2 S {
  {INSERT t1 {} {i 1 t Sukhothai}}
  {INSERT t1 {} {i 2 t Ayutthaya}}
  {INSERT t1 {} {i 3 t Thonburi}}
}
do_changeset_invert_test 2.1.3 S {
  {DELETE t1 {i 1 t Sukhothai} {}}
  {DELETE t1 {i 2 t Ayutthaya} {}}
  {DELETE t1 {i 3 t Thonburi} {}}
}
do_test 2.1.4 { S delete } {}

do_test 2.2.1 {
  sqlite3session S db main
  S attach t1
  execsql { DELETE FROM t1 WHERE 1 }
} {}
do_changeset_test 2.2.2 S {
  {DELETE t1 {i 1 t Sukhothai} {}}
  {DELETE t1 {i 2 t Ayutthaya} {}}
  {DELETE t1 {i 3 t Thonburi} {}}
}
do_changeset_invert_test 2.2.3 S {
  {INSERT t1 {} {i 1 t Sukhothai}}
  {INSERT t1 {} {i 2 t Ayutthaya}}
  {INSERT t1 {} {i 3 t Thonburi}}
}
do_test 2.2.4 { S delete } {}

do_test 2.3.1 {
  execsql { DELETE FROM t1 }
  sqlite3session S db main
  execsql { INSERT INTO t1 VALUES(1, 'Sukhothai') }
................................................................................
    UPDATE t1 SET x = 10 WHERE x = 1;
    UPDATE t1 SET y = 'Surin' WHERE x = 2;
    UPDATE t1 SET x = 20, y = 'Thapae' WHERE x = 3;
  }
} {}

do_changeset_test 2.3.2 S {
  {INSERT t1 {} {i 10 t Sukhothai}} 
  {DELETE t1 {i 1 t Sukhothai} {}} 
  {UPDATE t1 {i 2 t Ayutthaya} {{} {} t Surin}} 
  {DELETE t1 {i 3 t Thonburi} {}} 
  {INSERT t1 {} {i 20 t Thapae}} 
}

do_changeset_invert_test 2.3.3 S {
  {DELETE t1 {i 10 t Sukhothai} {}} 
  {INSERT t1 {} {i 1 t Sukhothai}} 
  {UPDATE t1 {{} {} t Surin} {i 2 t Ayutthaya}} 
  {INSERT t1 {} {i 3 t Thonburi}} 
  {DELETE t1 {i 20 t Thapae} {}}
}
do_test 2.3.4 { S delete } {}

do_test 2.4.1 {
  sqlite3session S db main
  S attach t1
  execsql { INSERT INTO t1 VALUES(100, 'Bangkok') }

  sqlite3session S db main
  S attach t1
  execsql { INSERT INTO t1 VALUES(1, 'Sukhothai') }
  execsql { INSERT INTO t1 VALUES(2, 'Ayutthaya') }
  execsql { INSERT INTO t1 VALUES(3, 'Thonburi') }
} {}
do_changeset_test 2.1.2 S {
  {INSERT t1 0 {} {i 1 t Sukhothai}}
  {INSERT t1 0 {} {i 2 t Ayutthaya}}
  {INSERT t1 0 {} {i 3 t Thonburi}}
}
do_changeset_invert_test 2.1.3 S {
  {DELETE t1 0 {i 1 t Sukhothai} {}}
  {DELETE t1 0 {i 2 t Ayutthaya} {}}
  {DELETE t1 0 {i 3 t Thonburi} {}}
}
do_test 2.1.4 { S delete } {}

do_test 2.2.1 {
  sqlite3session S db main
  S attach t1
  execsql { DELETE FROM t1 WHERE 1 }
} {}
do_changeset_test 2.2.2 S {
  {DELETE t1 0 {i 1 t Sukhothai} {}}
  {DELETE t1 0 {i 2 t Ayutthaya} {}}
  {DELETE t1 0 {i 3 t Thonburi} {}}
}
do_changeset_invert_test 2.2.3 S {
  {INSERT t1 0 {} {i 1 t Sukhothai}}
  {INSERT t1 0 {} {i 2 t Ayutthaya}}
  {INSERT t1 0 {} {i 3 t Thonburi}}
}
do_test 2.2.4 { S delete } {}

do_test 2.3.1 {
  execsql { DELETE FROM t1 }
  sqlite3session S db main
  execsql { INSERT INTO t1 VALUES(1, 'Sukhothai') }
................................................................................
    UPDATE t1 SET x = 10 WHERE x = 1;
    UPDATE t1 SET y = 'Surin' WHERE x = 2;
    UPDATE t1 SET x = 20, y = 'Thapae' WHERE x = 3;
  }
} {}

do_changeset_test 2.3.2 S {
  {INSERT t1 0 {} {i 10 t Sukhothai}} 
  {DELETE t1 0 {i 1 t Sukhothai} {}} 
  {UPDATE t1 0 {i 2 t Ayutthaya} {{} {} t Surin}} 
  {DELETE t1 0 {i 3 t Thonburi} {}} 
  {INSERT t1 0 {} {i 20 t Thapae}} 
}

do_changeset_invert_test 2.3.3 S {
  {DELETE t1 0 {i 10 t Sukhothai} {}} 
  {INSERT t1 0 {} {i 1 t Sukhothai}} 
  {UPDATE t1 0 {{} {} t Surin} {i 2 t Ayutthaya}} 
  {INSERT t1 0 {} {i 3 t Thonburi}} 
  {DELETE t1 0 {i 20 t Thapae} {}}
}
do_test 2.3.4 { S delete } {}

do_test 2.4.1 {
  sqlite3session S db main
  S attach t1
  execsql { INSERT INTO t1 VALUES(100, 'Bangkok') }

  CREATE TABLE t1(a PRIMARY KEY, b);
  INSERT INTO t1 VALUES('i', 'one');
}
do_iterator_test 1.1 t1 {
  DELETE FROM t1 WHERE a = 'i';
  INSERT INTO t1 VALUES('ii', 'two');
} {
  {DELETE t1 {t i t one} {}} 
  {INSERT t1 {} {t ii t two}}
}
do_iterator_test 1.2 t1 {
  INSERT INTO t1 VALUES(1.5, 99.9)
} {
  {INSERT t1 {} {f 1.5 f 99.9}}
}


# Execute each of the following blocks of SQL on database [db1]. Collect
# changes using a session object. Apply the resulting changeset to
# database [db2]. Then check that the contents of the two databases are
# identical.
................................................................................

foreach {tn sql changeset} {
  1 {
    INSERT INTO t1 VALUES(123);
    INSERT INTO t1 VALUES(NULL);
    INSERT INTO t1 VALUES(456);
  } {
    {INSERT t1 {} {i 456}} 
    {INSERT t1 {} {i 123}}
  }

  2 {
    UPDATE t1 SET a = NULL;
  } {
    {DELETE t1 {i 456} {}}
    {DELETE t1 {i 123} {}}
  }

  3 { DELETE FROM t1 } { }

  4 { 
    INSERT INTO t3 VALUES(NULL, NULL)
  } {
    {INSERT t3 {} {n {} i 1}} 
  }

  5 { INSERT INTO t2 VALUES(1, 2, NULL) }    { }
  6 { INSERT INTO t2 VALUES(1, NULL, 3) }    { }
  7 { INSERT INTO t2 VALUES(1, NULL, NULL) } { }
  8 { INSERT INTO t2 VALUES(1, 2, 3) }       { {INSERT t2 {} {i 1 i 2 i 3}} }
  9 { DELETE FROM t2 WHERE 1 }               { {DELETE t2 {i 1 i 2 i 3} {}} }

} {
  do_iterator_test 4.$tn {t1 t2 t3} $sql $changeset
}


#-------------------------------------------------------------------------
................................................................................
test_reset
do_execsql_test 5.0 {
  CREATE TABLE t1(a PRIMARY KEY);
  CREATE TABLE t2(x, y PRIMARY KEY);
}

foreach {tn sql changeset} {
  1 { INSERT INTO t1 VALUES(35) }     { {INSERT t1 {} {i 35}} }
  2 { INSERT INTO t2 VALUES(36, 37) } { {INSERT t2 {} {i 36 i 37}} }
  3 { 
    DELETE FROM t1 WHERE 1;
    UPDATE t2 SET x = 34;
  } { 
    {UPDATE t2 {i 36 i 37} {i 34 {} {}}}
    {DELETE t1 {i 35} {}}
  }
} {
  do_iterator_test 5.$tn * $sql $changeset
}














finish_test

  CREATE TABLE t1(a PRIMARY KEY, b);
  INSERT INTO t1 VALUES('i', 'one');
}
do_iterator_test 1.1 t1 {
  DELETE FROM t1 WHERE a = 'i';
  INSERT INTO t1 VALUES('ii', 'two');
} {
  {DELETE t1 0 {t i t one} {}} 
  {INSERT t1 0 {} {t ii t two}}
}
do_iterator_test 1.2 t1 {
  INSERT INTO t1 VALUES(1.5, 99.9)
} {
  {INSERT t1 0 {} {f 1.5 f 99.9}}
}


# Execute each of the following blocks of SQL on database [db1]. Collect
# changes using a session object. Apply the resulting changeset to
# database [db2]. Then check that the contents of the two databases are
# identical.
................................................................................

foreach {tn sql changeset} {
  1 {
    INSERT INTO t1 VALUES(123);
    INSERT INTO t1 VALUES(NULL);
    INSERT INTO t1 VALUES(456);
  } {
    {INSERT t1 0 {} {i 456}} 
    {INSERT t1 0 {} {i 123}}
  }

  2 {
    UPDATE t1 SET a = NULL;
  } {
    {DELETE t1 0 {i 456} {}}
    {DELETE t1 0 {i 123} {}}
  }

  3 { DELETE FROM t1 } { }

  4 { 
    INSERT INTO t3 VALUES(NULL, NULL)
  } {
    {INSERT t3 0 {} {n {} i 1}} 
  }

  5 { INSERT INTO t2 VALUES(1, 2, NULL) }    { }
  6 { INSERT INTO t2 VALUES(1, NULL, 3) }    { }
  7 { INSERT INTO t2 VALUES(1, NULL, NULL) } { }
  8 { INSERT INTO t2 VALUES(1, 2, 3) }       { {INSERT t2 0 {} {i 1 i 2 i 3}} }
  9 { DELETE FROM t2 WHERE 1 }               { {DELETE t2 0 {i 1 i 2 i 3} {}} }

} {
  do_iterator_test 4.$tn {t1 t2 t3} $sql $changeset
}


#-------------------------------------------------------------------------
................................................................................
test_reset
do_execsql_test 5.0 {
  CREATE TABLE t1(a PRIMARY KEY);
  CREATE TABLE t2(x, y PRIMARY KEY);
}

foreach {tn sql changeset} {
  1 { INSERT INTO t1 VALUES(35) }     { {INSERT t1 0 {} {i 35}} }
  2 { INSERT INTO t2 VALUES(36, 37) } { {INSERT t2 0 {} {i 36 i 37}} }
  3 { 
    DELETE FROM t1 WHERE 1;
    UPDATE t2 SET x = 34;
  } { 
    {UPDATE t2 0 {i 36 i 37} {i 34 {} {}}}
    {DELETE t1 0 {i 35} {}}
  }
} {
  do_iterator_test 5.$tn * $sql $changeset
}

#-------------------------------------------------------------------------
# The next block of tests verify that the "indirect" flag is set 
# correctly within changesets. The indirect flag is set for a change
# if either of the following are true:
#
#   * The sqlite3session_indirect() API has been used to set the session
#     indirect flag to true, or
#   * The change was made by a trigger.
#
# If the same row is updated more than once during a session, then the 
# change is considered indirect only if all changes meet the criteria 
# above.
#
test_reset
db function indirect [list S indirect]

do_execsql_test 6.0 {
  CREATE TABLE t1(a PRIMARY KEY, b, c);

  CREATE TABLE t2(x PRIMARY KEY, y);
  CREATE TRIGGER AFTER INSERT ON t2 WHEN new.x%2 BEGIN
    INSERT INTO t2 VALUES(new.x+1, NULL);
  END;
}

do_iterator_test 6.1.1 * {
  INSERT INTO t1 VALUES(1, 'one', 'i');
  SELECT indirect(1);
  INSERT INTO t1 VALUES(2, 'two', 'ii');
  SELECT indirect(0);
  INSERT INTO t1 VALUES(3, 'three', 'iii');
} {
  {INSERT t1 0 {} {i 1 t one t i}}
  {INSERT t1 1 {} {i 2 t two t ii}}
  {INSERT t1 0 {} {i 3 t three t iii}}
}

do_iterator_test 6.1.2 * {
  SELECT indirect(1);
  UPDATE t1 SET c = 'I' WHERE a = 1;
  SELECT indirect(0);
} {
  {UPDATE t1 1 {i 1 {} {} t i} {{} {} {} {} t I}}
}
do_iterator_test 6.1.3 * {
  SELECT indirect(1);
  UPDATE t1 SET c = '.' WHERE a = 1;
  SELECT indirect(0);
  UPDATE t1 SET c = 'o' WHERE a = 1;
} {
  {UPDATE t1 0 {i 1 {} {} t I} {{} {} {} {} t o}}
}
do_iterator_test 6.1.4 * {
  SELECT indirect(0);
  UPDATE t1 SET c = 'x' WHERE a = 1;
  SELECT indirect(1);
  UPDATE t1 SET c = 'i' WHERE a = 1;
} {
  {UPDATE t1 0 {i 1 {} {} t o} {{} {} {} {} t i}}
}
do_iterator_test 6.1.4 * {
  SELECT indirect(1);
  UPDATE t1 SET c = 'y' WHERE a = 1;
  SELECT indirect(1);
  UPDATE t1 SET c = 'I' WHERE a = 1;
} {
  {UPDATE t1 1 {i 1 {} {} t i} {{} {} {} {} t I}}
}

do_iterator_test 6.1.5 * {
  INSERT INTO t2 VALUES(1, 'x');
} {
  {INSERT t2 0 {} {i 1 t x}}
  {INSERT t2 1 {} {i 2 n {}}}
}

do_iterator_test 6.1.6 * {
  SELECT indirect(1);
  INSERT INTO t2 VALUES(3, 'x');
  SELECT indirect(0);
  UPDATE t2 SET y = 'y' WHERE x>2;
} {
  {INSERT t2 0 {} {i 3 t y}}
  {INSERT t2 0 {} {i 4 t y}}
}

do_iterator_test 6.1.7 * {
  SELECT indirect(1);
  DELETE FROM t2 WHERE x = 4;
  SELECT indirect(0);
  INSERT INTO t2 VALUES(4, 'new');
} {
  {UPDATE t2 0 {i 4 t y} {{} {} t new}}
}

finish_test

#-------------------------------------------------------------------------
# Test OOM error handling when collecting and applying a simple changeset.
#
# Test 1.1 attaches tables individually by name to the session object. 
# Whereas test 1.2 passes NULL to sqlite3session_attach() to attach all
# tables.
#
do_faultsim_test pagerfault-1.1 -faults oom-* -prep {
  catch {db2 close}
  catch {db close}
  faultsim_restore_and_reopen
  sqlite3 db2 test.db2
} -body {
  do_then_apply_sql {
    INSERT INTO t1 VALUES(7, 8, 9);
................................................................................
  }
} -test {
  faultsim_test_result {0 {}} {1 SQLITE_NOMEM}
  faultsim_integrity_check
  if {$testrc==0} { compare_db db db2 }
}

do_faultsim_test pagerfault-1.2 -faults oom-* -prep {
  catch {db2 close}
  catch {db close}
  faultsim_restore_and_reopen
} -body {
  sqlite3session S db main
  S attach *
  execsql {
................................................................................
    sqlite3 db2 test.db2
    sqlite3changeset_apply db2 $::changeset xConflict
    compare_db db db2 
  }
}

#-------------------------------------------------------------------------
# The following block of tests - pagerfault-2.* - are designed to check 
# the handling of faults in the sqlite3changeset_apply() function.
#
catch {db close}
catch {db2 close}
forcedelete test.db2 test.db
sqlite3 db2 test.db2
sqlite3 db test.db
................................................................................
  3 OMIT { UPDATE t1 SET c = 'banana' WHERE b = 'orange' }            {}
  4 REPLACE { INSERT INTO t2 VALUES('keyvalue', 'value 1') } {
    INSERT INTO t2 VALUES('keyvalue', 'value 2');
  }
} {
  proc xConflict args [list return $conflict_policy]

  do_faultsim_test pagerfault-2.$tn -faults oom-transient -prep {
    catch {db2 close}
    catch {db close}
    faultsim_restore_and_reopen
    set ::changeset [changeset_from_sql $::sql]
    sqlite3 db2 test.db2
    sqlite3_db_config_lookaside db2 0 0 0
    execsql $::sql2 db2
................................................................................
}

#-------------------------------------------------------------------------
# This test case is designed so that a malloc() failure occurs while
# resizing the session object hash-table from 256 to 512 buckets. This
# is not an error, just a sub-optimal condition.
#
do_faultsim_test pagerfault-3 -faults oom-* -prep {
  catch {db2 close}
  catch {db close}
  faultsim_restore_and_reopen
  sqlite3 db2 test.db2

  sqlite3session S db main
  S attach t1
................................................................................
    INSERT INTO t1 VALUES(4, 16);
  } db2
} {}

faultsim_save_and_close
db2 close

do_faultsim_test pagerfault-4 -faults oom-* -prep {
  catch {db2 close}
  catch {db close}
  faultsim_restore_and_reopen
  sqlite3 db2 test.db2
  sqlite3session S db main
  S attach t1
  execsql {
................................................................................
set changeset [changeset_from_sql {
  INSERT INTO t1 VALUES('xxx', 'yyy');
  DELETE FROM t1 WHERE a = 'string';
  UPDATE t1 SET a = 20 WHERE b = 2;
}]
db close

do_faultsim_test pagerfault-5 -faults oom* -body {
  set ::inverse [sqlite3changeset_invert $::changeset]
  set {} {}
} -test {
  faultsim_test_result {0 {}} {1 SQLITE_NOMEM}
  if {$testrc==0} {
    set x [list]
    sqlite3session_foreach c $::inverse { lappend x $c }
    foreach c {
        {DELETE t1 {t xxx t yyy} {}} 
        {INSERT t1 {} {t string i 1}} 
        {UPDATE t1 {i 20 {} {}} {i 4 i 2}}
    } { lappend y $c }
    if {$x != $y} { error "changeset no good" }
  }
}

finish_test

#-------------------------------------------------------------------------
# Test OOM error handling when collecting and applying a simple changeset.
#
# Test 1.1 attaches tables individually by name to the session object. 
# Whereas test 1.2 passes NULL to sqlite3session_attach() to attach all
# tables.
#
do_faultsim_test 1.1 -faults oom-* -prep {
  catch {db2 close}
  catch {db close}
  faultsim_restore_and_reopen
  sqlite3 db2 test.db2
} -body {
  do_then_apply_sql {
    INSERT INTO t1 VALUES(7, 8, 9);
................................................................................
  }
} -test {
  faultsim_test_result {0 {}} {1 SQLITE_NOMEM}
  faultsim_integrity_check
  if {$testrc==0} { compare_db db db2 }
}

do_faultsim_test 1.2 -faults oom-* -prep {
  catch {db2 close}
  catch {db close}
  faultsim_restore_and_reopen
} -body {
  sqlite3session S db main
  S attach *
  execsql {
................................................................................
    sqlite3 db2 test.db2
    sqlite3changeset_apply db2 $::changeset xConflict
    compare_db db db2 
  }
}

#-------------------------------------------------------------------------
# The following block of tests - 2.* - are designed to check 
# the handling of faults in the sqlite3changeset_apply() function.
#
catch {db close}
catch {db2 close}
forcedelete test.db2 test.db
sqlite3 db2 test.db2
sqlite3 db test.db
................................................................................
  3 OMIT { UPDATE t1 SET c = 'banana' WHERE b = 'orange' }            {}
  4 REPLACE { INSERT INTO t2 VALUES('keyvalue', 'value 1') } {
    INSERT INTO t2 VALUES('keyvalue', 'value 2');
  }
} {
  proc xConflict args [list return $conflict_policy]

  do_faultsim_test 2.$tn -faults oom-transient -prep {
    catch {db2 close}
    catch {db close}
    faultsim_restore_and_reopen
    set ::changeset [changeset_from_sql $::sql]
    sqlite3 db2 test.db2
    sqlite3_db_config_lookaside db2 0 0 0
    execsql $::sql2 db2
................................................................................
}

#-------------------------------------------------------------------------
# This test case is designed so that a malloc() failure occurs while
# resizing the session object hash-table from 256 to 512 buckets. This
# is not an error, just a sub-optimal condition.
#
do_faultsim_test 3 -faults oom-* -prep {
  catch {db2 close}
  catch {db close}
  faultsim_restore_and_reopen
  sqlite3 db2 test.db2

  sqlite3session S db main
  S attach t1
................................................................................
    INSERT INTO t1 VALUES(4, 16);
  } db2
} {}

faultsim_save_and_close
db2 close

do_faultsim_test 4 -faults oom-* -prep {
  catch {db2 close}
  catch {db close}
  faultsim_restore_and_reopen
  sqlite3 db2 test.db2
  sqlite3session S db main
  S attach t1
  execsql {
................................................................................
set changeset [changeset_from_sql {
  INSERT INTO t1 VALUES('xxx', 'yyy');
  DELETE FROM t1 WHERE a = 'string';
  UPDATE t1 SET a = 20 WHERE b = 2;
}]
db close

do_faultsim_test 5 -faults oom* -body {
  set ::inverse [sqlite3changeset_invert $::changeset]
  set {} {}
} -test {
  faultsim_test_result {0 {}} {1 SQLITE_NOMEM}
  if {$testrc==0} {
    set x [list]
    sqlite3session_foreach c $::inverse { lappend x $c }
    foreach c {
        {DELETE t1 0 {t xxx t yyy} {}} 
        {INSERT t1 0 {} {t string i 1}} 
        {UPDATE t1 0 {i 20 {} {}} {i 4 i 2}}
    } { lappend y $c }
    if {$x != $y} { error "changeset no good" }
  }
}

finish_test

/*
** Session handle structure.
*/
struct sqlite3_session {
  sqlite3 *db;                    /* Database handle session is attached to */
  char *zDb;                      /* Name of database session is attached to */
  int bEnable;                    /* True if currently recording */

  int bAutoAttach;                /* True to auto-attach tables */
  int rc;                         /* Non-zero if an error has occurred */
  sqlite3_session *pNext;         /* Next session object on same db. */
  SessionTable *pTable;           /* List of attached tables */
};

/*
................................................................................
  int nChangeset;                 /* Number of bytes in aChangeset */
  u8 *pNext;                      /* Pointer to next change within aChangeset */
  int rc;                         /* Iterator error code */
  sqlite3_stmt *pConflict;        /* Points to conflicting row, if any */
  char *zTab;                     /* Current table */
  int nCol;                       /* Number of columns in zTab */
  int op;                         /* Current operation */

  sqlite3_value **apValue;        /* old.* and new.* values */
};

/*
** Each session object maintains a set of the following structures, one
** for each table the session object is monitoring. The structures are
** stored in a linked list starting at sqlite3_session.pTable.
................................................................................

/*
** For each row modified during a session, there exists a single instance of
** this structure stored in a SessionTable.aChange[] hash table.
*/
struct SessionChange {
  int bInsert;                    /* True if row was inserted this session */

  int nRecord;                    /* Number of bytes in buffer aRecord[] */
  u8 *aRecord;                    /* Buffer containing old.* record */
  SessionChange *pNext;           /* For hash-table collisions */
};

/*
** Instances of this structure are used to build strings or binary records.
................................................................................

static void sessionPreupdateOneChange(
  int op,
  sqlite3_session *pSession,
  SessionTable *pTab
){
  sqlite3 *db = pSession->db;
  SessionChange *pChange;
  SessionChange *pC;
  int iHash; 
  int bNullPk = 0; 
  int rc = SQLITE_OK;

  if( pSession->rc ) return;

  /* Load table details if required */
................................................................................
  if( sessionGrowHash(pSession, pTab) ) return;

  /* Search the hash table for an existing entry for rowid=iKey2. If
  ** one is found, store a pointer to it in pChange and unlink it from
  ** the hash table. Otherwise, set pChange to NULL.
  */
  rc = sessionPreupdateHash(db, pTab, op==SQLITE_INSERT, &iHash, &bNullPk);
  if( bNullPk==0 ){

    for(pC=pTab->apChange[iHash]; rc==SQLITE_OK && pC; pC=pC->pNext){
      int bEqual;
      rc = sessionPreupdateEqual(db, pTab, pC, op==SQLITE_INSERT, &bEqual);
      if( bEqual ) break;
    }
    if( pC==0 ){
      /* Create a new change object containing all the old values (if
       ** this is an SQLITE_UPDATE or SQLITE_DELETE), or just the PK
       ** values (if this is an INSERT). */

      int nByte;              /* Number of bytes to allocate */
      int i;                  /* Used to iterate through columns */
  

      pTab->nEntry++;
  
      /* Figure out how large an allocation is required */
      nByte = sizeof(SessionChange);
      for(i=0; i<pTab->nCol && rc==SQLITE_OK; i++){
        sqlite3_value *p = 0;
        if( op!=SQLITE_INSERT ){
................................................................................
        }
        if( p && rc==SQLITE_OK ){
          rc = sessionSerializeValue(&pChange->aRecord[nByte], p, &nByte);
        }
      }
      if( rc==SQLITE_OK ){
        /* Add the change back to the hash-table */



        pChange->nRecord = nByte;
        pChange->bInsert = (op==SQLITE_INSERT);
        pChange->pNext = pTab->apChange[iHash];
        pTab->apChange[iHash] = pChange;
      }else{
        sqlite3_free(pChange);






      }
    }
  }

  /* If an error has occurred, mark the session object as failed. */
  if( rc!=SQLITE_OK ){
    pSession->rc = rc;
................................................................................
    SessionBuffer buf2 = {0,0,0}; /* Buffer to accumulate new.* record in */
    int bNoop = 1;                /* Set to zero if any values are modified */
    int nRewind = pBuf->nBuf;     /* Set to zero if any values are modified */
    int i;                        /* Used to iterate through columns */
    u8 *pCsr = p->aRecord;        /* Used to iterate through old.* values */

    sessionAppendByte(pBuf, SQLITE_UPDATE, pRc);

    for(i=0; i<sqlite3_column_count(pStmt); i++){
      int bChanged = 0;
      int nAdvance;
      int eType = *pCsr;
      switch( eType ){
        case SQLITE_NULL:
          nAdvance = 1;
................................................................................
        for(p=pTab->apChange[i]; rc==SQLITE_OK && p; p=p->pNext){
          rc = sessionSelectBind(pSel, nCol, abPK, p->aRecord, p->nRecord);
          if( rc==SQLITE_OK ){
            if( sqlite3_step(pSel)==SQLITE_ROW ){
              int iCol;
              if( p->bInsert ){
                sessionAppendByte(&buf, SQLITE_INSERT, &rc);

                for(iCol=0; iCol<nCol; iCol++){
                  sessionAppendCol(&buf, pSel, iCol, &rc);
                }
              }else{
                sessionAppendUpdate(&buf, pSel, p, abPK, &rc);
              }
            }else if( !p->bInsert ){
              /* A DELETE change */
              sessionAppendByte(&buf, SQLITE_DELETE, &rc);

              sessionAppendBlob(&buf, p->aRecord, p->nRecord, &rc);
            }
            if( rc==SQLITE_OK ){
              rc = sqlite3_reset(pSel);
            }
          }
        }
................................................................................
  if( bEnable>=0 ){
    pSession->bEnable = bEnable;
  }
  ret = pSession->bEnable;
  sqlite3_mutex_leave(sqlite3_db_mutex(pSession->db));
  return ret;
}















/*
** Create an iterator used to iterate through the contents of a changeset.
*/
int sqlite3changeset_start(
  sqlite3_changeset_iter **pp,    /* OUT: Changeset iterator handle */
  int nChangeset,                 /* Size of buffer pChangeset in bytes */
................................................................................
  c = *(aChange++);
  if( c=='T' ){
    int nByte;                    /* Bytes to allocate for apValue */
    aChange += sessionVarintGet(aChange, &p->nCol);
    p->zTab = (char *)aChange;
    aChange += (strlen((char *)aChange) + 1);
    p->op = *(aChange++);

    sqlite3_free(p->apValue);
    nByte = sizeof(sqlite3_value *) * p->nCol * 2;
    p->apValue = (sqlite3_value **)sqlite3_malloc(nByte);
    if( !p->apValue ){
      return (p->rc = SQLITE_NOMEM);
    }
    memset(p->apValue, 0, sizeof(sqlite3_value*)*p->nCol*2);
  }else{
    p->op = c;

  }
  if( p->op!=SQLITE_UPDATE && p->op!=SQLITE_DELETE && p->op!=SQLITE_INSERT ){
    return (p->rc = SQLITE_CORRUPT);
  }

  /* If this is an UPDATE or DELETE, read the old.* record. */
  if( p->op!=SQLITE_INSERT ){
................................................................................
** from a changeset iterator. They may only be called after changeset_next()
** has returned SQLITE_ROW.
*/
int sqlite3changeset_op(
  sqlite3_changeset_iter *pIter,  /* Iterator handle */
  const char **pzTab,             /* OUT: Pointer to table name */
  int *pnCol,                     /* OUT: Number of columns in table */
  int *pOp                        /* OUT: SQLITE_INSERT, DELETE or UPDATE */

){
  *pOp = pIter->op;
  *pnCol = pIter->nCol;
  *pzTab = pIter->zTab;

  return SQLITE_OK;
}

/*
** This function may only be called while the iterator is pointing to an
** SQLITE_UPDATE or SQLITE_DELETE change (see sqlite3changeset_op()).
** Otherwise, SQLITE_MISUSE is returned.
................................................................................
        i += nByte;
        break;
      }

      case SQLITE_INSERT:
      case SQLITE_DELETE: {
        int nByte;
        u8 *aEnd = &aIn[i+1];

        sessionReadRecord(&aEnd, nCol, 0);
        aOut[i] = (eType==SQLITE_DELETE ? SQLITE_INSERT : SQLITE_DELETE);

        nByte = aEnd - &aIn[i+1];
        memcpy(&aOut[i+1], &aIn[i+1], nByte);
        i += 1 + nByte;

        break;
      }

      case SQLITE_UPDATE: {
        int nByte1;              /* Size of old.* record in bytes */
        int nByte2;              /* Size of new.* record in bytes */
        u8 *aEnd = &aIn[i+1];    

        sessionReadRecord(&aEnd, nCol, 0);
        nByte1 = aEnd - &aIn[i+1];
        sessionReadRecord(&aEnd, nCol, 0);
        nByte2 = aEnd - &aIn[i+1] - nByte1;

        aOut[i] = SQLITE_UPDATE;
        memcpy(&aOut[i+1], &aIn[i+1+nByte1], nByte2);
        memcpy(&aOut[i+1+nByte2], &aIn[i+1], nByte1);


        i += 1 + nByte1 + nByte2;
        break;
      }

      default:
        sqlite3_free(aOut);
        return SQLITE_CORRUPT;
    }
................................................................................
  sqlite3_stmt *pSelect           /* SELECT statement from sessionSelectRow() */
){
  int rc;                         /* Return code */
  int nCol;                       /* Number of columns in table */
  int op;                         /* Changset operation (SQLITE_UPDATE etc.) */
  const char *zDummy;             /* Unused */

  sqlite3changeset_op(pIter, &zDummy, &nCol, &op);
  rc = sessionBindRow(pIter, 
      op==SQLITE_INSERT ? sqlite3changeset_new : sqlite3changeset_old,
      nCol, abPK, pSelect
  );

  if( rc==SQLITE_OK ){
    rc = sqlite3_step(pSelect);
................................................................................
){
  int res;                        /* Value returned by conflict handler */
  int rc;
  int nCol;
  int op;
  const char *zDummy;

  sqlite3changeset_op(pIter, &zDummy, &nCol, &op);

  assert( eType==SQLITE_CHANGESET_CONFLICT || eType==SQLITE_CHANGESET_DATA );
  assert( SQLITE_CHANGESET_CONFLICT+1==SQLITE_CHANGESET_CONSTRAINT );
  assert( SQLITE_CHANGESET_DATA+1==SQLITE_CHANGESET_NOTFOUND );

  /* Bind the new.* PRIMARY KEY values to the SELECT statement. */
  if( pbReplace ){
................................................................................
  int nCol;
  int rc = SQLITE_OK;

  assert( p->pDelete && p->pUpdate && p->pInsert && p->pSelect );
  assert( p->azCol && p->abPK );
  assert( !pbReplace || *pbReplace==0 );

  sqlite3changeset_op(pIter, &zDummy, &nCol, &op);

  if( op==SQLITE_DELETE ){

    /* Bind values to the DELETE statement. */
    rc = sessionBindRow(pIter, sqlite3changeset_old, nCol, 0, p->pDelete);
    if( rc==SQLITE_OK && sqlite3_bind_parameter_count(p->pDelete)>nCol ){
      rc = sqlite3_bind_int(p->pDelete, nCol+1, pbRetry==0);
................................................................................
  rc = sqlite3_exec(db, "SAVEPOINT changeset_apply", 0, 0, 0);
  while( rc==SQLITE_OK && SQLITE_ROW==sqlite3changeset_next(pIter) ){
    int nCol;
    int op;
    int bReplace = 0;
    int bRetry = 0;
    const char *zNew;
    sqlite3changeset_op(pIter, &zNew, &nCol, &op);

    if( zTab==0 || sqlite3_strnicmp(zNew, zTab, nTab+1) ){
      sqlite3_free(sApply.azCol);
      sqlite3_finalize(sApply.pDelete);
      sqlite3_finalize(sApply.pUpdate); 
      sqlite3_finalize(sApply.pInsert);
      sqlite3_finalize(sApply.pSelect);

/*
** Session handle structure.
*/
struct sqlite3_session {
  sqlite3 *db;                    /* Database handle session is attached to */
  char *zDb;                      /* Name of database session is attached to */
  int bEnable;                    /* True if currently recording */
  int bIndirect;                  /* True if all changes are indirect */
  int bAutoAttach;                /* True to auto-attach tables */
  int rc;                         /* Non-zero if an error has occurred */
  sqlite3_session *pNext;         /* Next session object on same db. */
  SessionTable *pTable;           /* List of attached tables */
};

/*
................................................................................
  int nChangeset;                 /* Number of bytes in aChangeset */
  u8 *pNext;                      /* Pointer to next change within aChangeset */
  int rc;                         /* Iterator error code */
  sqlite3_stmt *pConflict;        /* Points to conflicting row, if any */
  char *zTab;                     /* Current table */
  int nCol;                       /* Number of columns in zTab */
  int op;                         /* Current operation */
  int bIndirect;                  /* True if current change was indirect */
  sqlite3_value **apValue;        /* old.* and new.* values */
};

/*
** Each session object maintains a set of the following structures, one
** for each table the session object is monitoring. The structures are
** stored in a linked list starting at sqlite3_session.pTable.
................................................................................

/*
** For each row modified during a session, there exists a single instance of
** this structure stored in a SessionTable.aChange[] hash table.
*/
struct SessionChange {
  int bInsert;                    /* True if row was inserted this session */
  int bIndirect;                  /* True if this change is "indirect" */
  int nRecord;                    /* Number of bytes in buffer aRecord[] */
  u8 *aRecord;                    /* Buffer containing old.* record */
  SessionChange *pNext;           /* For hash-table collisions */
};

/*
** Instances of this structure are used to build strings or binary records.
................................................................................

static void sessionPreupdateOneChange(
  int op,
  sqlite3_session *pSession,
  SessionTable *pTab
){
  sqlite3 *db = pSession->db;


  int iHash; 
  int bNullPk = 0; 
  int rc = SQLITE_OK;

  if( pSession->rc ) return;

  /* Load table details if required */
................................................................................
  if( sessionGrowHash(pSession, pTab) ) return;

  /* Search the hash table for an existing entry for rowid=iKey2. If
  ** one is found, store a pointer to it in pChange and unlink it from
  ** the hash table. Otherwise, set pChange to NULL.
  */
  rc = sessionPreupdateHash(db, pTab, op==SQLITE_INSERT, &iHash, &bNullPk);
  if( rc==SQLITE_OK && bNullPk==0 ){
    SessionChange *pC;
    for(pC=pTab->apChange[iHash]; rc==SQLITE_OK && pC; pC=pC->pNext){
      int bEqual;
      rc = sessionPreupdateEqual(db, pTab, pC, op==SQLITE_INSERT, &bEqual);
      if( bEqual ) break;
    }
    if( pC==0 ){
      /* Create a new change object containing all the old values (if
       ** this is an SQLITE_UPDATE or SQLITE_DELETE), or just the PK
       ** values (if this is an INSERT). */
      SessionChange *pChange; /* New change object */
      int nByte;              /* Number of bytes to allocate */
      int i;                  /* Used to iterate through columns */
  
      assert( rc==SQLITE_OK );
      pTab->nEntry++;
  
      /* Figure out how large an allocation is required */
      nByte = sizeof(SessionChange);
      for(i=0; i<pTab->nCol && rc==SQLITE_OK; i++){
        sqlite3_value *p = 0;
        if( op!=SQLITE_INSERT ){
................................................................................
        }
        if( p && rc==SQLITE_OK ){
          rc = sessionSerializeValue(&pChange->aRecord[nByte], p, &nByte);
        }
      }
      if( rc==SQLITE_OK ){
        /* Add the change back to the hash-table */
        if( pSession->bIndirect || sqlite3_preupdate_depth(pSession->db) ){
          pChange->bIndirect = 1;
        }
        pChange->nRecord = nByte;
        pChange->bInsert = (op==SQLITE_INSERT);
        pChange->pNext = pTab->apChange[iHash];
        pTab->apChange[iHash] = pChange;
      }else{
        sqlite3_free(pChange);
      }
    }else if( rc==SQLITE_OK && pC->bIndirect ){
      /* If the existing change is considered "indirect", but this current
      ** change is "direct", mark the change object as direct. */
      if( sqlite3_preupdate_depth(pSession->db)==0 && pSession->bIndirect==0 ){
        pC->bIndirect = 0;
      }
    }
  }

  /* If an error has occurred, mark the session object as failed. */
  if( rc!=SQLITE_OK ){
    pSession->rc = rc;
................................................................................
    SessionBuffer buf2 = {0,0,0}; /* Buffer to accumulate new.* record in */
    int bNoop = 1;                /* Set to zero if any values are modified */
    int nRewind = pBuf->nBuf;     /* Set to zero if any values are modified */
    int i;                        /* Used to iterate through columns */
    u8 *pCsr = p->aRecord;        /* Used to iterate through old.* values */

    sessionAppendByte(pBuf, SQLITE_UPDATE, pRc);
    sessionAppendByte(pBuf, p->bIndirect, pRc);
    for(i=0; i<sqlite3_column_count(pStmt); i++){
      int bChanged = 0;
      int nAdvance;
      int eType = *pCsr;
      switch( eType ){
        case SQLITE_NULL:
          nAdvance = 1;
................................................................................
        for(p=pTab->apChange[i]; rc==SQLITE_OK && p; p=p->pNext){
          rc = sessionSelectBind(pSel, nCol, abPK, p->aRecord, p->nRecord);
          if( rc==SQLITE_OK ){
            if( sqlite3_step(pSel)==SQLITE_ROW ){
              int iCol;
              if( p->bInsert ){
                sessionAppendByte(&buf, SQLITE_INSERT, &rc);
                sessionAppendByte(&buf, p->bIndirect, &rc);
                for(iCol=0; iCol<nCol; iCol++){
                  sessionAppendCol(&buf, pSel, iCol, &rc);
                }
              }else{
                sessionAppendUpdate(&buf, pSel, p, abPK, &rc);
              }
            }else if( !p->bInsert ){
              /* A DELETE change */
              sessionAppendByte(&buf, SQLITE_DELETE, &rc);
              sessionAppendByte(&buf, p->bIndirect, &rc);
              sessionAppendBlob(&buf, p->aRecord, p->nRecord, &rc);
            }
            if( rc==SQLITE_OK ){
              rc = sqlite3_reset(pSel);
            }
          }
        }
................................................................................
  if( bEnable>=0 ){
    pSession->bEnable = bEnable;
  }
  ret = pSession->bEnable;
  sqlite3_mutex_leave(sqlite3_db_mutex(pSession->db));
  return ret;
}

/*
** Enable or disable the session object passed as the first argument.
*/
int sqlite3session_indirect(sqlite3_session *pSession, int bIndirect){
  int ret;
  sqlite3_mutex_enter(sqlite3_db_mutex(pSession->db));
  if( bIndirect>=0 ){
    pSession->bIndirect = bIndirect;
  }
  ret = pSession->bIndirect;
  sqlite3_mutex_leave(sqlite3_db_mutex(pSession->db));
  return ret;
}

/*
** Create an iterator used to iterate through the contents of a changeset.
*/
int sqlite3changeset_start(
  sqlite3_changeset_iter **pp,    /* OUT: Changeset iterator handle */
  int nChangeset,                 /* Size of buffer pChangeset in bytes */
................................................................................
  c = *(aChange++);
  if( c=='T' ){
    int nByte;                    /* Bytes to allocate for apValue */
    aChange += sessionVarintGet(aChange, &p->nCol);
    p->zTab = (char *)aChange;
    aChange += (strlen((char *)aChange) + 1);
    p->op = *(aChange++);
    p->bIndirect = *(aChange++);
    sqlite3_free(p->apValue);
    nByte = sizeof(sqlite3_value *) * p->nCol * 2;
    p->apValue = (sqlite3_value **)sqlite3_malloc(nByte);
    if( !p->apValue ){
      return (p->rc = SQLITE_NOMEM);
    }
    memset(p->apValue, 0, sizeof(sqlite3_value*)*p->nCol*2);
  }else{
    p->op = c;
    p->bIndirect = *(aChange++);
  }
  if( p->op!=SQLITE_UPDATE && p->op!=SQLITE_DELETE && p->op!=SQLITE_INSERT ){
    return (p->rc = SQLITE_CORRUPT);
  }

  /* If this is an UPDATE or DELETE, read the old.* record. */
  if( p->op!=SQLITE_INSERT ){
................................................................................
** from a changeset iterator. They may only be called after changeset_next()
** has returned SQLITE_ROW.
*/
int sqlite3changeset_op(
  sqlite3_changeset_iter *pIter,  /* Iterator handle */
  const char **pzTab,             /* OUT: Pointer to table name */
  int *pnCol,                     /* OUT: Number of columns in table */
  int *pOp,                       /* OUT: SQLITE_INSERT, DELETE or UPDATE */
  int *pbIndirect                 /* OUT: True if change is indirect */
){
  *pOp = pIter->op;
  *pnCol = pIter->nCol;
  *pzTab = pIter->zTab;
  if( pbIndirect ) *pbIndirect = pIter->bIndirect;
  return SQLITE_OK;
}

/*
** This function may only be called while the iterator is pointing to an
** SQLITE_UPDATE or SQLITE_DELETE change (see sqlite3changeset_op()).
** Otherwise, SQLITE_MISUSE is returned.
................................................................................
        i += nByte;
        break;
      }

      case SQLITE_INSERT:
      case SQLITE_DELETE: {
        int nByte;
        u8 *aEnd = &aIn[i+2];

        sessionReadRecord(&aEnd, nCol, 0);
        aOut[i] = (eType==SQLITE_DELETE ? SQLITE_INSERT : SQLITE_DELETE);
        aOut[i+1] = aIn[i+1];
        nByte = aEnd - &aIn[i+2];
        memcpy(&aOut[i+2], &aIn[i+2], nByte);

        i += 2 + nByte;
        break;
      }

      case SQLITE_UPDATE: {
        int nByte1;              /* Size of old.* record in bytes */
        int nByte2;              /* Size of new.* record in bytes */
        u8 *aEnd = &aIn[i+2];    

        sessionReadRecord(&aEnd, nCol, 0);
        nByte1 = aEnd - &aIn[i+2];
        sessionReadRecord(&aEnd, nCol, 0);
        nByte2 = aEnd - &aIn[i+2] - nByte1;

        aOut[i] = SQLITE_UPDATE;
        aOut[i+1] = aIn[i+1];
        memcpy(&aOut[i+2], &aIn[i+2+nByte1], nByte2);
        memcpy(&aOut[i+2+nByte2], &aIn[i+2], nByte1);

        i += 2 + nByte1 + nByte2;
        break;
      }

      default:
        sqlite3_free(aOut);
        return SQLITE_CORRUPT;
    }
................................................................................
  sqlite3_stmt *pSelect           /* SELECT statement from sessionSelectRow() */
){
  int rc;                         /* Return code */
  int nCol;                       /* Number of columns in table */
  int op;                         /* Changset operation (SQLITE_UPDATE etc.) */
  const char *zDummy;             /* Unused */

  sqlite3changeset_op(pIter, &zDummy, &nCol, &op, 0);
  rc = sessionBindRow(pIter, 
      op==SQLITE_INSERT ? sqlite3changeset_new : sqlite3changeset_old,
      nCol, abPK, pSelect
  );

  if( rc==SQLITE_OK ){
    rc = sqlite3_step(pSelect);
................................................................................
){
  int res;                        /* Value returned by conflict handler */
  int rc;
  int nCol;
  int op;
  const char *zDummy;

  sqlite3changeset_op(pIter, &zDummy, &nCol, &op, 0);

  assert( eType==SQLITE_CHANGESET_CONFLICT || eType==SQLITE_CHANGESET_DATA );
  assert( SQLITE_CHANGESET_CONFLICT+1==SQLITE_CHANGESET_CONSTRAINT );
  assert( SQLITE_CHANGESET_DATA+1==SQLITE_CHANGESET_NOTFOUND );

  /* Bind the new.* PRIMARY KEY values to the SELECT statement. */
  if( pbReplace ){
................................................................................
  int nCol;
  int rc = SQLITE_OK;

  assert( p->pDelete && p->pUpdate && p->pInsert && p->pSelect );
  assert( p->azCol && p->abPK );
  assert( !pbReplace || *pbReplace==0 );

  sqlite3changeset_op(pIter, &zDummy, &nCol, &op, 0);

  if( op==SQLITE_DELETE ){

    /* Bind values to the DELETE statement. */
    rc = sessionBindRow(pIter, sqlite3changeset_old, nCol, 0, p->pDelete);
    if( rc==SQLITE_OK && sqlite3_bind_parameter_count(p->pDelete)>nCol ){
      rc = sqlite3_bind_int(p->pDelete, nCol+1, pbRetry==0);
................................................................................
  rc = sqlite3_exec(db, "SAVEPOINT changeset_apply", 0, 0, 0);
  while( rc==SQLITE_OK && SQLITE_ROW==sqlite3changeset_next(pIter) ){
    int nCol;
    int op;
    int bReplace = 0;
    int bRetry = 0;
    const char *zNew;
    sqlite3changeset_op(pIter, &zNew, &nCol, &op, 0);

    if( zTab==0 || sqlite3_strnicmp(zNew, zTab, nTab+1) ){
      sqlite3_free(sApply.azCol);
      sqlite3_finalize(sApply.pDelete);
      sqlite3_finalize(sApply.pUpdate); 
      sqlite3_finalize(sApply.pInsert);
      sqlite3_finalize(sApply.pSelect);

** no-op, and may be used to query the current state of the session.
**
** The return value indicates the final state of the session object: 0 if 
** the session is disabled, or 1 if it is enabled.
*/
int sqlite3session_enable(sqlite3_session *pSession, int bEnable);






























/*
** CAPI3REF: Attach A Table To A Session Object
**
** If argument zTab is not NULL, then it is the name of a table to attach
** to the session object passed as the first argument. All subsequent changes 
** made to the table while the session object is enabled will be recorded. See 
** documentation for [sqlite3session_changeset()] for further details.
................................................................................
** is not the case, this function returns [SQLITE_MISUSE].
**
** If argument pzTab is not NULL, then *pzTab is set to point to a
** nul-terminated utf-8 encoded string containing the name of the table
** affected by the current change. The buffer remains valid until either
** sqlite3changeset_next() is called on the iterator or until the 
** conflict-handler function returns. If pnCol is not NULL, then *pnCol is 
** set to the number of columns in the table affected by the change. Finally,



** if pOp is not NULL, then *pOp is set to one of [SQLITE_INSERT], 
** [SQLITE_DELETE] or [SQLITE_UPDATE], depending on the type of change that 
** the iterator currently points to.
**
** If no error occurs, SQLITE_OK is returned. If an error does occur, an
** SQLite error code is returned. The values of the output variables may not
** be trusted in this case.
*/
int sqlite3changeset_op(
  sqlite3_changeset_iter *pIter,  /* Iterator object */
  const char **pzTab,             /* OUT: Pointer to table name */
  int *pnCol,                     /* OUT: Number of columns in table */
  int *pOp                        /* OUT: SQLITE_INSERT, DELETE or UPDATE */

);

/*
** CAPI3REF: Obtain old.* Values From A Changeset Iterator
**
** The pIter argument passed to this function may either be an iterator
** passed to a conflict-handler by [sqlite3changeset_apply()], or an iterator

** no-op, and may be used to query the current state of the session.
**
** The return value indicates the final state of the session object: 0 if 
** the session is disabled, or 1 if it is enabled.
*/
int sqlite3session_enable(sqlite3_session *pSession, int bEnable);

/*
** CAPI3REF: Set Or Clear the Indirect Change Flag
**
** Each change recorded by a session object is marked as either direct or
** indirect. A change is marked as indirect if either:
**
** <ul>
**   <li> The session object "indirect" flag is set when the change is
**        made, or
**   <li> The change is made by an SQL trigger or foreign key action 
**        instead of directly as a result of a users SQL statement.
** </ul>
**
** If a single row is affected by more than one operation within a session,
** then the change is considered indirect if all operations meet the criteria
** for an indirect change above, or direct otherwise.
**
** This function is used to set, clear or query the session object indirect
** flag.  If the second argument passed to this function is zero, then the
** indirect flag is cleared. If it is greater than zero, the indirect flag
** is set. Passing a value less than zero does not modify the current value
** of the indirect flag, and may be used to query the current state of the 
** indirect flag for the specified session object.
**
** The return value indicates the final state of the indirect flag: 0 if 
** it is clear, or 1 if it is set.
*/
int sqlite3session_indirect(sqlite3_session *pSession, int bIndirect);

/*
** CAPI3REF: Attach A Table To A Session Object
**
** If argument zTab is not NULL, then it is the name of a table to attach
** to the session object passed as the first argument. All subsequent changes 
** made to the table while the session object is enabled will be recorded. See 
** documentation for [sqlite3session_changeset()] for further details.
................................................................................
** is not the case, this function returns [SQLITE_MISUSE].
**
** If argument pzTab is not NULL, then *pzTab is set to point to a
** nul-terminated utf-8 encoded string containing the name of the table
** affected by the current change. The buffer remains valid until either
** sqlite3changeset_next() is called on the iterator or until the 
** conflict-handler function returns. If pnCol is not NULL, then *pnCol is 
** set to the number of columns in the table affected by the change. If
** pbIncorrect is not NULL, then *pbIndirect is set to true (1) if the change
** is an indirect change, or false (0) otherwise. See the documentation for
** [sqlite3session_indirect()] for a description of direct and indirect
** changes. Finally, if pOp is not NULL, then *pOp is set to one of 
** [SQLITE_INSERT], [SQLITE_DELETE] or [SQLITE_UPDATE], depending on the 
** type of change that the iterator currently points to.
**
** If no error occurs, SQLITE_OK is returned. If an error does occur, an
** SQLite error code is returned. The values of the output variables may not
** be trusted in this case.
*/
int sqlite3changeset_op(
  sqlite3_changeset_iter *pIter,  /* Iterator object */
  const char **pzTab,             /* OUT: Pointer to table name */
  int *pnCol,                     /* OUT: Number of columns in table */
  int *pOp,                       /* OUT: SQLITE_INSERT, DELETE or UPDATE */
  int *pbIndirect                 /* OUT: True for an 'indirect' change */
);

/*
** CAPI3REF: Obtain old.* Values From A Changeset Iterator
**
** The pIter argument passed to this function may either be an iterator
** passed to a conflict-handler by [sqlite3changeset_apply()], or an iterator

}

/*
** Tclcmd:  $session attach TABLE
**          $session changeset
**          $session delete
**          $session enable BOOL

*/
static int test_session_cmd(
  void *clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
................................................................................
    int nArg;
    const char *zMsg;
    int iSub;
  } aSub[] = {
    { "attach",    1, "TABLE", }, /* 0 */
    { "changeset", 0, "",      }, /* 1 */
    { "delete",    0, "",      }, /* 2 */
    { "enable",    1, "",      }, /* 3 */

    { 0 }
  };
  int iSub;
  int rc;

  if( objc<2 ){
    Tcl_WrongNumArgs(interp, 1, objv, "SUBCOMMAND ...");
................................................................................
    case 3: {      /* enable */
      int val;
      if( Tcl_GetBooleanFromObj(interp, objv[2], &val) ) return TCL_ERROR;
      val = sqlite3session_enable(pSession, val);
      Tcl_SetObjResult(interp, Tcl_NewBooleanObj(val));
      break;
    }








  }

  return TCL_OK;
}

static void test_session_del(void *clientData){
  sqlite3_session *pSession = (sqlite3_session *)clientData;
................................................................................
  int op;                         /* SQLITE_UPDATE, DELETE or INSERT */
  const char *zTab;               /* Name of table conflict is on */
  int nCol;                       /* Number of columns in table zTab */

  pEval = Tcl_DuplicateObj(p->pScript);
  Tcl_IncrRefCount(pEval);

  sqlite3changeset_op(pIter, &zTab, &nCol, &op);

  /* Append the operation type. */
  Tcl_ListObjAppendElement(0, pEval, Tcl_NewStringObj(
      op==SQLITE_INSERT ? "INSERT" :
      op==SQLITE_UPDATE ? "UPDATE" : 
      "DELETE", -1
  ));
................................................................................
  while( SQLITE_ROW==sqlite3changeset_next(pIter) ){
    int nCol;                     /* Number of columns in table */
    int op;                       /* SQLITE_INSERT, UPDATE or DELETE */
    const char *zTab;             /* Name of table change applies to */
    Tcl_Obj *pVar;                /* Tcl value to set $VARNAME to */
    Tcl_Obj *pOld;                /* Vector of old.* values */
    Tcl_Obj *pNew;                /* Vector of new.* values */


    sqlite3changeset_op(pIter, &zTab, &nCol, &op);
    pVar = Tcl_NewObj();
    Tcl_ListObjAppendElement(0, pVar, Tcl_NewStringObj(
          op==SQLITE_INSERT ? "INSERT" :
          op==SQLITE_UPDATE ? "UPDATE" : 
          "DELETE", -1
    ));
    Tcl_ListObjAppendElement(0, pVar, Tcl_NewStringObj(zTab, -1));


    pOld = Tcl_NewObj();
    if( op!=SQLITE_INSERT ){
      int i;
      for(i=0; i<nCol; i++){
        sqlite3_value *pVal;
        sqlite3changeset_old(pIter, i, &pVal);

}

/*
** Tclcmd:  $session attach TABLE
**          $session changeset
**          $session delete
**          $session enable BOOL
**          $session indirect BOOL
*/
static int test_session_cmd(
  void *clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
................................................................................
    int nArg;
    const char *zMsg;
    int iSub;
  } aSub[] = {
    { "attach",    1, "TABLE", }, /* 0 */
    { "changeset", 0, "",      }, /* 1 */
    { "delete",    0, "",      }, /* 2 */
    { "enable",    1, "BOOL",  }, /* 3 */
    { "indirect",  1, "BOOL",  }, /* 4 */
    { 0 }
  };
  int iSub;
  int rc;

  if( objc<2 ){
    Tcl_WrongNumArgs(interp, 1, objv, "SUBCOMMAND ...");
................................................................................
    case 3: {      /* enable */
      int val;
      if( Tcl_GetBooleanFromObj(interp, objv[2], &val) ) return TCL_ERROR;
      val = sqlite3session_enable(pSession, val);
      Tcl_SetObjResult(interp, Tcl_NewBooleanObj(val));
      break;
    }

    case 4: {      /* indirect */
      int val;
      if( Tcl_GetBooleanFromObj(interp, objv[2], &val) ) return TCL_ERROR;
      val = sqlite3session_indirect(pSession, val);
      Tcl_SetObjResult(interp, Tcl_NewBooleanObj(val));
      break;
    }
  }

  return TCL_OK;
}

static void test_session_del(void *clientData){
  sqlite3_session *pSession = (sqlite3_session *)clientData;
................................................................................
  int op;                         /* SQLITE_UPDATE, DELETE or INSERT */
  const char *zTab;               /* Name of table conflict is on */
  int nCol;                       /* Number of columns in table zTab */

  pEval = Tcl_DuplicateObj(p->pScript);
  Tcl_IncrRefCount(pEval);

  sqlite3changeset_op(pIter, &zTab, &nCol, &op, 0);

  /* Append the operation type. */
  Tcl_ListObjAppendElement(0, pEval, Tcl_NewStringObj(
      op==SQLITE_INSERT ? "INSERT" :
      op==SQLITE_UPDATE ? "UPDATE" : 
      "DELETE", -1
  ));
................................................................................
  while( SQLITE_ROW==sqlite3changeset_next(pIter) ){
    int nCol;                     /* Number of columns in table */
    int op;                       /* SQLITE_INSERT, UPDATE or DELETE */
    const char *zTab;             /* Name of table change applies to */
    Tcl_Obj *pVar;                /* Tcl value to set $VARNAME to */
    Tcl_Obj *pOld;                /* Vector of old.* values */
    Tcl_Obj *pNew;                /* Vector of new.* values */
    int bIndirect;

    sqlite3changeset_op(pIter, &zTab, &nCol, &op, &bIndirect);
    pVar = Tcl_NewObj();
    Tcl_ListObjAppendElement(0, pVar, Tcl_NewStringObj(
          op==SQLITE_INSERT ? "INSERT" :
          op==SQLITE_UPDATE ? "UPDATE" : 
          "DELETE", -1
    ));
    Tcl_ListObjAppendElement(0, pVar, Tcl_NewStringObj(zTab, -1));
    Tcl_ListObjAppendElement(0, pVar, Tcl_NewBooleanObj(bIndirect));

    pOld = Tcl_NewObj();
    if( op!=SQLITE_INSERT ){
      int i;
      for(i=0; i<nCol; i++){
        sqlite3_value *pVal;
        sqlite3changeset_old(pIter, i, &pVal);