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

Artifact 984090e8e9d1b331d2e8111daf6e5d61dda0bef7:


# 2007 March 24
#
# 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.
#
# $Id: exclusive2.test,v 1.10 2008/11/27 02:22:11 drh Exp $

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

# Do not use a codec for tests in this file, as the database file is
# manipulated directly using tcl scripts (using the [hexio_write] command).
#
do_not_use_codec

ifcapable {!pager_pragmas} {
  finish_test
  return
}

# Tests in this file verify that locking_mode=exclusive causes SQLite to
# use cached pages even if the database is changed on disk. This doesn't
# work with mmap.
if {[permutation]=="mmap"} {
  finish_test
  return
}

# This module does not work right if the cache spills at unexpected
# moments.  So disable the soft-heap-limit.
#
sqlite3_soft_heap_limit 0

proc pagerChangeCounter {filename new {fd ""}} {
  if {$fd==""} {
    set fd [open $filename RDWR]
    fconfigure $fd -translation binary -encoding binary
    set needClose 1
  } else {
    set needClose 0
  }
  if {$new ne ""} {
    seek $fd 24
    set a [expr {($new&0xFF000000)>>24}]
    set b [expr {($new&0x00FF0000)>>16}]
    set c [expr {($new&0x0000FF00)>>8}]
    set d [expr {($new&0x000000FF)}]
    puts -nonewline $fd [binary format cccc $a $b $c $d]
    flush $fd
  }

  seek $fd 24
  foreach {a b c d} [list 0 0 0 0] {}
  binary scan [read $fd 4] cccc a b c d
  set  ret [expr ($a&0x000000FF)<<24]
  incr ret [expr ($b&0x000000FF)<<16]
  incr ret [expr ($c&0x000000FF)<<8]
  incr ret [expr ($d&0x000000FF)<<0]

  if {$needClose} {close $fd}
  return $ret
}

proc readPagerChangeCounter {filename} {
  set fd [open $filename RDONLY]
  fconfigure $fd -translation binary -encoding binary

  seek $fd 24
  foreach {a b c d} [list 0 0 0 0] {}
  binary scan [read $fd 4] cccc a b c d
  set  ret [expr ($a&0x000000FF)<<24]
  incr ret [expr ($b&0x000000FF)<<16]
  incr ret [expr ($c&0x000000FF)<<8]
  incr ret [expr ($d&0x000000FF)<<0]

  close $fd
  return $ret
}


proc t1sig {{db db}} {
  execsql {SELECT count(*), md5sum(a) FROM t1} $db
}
do_test exclusive2-1.0 {
  readPagerChangeCounter test.db
} {0}

#-----------------------------------------------------------------------
# The following tests - exclusive2-1.X - check that:
#
# 1-3:   Build a database with connection 1, calculate a signature.
# 4-7:   Modify the database using a second connection in a way that
#        does not modify the freelist, then reset the pager change-counter
#        to the value it had before the modifications.
# 8:     Check that using the first connection, the database signature
#        is still the same. This is because it uses the in-memory cache.
#        It can't tell the db has changed because we reset the change-counter.
# 9:     Increment the change-counter.
# 10:    Ensure that the first connection now sees the updated database. It
#        sees the change-counter has been incremented and discards the 
#        invalid in-memory cache.
#
# This will only work if the database cache is large enough to hold 
# the entire database. In the case of 1024 byte pages, this means
# the cache size must be at least 17. Otherwise, some pages will be
# loaded from the database file in step 8.
#
# For similar reasons, this test does not work with the memsubsys1 permutation.
# Permutation memsubsys1 configures the pcache subsystem to use a static
# allocation of 24 pages (shared between all pagers). This is not enough for
# this test.
#
do_test exclusive2-1.1 {
  execsql {
    BEGIN;
    CREATE TABLE t1(a, b);
    INSERT INTO t1(a, b) VALUES(randstr(10, 400), 0);
    INSERT INTO t1(a, b) VALUES(randstr(10, 400), 0);
    INSERT INTO t1(a, b) SELECT randstr(10, 400), 0 FROM t1;
    INSERT INTO t1(a, b) SELECT randstr(10, 400), 0 FROM t1;
    INSERT INTO t1(a, b) SELECT randstr(10, 400), 0 FROM t1;
    INSERT INTO t1(a, b) SELECT randstr(10, 400), 0 FROM t1;
    INSERT INTO t1(a, b) SELECT randstr(10, 400), 0 FROM t1;
    COMMIT;
    SELECT count(*) FROM t1;
  }
} {64}
do_test exclusive2-1.2.1 {
  # Make sure the pager cache is large enough to store the 
  # entire database.
  set nPage [expr [file size test.db]/1024]
  if {$::SQLITE_DEFAULT_CACHE_SIZE < $nPage} {
    execsql "PRAGMA cache_size = $nPage"
  }
  expr {[execsql {PRAGMA cache_size}] >= $nPage}
} {1}
do_test exclusive2-1.2 {
  set ::sig [t1sig]
  readPagerChangeCounter test.db
} {1}
do_test exclusive2-1.3 {
  t1sig
} $::sig
do_test exclusive2-1.4 {
  sqlite3 db2 test.db
  t1sig db2
} $::sig
do_test exclusive2-1.5 {
  execsql {
    UPDATE t1 SET b=a, a=0;
  } db2
  expr {[t1sig db2] eq $::sig}
} 0
do_test exclusive2-1.6 {
  readPagerChangeCounter test.db
} {2}
do_test exclusive2-1.7 {
  pagerChangeCounter test.db 1
} {1}
if {[permutation] != "memsubsys1"} {
  do_test exclusive2-1.9 {
    t1sig
    expr {[t1sig] eq $::sig}
  } {1}
}
do_test exclusive2-1.10 {
  pagerChangeCounter test.db 2
} {2}
do_test exclusive2-1.11 {
  expr {[t1sig] eq $::sig}
} {0}
db2 close

#--------------------------------------------------------------------
# These tests - exclusive2-2.X - are similar to exclusive2-1.X, 
# except that they are run with locking_mode=EXCLUSIVE.
#
# 1-3:   Build a database with exclusive-access connection 1, 
#        calculate a signature.
# 4:     Corrupt the database by writing 10000 bytes of garbage
#        starting at the beginning of page 2. Check that connection 1
#        still works. It should be accessing the in-memory cache.
# 5-6:   Modify the dataase change-counter. Connection 1 still works
#        entirely from in-memory cache, because it doesn't check the
#        change-counter.
# 7-8    Set the locking-mode back to normal. After the db is unlocked,
#        SQLite detects the modified change-counter and discards the
#        in-memory cache. Then it finds the corruption caused in step 4....
#
# As above, this test is only applicable if the pager cache is
# large enough to hold the entire database. With 1024 byte pages,
# this means 19 pages.  We also need to disable the soft-heap-limit
# to prevent memory-induced cache spills.
#
do_test exclusive2-2.1 {
  execsql {PRAGMA cache_size=1000;}
  execsql {PRAGMA locking_mode = exclusive;}
  execsql {
    BEGIN;
    DELETE FROM t1;
    INSERT INTO t1(a) VALUES(randstr(10, 400));
    INSERT INTO t1(a) VALUES(randstr(10, 400));
    INSERT INTO t1(a) SELECT randstr(10, 400) FROM t1;
    INSERT INTO t1(a) SELECT randstr(10, 400) FROM t1;
    INSERT INTO t1(a) SELECT randstr(10, 400) FROM t1;
    INSERT INTO t1(a) SELECT randstr(10, 400) FROM t1;
    INSERT INTO t1(a) SELECT randstr(10, 400) FROM t1;
    COMMIT;
    SELECT count(*) FROM t1;
  }
} {64}
do_test exclusive2-2.2.1 {
  # Make sure the pager cache is large enough to store the 
  # entire database.
  set nPage [expr [file size test.db]/1024]
  if {$::SQLITE_DEFAULT_CACHE_SIZE < $nPage} {
    execsql "PRAGMA cache_size = $nPage"
  }
  expr {[execsql {PRAGMA cache_size}] >= $nPage}
} {1}
do_test exclusive2-2.2 {
  set ::sig [t1sig]
  readPagerChangeCounter test.db
} {3}
do_test exclusive2-2.3 {
  t1sig
} $::sig

do_test exclusive2-2.4 {
  set ::fd [open test.db RDWR]
  fconfigure $::fd -translation binary
  seek $::fd 1024
  puts -nonewline $::fd [string repeat [binary format c 0] 10000]
  flush $::fd
  t1sig
} $::sig

do_test exclusive2-2.5 {
  pagerChangeCounter test.db 5 $::fd
} {5}
do_test exclusive2-2.6 {
  t1sig
} $::sig
do_test exclusive2-2.7 {
  execsql {PRAGMA locking_mode = normal}
  t1sig
} $::sig

do_test exclusive2-2.8 {
  set rc [catch {t1sig} msg]
  list $rc $msg
} {1 {database disk image is malformed}}

#--------------------------------------------------------------------
# These tests - exclusive2-3.X - verify that the pager change-counter
# is only incremented by the first change when in exclusive access
# mode. In normal mode, the change-counter is incremented once
# per write-transaction.
#

db close
catch {close $::fd}
forcedelete test.db
forcedelete test.db-journal

do_test exclusive2-3.0 {
  sqlite3 db test.db
  execsql {
    BEGIN;
    CREATE TABLE t1(a UNIQUE);
    INSERT INTO t1 VALUES(randstr(200, 200));
    INSERT INTO t1 VALUES(randstr(200, 200));
    COMMIT;
  }
  readPagerChangeCounter test.db
} {1}
do_test exclusive2-3.1 {
  execsql {
    INSERT INTO t1 VALUES(randstr(200, 200));
  }
  readPagerChangeCounter test.db
} {2}
do_test exclusive2-3.2 {
  execsql {
    INSERT INTO t1 VALUES(randstr(200, 200));
  }
  readPagerChangeCounter test.db
} {3}
do_test exclusive2-3.3 {
  execsql {
    PRAGMA locking_mode = exclusive;
    INSERT INTO t1 VALUES(randstr(200, 200));
  }
  readPagerChangeCounter test.db
} {4}
do_test exclusive2-3.4 {
  execsql {
    INSERT INTO t1 VALUES(randstr(200, 200));
  }
  readPagerChangeCounter test.db
} {4}
do_test exclusive2-3.5 {
  execsql {
    PRAGMA locking_mode = normal;
    INSERT INTO t1 VALUES(randstr(200, 200));
  }
  readPagerChangeCounter test.db
} {4}
do_test exclusive2-3.6 {
  execsql {
    INSERT INTO t1 VALUES(randstr(200, 200));
  }
  readPagerChangeCounter test.db
} {5}
sqlite3_soft_heap_limit $cmdlinearg(soft-heap-limit)

finish_test