tree 5e89bd4ae207a4564f5df8f2d67eeba5fb555b0d
parent 75dcc4f040199f410e680fc5938aeae53c501d7a
author Fyodor Kupolov <fkupolov@google.com> 1508972975 -0700
committer Fyodor Kupolov <fkupolov@google.com> 1509042079 -0700

Initial version of compatibility WAL

In this mode, only database journal mode will be changed, connection pool
size will still be limited to a single connection.

If enabled, compatibility WAL mode will be used if an app hasn't explicitly
 requested journal mode, by calling disable/enableWriteAheadLogging.

Compatibility WAL mode is controlled by debug.sqlite.use_compatibility_wal
property and db_use_compatibility_wal config resource.

Impact on write performance:
On ext4, with WAL, there is approx 300% increase in speed of update operations
On f2fs, with WAL, there is approx 5% increase in speed of update operations

Impact on number of writes:
On ext4, switching to WAL reduces the number of writes by approx 50%.
On f2fs, switching to WAL increases the number of writes by approx 15%.

Test: CtsDatabaseTestCases
Test: manual, running device
Bug: 33044236
Change-Id: Iaffb5651df39d8c9f710d7dbbe174f9c0d8a3186