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# 2023 January 31
#
# 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.
#
#***********************************************************************
#
set testdir [file dirname $argv0]
source $testdir/tester.tcl
set testprefix pendingrace
# This test file tests that a race condition surrounding hot-journal
# rollback that once existed has been resolved. The problem was that
# if, when attempting to upgrade from a SHARED to EXCLUSIVE lock in
# order to roll back a hot journal, a connection failed to take the
# lock, the file-descriptor was left holding a PENDING lock for
# a very short amount of time. In a multi-threaded deployment, this
# could allow a second connection to read the database without rolling
# back the hot journal.
#
testvfs tvfs
db close
sqlite3 db test.db -vfs tvfs
# Create a 20 page database using connection [db]. Connection [db] uses
# Tcl VFS wrapper "tvfs", but it is configured to do straight pass-through
# for now.
#
do_execsql_test 1.0 {
PRAGMA cache_size = 5;
CREATE TABLE t1(a, b);
CREATE INDEX i1 ON t1(a, b);
WITH s(i) AS (
SELECT 1 UNION ALL SELECT i+1 FROM s WHERE i<10
)
INSERT INTO t1 SELECT hex(randomblob(100)), hex(randomblob(100)) FROM s;
} {}
do_test 1.1a {
set nPg [db one { PRAGMA page_count }]
expr ($nPg==20 || $nPg==21)
} 1
# Simulate a crash in another process. This leaves the db with a hot-journal.
# Without the journal the db is corrupt.
#
sqlite3 db2 test.db
do_execsql_test -db db2 1.1 {
PRAGMA cache_size = 5;
BEGIN;
UPDATE t1 SET b=hex(randomblob(100));
}
db_save
db2 close
proc my_db_restore {} {
forcecopy sv_test.db-journal test.db-journal
set fd1 [open sv_test.db r]
fconfigure $fd1 -encoding binary -translation binary
set data [read $fd1]
close $fd1
set fd1 [open test.db w]
fconfigure $fd1 -encoding binary -translation binary
puts -nonewline $fd1 $data
close $fd1
}
my_db_restore
do_test 1.2 {
file exists test.db-journal
} {1}
# Set up connection [db2] to use Tcl VFS wrapper [tvfs2]. Which is configured
# so that the first call to xUnlock() fails. And then all VFS calls thereafter
# fail as well.
#
testvfs tvfs2
tvfs2 filter xUnlock
tvfs2 script xUnlock
set ::seen_unlock 0
proc xUnlock {args} {
if {$::seen_unlock==0} {
set ::seen_unlock 1
tvfs2 ioerr 1 1
tvfs2 filter {xLock xUnlock}
}
return ""
}
sqlite3 db2 test.db -vfs tvfs2
# Configure [tvfs] (used by [db]) so that within the first call to xAccess,
# [db2] attempts to read the db. This causes [db2] to fail to upgrade to
# EXCLUSIVE, leaving it with a PENDING lock. Which it holds on to,
# as the xUnlock() and all subsequent VFS calls fail.
#
tvfs filter xAccess
tvfs script xAccess
set ::seen_access 0
proc xAccess {args} {
if {$::seen_access==0} {
set ::seen_access 1
catch { db2 eval { SELECT count(*)+0 FROM t1 } }
breakpoint
}
return ""
}
# Run an integrity check using [db].
do_catchsql_test 1.3 {
PRAGMA integrity_check
} {1 {database is locked}}
db close
db2 close
tvfs delete
tvfs2 delete
finish_test
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