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Fix a bug whereby an old snapshot could be checkpointed (and subsequent transactions discarded) if the last connection to disconnect from a WAL database happended to be holding an out-of-date wal-index header.

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FossilOrigin-Name: d0c0034b0baa83046c1d6b94c886f7039e4e06f5
This commit is contained in:
dan
2010-05-06 17:28:08 +00:00
parent 6e5b37faef
commit b7d53f54ae
4 changed files with 82 additions and 20 deletions
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59
test/wal.test
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@ -276,6 +276,20 @@ do_test wal-4.5.7 {
} {ok}
db2 close
do_test wal-4.6.1 {
execsql {
DELETE FROM t2;
PRAGMA wal_checkpoint;
BEGIN;
INSERT INTO t2 VALUES('w', 'x');
SAVEPOINT save;
INSERT INTO t2 VALUES('y', 'z');
ROLLBACK TO save;
COMMIT;
SELECT * FROM t2;
}
} {w x}
reopen_db
do_test wal-5.1 {
@ -1340,7 +1354,52 @@ foreach {tn pgsz works} {
}
}
#-------------------------------------------------------------------------
# The following test - wal-19.* - fixes a bug that was present during
# development.
#
# When a database connection in WAL mode is closed, it attempts an
# EXCLUSIVE lock on the database file. If the lock is obtained, the
# connection knows that it is the last connection to disconnect from
# the database, so it runs a checkpoint operation. The bug was that
# the connection was not updating its private copy of the wal-index
# header before doing so, meaning that it could checkpoint an old
# snapshot.
#
do_test wal-19.1 {
file delete -force test.db test.db-wal test.db-journal
sqlite3 db test.db
sqlite3 db2 test.db
execsql {
PRAGMA journal_mode = WAL;
CREATE TABLE t1(a, b);
INSERT INTO t1 VALUES(1, 2);
INSERT INTO t1 VALUES(3, 4);
}
execsql { SELECT * FROM t1 } db2
} {1 2 3 4}
do_test wal-19.2 {
execsql {
INSERT INTO t1 VALUES(5, 6);
SELECT * FROM t1;
}
} {1 2 3 4 5 6}
do_test wal-19.3 {
db close
db2 close
file exists test.db-wal
} {0}
do_test wal-19.4 {
# When the bug was present, the following was returning {1 2 3 4} only,
# as [db2] had an out-of-date copy of the wal-index header when it was
# closed.
#
sqlite3 db test.db
execsql { SELECT * FROM t1 }
} {1 2 3 4 5 6}
catch { db2 close }
catch { db close }
finish_test