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Comment:Add tests to ensure that an sqlite3_snapshot_open() client cannot be tricked into reading a corrupt snapshot even if another process fails mid-checkpoint.
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SHA1: b908048b6cfa1ee2fe1f7a17bae475ddd9d0376c
User & Date: dan 2015-12-10 18:06:21.050
Context
2015-12-10
19:11
Return SQLITE_BUSY (not SQLITE_BUSY_SNAPSHOT) if sqlite3_snapshot_open() fails to obtain the shared checkpointer lock. (check-in: 5343060bcc user: dan tags: snapshot-get)
18:06
Add tests to ensure that an sqlite3_snapshot_open() client cannot be tricked into reading a corrupt snapshot even if another process fails mid-checkpoint. (check-in: b908048b6c user: dan tags: snapshot-get)
15:45
Have sqlite3_snapshot_open() avoid a race condition by taking a shared CHECKPOINTER lock while checking pInfo->nBackfillAttempted. (check-in: 8084eae0bc user: dan tags: snapshot-get)
Changes
Unified Diff Ignore Whitespace Patch
Changes to test/snapshot.test. 
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# 2015 December 7
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this file is testing the SELECT statement.
#
# $Id: select1.test,v 1.70 2009/05/28 01:00:56 drh Exp $

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

#-------------------------------------------------------------------------
# Check some error conditions in snapshot_get(). It is an error if:











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# 2015 December 7
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library. The focus
# of this file is the sqlite3_snapshot_xxx() APIs.
#


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

#-------------------------------------------------------------------------
# Check some error conditions in snapshot_get(). It is an error if:
︙︙
Added test/snapshot_fault.test. 










































































































































































































































































































































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# 2015 December 10
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library. The focus
# of this file is the sqlite3_snapshot_xxx() APIs.
#

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

#-------------------------------------------------------------------------
# Check that an sqlite3_snapshot_open() client cannot be tricked into
# reading a corrupt snapshot even if a second client fails while 
# checkpointing the db.
#
do_faultsim_test 1.0 -prep {
  faultsim_delete_and_reopen
  sqlite3 db2 test.db
  db2 eval { 
    CREATE TABLE t1(a, b UNIQUE, c UNIQUE);
    INSERT INTO t1 VALUES(1, randomblob(500), randomblob(500));
    INSERT INTO t1 VALUES(2, randomblob(500), randomblob(500));
    PRAGMA journal_mode = wal;
    INSERT INTO t1 VALUES(3, randomblob(500), randomblob(500));
    BEGIN;
      SELECT a FROM t1;
  }
  set ::snapshot [sqlite3_snapshot_get db2 main] 
  db2 eval COMMIT
  db2 eval {
    UPDATE t1 SET b=randomblob(501), c=randomblob(501) WHERE a=1;
    INSERT INTO t1 VALUES(4, randomblob(500), randomblob(500));
    INSERT INTO t1 VALUES(5, randomblob(500), randomblob(500));
    INSERT INTO t1 VALUES(6, randomblob(500), randomblob(500));
  }
} -body {
  db eval { PRAGMA wal_checkpoint }
} -test {
  db2 eval BEGIN
  if {[catch { sqlite3_snapshot_open db2 main $::snapshot } msg]} {
    if {$msg != "SQLITE_BUSY_SNAPSHOT" && $msg != "SQLITE_BUSY"} {
      error "error is $msg" 
    }
  } else {
    set res [db2 eval { 
      SELECT a FROM t1;
      PRAGMA integrity_check;
    }]
    if {$res != "1 2 3 ok"} { error "res is $res" }
  }

  sqlite3_snapshot_free $::snapshot
}

#-------------------------------------------------------------------------
# This test is similar to the previous one. Except, after the 
# "PRAGMA wal_checkpoint" command fails the db is closed and reopened
# so as to require wal file recovery. It should not be possible to open
# a snapshot that is part of the body of a recovered wal file.
#
do_faultsim_test 2.0 -prep {
  faultsim_delete_and_reopen
  db eval { 
    CREATE TABLE t1(a, b UNIQUE, c UNIQUE);
    INSERT INTO t1 VALUES(1, randomblob(500), randomblob(500));
    INSERT INTO t1 VALUES(2, randomblob(500), randomblob(500));
    PRAGMA journal_mode = wal;
    INSERT INTO t1 VALUES(3, randomblob(500), randomblob(500));
    BEGIN;
      SELECT a FROM t1;
  }
  set ::snapshot [sqlite3_snapshot_get db main] 
  db eval COMMIT

  db eval {
    UPDATE t1 SET b=randomblob(501), c=randomblob(501) WHERE a=1;
    INSERT INTO t1 VALUES(4, randomblob(500), randomblob(500));
    INSERT INTO t1 VALUES(5, randomblob(500), randomblob(500));
    INSERT INTO t1 VALUES(6, randomblob(500), randomblob(500));
  }
} -body {
  db eval { PRAGMA wal_checkpoint }
} -test {

  db_save
  db close
  db_restore_and_reopen
  db eval { SELECT * FROM t1 }
  
  db eval BEGIN
  if {[catch { sqlite3_snapshot_open db main $::snapshot } msg]} {
    if {$msg != "SQLITE_BUSY_SNAPSHOT" && $msg != "SQLITE_BUSY"} {
      error "error is $msg" 
    }
  } else {
    # This branch should actually never be taken. But it was useful in
    # determining whether or not this test was actually working (by 
    # running a modified version of SQLite that allowed snapshots to be
    # opened following a recovery).
    error "TEST HAS FAILED"

    set res [db eval { 
      SELECT a FROM t1;
      PRAGMA integrity_check;
    }]
    if {$res != "1 2 3 ok"} { error "res is $res" }
  }

  sqlite3_snapshot_free $::snapshot
}

#-------------------------------------------------------------------------
# Test the handling of faults that occur within sqlite3_snapshot_open().
#
do_faultsim_test 3.0 -prep {
  faultsim_delete_and_reopen
  db eval { 
    CREATE TABLE t1(a, b UNIQUE, c UNIQUE);
    INSERT INTO t1 VALUES(1, randomblob(500), randomblob(500));
    INSERT INTO t1 VALUES(2, randomblob(500), randomblob(500));
    PRAGMA journal_mode = wal;
    INSERT INTO t1 VALUES(3, randomblob(500), randomblob(500));
    BEGIN;
      SELECT a FROM t1;
  }
  set ::snapshot [sqlite3_snapshot_get db main] 
  db eval COMMIT
  db eval {
    UPDATE t1 SET b=randomblob(501), c=randomblob(501) WHERE a=1;
    INSERT INTO t1 VALUES(4, randomblob(500), randomblob(500));
    INSERT INTO t1 VALUES(5, randomblob(500), randomblob(500));
    INSERT INTO t1 VALUES(6, randomblob(500), randomblob(500));
    BEGIN;
  }
} -body {
  if { [catch { sqlite3_snapshot_open db main $::snapshot } msg] } {
    error $msg
  }
} -test {
  faultsim_test_result {0 {}} {1 SQLITE_IOERR} \
                              {1 SQLITE_IOERR_NOMEM} {1 SQLITE_IOERR_READ}
  if {$testrc==0} {
    set res [db eval { 
      SELECT a FROM t1;
      PRAGMA integrity_check;
    }]
    if {$res != "1 2 3 ok"} { error "res is $res" }
  }

  sqlite3_snapshot_free $::snapshot
}



finish_test