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Overview
Comment:Add OOM tests and related fixes for the session module.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | sessions
Files: files | file ages | folders
SHA1: 06048a68b351e3eb15a890cb54db8a1d4b345fbc
User & Date: dan 2011-03-22 12:08:00
Context
2011-03-22
15:21
If a NULL pointer is passed to sqlite3session_attach() in place of a table name, attach all database tables to the session object. check-in: e9037e4e user: dan tags: sessions
12:08
Add OOM tests and related fixes for the session module. check-in: 06048a68 user: dan tags: sessions
02:03
Fix a couple typos for consistency in sessions documentation. check-in: 510198f1 user: shaneh tags: sessions
Changes
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Changes to ext/session/session_common.tcl.

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  S delete
}

proc do_common_sql {sql} {
  execsql $sql db
  execsql $sql db2
}


















proc do_then_apply_sql {sql {dbname main}} {
  proc xConflict args { return "OMIT" }

  set rc [catch {
    sqlite3session S db $dbname
    db eval "SELECT name FROM $dbname.sqlite_master WHERE type = 'table'" {
      S attach $name
    }
    db eval $sql
    sqlite3changeset_apply db2 [S changeset] xConflict
................................................................................
    $db1 eval "PRAGMA table_info = $tbl" { lappend col1 $name }
    $db2 eval "PRAGMA table_info = $tbl" { lappend col2 $name }
    if {$col1 != $col2} { error "table $tbl schema mismatch" }

    set sql "SELECT * FROM $tbl ORDER BY [join $col1 ,]"
    set data1 [$db1 eval $sql]
    set data2 [$db2 eval $sql]



    if {$data1 != $data2} { error "table $tbl data mismatch" }

  }

  return ""
}










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  S delete
}

proc do_common_sql {sql} {
  execsql $sql db
  execsql $sql db2
}

proc changeset_from_sql {sql {dbname main}} {
  set rc [catch {
    sqlite3session S db $dbname
    db eval "SELECT name FROM $dbname.sqlite_master WHERE type = 'table'" {
      S attach $name
    }
    db eval $sql
    S changeset
  } changeset]
  catch { S delete }

  if {$rc} {
    error $changeset
  }
  return $changeset
}

proc do_then_apply_sql {sql {dbname main}} {
  proc xConflict args { return "OMIT" }

  set rc [catch {
    sqlite3session S db $dbname
    db eval "SELECT name FROM $dbname.sqlite_master WHERE type = 'table'" {
      S attach $name
    }
    db eval $sql
    sqlite3changeset_apply db2 [S changeset] xConflict
................................................................................
    $db1 eval "PRAGMA table_info = $tbl" { lappend col1 $name }
    $db2 eval "PRAGMA table_info = $tbl" { lappend col2 $name }
    if {$col1 != $col2} { error "table $tbl schema mismatch" }

    set sql "SELECT * FROM $tbl ORDER BY [join $col1 ,]"
    set data1 [$db1 eval $sql]
    set data2 [$db2 eval $sql]
    if {$data1 != $data2} { 
      puts "$data1"
      puts "$data2"
      error "table $tbl data mismatch" 
    }
  }

  return ""
}



Changes to ext/session/sessionfault.test.

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source [file join [file dirname [info script]] session_common.tcl]
source $testdir/tester.tcl

set testprefix sessionfault

forcedelete test.db2
sqlite3 db2 test.db2

do_common_sql {
  CREATE TABLE t1(a, b, c, PRIMARY KEY(a, b));
  INSERT INTO t1 VALUES(1, 2, 3);
  INSERT INTO t1 VALUES(4, 5, 6);
}
faultsim_save_and_close
db2 close



# Test OOM error handling when collecting and applying a simple changeset.
#
do_faultsim_test pagerfault-1 -faults oom-* -prep {
  catch {db2 close}
  catch {db close}
  faultsim_restore_and_reopen
  sqlite3 db2 test.db2
................................................................................
  }
} -test {
  faultsim_test_result {0 {}} {1 SQLITE_NOMEM}
  faultsim_integrity_check
  if {$testrc==0} { compare_db db 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-2 -faults oom-* -prep {
  catch {db2 close}
  catch {db close}
  faultsim_restore_and_reopen
  sqlite3 db2 test.db2

  sqlite3session S db main
  S attach t1
................................................................................
proc xConflict {op tbl type args} {
  if { $type=="CONFLICT" || $type=="DATA" } {
    return "REPLACE"
  }
  return "OMIT"
}

do_test 3.0 {
  execsql {
    PRAGMA encoding = 'utf16';
    CREATE TABLE t1(a PRIMARY KEY, b);
    INSERT INTO t1 VALUES(5, 32);
  }
  execsql {
    PRAGMA encoding = 'utf16';
................................................................................
    INSERT INTO t1 VALUES(4, 16);
  } db2
} {}

faultsim_save_and_close
db2 close

do_faultsim_test pagerfault-3 -faults oom-transient -prep {
  catch {db2 close}
  catch {db close}
  faultsim_restore_and_reopen
  sqlite3 db2 test.db2
  sqlite3session S db main
  S attach t1
  execsql {
................................................................................
} -body {
  sqlite3changeset_apply db2 [S changeset] xConflict
} -test {
  catch { S delete }
  faultsim_test_result {0 {}} {1 SQLITE_NOMEM}
  if {$testrc==0} { compare_db db db2 }
}








































finish_test







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source [file join [file dirname [info script]] session_common.tcl]
source $testdir/tester.tcl

set testprefix sessionfault

forcedelete test.db2
sqlite3 db2 test.db2

do_common_sql {
  CREATE TABLE t1(a, b, c, PRIMARY KEY(a, b));
  INSERT INTO t1 VALUES(1, 2, 3);
  INSERT INTO t1 VALUES(4, 5, 6);
}
faultsim_save_and_close
db2 close


#-------------------------------------------------------------------------
# Test OOM error handling when collecting and applying a simple changeset.
#
do_faultsim_test pagerfault-1 -faults oom-* -prep {
  catch {db2 close}
  catch {db close}
  faultsim_restore_and_reopen
  sqlite3 db2 test.db2
................................................................................
  }
} -test {
  faultsim_test_result {0 {}} {1 SQLITE_NOMEM}
  faultsim_integrity_check
  if {$testrc==0} { 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
do_common_sql {
  CREATE TABLE t1(a, b, c, PRIMARY KEY(a, b));
  INSERT INTO t1 VALUES('apple', 'orange', 'pear');

  CREATE TABLE t2(x PRIMARY KEY, y);
}
db2 close
faultsim_save_and_close


foreach {tn conflict_policy sql sql2} {
  1 OMIT { INSERT INTO t1 VALUES('one text', 'two text', X'00ff00') } {}
  2 OMIT { DELETE FROM t1 WHERE a = 'apple' }                         {}
  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
  } -body {
    sqlite3changeset_apply db2 $::changeset xConflict
  } -test {
    faultsim_test_result {0 {}} {1 SQLITE_NOMEM}
    faultsim_integrity_check
    if {$testrc==0} { compare_db db 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
................................................................................
proc xConflict {op tbl type args} {
  if { $type=="CONFLICT" || $type=="DATA" } {
    return "REPLACE"
  }
  return "OMIT"
}

do_test 4.0 {
  execsql {
    PRAGMA encoding = 'utf16';
    CREATE TABLE t1(a PRIMARY KEY, b);
    INSERT INTO t1 VALUES(5, 32);
  }
  execsql {
    PRAGMA encoding = 'utf16';
................................................................................
    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 {
................................................................................
} -body {
  sqlite3changeset_apply db2 [S changeset] xConflict
} -test {
  catch { S delete }
  faultsim_test_result {0 {}} {1 SQLITE_NOMEM}
  if {$testrc==0} { compare_db db db2 }
}

#-------------------------------------------------------------------------
# This block of tests verifies that OOM faults in the 
# sqlite3changeset_invert() function are handled correctly.
#
catch {db close}
catch {db2 close}
forcedelete test.db
sqlite3 db test.db
execsql {
  CREATE TABLE t1(a, b, PRIMARY KEY(b));
  CREATE TABLE t2(a PRIMARY KEY, b);
  INSERT INTO t1 VALUES('string', 1);
  INSERT INTO t1 VALUES(4, 2);
  INSERT INTO t1 VALUES(X'FFAAFFAAFFAA', 3);
}
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

Changes to ext/session/sqlite3session.c.

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  if( iVal<0 || iVal>=pIter->nCol ){
    return SQLITE_RANGE;
  }
  *ppValue = pIter->apValue[pIter->nCol+iVal];
  return SQLITE_OK;
}









/*
** This function may only be called with a changeset iterator that has been
** passed to an SQLITE_CHANGESET_DATA or SQLITE_CHANGESET_CONFLICT 
** conflict-handler function. Otherwise, SQLITE_MISUSE is returned.
**
** If successful, *ppValue is set to point to an sqlite3_value structure
** containing the iVal'th value of the conflicting record.
................................................................................

  if( rc==SQLITE_OK ){
    rc = sqlite3_prepare_v2(db, (char *)buf.aBuf, buf.nBuf, &p->pInsert, 0);
  }
  sqlite3_free(buf.aBuf);
  return rc;
}



















/*
** Iterator pIter must point to an SQLITE_INSERT entry. This function 
** transfers new.* values from the current iterator entry to statement
** pStmt. The table being inserted into has nCol columns.
**
** New.* value $i 0 from the iterator is bound to variable ($i+1) of 
................................................................................
** are transfered to the statement. Otherwise, if abPK is not NULL, it points
** to an array nCol elements in size. In this case only those values for 
** which abPK[$i] is true are read from the iterator and bound to the 
** statement.
**
** An SQLite error code is returned if an error occurs. Otherwise, SQLITE_OK.
*/
static int sessionBindValues(
  sqlite3_changeset_iter *pIter,  /* Iterator to read values from */
  int(*xIterValue)(sqlite3_changeset_iter *, int, sqlite3_value **),
  int nCol,                       /* Number of columns */
  u8 *abPK,                       /* If not NULL, bind only if true */
  sqlite3_stmt *pStmt             /* Bind values to this statement */
){
  int i;
  int rc = SQLITE_OK;







  for(i=0; rc==SQLITE_OK && i<nCol; i++){
    if( !abPK || abPK[i] ){
      sqlite3_value *pVal;
      rc = xIterValue(pIter, i, &pVal);
      if( rc==SQLITE_OK ){
        rc = sqlite3_bind_value(pStmt, i+1, pVal);
      }
    }
  }
  return rc;
}

/*
** SQL statement pSelect is as generated by the sessionSelectRow() function.
** This function binds the primary key values from the change that changeset
** iterator pIter points to to the SELECT and attempts to seek to the table
** entry. If a row is found, the SELECT statement left pointing at the row 
** and SQLITE_ROW is returned. Otherwise, if no row is found and no error
** has occured, the statement is reset and SQLITE_OK is returned. If an
** error occurs, an SQLite error code is returned.




**
** If the iterator currently points to an INSERT record, bind values from the
** new.* record to the SELECT statement. Or, if it points to a DELETE or
** UPDATE, bind values from the old.* record. 
*/
static int sessionSeekToRow(
  sqlite3 *db,                    /* Database handle */
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  u8 *abPK,                       /* Primary key flags array */
  sqlite3_stmt *pSelect           /* SELECT statement from sessionSelectRow() */
){
  int rc = SQLITE_OK;             /* 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 = sessionBindValues(pIter, 
      op==SQLITE_INSERT ? sqlite3changeset_new : sqlite3changeset_old,
      nCol, abPK, pSelect
  );

  if( rc==SQLITE_OK ){
    rc = sqlite3_step(pSelect);
    if( rc!=SQLITE_ROW ) rc = sqlite3_reset(pSelect);
................................................................................
    /* There exists another row with the new.* primary key. */
    pIter->pConflict = p->pSelect;
    res = xConflict(pCtx, eType, pIter);
    pIter->pConflict = 0;
    rc = sqlite3_reset(p->pSelect);
  }else if( rc==SQLITE_OK ){
    /* No other row with the new.* primary key. */
    rc = sqlite3_reset(p->pSelect);
    if( rc==SQLITE_OK ){
      res = xConflict(pCtx, eType+1, pIter);
      if( res==SQLITE_CHANGESET_REPLACE ) rc = SQLITE_MISUSE;
    }
  }

  if( rc==SQLITE_OK ){
    switch( res ){
      case SQLITE_CHANGESET_REPLACE:
        if( pbReplace ) *pbReplace = 1;
        break;
................................................................................
  assert( !pbReplace || *pbReplace==0 );

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

  if( op==SQLITE_DELETE ){

    /* Bind values to the DELETE statement. */
    rc = sessionBindValues(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);
    }
    if( rc!=SQLITE_OK ) return rc;

    sqlite3_step(p->pDelete);
    rc = sqlite3_reset(p->pDelete);
................................................................................
    }

  }else if( op==SQLITE_UPDATE ){
    int i;

    /* Bind values to the UPDATE statement. */
    for(i=0; rc==SQLITE_OK && i<nCol; i++){
      sqlite3_value *pOld = 0;
      sqlite3_value *pNew = 0;
      rc = sqlite3changeset_old(pIter, i, &pOld);
      if( rc==SQLITE_OK ){
        rc = sqlite3changeset_new(pIter, i, &pNew);
      }
      if( rc==SQLITE_OK ){
        if( pOld ) sqlite3_bind_value(p->pUpdate, i*3+1, pOld);
        sqlite3_bind_int(p->pUpdate, i*3+2, !!pNew);
        if( pNew ) sqlite3_bind_value(p->pUpdate, i*3+3, pNew);
      }
    }
    if( rc==SQLITE_OK ) rc = sqlite3_bind_int(p->pUpdate, nCol*3+1, pbRetry==0);
    if( rc!=SQLITE_OK ) return rc;

    /* Attempt the UPDATE. In the case of a NOTFOUND or DATA conflict,
    ** the result will be SQLITE_OK with 0 rows modified. */
    sqlite3_step(p->pUpdate);
    rc = sqlite3_reset(p->pUpdate);

................................................................................
      rc = sessionConflictHandler(
          SQLITE_CHANGESET_CONFLICT, p, pIter, xConflict, pCtx, 0
      );
    }

  }else{
    assert( op==SQLITE_INSERT );
    rc = sessionBindValues(pIter, sqlite3changeset_new, nCol, 0, p->pInsert);
    if( rc!=SQLITE_OK ) return rc;

    sqlite3_step(p->pInsert);
    rc = sqlite3_reset(p->pInsert);
    if( rc==SQLITE_CONSTRAINT ){
      rc = sessionConflictHandler(
          SQLITE_CHANGESET_CONFLICT, p, pIter, xConflict, pCtx, pbReplace
................................................................................
      rc = sessionApplyOneOp(pIter, &sApply, xConflict, pCtx, &bReplace, 0);
    }

    if( bReplace ){
      assert( pIter->op==SQLITE_INSERT );
      rc = sqlite3_exec(db, "SAVEPOINT replace_op", 0, 0, 0);
      if( rc==SQLITE_OK ){
        rc = sessionBindValues(pIter, 
            sqlite3changeset_new, sApply.nCol, sApply.abPK, sApply.pDelete);
        sqlite3_bind_int(sApply.pDelete, sApply.nCol+1, 1);
      }
      if( rc==SQLITE_OK ){
        sqlite3_step(sApply.pDelete);
        rc = sqlite3_reset(sApply.pDelete);
      }







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  if( iVal<0 || iVal>=pIter->nCol ){
    return SQLITE_RANGE;
  }
  *ppValue = pIter->apValue[pIter->nCol+iVal];
  return SQLITE_OK;
}

/*
** The following two macros are used internally. They are similar to the
** sqlite3changeset_new() and sqlite3changeset_old() functions, except that
** they omit all error checking and return a pointer to the requested value.
*/
#define sessionChangesetNew(pIter, iVal) (pIter)->apValue[(pIter)->nCol+(iVal)]
#define sessionChangesetOld(pIter, iVal) (pIter)->apValue[(iVal)]

/*
** This function may only be called with a changeset iterator that has been
** passed to an SQLITE_CHANGESET_DATA or SQLITE_CHANGESET_CONFLICT 
** conflict-handler function. Otherwise, SQLITE_MISUSE is returned.
**
** If successful, *ppValue is set to point to an sqlite3_value structure
** containing the iVal'th value of the conflicting record.
................................................................................

  if( rc==SQLITE_OK ){
    rc = sqlite3_prepare_v2(db, (char *)buf.aBuf, buf.nBuf, &p->pInsert, 0);
  }
  sqlite3_free(buf.aBuf);
  return rc;
}

/*
** A wrapper around sqlite3_bind_value() that detects an extra problem. 
** See comments in the body of this function for details.
*/
static int sessionBindValue(
  sqlite3_stmt *pStmt,            /* Statement to bind value to */
  int i,                          /* Parameter number to bind to */
  sqlite3_value *pVal             /* Value to bind */
){
  if( (pVal->type==SQLITE_TEXT || pVal->type==SQLITE_BLOB) && pVal->z==0 ){
    /* This condition occurs when an earlier OOM in a call to
    ** sqlite3_value_text() or sqlite3_value_blob() (perhaps from within
    ** a conflict-hanler) has zeroed the pVal->z pointer. Return NOMEM. */
    return SQLITE_NOMEM;
  }
  return sqlite3_bind_value(pStmt, i, pVal);
}

/*
** Iterator pIter must point to an SQLITE_INSERT entry. This function 
** transfers new.* values from the current iterator entry to statement
** pStmt. The table being inserted into has nCol columns.
**
** New.* value $i 0 from the iterator is bound to variable ($i+1) of 
................................................................................
** are transfered to the statement. Otherwise, if abPK is not NULL, it points
** to an array nCol elements in size. In this case only those values for 
** which abPK[$i] is true are read from the iterator and bound to the 
** statement.
**
** An SQLite error code is returned if an error occurs. Otherwise, SQLITE_OK.
*/
static int sessionBindRow(
  sqlite3_changeset_iter *pIter,  /* Iterator to read values from */
  int(*xValue)(sqlite3_changeset_iter *, int, sqlite3_value **),
  int nCol,                       /* Number of columns */
  u8 *abPK,                       /* If not NULL, bind only if true */
  sqlite3_stmt *pStmt             /* Bind values to this statement */
){
  int i;
  int rc = SQLITE_OK;

  /* Neither sqlite3changeset_old or sqlite3changeset_new can fail if the
  ** argument iterator points to a suitable entry. Make sure that xValue 
  ** is one of these to guarantee that it is safe to ignore the return 
  ** in the code below. */
  assert( xValue==sqlite3changeset_old || xValue==sqlite3changeset_new );

  for(i=0; rc==SQLITE_OK && i<nCol; i++){
    if( !abPK || abPK[i] ){
      sqlite3_value *pVal;
      (void)xValue(pIter, i, &pVal);

      rc = sessionBindValue(pStmt, i+1, pVal);

    }
  }
  return rc;
}

/*
** SQL statement pSelect is as generated by the sessionSelectRow() function.
** This function binds the primary key values from the change that changeset
** iterator pIter points to to the SELECT and attempts to seek to the table
** entry. If a row is found, the SELECT statement left pointing at the row 
** and SQLITE_ROW is returned. Otherwise, if no row is found and no error
** has occured, the statement is reset and SQLITE_OK is returned. If an
** error occurs, the statement is reset and an SQLite error code is returned.
**
** If this function returns SQLITE_ROW, the caller must eventually reset() 
** statement pSelect. If any other value is returned, the statement does
** not require a reset().
**
** If the iterator currently points to an INSERT record, bind values from the
** new.* record to the SELECT statement. Or, if it points to a DELETE or
** UPDATE, bind values from the old.* record. 
*/
static int sessionSeekToRow(
  sqlite3 *db,                    /* Database handle */
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  u8 *abPK,                       /* Primary key flags array */
  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);
    if( rc!=SQLITE_ROW ) rc = sqlite3_reset(pSelect);
................................................................................
    /* There exists another row with the new.* primary key. */
    pIter->pConflict = p->pSelect;
    res = xConflict(pCtx, eType, pIter);
    pIter->pConflict = 0;
    rc = sqlite3_reset(p->pSelect);
  }else if( rc==SQLITE_OK ){
    /* No other row with the new.* primary key. */


    res = xConflict(pCtx, eType+1, pIter);
    if( res==SQLITE_CHANGESET_REPLACE ) rc = SQLITE_MISUSE;

  }

  if( rc==SQLITE_OK ){
    switch( res ){
      case SQLITE_CHANGESET_REPLACE:
        if( pbReplace ) *pbReplace = 1;
        break;
................................................................................
  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);
    }
    if( rc!=SQLITE_OK ) return rc;

    sqlite3_step(p->pDelete);
    rc = sqlite3_reset(p->pDelete);
................................................................................
    }

  }else if( op==SQLITE_UPDATE ){
    int i;

    /* Bind values to the UPDATE statement. */
    for(i=0; rc==SQLITE_OK && i<nCol; i++){
      sqlite3_value *pOld = sessionChangesetOld(pIter, i);
      sqlite3_value *pNew = sessionChangesetNew(pIter, i);

      sqlite3_bind_int(p->pUpdate, i*3+2, !!pNew);
      if( pOld ){
        rc = sessionBindValue(p->pUpdate, i*3+1, pOld);
      }
      if( rc==SQLITE_OK && pNew ){
        rc = sessionBindValue(p->pUpdate, i*3+3, pNew);
      }
    }
    if( rc==SQLITE_OK ) sqlite3_bind_int(p->pUpdate, nCol*3+1, pbRetry==0);

    if( rc!=SQLITE_OK ) return rc;

    /* Attempt the UPDATE. In the case of a NOTFOUND or DATA conflict,
    ** the result will be SQLITE_OK with 0 rows modified. */
    sqlite3_step(p->pUpdate);
    rc = sqlite3_reset(p->pUpdate);

................................................................................
      rc = sessionConflictHandler(
          SQLITE_CHANGESET_CONFLICT, p, pIter, xConflict, pCtx, 0
      );
    }

  }else{
    assert( op==SQLITE_INSERT );
    rc = sessionBindRow(pIter, sqlite3changeset_new, nCol, 0, p->pInsert);
    if( rc!=SQLITE_OK ) return rc;

    sqlite3_step(p->pInsert);
    rc = sqlite3_reset(p->pInsert);
    if( rc==SQLITE_CONSTRAINT ){
      rc = sessionConflictHandler(
          SQLITE_CHANGESET_CONFLICT, p, pIter, xConflict, pCtx, pbReplace
................................................................................
      rc = sessionApplyOneOp(pIter, &sApply, xConflict, pCtx, &bReplace, 0);
    }

    if( bReplace ){
      assert( pIter->op==SQLITE_INSERT );
      rc = sqlite3_exec(db, "SAVEPOINT replace_op", 0, 0, 0);
      if( rc==SQLITE_OK ){
        rc = sessionBindRow(pIter, 
            sqlite3changeset_new, sApply.nCol, sApply.abPK, sApply.pDelete);
        sqlite3_bind_int(sApply.pDelete, sApply.nCol+1, 1);
      }
      if( rc==SQLITE_OK ){
        sqlite3_step(sApply.pDelete);
        rc = sqlite3_reset(sApply.pDelete);
      }