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SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

Artifact f6c5ef7cb93bf92fbb4e864ecc5c87df7d3a250064838822db5b4d3a5563ede4:


# 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
ifcapable !snapshot {finish_test; return}
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_ERROR_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_ERROR_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 $msg
  }
} -test {
  faultsim_test_result {0 {}} {1 SQLITE_IOERR} {1 SQLITE_NOMEM} \
                              {1 SQLITE_IOERR_NOMEM} {1 SQLITE_IOERR_READ}
  if {$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
}

#-------------------------------------------------------------------------
# Test the handling of faults that occur within sqlite3_snapshot_recover().
#
reset_db
do_execsql_test 4.0 {
  PRAGMA journal_mode = wal;
  CREATE TABLE t1(zzz);
  INSERT INTO t1 VALUES('abc');
  INSERT INTO t1 VALUES('def');
} {wal}
faultsim_save_and_close

do_test 4.0.1 {
  faultsim_restore_and_reopen
  db eval { SELECT * FROM sqlite_master } 
  sqlite3_snapshot_recover db main
} {}
db close

do_faultsim_test 4.0 -faults oom* -prep {
  faultsim_restore_and_reopen
  db eval { SELECT * FROM sqlite_master } 
} -body {
  sqlite3_snapshot_recover db main
} -test {
  faultsim_test_result {0 {}} {1 SQLITE_NOMEM} {1 SQLITE_IOERR_NOMEM}
}

# The following test cases contrive to call sqlite3_snapshot_recover()
# before all pages of the *-shm file have been mapped. This tests an
# extra branch of error handling logic in snapshot_recover().
#
reset_db
do_execsql_test 4.1.0 {
  PRAGMA page_size = 512;
  PRAGMA journal_mode = wal;
  PRAGMA wal_autocheckpoint = 0;
  CREATE TABLE t1(zzz);
  INSERT INTO t1 VALUES(randomblob( 500 * 9500 ));
  PRAGMA user_version = 211;
} {wal 0}

do_test 4.1.1 {
  list [file size test.db-shm] [file size test.db]
} {98304 512}

faultsim_save_and_close
do_faultsim_test 4.1 -faults shm* -prep {
  catch { db2 close } 
  catch { db close } 
  faultsim_restore_and_reopen
  sqlite3 db2 test.db
  db2 eval { SELECT * FROM sqlite_master } 
  db eval BEGIN
  sqlite3_snapshot_get_blob db main
  db eval COMMIT
} -body {
  sqlite3_snapshot_recover db main
} -test {
  faultsim_test_result {0 {}} {1 SQLITE_IOERR}
}

#-------------------------------------------------------------------------
# Test the handling of faults that occur within sqlite3_snapshot_get().
#
reset_db
do_execsql_test 5.0 {
  PRAGMA page_size = 512;
  PRAGMA journal_mode = wal;
  PRAGMA wal_autocheckpoint = 0;
  CREATE TABLE t1(zzz);
  INSERT INTO t1 VALUES(randomblob( 5000 ));
  PRAGMA user_version = 211;
} {wal 0}
faultsim_save_and_close

do_faultsim_test 5 -prep {
  faultsim_restore_and_reopen
  execsql { SELECT count(*) FROM sqlite_master }
  execsql BEGIN
} -body {
  sqlite3_snapshot_get_blob db main
  set {} {}
} -test {
  execsql END
  faultsim_test_result {0 {}} {1 SQLITE_IOERR} {1 SQLITE_NOMEM}
}


finish_test