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Commit 2e2f01e4 authored by Fyodor Kupolov's avatar Fyodor Kupolov
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Use NORMAL synchronous mode for WAL journal mode 

When synchronous is NORMAL (1), the SQLite database engine will still
sync at the most critical moments, but less often than in FULL mode.

With this change, the number of writes is reduced by 50%,
more than 5x improvement in write performance, read performance is
the same.

Test: Manual + SQLiteDatabaseTest
Bug: 76033286
Change-Id: I13526962bbaeae028a9c6cb668aa9f94bbc2a44d
parent 1072d0d1

core/res/res/values/config.xml

+9 −5
Original line number Diff line number Diff line
@@ -1826,12 +1826,16 @@ 
    <string name="db_default_sync_mode" translatable="false">FULL</string>



    <!-- The database synchronization mode when using Write-Ahead Logging.

         FULL is safest and preserves durability at the cost of extra fsyncs.

         NORMAL sacrifices durability in WAL mode because syncs are only performed before

         and after checkpoint operations.  If checkpoints are infrequent and power loss

         occurs, then committed transactions could be lost and applications might break.

         From https://www.sqlite.org/pragma.html#pragma_synchronous:

         WAL mode is safe from corruption with synchronous=NORMAL, and probably DELETE mode is safe

         too on modern filesystems. WAL mode is always consistent with synchronous=NORMAL, but WAL

         mode does lose durability. A transaction committed in WAL mode with

         synchronous=NORMAL might roll back following a power loss or system crash.

         Transactions are durable across application crashes regardless of the synchronous setting

         or journal mode. The synchronous=NORMAL setting is a good choice for most applications

         running in WAL mode.

         Choices are: FULL, NORMAL, OFF. -->

    <string name="db_wal_sync_mode" translatable="false">FULL</string>

    <string name="db_wal_sync_mode" translatable="false">NORMAL</string>



    <!-- The Write-Ahead Log auto-checkpoint interval in database pages (typically 1 to 4KB).

         The log is checkpointed automatically whenever it exceeds this many pages.